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[HVAC] Honeywell VisionPro IAQRecently moved to a house (R2000 construction in Peterborough area) that is heated by electricity - heatpump with aux electric heater. It has a nice Honeywell IAQ system but I am unable to determine how to control when the aux heat is activated. My primary concern is cost not comfort so I would rather the heat pump supply as much of the heat as possible. Currently, aux heat is coming on frequently even when the setpoint is within 2C or less of the actual temperature. (setpoint = 20, temp =18, outside = 1) I do not see any option without an outdoor sensor to set this. Any ideas? |
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If you're concerned about the aux strips drawing too much "hydro" as you Canooks call it -- you need to adjust IAQ setting #360 Aux heat lockout » ths.gardenweb.com/discus ··· aux-heat |
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That would work for someone who likes a cold house. No way will a heatpump keep up when the outside temps are very low. |
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2 recommendations |
Jack the OP suggested "My primary concern is cost not comfort" so I provided advice on how to save cost over comfort. |
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I don't think the OP understands that. I assure you he will be uncomfortable. Personally I will be comfortable regardless of the cost. I worked too hard in my working years to freeze in my retirement. We keep the thermostat set at a fixed 73 degrees 24/7. |
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lutful... of ideas Premium Member join:2005-06-16 Ottawa, ON |
to ramsaymike
Auxiliary heat, when enabled, will be called when thermostat wants to warm up the home very quickly from a lower temp setting.
For example: a) Just one program, optimized for evening: The aux heater may be called as needed during very cold days, otherwise heat pump will try to maintain the programmed temp.
b) Just two programs, one for late night: the aux heater may also be called on less cold days, at the start of the morning program.
If you want several programs, try using a small temp difference when warming up the home. |
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to OldCableGuy
This was my first thought but the manual says that a outdoor sensor is needed (Only shown for heat pump applications with an outdoor temperature sensor present.) Note that I have not checked the thermostat. I will check next time.... Thanks. |
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ramsaymike |
to Jack in VA
I think I understand the cost versus comfort situation. We spend most of the winter in the south so comfort is not an issue for the coldest part of the winter. Electricity is very expensive here and with time of use rates a little control can save money. It is really a case of understanding how it works especially after heating with natural gas! |
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walta join:2001-05-22 Saint Louis, MO |
to ramsaymike
This thermostat is very near the top of the Honeywell line the only reason get this model is if it is controlling more than just the heat pump. It likely controls a humidifier and or heat recovery ventilator. I think you are crippling the system if you do not have the remote sensors. You will be much happier if you add the outdoor sensor. It gives your system much better data on how it should operate your systems. The best feature of this thermostat is the remote indoor sensor. Consider installing the indoor sensor in a room you spend the most time. This link is to the installers manual. » site.theenergyconscious. ··· stem.pdfBe very careful there are hundreds of adjustable settings. If you are willing to tolerate greater deviation from the set point rewire and program the system for 3 heat stages. Strip heat on stage #3, no connection on stage #2 and heat pump on #1 Also reducing the number of cycles per hour will increase the deviation from set point before the system runs. In my opinion this thermostat was designed to provide the highest level of comfort without regard to fuel cost. You may be able to force it to do what you want but this thermostat will fight you every step of the way. Walta |
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mackey Premium Member join:2007-08-20 |
to ramsaymike
There are 2 ways the aux heat can come on with heat pumps: 1) thermostat 2) defrost cycle. The first thing you need to do is figure out which one is triggering it.
I know someone in Pennsylvania who decided he would rather have cold air for a few minutes instead of using the aux heat and had his installer disconnect the defrost cycle signal wire. |
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to walta
You are correct walta, it does control the HRV as well. This is a very tight house (R2000 standard) and I really have not figured out how everything is interconnected. I think the outdoor sensor is a good idea - it looks to be something that it easy to add. My real challenge is how to minimize cost when the house is empty over the winter. I was thinking about adding a wifi thermostat but will need to reconsider as I see this thing (IAQ) is not quite your average run of the mill unit. Thanks for the input.
