Heat Pumps and Electric Heating - outside unit not starting

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tony6677
10-04-09, 12:02 PM
i have a miller heat pump system and when i call for heat or ac the outside unit does not start emergeny heat works fine. there is a button on the unit that will start unit manually

Mad39er
10-04-09, 03:22 PM
That button is a contactor. If it's not being sucked in, then something on the low voltage side of the system is not sending the requisite voltage through. You'll need a voltmeter if you want to investigate any farther without just changing parts blindly.
dun11
10-05-09, 06:33 AM
Sounds like a high pressure switch to me, if you push it in will it run for awhile ?

tony6677
10-07-09, 11:23 AM
That button is a contactor. If it's not being sucked in, then something on the low voltage side of the system is not sending the requisite voltage through. You'll need a voltmeter if you want to investigate any farther without just changing parts blindly.

i checked the low voltage side and got nothing and this is connected to a control board there is 24v supplied from thermostat to board
tony6677
10-07-09, 11:29 AM
Sounds like a high pressure switch to me, if you push it in will it run for awhile ?

if i push it in and hold it it will run as long as i hold it
Houston204
10-07-09, 12:27 PM
R to C should always have 24VAC , even with no demand.
Do you have 24 volts between Y and C with cooling demand?

http://i151.photobucket.com/albums/s160/Houston204/HeatPump.jpg


Color codes vary.
tony6677
10-07-09, 01:03 PM
R to C should always have 24VAC , even with no demand.
Do you have 24 volts between Y and C with cooling demand?

http://i151.photobucket.com/albums/s160/Houston204/HeatPump.jpg


Color codes vary.

yes but there is no low voltage to contact
Houston204
10-07-09, 03:22 PM
Sounds like a pressure switch lockout.
tony6677
10-07-09, 03:46 PM
do you have to replace control board to solve this?
Houston204
10-07-09, 04:25 PM
If it is a hi pressure switch lockout, it may be as simple as a cheap capacitor.

http://i151.photobucket.com/albums/s160/Houston204/Baddualcap.jpg


If it a low pressure switch, you probably have a leaking evaporator coil.

http://i151.photobucket.com/albums/s160/Houston204/Evaporatorcoil.jpg


The liquid line filter drier is the second most common leak and Much cheaper to replace.

http://i151.photobucket.com/albums/s160/Houston204/Liquid_Line_Filter_Drier.jpg


Oil can be an indication of a refrigerant leak. Soap and water in a spray bottle can help locate the leak for much less than the $90 per hour that a pro will charge you. You would still need them to repair and refill your system.
tony6677
10-09-09, 04:50 AM
the system has the correct charge would the defrost thermostat or outside thermostat have anything to do with it?
dun11
10-09-09, 05:23 AM
Post a pic of this "button" if its a contactor do you have 24v at the coil?
tony6677
10-10-09, 09:22 AM
there is no low voltage going to contact
Houston204
10-10-09, 09:27 PM
How do you know it has the correct charge if it isn't running?

I would trace the 24 volt circuit between the Y terminal and your contactor. Where does control voltage stop?
Yes it could be your defrost timer, but I recommend verifying this before replacing your timer. Pictures can be posted on this site using Photobucket. Someone here may be able to offer greater assistance with a few pics.

Reset buttons can be located on the pressure switch in the unit or outside of the unit near the refrigerant lines.


I'm confident that you a pushing a contactor but here is a pic...
http://i151.photobucket.com/albums/s160/Houston204/Contactor.jpg