Montreal_Canada concerns about 2,500 sq ft house

[Montreal_Canada]

Quote:
Originally Posted by RyanHughes
Update: I just looked closer into Lennox's engineering data for the G60, and it says "Terminal for continuous low speed blower operation." There's your answer. Looks like these things can be setup for continuous low speed operation. I'm not sure what the "low speed" is, though. This is good for comfort; however, a multi-speed blower cannot vary its speed and isn't as efficient as an ECM variable-speed blower.

So, that means the variable-speed blower will turn with anything b/w 0 and some speed constantly (or not) to produce a constant flow for filtering and temperature exchange, and the low-speed one will do samething, but with only one pre-adjusted speed only, right ?

[beenthere]

The G60, the contractor can set the fan on speed to a setting independant of heating and cooling speed.

The G61 with VS, will run the fan at 50% of the set high cooling speed(CFM). It doesn't vary like people think.
It varies its speed to maintain set air flow. As your filter gets dirty, it wil speed up to maintain CFM.

[Montreal_Canada]

The G61 with VS, will run the fan at 50% of the set high cooling speed(CFM). It doesn't vary like people think.
It varies its speed to maintain set air flow. As your filter gets dirty, it wil speed up to maintain CFM.

If I have to choose between G61MPV60-90 and G61MPV60-110, knowing that my total house area (w/o basement) is about 2,600 sq.ft., and with basement about 3,250 sq.ft (garage non included), and that house is built in early 80-ies, when they used to use 2x4 instead of 2x6 for external walls (ergo: my external thermo insulation is not the best), what is the better choise ?
Contractor "A" says, that 90,000 BTUs are good enough for this area, and that first stage delivering 60K BTUs will do the job, if not second stage of 90K for colder days will be OK (lets say we know that 90,000 are in reality 84,000),
Contractor "B" says, that it will be better to get a 110,000 BTU fournace, so we will be always sure that if first stage of 90,000 dosn't deliver all juice, second stage of 110,000 will do it. Especialy if price difference b/w both models is not too big ... I don't know how much exactly, anyways ...

But my question in this case is : knowing that a 110K fournace will always start from 90,000 and not from 60,000, is it a good choice ? (more gaz I believe for 90K first stage against 60K == more money spent, but for shorter time lap ??)

Anyone to post a word, PLEASE !! ;-)

Thanks!

[joatmon123]

Do you have a few years of historical fuel usage?

If so, you can figure out what your approx. BTU usage is using:
http://www.cmhc-schl.gc.ca/en/co/renoho/refash/refash_018.cfm

HDD data is available here:
http://www.climate.weatheroffice.ec.gc.ca/climateData/canada_e.html

[beenthere]

Probably be better off with the 90.
2 stage furnaces are for comfort. Long run times in first stage.
The larger unit won't give you those longer run times. So it would be a waste of money.

If you want. You can pay teh 50 dollar fee, and use teh hvac calc program to determine what size furnace you need.
http://hvaccomputer.com/talkref.asp

[Montreal_Canada]

[QUOTE=joatmon123;1912417]Do you have a few years of historical fuel usage?

If so, you can figure out what your approx. BTU usage is using:
http://www.cmhc-schl.gc.ca/en/co/renoho/refash/refash_018.cfm
QUOTE]

OK, I've got it !!!
Using 51 HDD/day (for -33 deg C in 1993, I got 49,823 Btu/h, and for 90,000 (for 90K fournace) x 94% x 60% (first stage) I have 50,760 Btu/h, so I'm covered even with the first stage, right ????

[beenthere]

Montreal has I believe 8213 HDDs.

[Montreal_Canada]

Montreal has I believe 8213 HDDs.

They say one can use any period for calculations, and I used a lap over 6 months - October 2007 - Mars 2008 for a total of 3846.3 HDDs, using exctly days included in my monthly statement from the Gaz Company.

On the other hand, if I decide to get the G61MPV with 90,000 Btu/h, they are two models : G61MPV-60C-090 and G61MPV-60C-091 ... What is the difference ???? The 60C I believe is the coil type, and since in variable speed there is not any type 48 for 3.5 tons heat pump, I have to use 60C and not 36C .... But what is this 91 and 90 ??

[beenthere]

That one I can't answer.

[Montreal_Canada]

That one I can't answer.

Thank you very much !! You did help me!

[Montreal_Canada]

Do you have a few years of historical fuel usage?

If so, you can figure out what your approx. BTU usage is using:
http://www.cmhc-schl.gc.ca/en/co/renoho/refash/refash_018.cfm

HDD data is available here:
http://www.climate.weatheroffice.ec.gc.ca/climateData/canada_e.html

Great job !!! Thank you very much !!!