1st time buying a furnace...help appreciated

[Jonny Morris]

Rehabbing a small 3/1 (975ft) in Montana. Buying a new furnace I read one calculation was 50/60 BTU x sq footage. Anyone in Montana guide me with preferred brands/ ones to avoid? Or what calculations you use?

[Jim Goebel]

@Jonny Morris

Hey Jonny, there's a little that goes into this.  Will depend on your zone as well as other things like insulation.  I've looked into/done this a couple times and I think your referenced calc seems 'in the ballpark.'  You've probably figured this out already but they are typically sold in increments of 20,000 Btu/hr, so you'll jump from 40k to 60k to 80k etc.  Anyways, I don't want to be the one that causes you to under-size, but I think you'll likely to be OK with a 60k Btu/hr unit.  Note though the two below points that might cause you to bump it up.  Also note that I'm not super familiar with your climate but I live in Des Moines IA.  It gets pretty darn cold here with long winters, and my assumption is that it might get slightly colder in Bozeman but certainly not on an order of magnitude or in a different stratosphere.

A few things that can require adding some size to your unit:

• if your blower has to push the air to 2 (or more) separate levels that can stress the capacity of the unit.  I think this could be as much as a 10-20% adder on required capacity.
• If you have a house that for whatever reason has poor insulation, you should plan for a higher capacity unit.

On the name brand stuff, what you'll find is that there's only a few brands that sell direct to a consumer.  Most brands sell through various dealer networks (often called Master Dealer Partnership, or something to that effect) which means that there's a ton of extra cost for the brands like Rheem, Carrier, Bryant, to name a few.  The shops that sell these things do the installs for them and you often can't get around their crazy markups.  Many of them are running around bidding 30 projects until they find poor Betty Sue that they hit with a 400% markup.

So, we use Goodman because we like their stuff and they sell direct to consumers.  Once you have the unit you are in a much stronger position to negotiate with a qualified installer.

I think there are at least a couple other options for brands that sell direct to consumer but I'm unfamiliar.