Heat pump thermostat question

[Michael Baugh]

Just visited someone with a heat pump, gotta question. The outdoor temperature was in the 20's, I realize there was precious little heat out there for it to relocate to inside. So the strip heaters needed to be doing their thing. But when the thermostat would initially call for heat, the blower would come on, and the heat pump would obviously be attempting to do its thing first, rather than immediately kicking in the heaters. So the unit is blowing cold air. Does a heat pump thermostat have a 2-stage sensor bulb, so that when it gets colder in the house because the heat pump isn't finding any heat out there, the heat strips get cut on? Or is there a time frame that goes past before the strips get cut on? The blower was delivering cold air. Obviously, any air coming out of the vents that was not being heated would be felt as cold, simply becuse it was room-air temperature moving past us. The thermostat was a General Electric unit, and I'm generally not impressed with GE stuff anyway. But my awareness of heat pump stuff is extremely slim, and I need a better overview of how that works. I realize that temperature setback is not seen as a good idea at night, because of it being a heat pump, but it would be damned agravating to have a cold breeze blowing past at night, too. Is this a typical problem encountered, especially since there are units that sense outside temperature and cause the thermostat to bypass the attempt to drag heat from outside when it's below

30 degrees or so? Is the GE thermostat the bottom of the line? Is there a reasonably priced unit that incorporates outdoor sensing and doesn't cause the unit to be blowing cold air? Educate me, please. Or give me some favorite URL's. Thanks ahead of time.

[Bloated Elvis]

Recently, "Michael Baugh" created this masterpiece for the newsgroup archives:

When I buy electronics, I usually try to do a bit of research on competitive models before making the purchase. I tend to like what I find in GE products in terms of cost/features/quality. But, they make a lot of stuff and don't always get it right.

I live in NC, and it's like 25F outside right now. My heat pump is running almost constantly, but I haven't seen the stage 2 light come on yet. If I crank the programmable thermostat up 4 degrees, the emergency strip (stage 2) kicks in.

This doesn't answer your question directly, but it may give you some comparative data to consider.

BE

[TURTLE]

This is Turtle.

Reply Below in Parts.

The installer can have the heat pump come on or go off at anytime or have the electric back up heat come on at anytime he wants it to by the way he sets up the 24 volt control circuits. Yes, 95% of all heat pump thermostat have a second stage heat on then set to come on 3 ºF colder than the Room set temperature. If he wired it up to do so. There is outdoor thermostats that can turn on the Electric back up heat and the heat pump to run together atany temperature he wants or it can turn the heat pump off at certain tempratures outside and just run the electric heat. Anything you described here as to not to your liking, a good Heat Pump installer can make it do anything you want it to do at any time or at any temperature outside or inside.

Well Here is your set up to stop this problem. Set outdoor thermostat to just turn heat pump off at 30ºF or less out side and just run the electric strips during this time. When the temperature goes above 30ºF outside. the heat pump will come back on and the Back up electric strips will go back to second stage heat of 3 degrees behind the set point of the thermostat. now the temperature outside goes under 30ºF you have hot air. Above 30ºf you just have warm air from the heat pump. now you can set the temperature to do this way on up to say 50 degree outside and have back up come on and turn heat pump off. Now there is 6 other ways to set this up but i chose this one for it was most commonly used.

G/E / Trane / American Standard are all the same brand now days and they have about 25% of all stuff sold in the US with their name on it. I have been told they are fair stuff but they truely are the highest priced. i would say just fair stuff.

Is there a

YES , Every Brand sold in the USA because the heat pump manufactor makes all the system just about 99% the same way and the installer will decide to wire it to do what you want it to do. ALL the controlling system is installed by the installer and the factory just makes the pieces to put together to do what you want. The Cheapest piece of HVAC equipment in the hands of a good installer can make it run like a Rolls Royce. Now remember one thing here. These good installer will not be the cheapest bidder. The Rookies will be the Lowest bidders.

My GOD, Have you got about 2 years to study the system and you might come work for me for a couple years and you will understand the system pretty good. If Not you will just have to try to ask me or others questions and piece it together. Now most URL's that are out there are there to sell you something and it just stear you to buy something and not to understand the systems. I will run a little research to see and let you know.

TURTLE

[markherm]

I use a Janitrol (I know, thin coils, etc.) heat pump to supplement my gas furnace in Minnesota. I've had it for twelve years now and haven't had a problem with it yet... It uses a outdoor thermostat located in the condenser to cut out the hp to the furnace. I set it at 33 degrees, below that the hp will run too long, imo. Of course being in the middle of Winter here in the North, it isn't being used at all. We have had some warm winters though when I have used it on/off all winter. I wouldn't have it at all if were not for the off-peak electric rate I receive, it was just raised to 3.8 cents per killowatt/hr. The first increase in electric since I have lived here. (12 yrs) I run the air in the summer as much as I want, very inexpensive when using the hp in that way. They also let me wire my furnace into the off-peak meter so all the electricity consumed by it is at the low rate. btw, the normal rate is 7.8 cent per Kwh.

[Michael S. Trachtenberg]

There's actually a lot heat in the air in the 20's. Just not enough to offset the heat loss from the house. I have a 2.5-ton unit that is rated for 18000-19000 BTU at 17°, depending on the blower coil it's matched with. Rated for 28000-29000 at 47°. I have R22 and understand R410 does an even better job in bitter cold. Installers are constrained in sizing because the units also handle A/C.

They tend to move more air, at a cooler temperature, than a furnace. If the temperature at the register isn't above ambient then there's a problem with the system.

Depends how it's set up and what the backup heat source is. Can be time, temperature rise, outside temp, etc. They also use backup if and when they defrost. My own system looks at the temperature of the air coming off the blower and kicks the strips in if necessary.

[Michael Baugh]

Thanks for the offer, but it looks like you and others answered my questions pretty doggone well. Including the advice that she needs to call the HVAC folks. And your reminder about the rookies being the less expensive. Medicine isn't be the only field where they refer to the business as "practice".

[vairxpert]

You didn't mention what brand and model heat pump you have and replacing an indoor thermostat most likely won't do a thing for you.

Many systems like the older Carriers have an adjustable thermostat in the condensor unit itself. I do know there was a large batch that got out that had the degree decals installed ass backwards. Setting the dial to 40 degrees was actually on the other side of the scale closer to 0 degrees. Once set correctly those thermostats are very reliable. Also if the indoor tstat is bumped up past a certain point the gas furnace (used in my area) will kick in for rapid heat up until the indoor temperature gets within a few degrees of setpoint.

Other units (newer) have remote sensors that go to control boards or thermostats. Sensors can be tested by checking resistance at a certain temperature. The indoor thermostats will usually let you see the outdoor temp. by pressing a certain combination of buttons. One other point is that if the sun is directly hitting the remote sensor it may register 20 degrees or higher than the real outdoor air temperature.

Heat pump set ups can get a little complicated and in all honesty you could make things much worse than they already are...you will probably save yourself a lot of grief by telling your friend to call an HVAC service tech.

George