questions about a heat pump issue
I have a new system that was installed just a few months ago. It’s an American Standard Freedom 95 Comfort-R forced hot air. Two stages of gas fired heat (highest is 60k BTU), one stage heat-pump / cooling 1.5 ton I think, 16 SEER.
Everything on this system works great except for a bit of an issue with the heat pump. When I purchased the system there was a claim that it could (efficiently) work all the way down to 25F. I thought this was ambitious but some of this modern stuff is pretty good. Well, turns out that it could not really do this. The system would stay on and would run indefinitely (using electricity) and only get up to maybe 60F or 65F when set to 70F.
OK, so the company came out and made some adjustments, checked for problems, refrigerant, and notably changed the crossover point to 35F. No-go, same result. They came out again and changed a few more settings (in the thermostat) but kept the 35F set point. Still mostly a problem, it worked great while they were here and the outside temp was 37F, but later that week it would sometimes work, sometimes not. Even one time I noticed it took 3 hours to get up to 67F when the outside temp was 48F, other days it might be faster or slower around the same temperatures.
They walked me through changing the set point to 40F, and this made things a little better, but still somewhat inconsistent. For reference, when on gas it can get the place up to 70F from 62F in less than 20 minutes. It’s a 1400 Sq. Ft. Condo in Boston. At my request, they did contact the manufacturer representative for an expert opinion but they said setting it to 40F was about all you could do, and they did not think it was any defect in the unit. They also said that even when within the temperature range needed, the unit can be affected by weather conditions like rain, sun, and wind. The condenser is located in a narrow alley outside my building, and right next to it is another condenser that I have for a Mitsubishi Mr. Slim 22 SEER heat pump that says it will work down to 15F and works great down to 5F!!!
My questions on this are, are these acceptable results? It only cost a little bit more to add the heat pump over the non-heat pump unit, and I had to pay some high electric bills during these trials, but with a set point of 40F the heat pump is only going to be working for a few months out of the year, and what about this inconsistent performance? Should I be expecting more? Could this unit be defective? Are there other units that COULD work down to 25F for a whole-house unit like this? American Standard only has one unit above this, with I think 19 SEER using a two-stage condense that is even larger than the gigantic one that I got. But it was a huge step up in price and would not have paid for itself anytime soon. I would like to hear from some other experts about this situation.
This leads me to another separate question I have about this. Does anyone know of some really powerful computer-controlled thermostats? The one that came with this system is pretty nice, but obviously it is not nice enough to detect that the heat pump isn’t cutting it and will keep running endlessly never reaching the temperature instead of switching fuels. I have seen there are some “Ethernet equipped” thermostats you can connect to your home network that provide a web management page, but looks like they otherwise have the same features as what I have.
I am talking about something REALLY computer controlled, like a piece of software. Something that would have more sensors and could detect which fuel to use based on actual output/consumption over time even being able to compensate in real time for weather or other conditions. Advanced energy management features that would get the most out of the multiple stages, variable speed fan, etc. I will bet there are some home automation products that might have this, but I thought I might ask if someone knows of anything that might be exactly what I am looking for.
Thanks very much in advance
The heat pump will "work" at the low temps they claimed.
It just won't be able to supply enough heat to maintain temp.
Your heat ump is sized to your cooling load, not your heating load, which is proper.
A thermostat like the Honeywell IAQ can be set up to use the HP first, and if it can't keep up. It will switch to the furnace.
Sounds to me like they either have some wiring issues, or thermostat settings, that are screwy.
There are so many things though, that it would be hard to diagnose over the net. Could be inproper charge...all kinds of things
Should not have to raise your lockout temp to get things to work...a good stat will monitor the heat pump running and if it cant keep up, should kick in a second stage of heat....being furnace, elec heat, or whatever.
Your heat pump is only 1.5 tons, the smallest size in a split system. As BeenThere stated, it is sized for the cooling load and not the heating load. Your gas furnace provides supplimental heating when the heat pump cannot provide enough btu's. As outdoor temps drop, so does the btu output of the heat pump. It may provide 18,000 btu's (1.5 tons) at 47F (the outdoor rating temp), but only 12,000 btu at 25F ambient.
The 16 seers are trick to install, they dont come in 1.5 tons though to my knowledge they only do even tonage. Usually the issue is with new installs is control wiring and fan settings.
I think another question would be how involved with heat pumps is the installing contractor. It's a growing segment of the business here in Chicago because gas and electric pricing made it an extremely inefficient choice until recently. Going through the training myself, I learned that ,at least in the Lennox units, very often you will not use the same coil for heat pump as for a/c. You need more coil volume for heat pump mode. If you don't have the correct coil or TXV matchup you would have a heating issue with the heat pump.
I agree with green jumper.
The 16i does have to be wired differently, have the install manuals in my van, forget exactly what the "combination" is. But know they are wired a little different on the low volt side.
I would contact the company who put it in with these ideas in mind.
If you follow wiring directions supplied with the O/D unit, it will run correctly....wiring schem for stat/furn shows it a little differently.
Actually, trane 800 series stat book has a 16i wiring configuration...now that I think of it.
Strange part is that you say sometimes it works good, sometimes it don't. It's also strange that the stat is not bringing on the gas furnace when the heat pump is not keeping up. I agree 100% that you may have more than one problem.
Hey, this is a great (and interesting) tip! I went to the Honeywell website to look at this thermometer, and it looks identical to the one I have except mine does not have the other white box, and my says "American Standard" instead of Honeywell. Yeah, I know my system is made by Honeywell.
Originally Posted by beenthere
My currect thermostat says "ACONT802AS32DAA" and "TH8320U1032" on the back. Are you thinking that the thermostat that I have does not have the feature to detect that the heat output is not enough and switch, whereas this higher end model you are mentioning can?
If that is the case, I will call my HVAC company and have them install one of these units. I already have Aprilaire filtration and humidification, but auto-switching fuels would probably be worth it.
What do you think?
I agree with you, but that is not what is happening. This thermostat will do "recovery" such that it starts working early enough so that it reaches set temp by the time you have set instead of starting at that time. But, on days I have been home all day it starts at like 3:00pm to "recover" to the temperature it needs to be at by 5:30pm. Seems like a long time to me.
Originally Posted by brianalan01
So, you are basically saying it "is what it is" and if I want this to work for a longer part of the year then I would have to improve my insulation?
Originally Posted by gary_g
My cooling load in the summer is very low, I am on the first floor of a 4-story building that is steel and concrete.
But, if I understand you correctly, if it is sized for the cooling load, then how often the heat pump gets used is entirely based on the heat loss of the particular dwelling. Because I imagine if you sized the unit for heating, it would be way oversized for cooling.
The IAQ has a better control logic.
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