Furnace sizing and Goodman GMH95 questions

[Homeowner314]

I posted duct trunk sizes this morning, it's the last post on page 3.

30x40 single story, 8' side walls, basement constructed of 8x8x16" concrete block, with the top two rows of blocks exposed to air, ten rows buried. Basement is not living space, furnace and water heater are down there. Isolated from the living space only by subfloor and thinly padded carpet, with vinyl flooring on about 1/5 of it.

Out of 140 linear feet of outside walls, 22' are sheltered by the garage and 20' sheltered by the enclosed porch, 98' are exposed. I'm assuming the sides are insulated with 3 5/8" of loose fill cellulose, sheathed with cellotex and 1/8" foam under the vinyl siding. I'll have to pull some siding and check the wall fill, if it has settled I will be pumping more in to get rid of the voids.

I'd assign R10 to the exposed walls, but what number do I use for the sheltered walls on my load calculations?


Ceiling:
Probably had 6" of cellulose upstairs, I'd call it 5" now. No big deal, 30 more bags would bring it up from R19 to R44, assuming the drywall can take 1.5lb / sq ft.

Windows: I've got 101 sq ft (rough opening) of 1994 vintage triple pane vinyl windows, a 54 square foot window that's about 60% fixed double pane and 40% sliding triple pane, and a 42 sq ft aluminum frame sliding door with an enclosed porch on the other side.

Doors: There are three 3' insulated steeel doors, one has a storm door over it, the other two are sheltered by the enclosed porch and the garage.

[beenthere]

Check to see what insulation you have in those walls. Probably the same as the others.

[Homeowner314]

Does 'probably the same as the others' mean I should treat the wall exposed to the garage the same as a wall exposed to the outdoors when calculating heat loss?

If the ceiling is blown cellulose, what are the chances the walls are too, is it a near certainty?

If the walls are cellulose, they are or they will soon be packed full. I'll take off some soffits and drill the cellotex to find out if there are any voids at the top.

I think my only important unknown variable now is infiltration. Maybe a blower door service will have a spring special when the heating season ends. It looks like this house needs nothing badly enough (except for a functioning furnace) that I can't do without it for March/April/May. And I've quite firmly decided that if the house can't run on a 46k that it needs to be fixed until it can.

BTW, if I cheap out and get the GMH against all advice, is there any difference other than staging between a TH6110D and a TH6220D?

[beenthere]

Yep, treat it the same as any other exposed wall.

Nope, just staging.

[JonesHVAC-R]

Thats just the excuse many people give for doing something a certain way.Ahhh... I got ya.

So you admit there is no reason to attempt to keep a high static pressure.No, I don't. Taking velocity, cfm, etc... I still stand behind my recommendation.

Length of duct absolutly plays a factor.

[JonesHVAC-R]

OK, did some checking.

The furnace is about 5' off center, so the supply trunks are 10' and 20', not 15' each. And they're only 8x10. Good enough for a variable speed 1200cfm, or will it ramp up and overwork itself and / or make wind noise?YIKES! 8x10??? That will allow approx. 310cfm and YES will definately create a wind noise along with whistling. These absolutely need upsized.

The bigger ducts I remembered seeing were the return trunks, 10x14 and very short. This allows approximately 670cfm, they need upsized as well.

You have some issues there that need addressed

[JonesHVAC-R]

Does 'probably the same as the others' mean I should treat the wall exposed to the garage the same as a wall exposed to the outdoors when calculating heat loss?

If the ceiling is blown cellulose, what are the chances the walls are too, is it a near certainty?

If the walls are cellulose, they are or they will soon be packed full. I'll take off some soffits and drill the cellotex to find out if there are any voids at the top.

I think my only important unknown variable now is infiltration. Maybe a blower door service will have a spring special when the heating season ends. It looks like this house needs nothing badly enough (except for a functioning furnace) that I can't do without it for March/April/May. And I've quite firmly decided that if the house can't run on a 46k that it needs to be fixed until it can.

BTW, if I cheap out and get the GMH against all advice, is there any difference other than staging between a TH6110D and a TH6220D?

TH6110D is 1 heat/1 cool andTH6220D is 2 heat/2 cool. Personally I would use a different model as those two are Honeywells lower end digital...

[beenthere]

Length of duct absolutly plays a factor.

Since we're talking about the OP's duct system. Its short enough that it doesn't need to reduce. Which is what I posted earlier.

[Homeowner314]

TH6110D is 1 heat/1 cool andTH6220D is 2 heat/2 cool. Personally I would use a different model as those two are Honeywells lower end digital...

OK, I'd love to see a good debate about t-stats. Looks like the only meaningful adjustment on the Pro 6000 series is that I can tell it to use 3 cycles or 5 cycles per hour.

What T-stat do you think I should buy and what would it do for me?

Should I get the White Rodgers that looks like the Comfortnet, should I kiss my budget goodbye and get the Comfortnet?

BTW, I talked to my installer yesterday, he's afraid of my undersized ducts too and wants to see the system and map out a duct plan ASAP.
He also told me I should buy a 80%, because I'd never get the money back for a 95% when I sell the place. I don't think he realizes how cheap I can source a 95% Goodman. If propane stays at $3, I can get the difference between 80% and 95% back in one winter. And I think I can get it back on resale if I sell the house this summer.

[beshvac]

. I don't think he realizes how cheap I can source a 95% Goodman. If propane stays at $3, I can get the difference between 80% and 95% back in one winter. And I think I can get it back on resale if I sell the house this summer.

You getting the equipment thru your installer or are you gonna buy online? I guess it wouldn't matter to you if you are going to sell the house and the new owners will be stuck with no equipment warranty.

[Homeowner314]

You getting the equipment thru your installer or are you gonna buy online? I guess it wouldn't matter to you if you are going to sell the house and the new owners will be stuck with no equipment warranty.

Right now, the installer is somebody who does not sell Goodman. (and his budget brand is Gibson, which costs him more than I'd pay for Goodman)

Amazing coincidence. I was looking up Goodman's warranty this morning and found that wonderful clause. I started another thread on the warranty at exactly the same time you pointed it out to me. But thanks for the heads-up, I would have been extremely unhappy to read the warranty papers upon receipt of the unit if you hadn't pointed that out and if I hadn't downloaded the warranty.

Anyway, does buying Goodcare from either the installer or the seller fix the problem?

[beshvac]

No

I used to work in a city that had 2 goodman distributors. It was a nightmare because you had to figure out which distributor provided the product because they would only warranty what was purchased from them. So warranty claims would get kicked back by them if the unit was purchased from the "other" guy.

[Homeowner314]

Thanks, beshvac.

If I buy from the local Goodman shop, instead of buying it online and using the (non-Goodman) installer I already know and trust, and pay the extra $$$ for Goodcare, will that be transferable to the buyer when I sell the house in a year or two?

If not, I suppose there's always a claim for 'warranty of merchantability and fitness for purpose' against the internet seller and/or Goodman for the short time I have the house. Especially if I buy it from a vendor who loudly proclaims the ten year/lifetime factory warranty in his internet advertising.