HVAC questions

[Ohioguy]

Back in March, we moved in to this 1979 house. We had a new Rheem furnace put in as part of the FHA rehab - everything had to be done before we moved in.

Furnace is all electric - no natural gas back in this subdivision. Had a bit of trouble with it at first - coolant leaked out. They fixed it, and it has been working ok since then, with a couple of annoyances.

Annoyance #1: a couple of the bedrooms are hotter in summer than the rest of the house, and colder in winter

Annoyance #2: on Fall/Spring days when it is cold in morning, and hot in afternoon, I have to manually switch the thermostat between heat and cold for it to do what it needs to do

Annoyance #3 showed up yesterday - furnace & blower running and running, but it kept getting colder in here. I went outside and noticed the heat pump was running, even though it was just 15 degrees out. Switched the thermostat over to emergency heat, so it would use the heat strips.

The thing just can't keep up with temps between 9 and 22 outside. Yesterday afternoon the temps inside rose just 9 degrees - to about 64 - after more than 8 hours of trying. I looked at the furnace, and realize they only hooked up 15kw of electric strips, not 30k as I had requested. That's probably why it can't keep up.

Annoyance #1 is probably caused by poor duct design and implementation. Main duct is along East side of house, and vents over there have a lot of air coming out. Vents on the West side, including those bedrooms, have a lot less air coming out. I would probably have to have the interior of the house busted up and ducts replaced to take care of this.

Annoyance #2, I may be able to take care of by switching over to a newer style digital thermostat.

I have to say, I wish I had a natural gas hookup here. At our last place, I had a Goodman 80% efficient gas furnace installed for a total of $1,300. I was very impressed with how quickly it could bring up the temps after we had been way, and I don't think I'll ever get used to how 'cold' the air from an electric furnace feels.

BTW, can anyone give me an idea how much most HVAC furnace repair places charge, per hour? There is a place nearby that I've used for duct cleaning and minor things in the past. They charge a $52 trip fee, and $90/hr. ($22.50 per 15 minutes) Is that pretty much average for the industry?

[dpb]

That's not "all electric" but an air-exchange heat-pump. 'All electric' is generally reserved for resistance heat only.

Would have been good application for ground reservoir heat pump--that area gets too cold for efficient air-exchange heating (as you've discovered).

One alternative (don't know how feasible for retrofit, though) would be LP "emergency" heat instead of resistance.

Agree on the chill factor of air-exchange heat pumps--the pleasant warm air feel when made the transition to a ground-exchange unit was "wunnerful indeed" :) . Not to mention the reduction by nearly 2/3rds of operating cost during cold weather.

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[bud--]

Make sure the dampers and registers to the "couple of bedrooms" are all the way open. You can partially close the dampers/registers to other rooms to force more supply air to the low flow bedrooms. (This is "balancing the system".)

Would think your system would have a "multistage" thermostat that turns on resistance heat as a second stage as the inside temp falls. There should be a temperature sensor that changes over from heat pump to resistance heat when it is too cold outside.

Can you connect the other 15kw (does the electrical service have the capacity)? Is the outside temp way below any normal low temperatures - so it is not worth worrying about?

There may be an applicable building code with a low outside design temperature at which the system should should provide adequate heat. (The system may violate the applicable code.) Or, was 30kw a requirement?

[gfretwell]

You are right about #1, it is a dict design problem I am not sure about whether there is a digital thermostat that auto switches from heat to cool but I suppose there may be. #3 was probably because you didn't have enough power in your house for

30kw of toaster wire heat. (125a, just for the heat strip).

You are certainly in a questionable area for all electric heat. It is common in the south but it doesn't get that cold here. Even in this unusual cold snap we only went down to 34 last night and it is back up to 50 already. 11AM

[hallerb]

Have you contacted the installer? you should have a warranty

[ransley]

You should have annoyance #1 as your electric bill when using the resistance heat, Electricity is probably double the cost of propane per Btu in your area. 9 months ago this was done?, what about that full warranty you have that might be reduced in march, use it and get your claim documented incase it goes past march. You can shut down registers somewhat to balance heat, but you have to know what the operating temp the unit is and not to go over its design temp or you will burn it out early. I would start start with the installer and a call to Rheem support as your claim will then be documented.

[trader4]

As usual, Harry is off in space. Most houses don't have heat exchangers to bring in fresh air and 100% is recirculated. I'm betting that's the case here.

[ransley]

Earth to Harry, Google residential electric furnaces, and what do you think he has, a Kenner easy bake oven?.

[ransley]

Dumped air? we dont do that on this side of the ocean.

[ransley]

Its FHA, its cheap.

[Ralph Mowery]

No one has mentioned how much insulation the house has. This plus the type of windows could make a big differance. Also how many sq/ft is the house and what is the btu or other heat rating of the heat pump ?

You mentioned the outside was just 15 deg outside. I guess this is in F and not C. You seem to talk of this as it could get much colder. Heat pumps do not work well when it gets below 20 or so deg F for long periods of time.

I am in the middle of North Carolina and it is unusual for it to get much below 20 deg for long periods of time. I have a heat pump and for the last few days it has been 10 to 15 deg at night and about 32 to 35 during the day for the last several days. The heatpump I have has not had any problems keeping up. We usually set it for 70 deg. It is a Trane that we put in after we bought the house several years ago as this was a 1980 house and the heat pump gave trouble about 2 years after we moved in. Being over 20 years old , I just replaced it with a more efficant unit.

They do make thermostats that will automatically switch from heat to cool. That is just a cost problem. The air ducts may not be ballanced for the differant rooms of the house.

[ransley]

You forgot the most important fact, Air Exchanges per day of the average home are enough to ensure you breath new air. Only in a modern home with the house covered with house wrap, tight sealing windows, doors, and all areas sealed do Air exchanges per day go low enough to be unhealthy. We do Blower Door tests in the US, how do you verify a tight house, do you guess. I had my house tested, it rated loose. No old house here needs the 1000$+ needed to instal HRV systems

[ransley]

Yea we know yours are way Over 100% efficient.

[clare]

They are made by Lucas. The furnaces are better than the vacuum cleaners - "the only thing Lucas makes that doesn't suck"