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  1. #14
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  2. #15
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    The stat generally should have no need to call for heat when the outdoor unit is on a time delay. It should be observing the same 4-5 minute delay that the outdoor unit would, and in all likelihood, the only time you would ever want to call for heat that soon after the end of the previous call for heat would be a manual thermostat adjustment anyway. In the real world, then, that issue shouldn't come up at all, or at least not regularly.

    During defrost cycles, the indoor blower must be running for the defrost cycle to be effective. There has to be airflow over the indoor coil; that's where the system gets the heat that it uses to burn the frost off of the outdoor coil. Defrosting is literally a short run in cooling mode, but with the outdoor fan off so that the outdoor coils get hot. Since it is cooling mode, the indoor coil will start getting cold, so the air blowing from the vents may start at lukewarm but will actually get cold after a couple minutes.

    To prevent the annoyance of cold air blowing occasionally while you're trying to heat, heat pumps with electric backup are usually configured to use their auxilary electric heating elements to reheat the cold air. That way the heat pump can have its defrost cycle without disturbing you with a burst of cold air when you wanted warm. Since all-electric heat pumps have their heating elements downstream of the indoor coil, the heat pump can go right back to heating after a defrost cycle without any trouble.

    With dual fuel systems, there is less consensus on how to deal with defrosts. You can wire up any dual fuel system to run the furnace during defrost cycles; that prevents the cold air issue. But furnaces have to go upstream of the indoor coil. So you need some kind of protection device (either a high pressure switch on the heat pump or a thermal limit switch on the indoor coil) that will shut off the furnace if the indoor coil gets so hot *during* the defrost that it puts the heat pump in a dangerous pressure condition. It's also very hard on the heat pump to try to start up the heat pump in heating mode again right after the defrost, because the indoor coil will still be hot from the furnace output. Some dual fuel systems will go ahead and run the furnace only during the actual defrost cycle, despite these concerns, and try to go right back into heat pump heating as soon as the defrost cycle is over. Depending on the setup, that can be workable, but it depends a lot on the smarts of the installer to configure everything just right. In my book, you really should only set up this way if you have the thermal limit switch; a high pressure switch on the heat pump isn't really sufficient.

    There are two common ways to deal with those concerns. The simple way is to just let the system blow cold during defrosts. It's easy on the equipment, but isn't very good for comfort. The way Carrier dual fuel thermostats, Thermidistats, and the Infinity system deal with defrosts on dual fuel systems is that they operate the furnace during defrosts, and then when the defrost is complete, instead of shutting off the furnace and returning to heat pump heating, they keep the furnace going and use it to finish the entire call for heat. Only when it's time to start heating again after that heating cycle ends can it try to go back into heat pump mode. This limits to some extent how much heat you can get out of a dual fuel heat pump compared to an all-electric, because it will end up using the furnace after every defrost cycle, but it's easier on the equipment and it keeps things comfortable at all times.

    You can maximize the efficiency benefit and output of any heat pump setup somewhat by using minimal setbacks in heating season (or just set a single temperature and leave it). That cuts down on how much auxiliary heat you need. For example, if I want the house at 70 when I'm home and set the thermostat to 60 when I'm at work, the house will cool way down while I'm gone. The system will sit idle for several hours. Then when it's time for me to come home, it could take several hours of running the heat pump for it to catch up again. Thermostats generally won't start early enough to make it back to 70 on time (that might take the heat pump four hours), so even if you didn't need to defrost along the way (you probably will), you won't make it back to 70 in time. Depending on your particular thermostat setup, then, either the system just won't make it back to temperature anywhere near on time, or it will run the heat pump for awhile, realize it's not going to make it on time, and then run the expensive/fast heat source so it can hurry up and get to 70 on time. If you just maintained a steady temperature during the day, the heat pump could run all it needed to maintain 70, without needing the auxiliary heat at all (except for a few minutes at a defrost, maybe). The extra heat the house loses by staying warmer during that time period is made up for by the fact that the heat pump is a cheaper and more efficient source of heat.

