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Low mass boilers...what do you know about them?

 
 
Reply Tue 3 Jun, 2008 11:34 am
let me start by saying I know zero about furnaces, just what the nice salesguy told me. But after calling about a new furnace, i cant say why anyone in my situation wouldnt be out there buying a low mass.

Please correct or warn me about anything I'm missing here. I assume my chimney is ok (he said it shows 8 inch pipe on his computer screen) and of course they would plumb everything for me. I just dont know if i asked enough questions.

I have a 60 yr old furnace (estimating 30 yrs on the updated burner) and have baseboards and a coil heating my domestic water. The sales guy said he can install a low mass system for 6,000 plus 500 if this one has asbestos in it.

He said there is a 5 gallon tank in the unit vs me keeping 30 gallons at either 160 (winter) or 120 degrees (summer). He said when heat is called for, it will heat up in 2 min but if no heat is called for, the water will 'get cold.' But he said in his own tests in summer, the flame didnt turn on at all when he went away a week, it's insulated that well.

He said i'd have a 30 gallon hot water tank outside my furnace. I forgot what he said though..this is on a different burner than the heat part? I forgot why this is any different than my current 30 gallon boiler? Any ideas?

This is the part where i cant believe things. In the coldest January, my heat will run 10 hours a day (this doesnt include domestic hot water use as the thermostat doesnt keep count of that). So at 10 hours per day, saving 1.25 - .75 = .50 gallons (old nozzle minus new nozzle volume ), it appears I will save 10 hours x .5 gal x $4/gal = $20 dollars. Will i really save 20 bucks a day ????? Even if you half that for warmer months, 10 bucks a day is a less than 2 year payback

this cannot be true. What am i missing?
 
fishin
 
  2  
Reply Tue 3 Jun, 2008 01:01 pm
Re: Low mass boilers...what do you know about them?
luckydriver wrote:
let me start by saying I know zero about furnaces, just what the nice salesguy told me. But after calling about a new furnace, i cant say why anyone in my situation wouldnt be out there buying a low mass.


The $6,500+ up-front cost inhibits most people. Plus, most people don't have a 60 year old system to replace. The gains wouldn't be the same if you were replacing a 10 year old system.

Quote:
Please correct or warn me about anything I'm missing here. I assume my chimney is ok (he said it shows 8 inch pipe on his computer screen) and of course they would plumb everything for me. I just dont know if i asked enough questions.

I have a 60 yr old furnace (estimating 30 yrs on the updated burner) and have baseboards and a coil heating my domestic water. The sales guy said he can install a low mass system for 6,000 plus 500 if this one has asbestos in it.

He said there is a 5 gallon tank in the unit vs me keeping 30 gallons at either 160 (winter) or 120 degrees (summer). He said when heat is called for, it will heat up in 2 min but if no heat is called for, the water will 'get cold.' But he said in his own tests in summer, the flame didnt turn on at all when he went away a week, it's insulated that well.


This "magic" doens't have anything to do with it being insulated well. If he was gone for a week then there was no demand on the domestic hot water system. As you stated yourself, if there is no demand then the system lets the water "get cold". "Getting cold" = the furnace doesn't kick on.

In effect, this furnace acts as a 5 gallon hot water storage tank in combination with an on-demand hot water heater.

Quote:
He said i'd have a 30 gallon hot water tank outside my furnace. I forgot what he said though..this is on a different burner than the heat part? I forgot why this is any different than my current 30 gallon boiler? Any ideas?


Your current hot water tank stores your domestic hot water. The new system would use a 30 gallon storage tank for the heated water to be used in the heating loops (i.e. radiators). They'd set it up so that the furnace heats 30+ gallons of water to the preset temp for the radiators. If the thermostat tells the system it needs heat then the circulating pump kicks on and distributes the already heated water from the 30 gallon tank instead of firing the burner like your current furnace does. The new burner only kicks on when there is a demand + when the water in the loops is below the preset temp.

Quote:
This is the part where i cant believe things. In the coldest January, my heat will run 10 hours a day (this doesnt include domestic hot water use as the thermostat doesnt keep count of that). So at 10 hours per day, saving 1.25 - .75 = .50 gallons (old nozzle minus new nozzle volume ), it appears I will save 10 hours x .5 gal x $4/gal = $20 dollars. Will i really save 20 bucks a day ????? Even if you half that for warmer months, 10 bucks a day is a less than 2 year payback

this cannot be true. What am i missing?


