prestige iaq not starting aux heat


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Old 11-05-16, 07:19 AM
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prestige iaq not starting aux heat

I have a honeywell prestige thermostat with a eqpt interface modual. I have a unico heat pump with a boiler aux heat. when the heat pump fails (or I simulate a failure by powering the outside unit off) the thermostat will just stay status- heat on IE it will stay (lndefinetly) calling for heat pump and does not start the aux heat. I have the installer option set to ' do not let aux heat run with heat pump. and the temp differtial set to 2 degrees. I would expect after trying the heat pump for a short time with no heat increase the aux heat will kick in. it just stay on 'Heat on'
 
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Old 11-05-16, 07:51 AM
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Welcome to the forums.

My forum partner, Houston, knows more about that system than I do.

I wouldn't expect the system to default to aux heat until the differential is exceeded.

do not let aux heat run with heat pump
That might tell me that the aux heat will not run period.
What you need is the heatpump to lockout and then the boiler runs.

Has this system ever worked like you want it to ?
 
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Old 11-05-16, 08:29 AM
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>>That might tell me that the aux heat will not run perio

Thanks for the reply. I have seen a few of Houstons posts and he does seem very knowlagable on the prestige. Hopefully he can chime in on this one. I can set the mode to emergency heat and the aux heat will work as expected.
That might tell me that the aux heat will not run period.
What you need is the heatpump to lockout and then the boiler runs.

>>Has this system ever worked like you want it to ?

all exept this issue


>>What you need is the heatpump to lockout and then the boiler runs.

I see no way the thermostat could tell if the heat pump is locked out exept that the temp is not increasing.

>>I wouldn't expect the system to default to aux heat until the differential is exceeded.

correct. I am manually setting temp to max (75 deg) so the temp diff is at least 8 deg.

According to the help info when the temp diff set to 2 deg. Then the aux heat will only be used based on system preformance, load conditions, and how many degrees the temp set point is changed.

The only sensors hooked up to the thermostat are the delta T alerts. Would it be using that information to decide on "system prefonmanc" and if so why after 30 min of "heat on" with no temp increase would it not start the aux heat?
 
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Old 11-05-16, 08:34 AM
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>>That might tell me that the aux heat will not run period

The Aux heat will work as expected in 'emegency heat' mode
 
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Old 11-05-16, 08:57 AM
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Just thinking out loud.... you may have to set the heat pump up with a dual fuel switch setup so that the boiler can't be run when the heat pump is actually running.

With most stats when the temp is two or more degrees under the set temp the aux heat AND the heat pump run together to catch up. You've told the aux heat not to run.
 
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Old 11-05-16, 11:44 AM
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Update.. Setting the thermostat to 'allow heat pump to run with aux heat' will allow the aux heat to come on in a short time after sutting off the power to the outside unit. However... Now there is always power to y1 (heat pump) and to the aux heat, so the fan in the air handler is not allowed to turn on becouse the coil for the heat pump is cold.

I assume to fix this I need to route the yellow Y1 through a relay that shuts the power to Y1 off while the aux heat is on.

does that sound correct?
 
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Old 11-05-16, 12:27 PM
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You're on the right track. That's basically how a dual fuel switch would work.
 
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Old 11-06-16, 06:27 AM
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Thanks for the info.. I know I can rewire this to work as like. I would like to figure out the original issue. Why the thermostat will never start aux heat with the setttings I described. The info from the t-stat is a bit fague.
" aux heat will only be used based on system preformance, load conditions, and how many degrees the temp set point is changed"

I do not know where it gets data for "system preformance, load conditions, " as the only sensors it has are the "delta T alerts" There is no real comunication from t-stat to ait handler.

I have tested this for 3 hrs and the t-stat will remain on 'heat on' and never start the aux heat. If this feature worked from my very expensive t-stat I would not have to re-wire the unit.
 
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Old 11-06-16, 09:05 AM
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When you configure the Honeywell for dual fuel operation it will lock out Aux heat when the heat pump runs.

Most dual fuel systems have a gas furnace and a heat pump. Running a gas furnace and heat pump simultaneously would result in very high head pressure.

When an outdoor sensor is added to this control you can configure the control to lockout the heat pump below certain temperatures. The Aux heat can be set to lockout above a settable temperature.

If the heat pump fails set the stat for emergency heat.
 
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Old 11-06-16, 10:17 AM
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Thanks for the reply...

>>When you configure the Honeywell for dual fuel operation it will lock out Aux heat when the heat pump runs.

That seems to be a option. There Is a setting that says 'allow heat pump to run with aux heat' or 'do not allow'

Most dual fuel systems have a gas furnace and a heat pump. Running a gas furnace and heat pump simultaneously would result in very high head pressure.

What Would you suggest if I have a hot water coil as aux heat? I would Think I would want both to run if heat pump is not keeping up?


When an outdoor sensor is added to this control you can configure the control to lockout the heat pump below certain temperatures. The Aux heat can be set to lockout above a settable temperature.

I have 3 of these T-stats with 3 separate air handlers. The unico air handlers have a option to lock out heat pump as well (need to install a jumper on j-5). If possible I would like to use that instead of buying 3 outdoor sensors for the t_stats. This is where I do not have enough information. It appears this option might only be available if I am using the unico wireless remote thermostat. but I have not been able to confirm this with any body I have spoke to so far. here is my unit.

https://tech.unicosystem.com/downloa...nline/187/260/


>>If the heat pump fails set the stat for emergency heat.

That Is one of the issues giving me problems. If my heat pump fails I would want the aux heat to kick in on its own, In case I am away. So far I have not been able to get this to work with just the T-stat settings. The main issue seems to be that when the T-stat calls for aux heat it is still calling for the heat pump and the fan will not be allowed to run because the heat pump coil is cold.

Thanks again for the help...
 
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Old 11-06-16, 12:33 PM
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A single redlink wireless outdoor air sensor can be paired to multiple thermostats.
 
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Old 11-06-16, 02:46 PM
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>>A single redlink wireless outdoor air sensor can be paired to multiple thermostats.

Ahh, Good to know. Thanks....

Do You think it is worth while to try to get both the heat pump and the hot water running at the same time, when it is above 32 and the heat pump is not keeping up. or will it not make much of a difference? I have had a few different opinions on this one?
 
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Old 11-06-16, 03:11 PM
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I would run the hot water heat as aux heat but it is unlikely that it would help in defrost mode.

Just to clarify, have you been able to get the hot water heat to function as stage two heat (along with the heat pump)?
 
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Old 11-07-16, 02:04 AM
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Just to clarify, have you been able to get the hot water heat to function as stage two heat (along with the heat pump)?

The original installers did not have it set up like that. It is set for 1 stage of heat and 1 stage of aux heat. I can set it up like that, I was just not sure what the exact proper set up would be(I am convinced the original installers do not know what the correct set up should be eithier, they did not even have the boiler 32 deg lock out set). I live in mass.

There is also a venmar system tied into the air handler. This is on its own control and is set to run the fan of the air handler whenever it is running. Currently I have it set for the factory program scedual. something like runs on low for morning and eavening then every 20 min the rest of the times. The house was just built under the current streach code (very tight insulation)
 
 

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