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

 
 
fishin
 
  3  
Reply Tue 26 Aug, 2008 05:19 pm
@luckydriver,
Those numbers aren't any better than what he did. I mean, I've never seen your house or set foot in it but I could pick some random numbers too. Wink

For example, the only way to get an accurate infiltration factor number is to run the pressure test. The numbers they give you are averages based on the selection choices you made. What if your windows/doors/walls/ceilings are above or below the averages? You can have 4 different double pane windows that are each 12 sq/ft and they use the same loss factor for each. But it is highly unlikely that they are all the same. The heat transfer through the glass panes might be the same but it doesn't account for how each window is installed. How much air is flowing through the cracks/gaps around each window?

Looking at their numbers and user manual it looks like they are making a lot of assumptions that probably don't apply to you too. Their floor factor and wall factor are based on 4'x8' plywood panels for the subflooring and exterior sheathing. As I recall you have an old house so that probbaly isn't true in your case. If your house was built before the 1950s then the subfloor and exterior sheathing are probably 1"x boards which will have more air transfar than sheets of sheathing.

Even so, let's just say that the number it gives you is fairly accurate and you can heat your house on 110K BTU/hr.

Now it's the middle of Feburary and you're in the middle of a week-long -10 degree cold snap and at 110K BTU you are able to heat the house to 68 degrees. What do you have left over to heat domestic hot water so you can take showers/baths? The 110K BTU number only covers the baseboards. Your boiler is serving two purposes.
luckydriver
 
  1  
Reply Tue 26 Aug, 2008 05:40 pm
@fishin,
I realize i cant know all the true factors just by my calculation there but if i choose the 'worst' choice for each one, unless i knew for sure what it was like new windows etc, i would think my 110 estimate should be somewhat in the ballpark..or hope so. If i choose the least efficient choice, i dont see how i couldnt 'over' vs undersize. Not that thats good just saying.

and what you said about needing more for the domestic, if you add 'whatever' to the 110, you are approaching the 125 he said i would need plus 25 'extra' which i dont know if is really needed.

i guess i need to wait and see what he sends me for an estimate.

house was built 1952

0 Replies
 
fishin
 
  3  
Reply Tue 26 Aug, 2008 06:27 pm
@luckydriver,
Each piece of basebaord has it's own rate of heat transfer. Different materials and different surface areas (which is why he was counting fins) transfar heat from the heated water to the air at different rates.

Let's say baseboard "A" has fins that have 3 sq/in of surface area each and baseboard "B" has 2 sq/in each. If they each have the same number of fins baseboard A will be able to transfer more heat to the air. Some have 3/4" copper pipe in the center, some have 1". 1" has more surface area (as well as more water volume.).

That's why when you ran the Slant-Fin program it gives you different lengths for their different models of baseboard.

In your case, you CAN just take the length of pipe and diameter. He isn't sizing the boiler to the heating needs of the house. He's sizing it to the capacity of the existing baseboards. (interestingly, he came up with the same 191 ft. that the Slant-Fin program gives you for their Fine-Line 30 baseboards...). Your older baseboard units are probably slightly less efficent than installing new ones would be though.

But your own calculations are coming up right in the same ballpark he came up with. He estimated 105K BTU + 20K BTU for the radiator. You came up with 110K BTU but the slant-fin program isn't compensating for the mix of baseboard and radiator. The difference you have and what he came up with is 15K BTU - not worth quibbling about IMO plus, they don't make furances to custom specs without going into big $$. The off-the-shelf models are probably going to be rated in ~30K btu increments.
luckydriver
 
  1  
Reply Wed 27 Aug, 2008 06:07 am
@fishin,
Hmm maybe that i came up with 191 (didnt even see that until you did) and he did means we are right? lol.

And knowing there are 30 K increments makes this almost a no brainer...unless he says he has a 130K and a 160K and recommends the 160 then it becomes a bit more tricky.

In reading one of your other posts you did say you need enough BTU to heat the 191 ft of pipe no matter what. So it seems by definition there is a 'floor' BTU and then there is a MAX BTU that will fit thru the pipe. So i'm guessing unless there is a big difference, it's almost automatic what size to get within a narrow window
luckydriver
 
  1  
Reply Thu 4 Sep, 2008 10:08 am
@luckydriver,
finally got the estimate..what do you think?

remove dispose existing
columbia lv 125 low mass boiler
85% afue
1yr parts labor
limited lifetime warranty
domestic water mate
all piping wiring controls and permits
6232 20% down balance 30 days

1.25 gph
1.00 nozzle w/pump 140psi
175 input mbtu/hr
doe heating capacity 150
net irb rating 130.4
afue 85.0
water content 8 gallons
A jacket 34.5 inches
B overall length 43.25 inches
weight 390

columbia em 3123 boiler with domestic coil
85% afue
1yr parts labor
limited lifetime warranty
domestic water mate
all piping wiring controls and permits
4811 20% down balance 30 days

firing rate 1.25
input 175
net output 127
nozzle @140 psi beckett 1.00 80B
afue 85%
gpm tankless coil 5
no fire tubest 8 3 in
water capacity 22 gallons
weight 355

some people mentioned outdoor reset, i guess thats something extra id have to ask him about..what would that cost extra in your opinion?
luckydriver
 