I don't fully understand what you are trying to do with your math here but I don't think it really matters. (Nozzle size is only one of several factors that goes into figuring out how much you might save.)

Saving money by replacing a 60 year old furnace shouldn't surprise anyone. Furnaces (water boilers) produced in the 1970s where in the range of 65%-75% efficent. Older furnaces were even less efficent. Modern oil fired boilers can typically operate in the 80%-85% range without any problem (Federal regulations require that they be at least 80% efficent.) A mid-efficiency furnace will run in the 85%-90% range and a high efficiency furnace will run in the 90%-96% range.

So simple calculations should let you figure out that if you are going from say... a 60% efficiency furnace to a 90% efficiency model your oil consumption should drop by the 30% difference. Someone would just have to look at how much heating oil they use each year to figure out how much that would save them.

Every furnce sold since 1987 has an "AFUE rating". Ask what the rating is for this new furnace and then have someone test your old system (any oil burner tech should be able to do that test for under $100. - they won't be able to recreate the lab conditions but they can come close enough...) Then you'll have real numbers to look at based on something other than a salesman's pitch. Wink

NOTE: Those numbers aren't going to be a perfect predictor. They'll only tell you the differences in the furnaces themselves. The rest of your heating system (i.e. radiators, distribution piping, etc...) has an effect on overall efficiency too!
0 Replies
 
luckydriver
 
  2  
Reply Tue 3 Jun, 2008 06:04 pm
Re: Low mass boilers...what do you know about them?
fishin wrote:

The $6,500+ up-front cost inhibits most people. Plus, most people don't have a 60 year old system to replace. The gains wouldn't be the same if you were replacing a 10 year old system.


while i understand the sales guy was hedging his bet, will you stick your neck and and guesstimate what i may be saving by getting something new? 1300/gal year now.


Quote:
This "magic" doens't have anything to do with it being insulated well. If he was gone for a week then there was no demand on the domestic hot water system. As you stated yourself, if there is no demand then the system lets the water "get cold". "Getting cold" = the furnace doesn't kick on.

In effect, this furnace acts as a 5 gallon hot water storage tank in combination with an on-demand hot water heater.



hmmm thats so logical i cant believe i was impressed by it.

Quote:
Your current hot water tank stores your domestic hot water. The new system would use a 30 gallon storage tank for the heated water to be used in the heating loops (i.e. radiators). They'd set it up so that the furnace heats 30+ gallons of water to the preset temp for the radiators. If the thermostat tells the system it needs heat then the circulating pump kicks on and distributes the already heated water from the 30 gallon tank instead of firing the burner like your current furnace does. The new burner only kicks on when there is a demand + when the water in the loops is below the preset temp.



wow i totally misunderstood him. I thought the 30 gal was for the domestic and the 5 gal was for the heat. Ok you said the 30 gal was used for the baseboards. So during winter even if the 30 gal tank gets cold, it wont turn on unless heat is called for right? That sounds like huge savings to me

And year round i'm saving not heating the domestic water except on demand. Again that sounds like savings.

Quote:

I don't fully understand what you are trying to do with your math here but I don't think it really matters. (Nozzle size is only one of several factors that goes into figuring out how much you might save.)


ok but isnt the gallons per hour a 'true' number? So in theory if the new one did run as long as the old one, wouldnt i really be saving .5 gal/hour? But i sure would hope the new one ran much much less time. Do you think there's a circumstance where this new one would run longer?