Thanks mackey - I am new to heat pumps and am working on how the defrost works. I have a temperature recording system and will be instrumenting the entire heating system in an attempt to understand it better. |
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to ramsaymike
I would install the outside sensor and set the heat strips to only come-on if the OAT is below Xdeg, forcing the heat pump for the temps it can handle.
But I would also set the t-stat very low in the winter, and drain all water/blow-out the pipes so I don't need to worry about a failure and frozen/broken water pipes.
HW's WiFi thermostats are crazy-cool for keeping track of your winterized house from your smartphone; just last month I did actually have a blower failure at my Up North cabin, and noticed it with the WiFi t-stat which I check every day. Got it fixed right before the temps plunged below 0F the following day. |
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cowboyro
Premium Member
2015-Apr-6 10:27 am
Locking out the aux is a really bad idea especially if the unit isn't properly sized (or as some would say grossly oversized). It will never be able to recover from a setback in very cold weather. |
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lutful... of ideas Premium Member join:2005-06-16 Ottawa, ON |
to ramsaymike
said by ramsaymike:My real challenge is how to minimize cost when the house is empty over the winter. But that is very easy! Create a single program within 7C to 10C range, just enough to keep pipes from freezing. |
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said by lutful:Create a single program within 7C to 10C range When you say single program do you mean a permanent hold? Another wrinkle is that we have time of use rates so I would always prefer to heat during night and let it coast during the day when rates are double. |
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TexDave's not here Premium Member join:2012-10-20 |
to ramsaymike
If you're really set on disabling the auxiliary/emergency electric heat strips, just remove and tape off the line voltage wires feeding the heating elements. Kill the hydro (power) first. |
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lutful... of ideas Premium Member join:2005-06-16 Ottawa, ON |
to ramsaymike
said by ramsaymike:said by lutful:Create a single program within 7C to 10C range When you say single program do you mean a permanent hold? Yes. said by ramsaymike:Another wrinkle is that we have time of use rates so I would always prefer to heat during night and let it coast during the day when rates are double. The aux heater will probably be called every night, because you want the home to warm up to some high temp setting. You have to do some costing to see if single low temperature setting is better for your location. |
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walta join:2001-05-22 Saint Louis, MO |
to ramsaymike
If this building is to be unoccupied most of the winter. And the goal is to reduce the use of the strip heat.
Think about having a pro install an away switch.
When in the away mode the strip heat would be controlled by a second WIFI thermostat set for 40° and the VisionPro running the heat pump trying to maintain a setting at 50°
When in home mode the VisionPro controls everything.
Walta |
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Thanks to all for the ideas and discussion.
My goal is to optimize system costs at all times but especially when we are away for the 5-6 months in the winter. I will be adding an outdoor sensor and working on IAQ options - the AUX lockout (360) seems to be what I need. Internet connected control would be nice to work with the system remotely but that looks to be very expensive to add to the IAQ - I will just have to wait until we get home and see how things worked out.... |
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pende_tim Premium Member join:2004-01-04 Selbyville, DE |
If you poke around in the installer menu, there is a setting that controls the temperature drop VS setpoint for the strip heaters.
IIRC this option is enabled if the heating is set to 'economy" (rather than comfort). Once set to economy, a sebmenu should come up asking for a temperature differential. Set this to 3 degrees or so and the strip heaters will not engage unless the room temp drops 3 degrees below the setpoint. At this point the heatpump is being maxed out and can not provide the BTUs to keep the house at setpoint.
Also to maximize savings look at defrost timer which may be a dip switch on the outside unit - unless the unit has some type of automated defrost demand sensor. Depending on the location, this can be set to 60 or 90 minutes. A local HVAC company probably can provide advice on the interval if you chat them up.
When I am away I keep my house at 50* which seems to be a good setting for me.