  2  
Reply Thu 4 Sep, 2008 10:15 am
@luckydriver,
is the NET ibr rating what everyone has been asking me about as far as heat loss calculation? the next high and lowest on his sheet is 128 and 160 if so so this being the mid one seems to be right about where i need to be..i think.


oh and this may or may not be relevant but i just had one appraisal done of this house and they said it was 2900 sq ft...so maybe that will help determine what size i need Wink
luckydriver
 
  1  
Reply Thu 4 Sep, 2008 10:22 am
@luckydriver,
here's the low mass link

http://www.columbiaboiler.com/residential/LV/

regular
http://www.columbiaboiler.com/residential/emerald/
0 Replies
 
fishin
 
  2  
Reply Fri 5 Sep, 2008 12:36 pm
@luckydriver,
luckydriver wrote:

is the NET ibr rating what everyone has been asking me about as far as heat loss calculation? the next high and lowest on his sheet is 128 and 160 if so so this being the mid one seems to be right about where i need to be..i think.


oh and this may or may not be relevant but i just had one appraisal done of this house and they said it was 2900 sq ft...so maybe that will help determine what size i need Wink


No, the IRB number is the rated BTU output using the IRB standard calcualtion method. The IRB is a standards board and they've established a standard testing methodology that manufacturer's can use for hydronic heating equipment. It just allows you to compare between units and know that the numbers you are seeing have been determined using the same test. The DOE test isn't as specific so there is a lot of play in the numbers form those tests.

The IBR also has a test standard for doing heat loss calculations but I don't see those numbers there.

But it looks like the two furnaces he gave you on the estimes are very close in specs.

Ummm yeah, 2900 sq ft doesn't really mean much. Wink But if it helps you any, I replaced the furnace in one of the houses I used to own that was right at 1750 sq ft and I had to install a 160K BTU furnace to heat it. It had crap for insulation in the walls. Very Happy
luckydriver
 
  2  
Reply Fri 5 Sep, 2008 03:43 pm
@fishin,
well i assumed he used his 150K as his baseline so was he using the 150 DOE number then? im just trying to figure out if my number was right what maybe to get. Or split the difference even

no the 1750 you fed for 160K didnt help me, just makes me wonder if even his is undersized lol Smile
fishin
 
  1  
Reply Fri 5 Sep, 2008 09:29 pm
@luckydriver,
If I recall correctly the DOE calculation is the input BTUs x AFUE rating and then rounded off to the nearest 25K BTU increment.

The "net" values are what I was looking at. One of them is at 130.4 and the other at 127.
0 Replies
 
luckydriver
 
  1  
Reply Sat 20 Sep, 2008 06:33 am
@fishin,
in 2 weeks i'm having a blower test done. On the phone the guy told me windows arent usually worth replacing, but attic is the biggest heat loss. Then the walls.

his calculations wont include a heat loss but ill get a written report for 400 bucks that shows exactly what i need to do to seal up the place

so even if i get the wrong size furnace, at least the heat will stay in lol
luckydriver
 
  1  
Reply Mon 29 Sep, 2008 10:39 am
@luckydriver,
wow..what a difference on this 2nd estimate

frhgs1 new yorker 112-140 btu (thats what's on the estimate and i cant find his original spec sheet to clarify the frhgs1) is $8,000!!!

a traditional boiler with coil would be over 6000, 1200 more than the first guy.

This guy just seemed like a slick salesman and measured the baseboards and i appeared to have to ask all the difficult questions. The first guy may have not picked the size you all recommended but he did know the ancillary stuff about install better and presented it better. Actually this 2nd guy wanted to install the water tank in front of the 2 breaker boxes and i said is that to code? I dont wanna lean over a tank to get to my electrical. and they said you gotta buy their oil to get any warranty.

So i have to think about the 1st guy and his sizing some more and ask him about the ODR and his thoughts. It's getting close to winter

http://www.newyorkerboiler.com/products/steel/oil/fr_hgs
luckydriver
 
  1  
Reply Tue 30 Sep, 2008 11:26 am
@luckydriver,
http://www.columbiaboiler.com/residential/LV/

this one has the burner 'outside' the unit. My current one is inside the 'box'

since this is located right off my kitchen, in my utility room, i was wondering if i could (assuming this is louder than me current one) build some sort of sound deadening box around it?
luckydriver
 
  1  
Reply Tue 14 Oct, 2008 08:08 am
@luckydriver,
i may have found a decent contractor at last!

uses this in his own house
http://www.boyertownfurnace.com/pages/products-solaia-boilers.htm

with a riello burner and a smart 40 tank. Also told me to add a tekmar 260 to save even more. I'm waiting for his price but since he knows a lot more then the 2 other big dealers in town, i think i'd go with him over anyone else

also one of my other service guys got a furnace installed by him 3 years ago and is very happy with the service.
0 Replies
 
 

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