Quote:

So simple calculations should let you figure out that if you are going from say... a 60% efficiency furnace to a 90% efficiency model your oil consumption should drop by the 30% difference. Someone would just have to look at how much heating oil they use each year to figure out how much that would save them.


the numbers they write down on the paper each year indicate anywhere from 75 to a high of 82 percent years ago. however i dont know if that is accurate. I think they got it by putting something in the hole in the chimney pipe but am not sure. But like you said, this probably is closer to the 60's in 'real life'. I guess it's true there is no way i WONT save, it's just how long is the payback for 6500

Quote:

Every furnce sold since 1987 has an "AFUE rating". Ask what the rating is for this new furnace and then have someone test your old system (any oil burner tech should be able to do that test for under $100. - they won't be able to recreate the lab conditions but they can come close enough...) Then you'll have real numbers to look at based on something other than a salesman's pitch. Wink

NOTE: Those numbers aren't going to be a perfect predictor. They'll only tell you the differences in the furnaces themselves. The rest of your heating system (i.e. radiators, distribution piping, etc...) has an effect on overall efficiency too!


well nothing i can do about the pipes etc. But is the test the tech does every year when he cleans the burner any good or is your 100 dollar test something more extensive (i'm guessing yes).
0 Replies
 
fishin
 
  2  
Reply Tue 3 Jun, 2008 07:24 pm
Re: Low mass boilers...what do you know about them?
luckydriver wrote:
fishin wrote:

The $6,500+ up-front cost inhibits most people. Plus, most people don't have a 60 year old system to replace. The gains wouldn't be the same if you were replacing a 10 year old system.


while i understand the sales guy was hedging his bet, will you stick your neck and and guesstimate what i may be saving by getting something new? 1300/gal year now.


A typical furnace replacement for a 30 year old unit will have a payback period of between 6 and 10 years. It varies by how much heating you do and what you pay for heating oil. You mention below that your burner tech has been listing your current unit at ~75%. If you the new unit you are looking at is a 90% unit then you should use roughly 15% less oil.

1300 gallons at $4.50/gal (current price in my area) = $5,850.00/year.
If you reduce that by 15% (90% minus 75%) then you are at:
1105 gallons at $4.50/gal = $4,972.00/year.

That's a reduction of $878/year. If it's $6,500 to replace it then you have a payback period of 7.4 years. (That could be a few months high depending on your domestic hot water use) If prices continue going up then the payback period will be shorter. If they go down then it'll be longer...

Quote:
Quote:
Your current hot water tank stores your domestic hot water. The new system would use a 30 gallon storage tank for the heated water to be used in the heating loops (i.e. radiators). They'd set it up so that the furnace heats 30+ gallons of water to the preset temp for the radiators. If the thermostat tells the system it needs heat then the circulating pump kicks on and distributes the already heated water from the 30 gallon tank instead of firing the burner like your current furnace does. The new burner only kicks on when there is a demand + when the water in the loops is below the preset temp.



wow i totally misunderstood him. I thought the 30 gal was for the domestic and the 5 gal was for the heat. Ok you said the 30 gal was used for the baseboards. So during winter even if the 30 gal tank gets cold, it wont turn on unless heat is called for right? That sounds like huge savings to me


Right, it won't turn on unless the thermostat kicks it on. But there are trade-offs here. Your current setup doesn't have that storage tank. The new one will have to heat that 30 gallons of water in the tank as well as what is circulating to the radiatiors. It is much more efficent than your current system but not quite perfect. (There are always those damned trade-offs! Arrgh! Razz )

Quote:
And year round i'm saving not heating the domestic water except on demand. Again that sounds like savings.


True. Not as efficent as a stand alone on-demand water heater but you'd need natural gas or propane to go that route...

Quote:
Quote:

I don't fully understand what you are trying to do with your math here but I don't think it really matters. (Nozzle size is only one of several factors that goes into figuring out how much you might save.)


ok but isnt the gallons per hour a 'true' number? So in theory if the new one did run as long as the old one, wouldnt i really be saving .5 gal/hour? But i sure would hope the new one ran much much less time. Do you think there's a circumstance where this new one would run longer?


It's a true number but it is only one of several true numbers. I could reduce the nozzle size in a furnace by 50% without doing anything else but it isn't going to generate a savings. It would just mean that the furnace would burn twice as long to do it's job at the same level. Think of it as a water pipe filling a bucket. if I need 20 gallons of water I can use a 20 gallon bucket and a 3/4 water pipe and it might take 1 minute to fill the bucket. Of I can use teh same bucket and a 1/2" pipe. I'll still get 20 gallons in the end but it will take longer to fill it from the 1/2" pipe.