Obviously, turn off the water supply to the house and open faucets (and hose bibs outside) and leave open. This will help pipes drain so if there is a long term power failure, the damage will be reduced. |
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OK - how about this... As I am just interested in locking out AUX and don't really care about outdoor temperature, can I just put an appropriately sized resister in place of the sensor? So I put in a 50k or so (equivalent to~ -14C or 6F) and just let it lockout AUX above this temperature. Possible? |
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ramsaymike |
said by ramsaymike:can I just put an appropriately sized resister in place of the sensor? Any feedback on this???? |
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pende_tim Premium Member join:2004-01-04 Selbyville, DE
1 recommendation |
While that probably would work as you intended, consider the "Oh Shits" associated with this. 1. What if the outside temp drops dramatically and you need the aux heat to maintain temperature in the house. No matter how much of a deviation from the setpoint the house experiences, the aux heat will never come on. It is possible you could freeze some pipes.
2. What if there is a system failure on the heat pump? Unless you have a thermostat that communicates with the outdoor unit, you also may risk freezeups.
As I mentioned before, Have you looked in the IAQ menu and tried to find a way to give the aux heat a large differential from setpoint? This way the aux heat would only come on when the unit could not maintain setpoint or you commanded and temperature jump greater that the differential. |
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walta join:2001-05-22 Saint Louis, MO |
to ramsaymike
You are thinking about it backwards. When the system see the outdoor temp drop to low the system will lock out stage 1 heat and run only 2 and 3 that is opposite of your goal as the heat pump is stage 1.
Also the system uses outdoor temp for other functions I can think of 2. When it gets colder outdoors the system lowers the indoor humidly. With this system if you program 70°at 8:00AM the system will vary the start time to achieve that goal and outdoor temp is a variable.
Walt |
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Thanks but I have discarded this idea. I see now that with a fixed outdoor temp and a lockout temp set above it, AUX will NEVER come on no matter how cold it is actually outside. I think the outdoor sensor is a much better idea... |
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ramsaymike |
to pende_tim
said by pende_tim:tried to find a way to give the aux heat a large differential from setpoint The only control I see is changing the cycles per hour - not sure that would have the desired effect. I decided to go with a real outdoor sensor - seems like a safer option. |
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pende_tim Premium Member join:2004-01-04 Selbyville, DE 2 edits |
to walta
said by walta:When the system see the outdoor temp drop to low the system will lock out stage 1 heat and run only 2 and 3 that is opposite of your goal as the heat pump is stage 1. ramsaymike: As for the Backup Heat Differentials, In the installer Menu, #301 needs to be set to advanced. This unlocks a bunch of other settings. The one I was referring to was 308 "Backup Heat Droop". This determines how much the indoor temp needs to be below the setpoint before the aux heat comes on. Turn off comfort and it can be set from 2-15*F below room setpoint. However an OAT is really the proper way to go. walta: This thermostat may function as you describe however all the Honeywells I have used will only cycle into stage 2 heatpump if stage 1 can not satisfy. The OAT will lockout stage 3 (strip heaters ) if OAT is above the balance point. There is another setting called "Compressor lockout" that will shut down the compressor below a certain temperature. These two values can be set in the Installer Menu 312: "Outdoor Lockout-Backup Heat" and "Outdoor Lockout HeatPump" So lets say Balance point is 25* F and Compressor lockout is 5F*, then: Above 25*F Only Heatpump stage 1 and 2 can run, Aux heat will not engage to help meet temperature setpoint. Between 24* and 5* Heatpump stage 1 and 2 + Aux heat ( stage 3 ) can run as needed. Below 5* Only Aux heat will run. The only time strip heat will come on above 25* is during defrost cycle. The real prize to help save energy is to optimize the defrost cycle. A local shop could tell you what works for the area as timing is dependent on humidity and air temperature. Obviously the above temperature settings are examples and may not be best for your construction. If you have a manual look towards the back, around page 75 or so for the chart and text describing operation. |
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pende_tim |
to ramsaymike
Here is a page from installers manual showing the lockout bands |
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to pende_tim
Thanks for the feedback but it seems we are looking at different manuals. I have no 301 and compressor and AUX lockouts are 350 and 360. I think I understand how it works now. I agree with you about the defrost cycle - I need to learn more about it... |
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