    Keeping a steady temperature doesn't fit the conventional logic of setback thermostats (the more you set back, the more you save) because that logic assumes gas heating and electric cooling. With a heat pump providing heat, you have two heat sources; the heat pump is the cheap one and your gas/electric backup is more expensive. The backup tends to do things faster than the heat pump, but takes more energy and costs more to run. Bottom line, setting back the heat overnight or while you're at work is not a money or energy saver if you have a heat pump. Programmable thermostats are still worthwhile for heat pump systems, though, because the conventional logic still applies in cooling mode.

    Minimizing setpoint changes is especially important with the Carrier-type strategy of continuing with the furnace after each defrost. It won't change how often the system has to defrost, but it avoids conditions where you need a lot of heat all at once to heat the house back up. Back to my earlier example, if I needed to run the heat pump for four hours to catch up to 70 degrees again, even if my thermostat were smart enough to start four hours early, I would almost certainly have to defrost during that four hours of heat pump heating. So the system would run the heat pump until it was time to defrost, fire up the furnace, *and then finish the entire job of getting back to 70 with the furnace*. It starts looking less and less like a dual fuel system, and more and more like a system that uses a heat pump to maintain temperature when you're home and uses a furnace to recover after each setback period.

    As for what your installer said about other systems working just the same way, I don't particularly agree. You certainly won't catch an Infinity system with its pants down like you're describing; the whole point of Infinity is to orchestrate all the equipment to avoid such hiccups. There are philosophical differences about exactly how to handle defrosts on dual fuel, but very few people will argue for not using the furnace at all. Nobody wants intermittent bursts of AC during heating season.

    I forgot to mention earlier- the other characteristics you will tend to notice during defrosts, aside from the outdoor fan motor stopping while the compressor keeps running and the steaming, is the outdoor unit making a single punctuated "whoosh!" sound at the beginning and end of each defrost cycle. The whoosh is the sound of the reversing valve switching the heat pump between heating and cooling modes.

  3. #16
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    Feb 2006
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    103

    Talking

    wyounger, thank you for the explanation. I've already cautioned my wife about minimizing winter set backs with the heat pump and told her to either avoid the set back altogether or limit it to 2 degrees. I'm really beginning to believe the system was set up properly the first time and the second tech reconfigured the system to avoid the furnace running during defrost mode. Of course I really don't know. Certainly one would expect that Amana/Goodman understands the delay/defrost issues and it has one or more suggested setups to deal with the issue. Maybe I need to contact Amana/Goodman directly and ask how it recommends setting up the system? Maybe I need to suggest that the tech contact Amana/Goodman? At this point I'm abit at a loss about how to confirm whether the system is set up appropriately. By the time I get it all figured out, we will be into cooling season .

  4. #17
    Join Date
    Feb 2006
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    103
    wyounger, I've reread your post and given it some more thought. It seems that I need some more information. First, does my system have a thermal limit switch? If not, is this something that is easily added?

    If the thermal limit switch isn't a viable solution or if I want to be more conservative with the operation of the system, then I would prefer that the furnace fire when the heat pump goes into defrost, and to rely solely on the furnace for that heat call. To me this is a more acceptable solution than blowing cold air, particularly because I have a 96% furnace. Although I want the greater efficiency offered by a heat pump I'm not necessarily trying to squeeze the last dime out of it. (If I want the most efficient solution I would simply wear my coat in the house.)

    Assuming I want the furnace to fire during defrost can my system do it, or is my furnace, heat pump, or stat inadequate? I believe I have a vision pro 8000 series. Can the vision pro cause my furnace to fire during defrost? Can it handle the thermal limit switch solution if I wanted to go that way?