The AFCU factors all of those together for you. That's why it's a more helpful number to look at. To use nozzle size you'd also need to know exactly how many hours the furnace will actually run, how hot the fire it produces is, the size of the firebox, heat transfer properties of the materials used in construction, ambient daily air temps, etc...

There are a lot of circumstances where a new unit would run more - not all of them are bad either.

This is where you start getting into the pros/cons of a low mass furnace.

In your old furnace you have a huge cast iron housing. That's mass - big heavy stuff = mass. Wink Mass retains heat. Your furnace kicks on and all that cast iron heats up. Water runs through the cast iron jacket and heat transfers from the iron to the water. The water then gets pumped to the radiators. But it takes quite a bit of oil to burn long enough for all that mass to heat up. The advantage of a high-mass furnace is that the thermostat can call for heat and if the furnace is still hot it doesn't have to fire up again. The burner only kicks on when the water temp drops below a preset temp but it will maintain that water temp all the time - even if there is no demand for it. The system has to do this to keep itself together. Heating cast iron (or steel) causes it to expand. If the furnace heats up and then cools off often enough the interal gaskets will fail and the water jacket will start leaking - that's a pretty major repair and not something you want to have to do on a cold winter night. And the high mass furnace has to do this year round. Even in the summer when you are only using it for domestic hot water it has to fire to keep itself heated up several times a day. That's a waste and you are paying for it.

In a low mass system the water is the mass. The furnace is built out of lightweight materials - often ceramics. They don't retain heat well but the trade-off is that they heat up quickly. So the furnace kicks on and ignites and water starts heating to distribution temps within minutes. And it heats some extra (that 30 gallon tank!). Water does a pretty good job of holding heat (ever notice how a lake or pool will seem warm in the evenings after the sun has gone down? The land cools quickly but the water retains the heat it absorbed during the day longer!) so instead of relying on the mass of the furnace to heat water there is a large storage tank doing that job. The low mass furnaces are made of materials designed to expand and contract often so you don't have the issues of gaskets leaking and such. That means the furnace can go cold if there isn't any demand without any problems. In theory, it should fire less often - especially in the summer when it only needs to fire up to heat domestic hot water when you turn on a faucet.

IMO, the low mass systems lose some of their attraction if you have several heating zones and are living in a region with short summers.

Let's say you have a very large house with 4 heating zones. The thermostat in zone 1 kicks on and tells the furance it needs heat. So the furnace does it's thing and heats the circulating water for zone 1 and the 30 gallon tank.

20 minutes later zone 2 kicks in and decides it wants to be heated. So it's circulating pump kicks on and the water in the tank circulates to heat that zone. Now you are out of hot water. If zone 3 or 4 kick on the furnace has to light up and heat more water.

In the older high-mass designs the cast iron furnace would still retain enough heat to heat the water circulating from zone 3 or 4 so it would fire less often.

But there aren't many houses that have more than 2 zones and there are ways to deal with that with a low mass furnace too (i.e. bigger storage tanks, combining zones, etc...). I'm assuming that your sales guy surveyed your current system and calculated the total water volume for all the zones when he spec'd the 30 gallon tank.


Quote:
Quote:

So simple calculations should let you figure out that if you are going from say... a 60% efficiency furnace to a 90% efficiency model your oil consumption should drop by the 30% difference. Someone would just have to look at how much heating oil they use each year to figure out how much that would save them.


the numbers they write down on the paper each year indicate anywhere from 75 to a high of 82 percent years ago. however i dont know if that is accurate. I think they got it by putting something in the hole in the chimney pipe but am not sure. But like you said, this probably is closer to the 60's in 'real life'. I guess it's true there is no way i WONT save, it's just how long is the payback for 6500


*nods* They are measuring the burn effiency by looking at the exhaust gasses. That's as close as you are going to get outiside of the lab.

Quote:
Quote:

Every furnce sold since 1987 has an "AFUE rating". Ask what the rating is for this new furnace and then have someone test your old system (any oil burner tech should be able to do that test for under $100. - they won't be able to recreate the lab conditions but they can come close enough...) Then you'll have real numbers to look at based on something other than a salesman's pitch. Wink

NOTE: Those numbers aren't going to be a perfect predictor. They'll only tell you the differences in the furnaces themselves. The rest of your heating system (i.e. radiators, distribution piping, etc...) has an effect on overall efficiency too!


well nothing i can do about the pipes etc. But is the test the tech does every year when he cleans the burner any good or is your 100 dollar test something more extensive (i'm guessing yes).


