Gas furnace running with heat pump on cool

ssanderson87

Hello all. I have searched and searched to no avail to find an issue to this problem. I have a 3 ton Armstrong heat pump with propane aux heat, the whole system was installed new in 2017 . Last winter was cold so we were running off propane for a while, and my condensate drain ended up freezing and flooding my ceiling (system is in the attic). Fast forward a few months to spring and switch the thermostat over to auto, and my cool cycle was blowing extra hot air. Come to find out my gas furnace was running at the same time as my cool cycle on the heat pump. Did some quick diagnostics and found that aux heat also called for main cool. I used jumpers and connected R to Y,G and O at the same time to see how it reacts and it worked fine. I’ve been running the system all summer without a hitch by manually shutting off the gas valve to the furnace. Does anyone have any ideas how to resolve this issue? Is it wiring? Control board? Thank you in advance!

pedmec

You need model numbers of all the equipment plus the thermostat for members to help you.

ssanderson87

A96US2V045B12S-02 (gas furnace)
4SHP15LE136P-50 (heat pump) coil matched to H/P, model unknown at this time. 

Ecobee4 thermostat

I failed to mention in original post that I purchased a new thermostat and the symptoms did not change. 

EdTheHeaterMan

@109A_5 will tell ya, "you have Short somewhere," but that is his go to answer.

There is some wiring problem that will take an expert control wiring technician. Not every HVAC contractor has a person like that. Have you used the Find A Contractor link at the top of the page?

EdTheHeaterMan

If you are going to DIY this then look at the wiring that connects the thermostat to the air handler/furnace. Then look at the low voltage wire that connects the air handler/furnace to the outdoor unit. see if there is any of the insulation chafed where the circuit might be unintentionally completed.

Also, think back to the time when you did not have this problem... Then try to remember what happened just before the problem presented (was it last summer or last fall, or the summer before that?) If you can remember that, then look at that occurrence for a clue.

For example: When was the first Ecobee4 thermostat installed?

EdTheHeaterMan

By looking at the manual and wiring diagram for the furnace, there is the possibility of using a communicating thermostat. These thermostats do not have regular contacts that use that standard "analogue" wiring protocol. They use a three or four wire connection. two of the wires are to power up the thermostat and the other one or two wires send digital signals based on the input from the thermostat. There is no fan switch or cooling switch or heating switch like the Ecobee wiring design. That said, if the original thermostat was communicating and someone installed The Ecobee on the "Non Communicating" terminals (which is perfectly fine) without telling the control board (by way of some programing options) then the furnace control board may be operating on incorrect assumptions about what the Ecobee is telling it.

Someone needs to read the manual about 6 times to understand how to do this correctly. Even then the correct settings may not be easy to determine. There are jumpers that need to be cut and at least one DIP switch that needs to be set if you are using a duel fuel setup. (Duel Fuel is Heat Pump and Gas Furnace) I believe from you post that is what you have going on. The Ecobee may or may not be compatible with that set up.

ssanderson87

The ecobee was the original thermostat installed with the system. I purchased a new one earlier this year and replaced it, and when it did not work I returned the new one and reinstalled the original. I had also thought a wiring issue. I had considered purchasing all new wire and rerunning from the furnace to the h/p and to the thermostat to eliminate that as a cause. Just wanted to see if there was something else I should be looking for before wasting my time. 

HVACNUT

Was everything working properly prior to last winter?

EBEBRATT-Ed

Someone needs to sit down, get the wiring drawings for the heat pump, air handler and gas furnace and thermostat and make sure everything is compatible and figure out how to make things work.

ssanderson87

everything was working properly prior to last winter. I have checked all the wiring at the ends (heat pump, furnace and thermostat) and all is good. I have the original manuals for all the equipment, I just don’t know if that’s the direction I should be looking. With the electrical tests I’ve run connecting R to Y,G and O at the same time, everything worked fine which sort of eliminates an electrical short through the wires in my mind. 

HVACNUT

You mentioned that jumping R,Y,G,O got it working but you shut off the gas valve. Was the furnace still trying to ignite that way?
W on the furnace is connected to what? W on the thermostat? Nothing else?

ssanderson87

I’m sorry, I wasn’t clear. When connecting the R,Y,G,O, the gas was on. I wanted to rest if the gas would ignite when jumping the h/p system 

EdTheHeaterMan

@ssanderson87 On any normal gas furnace. when R on the furnace control is connected to W on the furnace control, the gas furnace will start The trial for ignition cycle and eventually operate the main burner. So... When you connect R, Y, G, and O on the thermostat, test to see if W on the furnace is getting power between W and C on the furnace control.

EdTheHeaterMan

@ssanderson87 I'm still checking and reading the I/O manual for each item, so there may be edits in the future. Look at each piece of equipment to see if you are wired this way. Remember Electric is colorblind so don't go by the colors. Just go by the letters on each part (Furnace. thermostat , Heat Pump) to see if they are correct R to Rc to R. G to G. Y1 yo Y1 to Y1... etc.

EdTheHeaterMan

@ssanderson87 Your Ecobee4 needs to be configured for dual fuel use. I'm not sure how to do that. It is programmed at the thermostat selecting 2 stage Gas Furnace and 1 stage Heat pump. The W2 may or may not be needed based on if using defrost tempering kit 67M41 from the heat pump manufacturer. As shown here connected between W1 Furnace and W1 Heat Pump

If you have that Accessory from the Heat Pump manufacturer, then select 1 stage furnace on the Ecobee4 and do not use W2 at the thermostat or the furnace

Also check to see if the Jumper on the control board has been cut as indicated here. That lets the Furnace and the Heat Pump know that the Heat pump should not operate when the gas is being used. BUT You must also tell the thermostat that the heat pump should not operate when the fas burner is operating.. That is done in the Ecobee equipment setup menu. I can't help you there. You need to be at the thermostat to do that.

ssanderson87

hey hey all, sorry for the long time since my last response. Had to take a last minute trip out of the country for work. Got back up to the furnace today and replaced the 7 strand wire from the thermostat to the furnace in the attic and everything seems to be working as it should now! Since none of the thermostat setting have been changed the only thing I could think of is possibly a damaged wire during service at some point. As for now, all seems to be good, so keep my fingers crossed it stays that way! Thank you all again for all your help and advice!