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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22385
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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The emergency heat light is blinking on my thermostat when

Customer Question

The emergency heat light is blinking on my thermostat when it is in the cooling mode (heat pump)and the outside compressor unit shuts down while the inside fan blower keeps going. The manual for the system (Coleman Evcon 98 vintage) indicates that this light will blink if the safety lock out device opens because of either the high temperature switch or the high pressure switch opening. The tech who looked at it seemed to think that the problem is with the thermostat. The freon was within the normal operating parameters. I am leaning towards the safety lock-out device (whatever that looks like) being bad. What is your opinion?
Submitted: 1 year ago.
Category: HVAC
Expert:  BillyHvac replied 1 year ago.
The emergency heat code is for when you are heating and the heat pump fails or locks out because it cant keep up.
If this is happening in COOL mode then you have an issue with the thermostat.
The thermostat code is different than the furnace code. Basically the thermostat is thinking it is in heat and the heat pump couldnt keep up.
Looks like you will need to replace the thermostat
Customer: replied 1 year ago.
I agree with your logic, but the manual does say something different: "Safety Lock-out: This device opens the circuit to the compressor contactor, stopping the compressor in response to either the High Pressure or High Temperature limit switches opening. The compressor will remain off, even though the limits close and will start up only when the Lock-out is reset. The Lock-out also illuminates the Emergency Heat Indicator. To reset the Lock-out, turn the indoor thermostat's System to "OFF" momentarily then, back to the selected mode. The system will start up after the 5 minute delay period is complete..." This is exactly what I have to do to get it back into the cool mode. However, it cycles this way maybe several times in maybe in a two hour period. So I have to constantly watch to see if the light comes on. Whenever it does, the outside unit is completely off, but the inside blower fan is still going. Nothing is coming out of the floor vents except recycle indoor air of whatever the room temperature is.
Expert:  BillyHvac replied 1 year ago.
OK...If the unit were in high pressure lockout...
either the outdoor coil would be plugged
the fan in top would not be working
it would be in a very hot spot during a portion of the day...and have a dirty coil
So it is something you would have to give input on..
when this occurs is at the same time of it over 100f at condenser?
Is the outdoor coil coated or plugged?
Is the outdoor fan running reliably?
Customer: replied 1 year ago.
We have had some rather hot days as of late in the lower 100 degree range, but the outside portion of the unit is in the shade after 10:00 am for the rest of the day. When it is running, everything seems fine. Got lots of cool air coming out of the floor registers and the house cools down well. The manual indicated that this Emergency Heat Light will turn on if there is not proper maintenance. Further into the manual it indicated, "If the emergency heat indicator light turns on with the system switch in the HEAT or COOL position, then the following maintenance problems could be the cause." It goes on to list a bunch of stuff regarding block ducts, dirty blower wheel, indoor and outdoor coils, dirty filter, registers not opened or blocked. I have checked all of this and cleaned everything up and the issue is the same. The outdoor fan is running good until the emergency heat light comes on at the thermostat. As soon as the emergency heat light comes on, the outside fan and compressor shut down.
Customer: replied 1 year ago.
I did not hear back regarding my last reply above regarding your questions above that. Please respond. Thanks.
Customer: replied 1 year ago.
Still waiting!
Customer: replied 1 year ago.
I went ahead and replaced the thermostat and the problem is still the same.
Customer: replied 1 year ago.
I fixed it myself. Turns out the compressor fan was not turning fast enough to get the proper flow of air through the coils. Thus, it was tripping either the high pressure or high temperature limit switch. I had my wife turn it off and on a couple of time from inside the house via the thermostat and I noticed how the fan started up really slow and the volume air didn't seem to be what I used to remember it was. It would maybe cycle three or four times before the limit switch would cut the power to the compressor and compressor fan. So I replaced the motor myself (not hard to do) and went ahead and replaced the associated capacitors just in case they were problematic too (only a little over $30 for them so worth it). Everything is working fine now and I got a new thermostat in the process which I really didn't need, but that was only another $30 too on-line.