Nope. That's the test. It's a rough estimate but as good as it gets once the furnace has been installed.
0 Replies
 
luckydriver
 
  2  
Reply Fri 6 Jun, 2008 11:18 am
fishin wrote:
1300 gallons at $4.50/gal (current price in my area) = $5,850.00/year.
If you reduce that by 15% (90% minus 75%) then you are at:
1105 gallons at $4.50/gal = $4,972.00/year.

That's a reduction of $878/year. If it's $6,500 to replace it then you have a payback period of 7.4 years. (That could be a few months high depending on your domestic hot water use) If prices continue going up then the payback period will be shorter. If they go down then it'll be longer...


And of course if it's really less than 75% , i'll really be racking up the savings Smile But Ill take your figure to be conservative. 878 is fantastic. See i have to decide in the next few months to move or refi. If i refi i am trying to get money out to buy a new furnace because i cant afford 5K next year for heat.



Quote:
Your current hot water tank stores your domestic hot water. The new system would use a 30 gallon storage tank for the heated water to be used in the heating loops (i.e. radiators). They'd set it up so that the furnace heats 30+ gallons of water to the preset temp for the radiators. If the thermostat tells the system it needs heat then the circulating pump kicks on and distributes the already heated water from the 30 gallon tank instead of firing the burner like your current furnace does. The new burner only kicks on when there is a demand + when the water in the loops is below the preset temp.



great explanation. you really know your stuff thanks. I think about this thread at times like yesterday when i turned on the hot water and 2 min later the furnace came on. Now if the water in there cooled to the point where it was cold, why didnt the furnace have it heated up already? I dont get why my furnace runs now when i call for hot water. shouldnt the water in there be 'heated' up already and my only delay is the actual water getting to the faucet? I'm convinced this isnt operating like its supposed to. And yes it also will just heat up when no water is being called for..very wasteful!

Quote:

Right, it won't turn on unless the thermostat kicks it on. But there are trade-offs here. Your current setup doesn't have that storage tank. The new one will have to heat that 30 gallons of water in the tank as well as what is circulating to the radiatiors. It is much more efficent than your current system but not quite perfect. (There are always those damned trade-offs! Arrgh! Razz )


Thats the part i didnt understand after your initial explanation. Now have 30 gallons inside that are constantly heated. Even when its' uncalled for. So if that 30 gal is moved outside, i thought it would have to be 'always' heated as well but per your post, it wont be heated unless there is demand for it. Thats where ill be saving tons.

so on those 'mild days' where the heat in the house is still turned on, but not being called for, in theory that 30 gallons can get 'cold' if heat is never called for (just correct me if i'm wrong)


Quote:
The low mass furnaces are made of materials designed to expand and contract often so you don't have the issues of gaskets leaking and such. That means the furnace can go cold if there isn't any demand without any problems. In theory, it should fire less often - especially in the summer when it only needs to fire up to heat domestic hot water when you turn on a faucet.


i hate that now..hearing it going on while we are just watching tv..if it was easier to get to the fuse box id kill the breaker during the day lol.

Quote:

IMO, the low mass systems lose some of their attraction if you have several heating zones and are living in a region with short summers.

Let's say you have a very large house with 4 heating zones. The thermostat in zone 1 kicks on and tells the furance it needs heat. So the furnace does it's thing and heats the circulating water for zone 1 and the 30 gallon tank.


well i have one thermostat for the whole house so assume that means i have one zone? And the guy didnt come out yet so i have no idea the size or other specs about installation


Quote:

*nods* They are measuring the burn effiency by looking at the exhaust gasses. That's as close as you are going to get outiside of the lab.


well ill assume the conservative 75% but assume it's even lower Smile And as you said there are other factors like it wont run all the time like the old one did. No 'percentage' can measure those savings.