  5. #18
    Join Date
    Feb 2006
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    103
    My confusion continues to grow. Spoke to the service supervisor. They are going to send someone to look at the system. He agreed that the furnace should fire when the heat pump is in defrost, but he said the stat is presently set to lock out the heat pump when the outside temp is 40 or below, and this makes it very unlikely that the heat pump will go into defrost except in unusual circumstances. Moreover, he said the system will never go into defrost on start up. So I'm still not sure why the blower is blowing while the outside heat pump fan is not turning and the furnace is not firing? This is when the tech says the system is re-circulating the indoor air without heating it or cooling it. Why would the system do this when the stat is set to auto fan? Does it have something to do with delays and is it an incorrect setup?

  6. #19
    Join Date
    Mar 2004
    Posts
    1,042
    This is where the skill of your installer becomes critical.

    It's not highly likely that you have a thermal limit switch on your coil/plenum area. It shouldn't be hard to add, though.

    If the system isn't running the heat pump at ambients below 40, that will cut down some on its need for defrosting. I have to agree that doesn't really fit that this would be defrost-related. I'm going to have to guess it's some kind of misconfiguration. Does it do this every time it starts up in heat pump heating mode?

    Whether or not the furnace runs during defrosts is a question of how the installer wired the system, not your thermostat. I'm not sure what the VisionPro does at the end of a defrost cycle with furnace operation. My general impression of the VisionPro at this point is that it looks great and has a revolutionary user interface, but the feature set that goes with it isn't to the same level. There are several other units out there that don't look as good and don't have the nifty features, but are more capable with respect to dehumidification control, humidification control, dual fuel logic, and handling dual fuel systems with two-stage furnaces. Honeywell will probably add those goodies to the VisionPro at some point, but unfortunately they haven't yet. And since consumers love the interface on them so much, contractors have a tendency to install them even when another thermostat would probably be a better choice from a technical perspective.

    Thankfully, it's a new system, and your contractor is obliged to make this work right. They'll probably need to completely review the low voltage wiring, furnace settings, and thermostat settings to figure out what exactly it's doing. This is a fairly high end, complicated system; give them another chance to look at it and sort out why it's doing what it's doing.

  7. #20
    Join Date
    Feb 2006
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    103
    Well, the tech was back out and set the stat so that it will allow the heat pump to cycle more than 3 times in a hour or some such adjustment. Frankly I have no idea if the system is set up correctly or not. I suspect it is, but I really don't know. The system is obviously sophisticated and its performance is an improvement over the old system. Nonetheless I do consider it a bit of an annoyance that neither the owner's manual nor the tech can provide a detailed explanation of its designed operation. For example. In the heat mode, when is the system suppose to go into first stage heat pump mode, second stage heat pump mode, first stage furnace, second stage furnace? How does the furnace operate during defrost? First stage heat, or second stage heat? Does the furnace finish the call for heat or does it go back to heat pump immediately after defrost? When is it suppose to go into delay? Is there a potential overlap or confusion between a stat delay and a furnace or outside unit delay? How often does it check to see if it should go into defrost mode? How does the variable speed blower choose its speed, and how does the speed relate to the where the system is in first stage heat pump, second stage heat pump, first stage furnace or second stage furnace? How is all of this affected if the stat blower is set to "circ" instead of "auto"? Why does my stat have a heat setting, cool setting, em. heat setting, but no "auto setting" whereby the system automatically flips back and forth between heat or cool depending upon the temp (it shows up in the user's manual but not on the stat)? Etc., etc.

  8. #21
    Join Date
    Apr 2005
    Location
    Kingston Ontario Canada
    Posts
    1,234
    Georgiaguy I can concur with what you are saying. I have a Carrier 38YZA heat pump and a varriable speed fancoil. I have owned this system for over four years and I'm still trying to figure out if it is working the way it was designed. I know more about it then the installing dealer, believe it or not! I still dont' think it's set up to Carrier's design specification. Most of these contractors in my area anyways, have this attitude, "as long as it works and they can get there hand in your pocket and leave as fast as they can, that's all that matters". I think it's ridiculous that they sell these fairly sophistocated heating and cooling sytstems and they don't have anybody to tell you how it really should work, when set up properly. I have even had a Carrier rep at my home that didn't really know that much. Can you believe it? Nevertheless, I know what your going through!

