Regular Guest
The house is a 1300 square feet built in 2000 with single pane aluminum windows in the Austin Tx area. It's going to have the attic spray foams after the A/C system is installed. And I have a bid for a Kenmore Conditioner unit NXH524GKA and a FXM4X3000A with one heat strip for heat from sears. However, I've found it difficult to get any real data on this unit. I do have gas evaluable for a furnace, however with the spray foam in the attic these could cause problems. So I'm hoping to move over to the Heat Pump. It really doesn't get to cold here, and with my solar panels it should help with the electric bill.
What type of electrical panel would I need to install this unit. With the house being built in 2000 it should work fine right, and is this a good heating and cooling options. I'm sure I'm missing something.
Thank you so much for your knowledge.
Global Moderator
It's what ICP calls the "entry level" units. Basic, no frills but it does have high & low pressure switches. If properly sized & installed, should do you just fine. Only drawback with Sears is being able to check out the dealer who is putting it in as they usually sub out the work.
I would think in such a mild climate, that would be a good system. 1 strip of backup heat takes a 30 amp circuit. May require more than a 100 amp main if everything else is electric.
Regular Guest
Thank you BaldLoonie for your help. Looks like I'm going to be learning a thing or to about electricity too. I took that picture of my outside electrical box and it looks like I only have a main breaker that is a 100. Can that be swapped out for a 125. I think I still have room on the panel for a couple more breakers. But I'm not sure. Will that set up work with my HP?
Thanks again for your help, and anyone else that wants to share.
Global Moderator
No, can't change the main without upgrading the whole service in most cases.
AOP Committee/Professional Member*
I hope you had a load-calc performed so you can do things to reduce the heat-gain/heat-loss, so equipment size might be reduced.Originally Posted by AUSTINTXAC
It would not cost that much to add storm windows to the single panes, which upgrades them to R-2. I'd use a fairly high infiltration rate to start; maybe, .7 or .8 (ACH) (natural) Air Changes per Hour.
My friend (Gary-ed)has a Free load-calc that you or your contractor can use (no guarantees of perfect accuracy) You have to print (2-pages) the results at this time cannot be saved. The Start Page has drop-downs to select your conditions. Read the instructions:
http://www.loadcalc.net/
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udarrell
Professional Member*
I'm in Round Rock. I'm not sure the city of Austin is gonna be cool with the heat strips only. Hopefully whoever does the job will be pulling a permit. Pretty ugly to get caught without one for contractor. I know somebody who got caught (not me) and got a $500 fine and had to go before city judge. It's also a ding on their license. Best bet if you are foaming house and money is tight. Go with lower end 90% furnace. The city will also inquire as to gas to electric and if proper permits were pulled for electrical upgrade for air handler. Don't try to outsmart these guys, they are a pain in my butt many times, but are fairly sharp and do catch things and get upset when you try to pull a fast one on them. They will come in and nitpick your house to no end, it will be within scope of their power which they don't exercise unless you piss them off. If you're cool with them, they are no problem.
I like DIY'ers. They pay better to fix.
Professional Member*
I would do the spray foam first. Ductwork can easily get damaged during the foam installation and will likely be in the way. Is hte foam going under the roof deck to seal the attic and make it a semi-conditioned space? For attic system this is what I would recommend. Use closed cell or add a vapor barrier under the the roof deck or you may have humidity issues on sunny days.
+1 on storm windows. In your climate, definitely get Low-E coated glass. IT will make a pretty big difference. I have storms on all my windows and I think they perform equal or even better than the double panel low-E argon filled vinyl windows at my last house. They reduce noise levels A LOT. Descent quality midrange Low-e storms only cost about $120-200 depending on size and take 30-45 minutes to install including prep time.
With storm and foam, I wonder if you'd only need a 1.5 ton system for a 1300sqft home. I would get a load calculation done. A 1.5 ton will be a quieter and use less energy and run a lot longer than 2 ton on the same size ductwork and registers.
AOP Committee/Professional Member*
Right On, motoguy! Those storm windows are cost effective.