Thanks again for all the advice, i cant wait in a month or so to maybe have him out for an estimate. This just seems a bit too easy of a decision (except the 6500 of course)
0 Replies
 
fishin
 
  2  
Reply Fri 6 Jun, 2008 12:21 pm
luckydriver wrote:
I think about this thread at times like yesterday when i turned on the hot water and 2 min later the furnace came on. Now if the water in there cooled to the point where it was cold, why didnt the furnace have it heated up already? I dont get why my furnace runs now when i call for hot water. shouldnt the water in there be 'heated' up already and my only delay is the actual water getting to the faucet? I'm convinced this isnt operating like its supposed to. And yes it also will just heat up when no water is being called for..very wasteful!


Actually, it's working as it is designed to do and it is really less wasteful that way.

You have two systems in one there. You have your room heating zone and your domestic hot water. The water between the two never mix and they never should. (Sometimes glycol alcohol - anti-freeze! - is added to the heating loops. It works better than water in retaining heat and it means that a zone that doens't kick on very often won't freeze if it happens to run through a cold area.)

The heated wtaer inside your furnace is for the heating zones - not domestic hot water.

The domestic hot water is only a small heating coil inside the furnace. It acts just like an on-demand hot water heater - you turn on a faucet and the furnace kicks on to provide you with hot water. The coil itself might store a half-gallon or so. But as soon as you open a faucet that's gone and replaced with cold water coming in from your water system that needs to be heated.

Personally, I'd opt to seperate my domestic hot water and the furnace and use a gas fired on-demand hot water heater if saving money was my big long-term issue. People who heat with oil generally don't do this because they don't want to deal with having an oil and a gas bill.

Quote:

Right, it won't turn on unless the thermostat kicks it on. But there are well i have one thermostat for the whole house so assume that means i have one zone? And the guy didnt come out yet so i have no idea the size or other specs about installation


*nods* Each zone would have it's own thermostst and there is normally only one per zone so it sounds like your entire house is on one zone.
0 Replies
 
luckydriver
 
  2  
Reply Fri 6 Jun, 2008 04:52 pm
fishin wrote:


The domestic hot water is only a small heating coil inside the furnace. It acts just like an on-demand hot water heater - you turn on a faucet and the furnace kicks on to provide you with hot water. The coil itself might store a half-gallon or so. But as soon as you open a faucet that's gone and replaced with cold water coming in from your water system that needs to be heated.





ok now i'm lost. In summer, the heat is off but yet we can be sitting in the living room watching tv and the furnace will kick on. I always assumed this was to keep the domestic hot. But from what you said, i have on on demand hot water and it should only kick on when i turn on the faucet?
0 Replies
 
fishin
 
  2  
Reply Fri 6 Jun, 2008 05:03 pm
luckydriver wrote:
fishin wrote:


The domestic hot water is only a small heating coil inside the furnace. It acts just like an on-demand hot water heater - you turn on a faucet and the furnace kicks on to provide you with hot water. The coil itself might store a half-gallon or so. But as soon as you open a faucet that's gone and replaced with cold water coming in from your water system that needs to be heated.





ok now i'm lost. In summer, the heat is off but yet we can be sitting in the living room watching tv and the furnace will kick on. I always assumed this was to keep the domestic hot. But from what you said, i have on on demand hot water and it should only kick on when i turn on the faucet?


I should clarify. You have an external domestic water storage tank so the furnace will kick on on occassion if the water temp in that tank drops below a preset level.

The furnace portion of the overall syatem operates as an on-demand heater but tThe furnace itself is unaware of that storage tank. It doesn't know the difference between that tank and you opening a faucet. In many cases there is no external storage tank installed on oil-fired furnaces that have a domestic hot water coil at all. Someone decided that they preferred to have one in your house and installed it. I've been around a lot of oil-fired furnaces and have only seen an external storage tank once that I can recall.
0 Replies
 
luckydriver
 
  2  
Reply Sat 7 Jun, 2008 06:01 am
fishin wrote:


I should clarify. You have an external domestic water storage tank so the furnace will kick on on occassion if the water temp in that tank drops below a preset level.

