propane boiler, is this the correct size??


  #1  
Old 09-21-03, 08:32 PM
paris401
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propane boiler, is this the correct size??

we are building a new home. we will be using propane to heat the house. the house is approx 3600 sq ft. i told the builder the i would also like to heat/finish the basement, which will add approx another 1500 sq ft.

he upgraded the boiler from a 4 section boiler upto a 6section boiler of 160000 btu's -

my question is , is this a sufficient size, and what is the approx cost of upgrading from a 4 to a 6 section boiler- the boiler is a utica.

thanks
 
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Old 09-22-03, 05:43 AM
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The only way to size any HVAC equipment is by the HVAC contractor doing heat load calculation. If they are just going by sq. ft. they are guestimating and may be way off.
 
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Old 09-22-03, 09:52 AM
MusicField
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Properly insulated basements have amazingly small heatloss numbers. My 960 sq.ft. below grade basement with R-18 insulation has a heatloss of less than 10k BTU.

Are you doing in-slab radiant heat for the basement or radiators/hydro air?

I would ask your contractor to show you the leat loss calculations, done room by room. If he can't, then you need to ask why. The last thing you want is a boiler that is too large for the house. Oversized boilers will short cycle, reducing efficiency, and increasing wear and tear on the boiler. Also, the room-by-room heat loss calc is required in order to determine the correct amount of baseboard radiators to be installed in each room. Too much baseboard and the room will be too hot, too little and the room will be too cold.

The rule of boiler sizing is that the boiler should be sized so that it runs continuously on the coldest day of the year, i.e., if on the coldest day of the year, your house looses 125,000 BTUs/hr at 72 degrees inside temperature, then the boiler should be capable of delivering a maximum of 125,000 BTUs/hr into the house (net, after efficiency calculations are taken into effect. For example, an 80% efficient 160,000 BTU/hr boiler delivers 128,000 BTUs/hr net heat into the house, the other 32,000 BTUs goes up the chimney.)

3,600 sq.ft. is a lot of house to be heating with propane. Have you considered oil? It will probably cost 25-35% less than heating with propane. The builder will like propane because the boiler is cheaper for him to buy and there is no expense of installing oil tanks, etc.
 
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Old 09-22-03, 10:21 AM
paris401
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musicfield.. thanks reply. we did consider oil (which i know is more efficient), but went with propane view its a summer house, which will see little use in the winter so we can keep the temperture at 50/55. its a convenience issue as not only will we heat with propane, but also will cook, clothes dryer/fireplace,bbq,pool heater. we already buried a 1000gallon tank in the yard, and had the 1st delivery last week at $ 1.19 a gallon, which seems very reasonable.

as to the heating calc, i will ask the builder next week when i see him for a copy. i have no doubt he/heating contractor did one, as the builder is VERY detailed .

we opt'd for a hydronic's system. one airhandler is in the basement (for the 1st floor), the other is in the attic for the 2nd floor.
i guess the unit for the basement will also be somewhere in the basement.

my big concern is that the boiler is sufficient for the house. originally the builder was giving me a utica 4 section boiler, and then after i told him i want to finish/heat the basement, he upgraded to a 6 section.

ref your comment about propane boilers being the cheaper then oil, do you have any idea of the cost of a utica dv200blp boiler.??.

thanks
ron
 
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Old 09-22-03, 10:45 AM
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??IF I have it right

You say air handlers. Dont see why you want to heat water then have it heat the air to heat the house .Just a lot of heat loss that way. When you could just put in 3 Lp furnaces and be done with it. This way you wont have a 160k burner comeing on if you just neeed a little heat down on the first floor or in the basement. To compare fuel cost go www.warmair.net ED
Just my .02 cents
 
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Old 09-22-03, 10:58 AM
paris401
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ed.. good points.. i will take this up with the builder this week, and let u know his reply

ron
 
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Old 09-22-03, 12:22 PM
MusicField
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Agree with Ed.

The best thing about hot water heat is the hot water radiating the heat into the space. The second best feature is the ability to install as many zone controls as you want. It is possible to zone each room independantly from each other with hydronic. If you got hydro air, then you defeat BOTH of these advantages of hydronics. Might just as well have warm air furnaces.

Not sure how far along you are in the building process, but if it's not too late to install insulation and hydronic tube in the basement slab, DO IT. If it's not too late to have radiators and piping installed throughout the house, DO IT, and leave the duct work for the air conditioning system. Yes, yes it will cost a few more bucks to do this, but compared to the total of what you are spending, it is small potatoes, and will result in greater comfort and efficiency, both immediately and in the long-term.

I have no idea what boilers cost, unless you are in the business of selling or installing boilers, that kind of information is not so easy to get at. The rational behind gas boilers being less exensive than oil boilers, is that oil boilers need to turn oil into a fine spray so it can be burned; not something that is easily done. In gas boilers, all they need to do is mix in the correct about of air, much easier to do.

The Utica dv200 boiler is only 80% efficient, which is about as inefficient as new boilers come. Replaced my boiler last year with a new Utica USC-4, which I like a lot, very quiet, 87% efficient. One of the things I like about it is it takes combustion air from the ouside of the house, so it does not depressurize the house while it is running.

If you want, check out the Utica website at www.uticaboilers.com. Good luck.
 
 

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