Austin TX summer design is 99 dry bulb, 74 wet bulb; or a low 30% RH. Well, the load-calc says 96F for Austin & 29 grains moisture difference using an indoor 75F with both.You ought to be able to get the load-calc down to at least 12-Btuh per sf; or 15,600-Btuh with a low latent load factor.
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udarrell
Professional Member*
They really knock the sound levels down too. I have 3 barges parked in the river behind my house (mississippi river is closed due to flooding) and I can't hear the whine of their turbodiesels idling from indoors. You can normally just faintly hear them when they throttle up.
Professional Member*
Yes, sealed attic can cause issues with furances that need combusion air from indoors. You could go with a direct vent high effciency furnace and 2 pipes through the roof (or a single coax termination). Might be cheaper than upgrading you electrical service... .and it will be more efficient too. They make 45k BTU high efficiency furnaces, which would be plenty.
Other option for a smaller home, with a small heat loss, is a combi boiler or a tankless water heater in a combi installation. In this set-up you use a hydronci coil on the air handler and run hot water through it for aux heat with your heat pump.
Regular Guest
I think your right about getting a Heat Pump outside and matching it up with a High Efficacy gas furnace. The Spray foam contractor stated that he could build a box around it and seal it up. Would it be cheaper to have a furnace then he electrical strips? Any Kenmore furnaces I should be looking at.
Professional Member*
Spray foam first then have an energy audit (blower door test etc) them have a manual j done then have the hvac replaced. Otherwise you will end up with an oversized unit. Be sure and get those ducts sealed up tight too. www.comfortinstitute.org
Global Moderator
How much time is spent each winter below freezing?
Professional Member*
It doesn't get that cold here. The furnace is safe in the attic. The only problem I've ever had with 90% furnaces was about 4 years ago when the drains that ran outside freezing and causing condensate to back up, and nobody I talked to could even remember that happening aside from that one winter in the last 15-20 years. Put heat tape on them and be done with it. The only thing I would be worried about is putting a Kenmore in. I don't know anybody who sells parts locally for it, aside from obviously Sears. I had to get a defrost board for a heat pump this last year and it took about a week to get parts.
I like DIY'ers. They pay better to fix.
Regular Guest
Really I would say less then 4 days. Austin Tx very hot 100 + Degrees for a month at a time and humid. I think really I wouldn't use the strips that much at all.
Professional Member*
I'd be real cautious sears DOESN'T INSTALL H V A C they sub out all work and pay piece meal (read about rough cases on this site)
Professional Member*
The heat strips will come on more than you realize around here. They don't only come on when its freezing. They come on with a large setback, when it goes into defrost or when it's losing capacity. Usually around 40, they'll start being used more and more. Several nights a year get down below 40. I think tonight it's supposed too. Your best bet around here with the size house you have and the low price of natural gas, if you're in the city and not using propane. Is to put in a variable speed 80% furnace with humidity control, put in a 16 seer straight cool a/c, seal your ducts up and maybe replace if they are old, blow in insulation, skip the foam stuff, take the money you save on the foam and put in some good windows and seal as many penetrations as you can.
I like DIY'ers. They pay better to fix.
Professional Member*
That's why you shouldn't use minimal setbacks only for comfort with heat pumps in heating mode. Setbacks in cooling have limited useless if sized correctly unless you have time of use metering. Actually a correctly sized actually system won't recover from more that 1or2fif at all in really hot weather.
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Professional Member*
Summer design temp 98'/ 75'F DB /WB
Winter design temp 30'F __ ASHRAE 99%
Your electric service would have to be evaluated for heat pump + 3kW ( or other) heat strip.
Total ... is about 5 kW
http://www.climate-zone.com/climate/.../texas/austin/
Heat gain is likely in low 20,000's BTU/HR
Heat Loss might be in the mid 10,000's BTU/HR "ball park" with the relatively High Winter Design Temperature of 30'F.
Designer Dan __ It's Not Rocket Science, But It is SCIENCE with Some Art. _ _ KEEP IT SIMPLE & SINCERE ___ __ www.mysimplifiedhvac.com ___ __ Define the Building Envelope & Perform a Detailed Load Calc: It's ALL About Windows & Make-up Air Requirements. Know Your Equipment Capabilities
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