The furnace portion of the overall syatem operates as an on-demand heater but tThe furnace itself is unaware of that storage tank. It doesn't know the difference between that tank and you opening a faucet. In many cases there is no external storage tank installed on oil-fired furnaces that have a domestic hot water coil at all. Someone decided that they preferred to have one in your house and installed it. I've been around a lot of oil-fired furnaces and have only seen an external storage tank once that I can recall.


oh that tank above the furnace is domestic water? I always thought it was some kind of expansion tank for safety lol..shows you what i know. (edit, i went in and looked and i'm positive the thing above is not hooked into the domestic..so it is an expansion tank). So im still lost. are you saying the thing registers the temp of the domestic and heats the 'main' container even though heat is not needed, except for water, which is not being called for. (hope that made sense)


I do know the coil for hot water was an afterthought here because there is a special box here that obviously someone had an electric water heater hooked up years a go. So i guess they added the coil plus that thing above my furnace?

and while i'm asking, what should that 'differential' thing be set on ? In summer i turn the Lo as low as possible and the hi to 120 but i never knew where was the best place to set the differential, which i assume is how cold the water will get before the burner kicks on?
0 Replies
 
luckydriver
 
  2  
Reply Tue 15 Jul, 2008 05:29 pm
i got my budget info today and it scared me

4.69 if you buy it all today. Since it's prepay it doesnt matter if the price goes down etc

Budget plan, your price will never go above 4.69 but will go lower if it does. .

so i guess 1148x 4.69 = 5384 for me this year..booo

Also, 40 cents per gallon insurance will be rolled into the budget calculation. (i dont know if this means 1148x.40 = 459 or what. It also says you will not be charged additional insurance fees if your actual usage is more than what was calculated at the start of the year.

(many companies that serve both schools and residents went out of business last year when they couldnt meet their prices)
0 Replies
 
luckydriver
 
  2  
Reply Fri 18 Jul, 2008 09:58 am
oops i called and the 40 cents is added in addition to the 4.69

so 5.09 x 1148 = 5843/ 11 = 531 a month.

I think that 6500 furnace i was looking at would have a REAL quick payback period compared to my 60 yr old clunker

What do you think? even 10% savings is 580 PER YEAR right?

this of course assumes i'm staying in the house
luckydriver
 
  2  
Reply Tue 19 Aug, 2008 08:58 am
@luckydriver,
Next monday this dealer is coming out to give me an estimate. Are there any questions other than what is in this thread, that i should be asking?
luckydriver
 
  3  
Reply Mon 25 Aug, 2008 03:29 pm
@luckydriver,
today the guy came out from the oil company i had the past 13 years. He looked at my boiler, took pics, and measured all around it (i have tight space). Told me about local code that he has to back stuff up 3 ft from my electrical box but the chimney will be grandfathered in since you cant move a chimney. Also stated even if i choose, i probably cant have the water tank or the boiler blocking my window even though a door is literally next to it for escape purposes. I may have to relocate a fridge and him run 8 ft of pipe over to the water tank. he will use the existing pipes that come up from my crawlspace and cut them so as to minimize possible disturbance of them. using about 6- 8 feet of feed and return.

(i'm doing these measurements from memory so dont hold me to them but they are pretty close)

He measured my cast iron baseboards and counted the fins and rows on the one standard radiator upstairs. The baseboards total 191 ft for about 105k btu and the one radiator is about 20K btu and he added 25K for pipe loss. The inside of the furnace was pretty unreadable. It said boiler size 257 but we dont know if that meant 257,000 btu or what. I have a 1.2 nozzle so based on that and what else he knows he estimated i have about 167K btu now. He thinks the newer burner was resized down to save money because it was probably oversized in the 1950s.

I know i read a post where it said if i'm getting about the same btu why bother replacing but he was confident even the standard burner would save me money and that the low mass could have a payback in as little as 4 years since i'm paying 5.09 a gallon this winter. I think the fact that water wont be heated until it's called for will be huge for me, especially in summer. My current burner turns on too much on these darn hot summer days and really makes me unhappy lol. I like that the domestic will be at a lower temp then the heating so i wont burn myself in winter anymore.

he said that if i had all radiators that he wouldnt recommend low mass because of all the cold water coming back to the u but since i only have one radiator, i'm ok. I currently use about 1150 gallons of oil a year and he estimated if he was to come into the house without any historical data, he'd estimate 800 gallons so i should have substantial savings,even with a standard burner. He's writing up estimates for conventional and low mass and ill report back when he does. he does think the unit is oversized for the house. Heating up 40 gallons of water constantly is also hurting my numbers.

