Choosing a Furnace for a New Building
I am building a new home about 2 1/2 hours north of Toronto (lake front).
Plan on using propane as fuel source. I have run 1/2" pex tubing in the poured basement floor to heat the walk out basement, and a forced air system to heat the main floor. The building is just over 1500sq ft, with a full basement. A wood stove will be installed in the basement as well.
I am looking for advice on brand of furnace to heat the main floor?
I have 3 quotes;
1) using a Payne 60,000btu model PG96VAT 96% 2 stage hi efficiency
2) using a Trane 80,000btu 94% 2 stage hi efficiency
3) using a York LX 100,000btu 96% 2 stage hi efficiency
Any and all advice would be appreciated, and if any more info is required please let me know.
you are going to need a boiler for the infloor heat in the basement, why not just use a blower coil with a hot water coil to heat the main floor?
depending on your propane/electricity prices maybe even a heat pump with a hot water coil on the blower.
Originally Posted by t527ed
My understanding is that electricity prices are heading much higher, so we are going to use propane.
Originally Posted by t527ed
I did ask one of the quotes about a system using a coil off the boiler into a forced air system. His response was that he had concerns about the system being able to supply the in floor heat, forced air system, and hot water demands.
Probably the guy quoting a Payne.
IF hte basement has a wood stove, I wouldn't include that in the load calculations. Toronto being near the lakes is more temperate than many think. WIth good insulation a newer 1500sqft home shouldn;t need more than a 60k BTU furnace in that climate. The Trane and York contractor have likely "padded" their sizing. They will need a LOT mroe ductwork, won;t heat as evenly and may be noisier and will fee draftier because there will be so mcuh air movement for that size of home. Hoenstly, 100k BTU's is rediculous even with almost no wall insulation.
2 stage is for comfort, not so you can oversize the system.
I agree with others, that you might consider a wall mount combi boiler and use a hydronic coil with a heat pump.
I personally think all fuels will somewhat trend each other. But that being said a heat pump will hedge you the best. It will always be cheaper to operate in mild weather (above 40F) and with a hybronic coil, you cna use both together and run the heat pump at current prices down to even 0F and add supplemental hot water. If propane prices get cheaper, you simply change your balance point ot 30, 35, 40F and whereever it's economical. Sometiems a nice balance point is around 35F since below that you start getting a lot of defrost cycles and efficiency takes a big hit.
Mostly agree with Moto, whichever contractor is quoting you a 100k furnace isn't too bright. But then again, can't believe you'd ever need the 80k the Trane person quoted unless you left the front door or a couple of windows open in winter. Did anyone ever compute a manual J or are they just using the WAG method? (WAG=wild a$$ guess)
In defense of the guy quoting the 100K furnace, it was to heat the whole building 1500sq ft main floor and 1500sq ft basement (prior to decision to use radiant heat in basement).
Originally Posted by wahoo
I have updated him and asked him to requote.
Foundation walls- ARXX (icf) (I don't have the R value available at the moment)
Above grade walls-1 1/2" ice and water shield on exterior + R24 blown in 2x6 walls
Flat ceilings - R50 blown in
Cathedral ceilings- R40 blown in
Here is the monthly average temps in degrees F for the area:
Jan -4 -16
Feb -2 -16
Mar 3 -11
April 10 -2
Oct 12 1
Nov 5 -4
Dec -2 -13
Remember too, that Toronto Design temp is 0F. That's actually that same as where I am in Iowa. But you have a TON more insulation than my home. At those insulation levels, I bet you need 25-30k upstairs and 10-15k BTU's downstairs as long as it's fairly tight construction. But if you have radiant floor heat, just throw in a small hydronic air handler and get a combi boiler. You probably only need a 1.5 ton AC or heat pump... design temp is only 84F... so almost 1/2 the cooling load of where I am
The basement will only needs 1/3 the capacity of the main floor if it's insulated. The ground temp only gets to around what 40-45F, so the heat loss is 1/2 there, there's few windows, air leakage should be minimal as well if the sill plate is sealed properly, and no roof, just a floor. If the concrete slab is insulated, the heat loss is pretty minimal. I bet the upstairs only need
Oh and you don't design by monthly averages. You use statistical data and design to the 99% outdoor temp in winter and 1% temperature in summer.
With that type of construction you could about heat it with a candle. I would defiantly look into hydronic coil for heat. In your situation it would be the best route to go.
I spoke with the contractor that had just quoted on a forced air system. He is going to quote with a boiler system supplying the radiant floor heat, coil for air handler, and on demand hot water. He still wants to supply the basement with some forced air heat, as he feels the ducting will be required to circulate air throughout both floors.
Originally Posted by jtrammel
By the way the basement floor is insulated as well.