New home being built, furnace questions.


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Old 01-30-12, 01:03 PM
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New home being built, furnace questions.

Hey everyone,

My first post so bear with me.

We are building a new home that will start digging in a few weeks. The home is a rambler with 1340 SQ Ft on the main and 1242 SQ ft in the basement. There is also a bedroom above the garage that is 282 Sq ft. The home is natural gas. The basement is unfinished.

After the home is built we are going to finish the basement but I want to prepare now for the furnace if need be. The builder says the furnace is the Tempstar T9MPX080J16A.

http://icpindexing.toddsit.com/docum...4021105102.pdf

It's single stage, 80,000btu, 95%.

Since I am going to finish the basement right off the bat will this furnace be sufficient to heat the whole house?

My concern is that it will heat the house but with the thermostat on the main floor the basement will stay too cold or if I crank it the main floor will be too hot.

Should I try to upgrade to a zone furnace that will allow a thermostat on the main and in the basement? Is there a better option here? The home will also have central ac. From what I know now seer 13. I will also insulate the basement between 2x4's and carpet/pad will be the flooring. The basement will be 3 bedrooms, 1 bath, 1 family room, 1 laundry room. The utility room will be unfinished as well as an unfinished storage room.

Hope I gave enough info, but I can provide any specifics if needed.

Thanks!
 
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Old 01-30-12, 03:01 PM
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your right on with the basement chasing the living room stat and a zoned system should be considered.even thesun swinging on the windows on the first floorr will satisfy the stat there,with the basement chilling out especially with the foundation and the ground temps.
 
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Old 01-31-12, 05:56 PM
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The size of that furnace should be enough for the size of your home. If you're finishing the basement I would assume that there would be some sort of duct work involved so that should solve your cold basement problem. The basement will obviously always be slightly colder than the floor above it (we all know heat rises) but with insulation and everything else the td between the 2 levels should be negligible. And PLEASE FOR THE LOVE OF GOD do not build a room around your furnace/water heater as close as possible. Leave some space for the service people :-)
 
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Old 01-31-12, 06:28 PM
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Two floor two units! Now is the time to talk to your builder and get away from the builder grade unit and go with a good unit.
 
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Old 02-01-12, 07:32 AM
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kyoung22 > I will leave some room for sure!

airman.1994 > I would love 2 furnaces one for each floor but then I would need 2 Ac units, etc. The cost for this would be prohibitive. Is the Tempstar I listed not a good unit? Is there a special furnace that is 2 units in 1 for the both floors?


Another question: If I do a multi-zone system for the upstairs and down, do I need a special furnace or is it just the dampers that make it multizone?
 
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Old 02-01-12, 11:00 AM
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You probably don't need AC for the basement. We have a full basement and it stays right at 50-55 all year round. If it gets too warm just turn off the heat and let mother earth do the job for you.

On the rare occasion that it gets hot around here we just go down to the basement and sleep.

NW WA State
 
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Old 02-01-12, 04:06 PM
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P.S.

What you might want in the basement is a dehumidifier. If it's a poured foundation it will be releasing tons (really) of water for a couple years. If it's concrete block, not so much.
 
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Old 02-01-12, 06:00 PM
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Tempstar is a builder grade unit. I'd ask builder for a name brand equipment. V
 
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Old 02-01-12, 09:09 PM
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80k is far too large for that type of house unless it has minimal insulation or glass walls.

Where are you located? In the northeast or southern ontario, 80k btus input/77k output can easily heat 2500+ sq ft. house (basement excluded) with a lot of capacity to spare. (The equivalent is over 15 1500W space heaters running on high ->5000 btu/hr each)



Did the builder do a room by room load calculation? It's not possible to correctly design a duct system without one.


The second floor should heat fine if the system is correctly designed and installed. Balancing can take care of the temperature difference between floors as long as the second floor has a return near the ceiling.

The brand name isn't important at all; the ductwork will make or break your hvac system.

What you might want to consider is a two-stage furnace with a variable speed blower. (tempstar model Tempstar® Heating & Cooling) These units run at 60-70% capacity the vast majority of the time and only switch to high when needed. Variable speed blowers maintain consistent airflow (as the filter gets dirty, vents get adjusted, etc) and save electricity.

To benefit from a two-stage model, it must be correctly sized though. (for best results, the combustion air should come from outside and a 2-stage t-stat must be used)
 

Last edited by user 10; 02-01-12 at 09:46 PM.
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Old 02-01-12, 09:13 PM
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Gross oversizing is BAD

Consequences:

- Excessive noise
- Short equipment lifespan due to insufficient airflow (undersized ducts)
- Short cycling
- Uneven heating and cooling


------------------------------------------
You can do a load calc yourself for $50 -> HVAC Software, HVAC-Calc for Heat Loss, Heat Load Calculations

If the hvac contractor just does things on new construction "by experience", he needs to be fired before it's too late.
 
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Old 02-02-12, 11:43 AM
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I live in Northern Utah.

Muggle > Not sure on the load calculation. I asked what furnace and this is what I was told for my home. It just got me thinking about the basement. I was reading about a 2 stage as well and that sounds like a good idea. Especially for comfort so I will see if I can upgrade to that.


I think at this point I am going to see how much it will cost to upgrade to a 2 stage/variable speed for sure.

I am still undecided about a zone system. I think that would work great to have a tstat on the main and in the basement but I have read zone dampers tend to break alot. Since my basement is going to be finished I don't want to be tearing out ceiling drywall to replace dampers.
 
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Old 02-02-12, 04:59 PM
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I wouldn't bother with zoning.

Proper sizing and design is critical though. Oversizing greatly diminishes the benefit 2-stage furnaces.

I would inquire about insulation values as well:

- R-value in attic
- Type of windows
- R-value in walls (2x4 R11 or 2x6 R19 - not sure what the code is down there)
 
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Old 02-02-12, 06:06 PM
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Mugg

I completey agree on the duct work. Saying that with the builder grade equipment you get a company that usely does lower quality work. That's why I said go for the name brand equipment. You at least get a lot of the hacks out the picture.
 
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Old 02-02-12, 06:56 PM
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A valid point.

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Old 02-02-12, 10:57 PM
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Properly designed and installed ductwork will eliminate 90% of the problems. Unfortunately, probably less than 20% of all residential systems are properly designed or installed.
 
 

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