I did ask about the ratings of new burners and he went into a detail about how in a lab is the only perfect way of doing it but that any new one he put in would be mid 80s. i have about 76-80 on my maintenance card now.

I asked tons of questions. I dont think he was evasive at all and answered them all in the course of 1.5 hours. But id like you to pick apart anything i've said or any other questions you can think of, i tried to be complete as i can remember here.

1 yr parts and labor on the unit and limited lifetime on the water tank. So id save one year on a service contract lol.

he mentioned 4500 for conv and 5500 for low mass but that differed from what he said on the phone so ill wait for the real estimate.
fishin
 
  3  
Reply Mon 25 Aug, 2008 05:40 pm
@luckydriver,
That all sounds about right to me. If you are paying $5.09 this winter for oil then a 4 year payback is probably a little optimistic but not way out of line.

Since you've thought about this a lot, investigated it pretty well and are willing and able to make the jump I'd pull the trigger and do it. Wink
luckydriver
 
  2  
Reply Tue 26 Aug, 2008 08:13 am
@fishin,
do you think how he calculated the BTUs by measuring all my baseboards is a good way of doing that? I'm hearing from others that he should have measured my rooms/windows/doors etc. and done it that way. I am aware of the online program to do this but havent taken the time to measure all that.

id hate to think a company that's been with me for 14 years and overall more than 50 is ripping people off by not sizing a boiler right.
fishin
 
  3  
Reply Tue 26 Aug, 2008 09:10 am
@luckydriver,
I think it's an apples/oranges thing.

You asked him about replacing a boiler. He sized a boiler based on your existing heat distribution system. The built-in assumption there is that you are happy with how your existing heat distribution system is functions (if you weren't you'd have asked to have the entire heating system replaced..).

If he was doing a complete heating audit then the ideal way would be to close all the winodws/doors and run a pressure test on the house, calculate in the heat losses through windows, look at the insulation in your attic, etc... You do that when you are looking at replacing your entire system - furnace and the baseboards/radiators. (Or if you have a forced hot air heating system because they operate on a different principle.)

He could run a full energy audit on your house (and charge you for doing it! Wink ) but your baseboards/radiators can only radiate "X" BTUs of heat into the house. Unless you are willing to replace them as well, then there isn't any point in sizing the furnace based on anything other than what you can actually use.
luckydriver
 
  2  
Reply Tue 26 Aug, 2008 10:18 am
@fishin,
He said i need 150K based on the 191 feet of pipe. Assume for a moment and he's way off and I only need 100K per the heat loss calculation. Is it possible to have a boiler of only 100K and have it function correctly through that length if pipe?
fishin
 
  3  
Reply Tue 26 Aug, 2008 03:51 pm
@luckydriver,
No. Any boiler you install with the existing baseboards still has to be able to heat all of the water in the baseboards to the correct temp. (The volume of water in the pipes is more important than it's length. Length just allows him to calculate volume.)

If you undersize the boiler in it would have to run more often than a properly sized furnace to heat the house and might not be able to keep up with demand during cold spells.

luckydriver
 
  2  
Reply Tue 26 Aug, 2008 04:29 pm
@fishin,
Ok this only took an hour.unsure why that guy couldnt do it in 1 hour! I was conservative when guessing about my walls and floor etc. I dont think there is insulation in the walls and it's plaster and outside is permastone. I have an unheated cement crawlspace no insulation.

http://i371.photobucket.com/albums/oo155/luckydriver/slantfinpage1.jpg

http://i371.photobucket.com/albums/oo155/luckydriver/slantfinpage2.jpg
luckydriver
 
  2  
Reply Tue 26 Aug, 2008 05:02 pm
@fishin,
"Any boiler you install with the existing baseboards still has to be able to heat all of the water in the baseboards to the correct temp. (The volume of water in the pipes is more important than it's length. Length just allows him to calculate volume.) If you undersize the boiler in it would have to run more often than a properly sized furnace to heat the house and might not be able to keep up with demand during cold spells."

ok see that confuses me.
It makes it seem like you can just take the feet and diameter and get the size of burner you need. No sense buying too big and not too small either. I just posted my other data so hopefully it sheds some more light.
 

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