    Thorton

    [Edited by thorton on 04-08-2006 at 02:40 PM]

  9. #22
    Join Date
    Mar 2004
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    1,042
    Originally posted by georgiaguy
    Well, the tech was back out and set the stat so that it will allow the heat pump to cycle more than 3 times in a hour or some such adjustment. Frankly I have no idea if the system is set up correctly or not. I suspect it is, but I really don't know. The system is obviously sophisticated and its performance is an improvement over the old system. Nonetheless I do consider it a bit of an annoyance that neither the owner's manual nor the tech can provide a detailed explanation of its designed operation. For example. In the heat mode, when is the system suppose to go into first stage heat pump mode, second stage heat pump mode, first stage furnace, second stage furnace? How does the furnace operate during defrost? First stage heat, or second stage heat? Does the furnace finish the call for heat or does it go back to heat pump immediately after defrost? When is it suppose to go into delay? Is there a potential overlap or confusion between a stat delay and a furnace or outside unit delay? How often does it check to see if it should go into defrost mode? How does the variable speed blower choose its speed, and how does the speed relate to the where the system is in first stage heat pump, second stage heat pump, first stage furnace or second stage furnace? How is all of this affected if the stat blower is set to "circ" instead of "auto"? Why does my stat have a heat setting, cool setting, em. heat setting, but no "auto setting" whereby the system automatically flips back and forth between heat or cool depending upon the temp (it shows up in the user's manual but not on the stat)? Etc., etc.
    The owner's manual can't tell you because it depends on how the installers and technicians have the system wired. If they can't tell you, well, all I can say is not to recommend them to your friends.

    In general, the logic in any multistage system is to use the lowest/slowest stage possible. If you are using a given stage steadily and you are losing ground, switch to the next higher/faster stage. The only exception is when there is a large difference between the commanded temperature and the current temperature (after a setback period, or if you change the setpoint by hand). Then systems will generally "hurry up" so they don't take forever to change the temperature. That is how your cooling will work, and how your heat would work if it were furnace-only.

    The dual fuel system adds some complexity. It's hard to pin down how exactly they set up your system, because the VisionPro can handle fuel selection on dual fuel systems... but there are also separate fossil fuel kits available that can do that, too, and they don't all work exactly the same. Generally, though, you would still expect to see the same sort of logic as I mentioned before; you use the lowest/slowest stage possible until it isn't sufficient to meet demand, or if there is a big change in setpoint that warrants "hurrying up". For comfort, the furnace should probably run during defrost cycles, though a few people will disagree because of concerns about hurting the compressor. If it does run during defrost, it should probably run on low. As it is, your system probably won't defrost again until November or December anyway.

    The circ setting has little effect on system operation overall. All it does is enforce logic at the thermostat that says that if the system has not run for X minutes out of the last hour, that the stat should switch the fan on for long enough to hit that prescribed threshhold, even in the absence of a call for heating or cooling. Otherwise it will act just the same as Auto fan mode. The Circ mode is just there to keep things from getting stagnant during seasons that don't require much heating or cooling.

    The system doesn't show Auto in the Heat/Cool/etc. modes because the techs didn't turn that option on in the installer menus.

  10. #23
    Join Date
    Feb 2006
    Posts
    103
    thorton, thank you for the moral support, and wyounger, thank you for all the information. I still say you should write the manuals. Since my last post I have gotten some previously missing answers. 1st there is apparently no fossil fuel kit installed because the Vision Pro doesn't need it. 2nd the stage one of the furnace is suppose to kick on and off during defrost to temper the air. 3rd, I don't think there is a plenum switch to protect the coil and apparently (reading between the lines) neither the tech nor Amana/Goodman think it is necessary.

    I think, but I'm not positive, that the system will automatically go from heat pump to furnace if the indoor temp is 4 degrees below the set temp. I'm not sure if it will go to the furnace if the heat pump is unable to meet the set temp for some pre-determined period of time. Perhaps you can venture a guess or can tell me if the Vision Pro allows for this possibility?

