McQuay Water Source Heat Pump Unit - Blower not working

[MeestahBig]

I have 4 of these McQuay units and two of them are having this exact same issue. Firstly the units are 10 years old. These are heat and a/c units in one. Model is WWLL and has been updated since here are some details about these units. http://www.mcquay.com/mcquaybiz/lite.../C_1140-11.pdf I have a basic setup. No external thremostat or anything extra. Just on/off swith and a high/low switch.

Here is the deal. The unit may run fine for hours, but eventually the fan blower will stop and the compressor will keep running. Then the unit will shut down with a high pressure fault. I checked voltage to the fan motor and that seems okay.

Both of the broken units are intermittant. Im stumped.

thanks!

[RegUS_PatOff]

[user=26845]MeestahBig[/user] wrote:

... eventually the fan blower will stop ...

... voltage to the fan motor and that seems okay...

If the Fan is getting OK voltage and it's not working ... it's bad

If you then remove power, can you turn the Fan?

Is it hot ?

[MeestahBig]

Hi, yes it seems like the fan is getting voltage. and yes the motor does get hot. wouldn't you expect it to get somehwat hot? or no? also what about the run capacitor. seems weird that two of my units would have the same exact issue at the same point in time.

another thing that seems odd to me was there is a red wire and black wire that comes off the hi/low switch and goes to the motor leads. It seems that BOTH of these wires have approx 110 voltage in them. I would think the hi/low switch would shut one of them off. I ohmed out the motor and that seemed fine. I noted more resistance for the red wire (low setting).

 

hmph

[RegUS_PatOff]

[user=26845]MeestahBig[/user] wrote:

... there is a red wire and black wire that comes off the hi/low switch and goes to the motor leads. It seems that BOTH of these wires have approx 110 voltage in them. I would think the hi/low switch would shut one of them off. I ohmed out the motor and that seemed fine. I noted more resistance for the red wire (low setting)...

I don't have a wiring diagram for that model, but if the Motor's Neutral was open,

(either internal or external) then you would measure the same voltage at the HI and Low Terminals...

but then the resistance tests wouldn't read.

Do you have a wiring diagram/installation you could post, or a link ?

model number ?

[ACtechGUY]

The reason you are seeing 110 volts on both the hi and low is because the voltage is feeding back thru the motor. You must disconnect the motor and take reading at the switch to the neutral wire.

That being said , it is very unlikely that the motor is receiving 110 on both the hi and low. If it were, then the motor would burn out shortly.

I would look real hard at the capacitors. They only last a short time. It is very possible you have 2 bad capacitors.

Fan motors WILL start and run with bad capacitors. They will run hot and shut down on internal Thermal protection.

[MeestahBig]

solved - I figured out how to test the motor properly to see if voltage was coming off the tabs on the ciruit board. voltage coming out was intermittant... I took the board off and poked around pressing on the relays (the black boxes) sure enough on both of my units the solder joints were cold for that relay. resolder and as good as new.

thx, Max