DNT1
07-24-05, 05:31 AM
Hey guys I have fairly good knowledge of the refrigerant side of the systems and my EPA card but electrical is not my strong point. I have a approx 8 year old Miller 4 ton heat pump the contactor will not pull in, the unit works when the contactor is pushed in by hand. I checked the voltage at the contactor and have 18 volts I checked the voltage at the transformer leads it looks like I have 4 leads two have 110 volts I assume incoming voltage and on the other two I have one that has 18 volts and one that has 5 volts. The model number/wiring schematic and any other info are unavaliable due to adverse enviromental problems in the installation area (the creek apparently covers the unit about every three or four years LOL) I am assuming that the transformer is bad so I am planning on replacing it my question is how can I get this unit back in operation temporarily untill the correct parts have been ordered (100 degress and high humidity) My thought was that the lead off the transformer with 5 volts probably feeds the defrost board (some electronics requires 5 volts?) and that the 18 volt side is for the thermostat to contactor which should be 24v. Can I just purchase a cheapo 110 volt to 24 volt transformer and wire it in. I do not have a account with a Miller supplier in my area and it may take me a few days to get the correct replacement part. I am assuming that if I jumper from a 110 volt source to the new transformer that I can just feed the 24 volt power back into the lead where I am reading 18 volt on the existing transformer which should be feeding the thermostat would should rthen send 24 volts to the contactor and pull that puppy in. Note: I have several years of experience with the refrigerant side and about 26 yrs with the ductwork side I have a real nice Fluke multimeter/Fluke Amp probe and wiring kits other fun stuff, just limited in my control knowledge any pointers would be appreciated. Oh by the way I know that I could just tape the contactor closed but would rather have it working correctly as it may be several days before I can get the parts and we do want to freeze the coil on the silly thing and risk compressor damage.