Poor heat loss done what do I do

mikea23

Boiler nets 155 the heat loss by my calcs are 70 for the snowmelt 125 for the home.

mikea23

Poor heat loss done what do I do

I installed a boiler and snowmelt system in a home a year ago the heating system mostly radiant works great. But I took this job over from another contractor all the parts were there boil,indirect,pumps,controlls. I made it clear that I dind'nt do the radiant design and did not install the manifolds, pex layout. I even over priced the job 20% hoping not to get it.

The system looks great and works great in heating but when the snow melt turns on the boiler cant keep up. the heat loss is off about 30,000 Btu's. If I upsize the poiler the primary loop is to small. I was thinking of adding a buffer tank do you think storing btu's would help.

I have no liabilty here its not my design and I made that clear from the begining. But I would still like to solve the problem without having the homowner spend a ton of money.

Mike A

Brad White

Percentages

Mike- What is the total calculated or presumed heat loss? What is the snow melting load? IOW: Is the 30,000 BTU's 50% of the boiler or 10%?

Leveraging storage into capacity has some merit but would have to be advanced ahead of a storm. The missing piece is how much you are off as a percentage of the whole.

What interest me is how your area's snow load corresponds to maximum heating load.

For example, here in Boston, when it is at or near the design cold (0 to 7 degrees above zero) it corresponds to a lower probability of snowfall. That kind of cold tends to be dry, high pressure air around here.

A snowstorm would be most likely when it is between 20 and 30 degrees peak of the bell curve. Less likely above and below those temperatures. Thus, a snow melt system here might get a head start and do most melting ahead of the inevitable back-door cold front that follows a typical Nor'easter here.

My point here is, do the loads coincide or does snow allow some reserve because you may not be at your lowest design temperature?

mikea23

> Mike- What is the total calculated or presumed

> heat loss? What is the snow melting load? IOW: Is

> the 30,000 BTU's 50% of the boiler or 10%?

> Leveraging storage into capacity has some merit

> but would have to be advanced ahead of a storm.

> The missing piece is how much you are off as a

> percentage of the whole.

>

> What interest me is

> how your area's snow load corresponds to maximum

> heating load.

>

> For example, here in Boston,

> when it is at or near the design cold (0 to 7

> degrees above zero) it corresponds to a lower

> probability of snowfall. That kind of cold tends

> to be dry, high pressure air around here.

>

> A

> snowstorm would be most likely when it is between

> 20 and 30 degrees peak of the bell curve. Less

> likely above and below those temperatures. Thus,

> a snow melt system here might get a head start

> and do most melting ahead of the inevitable

> back-door cold front that follows a typical

> Nor'easter here.

>

> My point here is, do the

> loads coincide or does snow allow some reserve

> because you may not be at your lowest design

> temperature?



Boiler nets 155 the heat loss by my calcs are 70 for the snowmelt 125 for the home.

Brad White

What is the location and weather patterns?

What is your confidence level in the house heat loss and snow melt density?

mikea23

I did the new numbers myself. I also installed the snowmelt. so I am confident in them

mikea23

The system is on Longisland NY 15 deg des temp

Mike T., Swampeast MO

Just for S&G let's say:

Your worst case 24-hour scenario needs 75% of your calculated space heating loss and 100% of your calculated snowmelting load.

125 mbh * .75 = 94 mbh * 24 hours = 2,256,000 btu

70 mbh * 24 hours = 1,680,000 btu

Will assume oil at 80% efficiency for the boiler so your possible input is

155 mbh * .80 = 124 mbh * 24 hours = 2,976,000 btu.

SO, you have a heating requirement of 2,256,000 + 1,680,000 = 3,936,000 btu over 24 hours

You can input 2,976,000 btu in these 24 hours.

This leaves a deficit of 960,000 btu.

Say you want to "buffer" these 960,000 btu. Let's say you'll heat the buffer to 210F and draw down to 140F before the buffer needs to be "recharged". So, each pound of water in the buffer is good for 70 btus.

960,000 / 70 = 13,714# of water.

13,714# / 8.33 = 1,646 gallons required for the buffer with an average temp to the snowmelt of 175F. That's a LOT of buffer!!!

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While heat loss calculations generally tend to be overstatements, I believe that snow melting loads tend to be understatements--particularly in the worst conditions when you want it most...

Sounds to me as if the most reasonable choice is to install a boiler dedicated to snow melt. The existing boiler will certainly be oversized to the space heating load, but not as terribly as I've seen...

Perry_3

For heavy snows....

Have someone snowblow off part of the snow.

You are problaby OK for lighter snows.

How many heavy snows do you get a year...

Alternately - wait another day for it to all melt.

I don't see a cheap solution given that the coil is undersized.

Perry

jp_2

snowblower

a snowblower is a lot cheaper than a new boiler??

why is that such a problem?