    I'm still suspect that there may be some confusion and redundancy between the stat delays and the heat pump delays. This is one area where the tech and I seem to be speaking a totally different language. I really don't understand what he is trying to tell me, except that he believes the system is set up correctly and there is no way to eliminate the redundancy if it exists.

    I've noticed that the stat sometimes indicates "heat on" under the stat's set temp, the blower is on, but the heat pump fan is not turning, and the air coming out of the vent seems to be recirculated air at best. I guess I need to actually go outside and listen to the compressor to see if it running without the fan. Certainly it couldn't be in defrost mode in these mild temperatures. I can not get the tech to explain to me why it would be blowing air before the heat pump turns on. Is this normal operation? One explanation he has for the feel of the air is that its recirculating air that is returned through floor ducts, because heat rises the returned air is a bit cooler than the air higher in the room. I understand that issue, but I still don't understand why the blower is even on, if the heat pump isn't on. Is this normal? Could I be wrong, and the heat pump compressor is on, but the heat pump fan is not? Could it be a redundant delay? If so, is it unavoidable or can it be corrected?

    My final question, is there a good reason for not turning on the stat option that automatically flips the system from heat to cool or vice versa, as the case may be?

  11. #24
    Join Date
    Apr 2005
    Location
    Kingston Ontario Canada
    Posts
    1,234
    Originally posted by georgiaguy
    thorton, thank you for the moral support, and wyounger, thank you for all the information. I still say you should write the manuals. Since my last post I have gotten some previously missing answers. 1st there is apparently no fossil fuel kit installed because the Vision Pro doesn't need it. 2nd the stage one of the furnace is suppose to kick on and off during defrost to temper the air. 3rd, I don't think there is a plenum switch to protect the coil and apparently (reading between the lines) neither the tech nor Amana/Goodman think it is necessary.

    I think, but I'm not positive, that the system will automatically go from heat pump to furnace if the indoor temp is 4 degrees below the set temp. I'm not sure if it will go to the furnace if the heat pump is unable to meet the set temp for some pre-determined period of time. Perhaps you can venture a guess or can tell me if the Vision Pro allows for this possibility?

    I'm still suspect that there may be some confusion and redundancy between the stat delays and the heat pump delays. This is one area where the tech and I seem to be speaking a totally different language. I really don't understand what he is trying to tell me, except that he believes the system is set up correctly and there is no way to eliminate the redundancy if it exists.

    I've noticed that the stat sometimes indicates "heat on" under the stat's set temp, the blower is on, but the heat pump fan is not turning, and the air coming out of the vent seems to be recirculated air at best. I guess I need to actually go outside and listen to the compressor to see if it running without the fan. Certainly it couldn't be in defrost mode in these mild temperatures. I can not get the tech to explain to me why it would be blowing air before the heat pump turns on. Is this normal operation? One explanation he has for the feel of the air is that its recirculating air that is returned through floor ducts, because heat rises the returned air is a bit cooler than the air higher in the room. I understand that issue, but I still don't understand why the blower is even on, if the heat pump isn't on. Is this normal? Could I be wrong, and the heat pump compressor is on, but the heat pump fan is not? Could it be a redundant delay? If so, is it unavoidable or can it be corrected?

    My final question, is there a good reason for not turning on the stat option that automatically flips the system from heat to cool or vice versa, as the case may be?
    Hi Georgiaguy! When my system goes into a defrost the "heat on" indicator is still showing on my thermidistat, for sure. I think that is the way it is suppose to do. On my system the fan does not quit, but speeds up because I have a setting for my strip heat to come on when the heat pump goes into a defrost mode. I'm not sure, but I would think that because your system is duel fuel and the installer has selected heat to come aux heat to come when defrost is called for, then this would be normal in your case, also. As far as selecting "auto" changeover from heat to cool, is, again, a personal preference. Myself, I keep mine set in "auto" for change between heat and cooling. However, when the temperature starts to change to a point that my heat pump might change from heating to cooling and then maybe back to heating, I shut the "auto" selection off. I don't want the heat pump heating and then cooling in the same day just to save some energy costs.

    Also in your last post you say that your system has to have a 4 degree drop before your furnace kicks in. I would think this is too much of a temp difference, personally, myself. Maybe the installing dealer choose this and you could complain to him that 4 degrees is too much and there could be a setting for more of a miner swing.

    Hope this helps,
    Thorton

  12. #25
    Join Date
    Mar 2004
    Posts
    1,042
    OK, now we've at least established that you don't have a separate fossil fuel kit.

    The VisionPro's dual fuel logic has a single switchover temp. Above that temperature, it's heat pump heating only, and below that temp, it's furnace heating only. I'm not aware of any override that comes into play when there's a large difference between the setpoint and actual temps.

    Here's another workable hypothesis on what it's doing as far as blowing air without running the compressor. They may have have have set the number of cycles per hour on the heat pump heating too high. If they had that set at 6, it could end a heat pump heating cycle and try to start again before the heat pump was willing. The VisionPro also has a cycle delay which prevents restarting the compressor too soon after it cycled off, but that's also configurable and may be off. (In general, the VisionPro has a LOT of configurability in the installer menus, which also gives the installer a lot of places to screw up.) If the cycle delay timer was off and the cycles per hour on the heat pump heating stages were set at something like 6, it might try to start the heat pump again shortly after the heat pump cycled off; in that case the stat would start the blower up again but the heat pump would refuse to start for a couple more minutes. For example, at 6 cycles per hour with the stat's internal delay turned off, it might want to run the heat pump for 8 minutes out of every 10. When it shuts off after the 8th minute, there's only two minutes before the stat would tell the heat pump to start again. The heat pump will refuse to start until it's been off for 4-5 minutes, though, so you would have 2-3 minutes of fan operation before the heat pump started up again. In practice, the redundant delays are probably better, because it will actually keep the stat and outdoor unit in better synch. They'll both be delaying at the same times. Also all compressor-driven stages (air conditioning or heat pump heating) should be driven at 3 cycles per hour.

    As for Auto changeover mode not being present, well, if you want it, there's no reason the contractor should hesitate to turn it on for you.

  13. #26
    Join Date
    Feb 2006
    Posts
    103
    thorton, it looks like my system can not switch between gas and electric based on demand, but only based on the balance point or a manual overide (i.e., flipping the stat to emergency heat). Seems odd to me, but given that the heat pump has two stages and the balance point is presently set at 40 degrees, it's hard to imagine that the heat pump couldn't keep up. I wonder what wyounger uses for a balance point. He is also in the Atlanta area.

    wyounger, I'll have to give some thought to your hypothesis. I know the tech changed the cycles but I'm not sure if he went from 3 to 6, or 6 to 3. In either event, yesterday morning I witnessed the same delay event (blower blowing, but compressor fan not turning). Moreover, I noticed that the stat said "Heat On". The Honeywell installation instructions (which I managed to download off the net) state:

    "The Thermostat has built-in compressor protection (minimum-off timer) that prevents the compressor from restarting too early after a shutdown. The minimum-off timer is activated after the compressor turns off. If there is a call during the minimum-off timer, the thermostat shows "Wait" in the display. When the minimum-off timer expires, "Cool On" or "Heat On" appears solidly in the display and the compressor and fan turn on."

    I've never seen the "Wait" display on the stat.

    I sent an email to Honeywell's customer service. Hopefully they will have an answer, but I'm not holding my breath.

    The installation instructions are much more informative than the owners' manual, but still could use your clarifications. For example, if the outside temp is below the balance point, the furnace will be used exclusively, but does the stat control whether it is firing in first stage or second stage, does the furnace control this function, or is the function simply lost all together?

    Is the answer different if the stat is in emergency mode?

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