Carrier 50HJQ012-6

[BobbyBJr]

Hello,
We installed a Carrier 50HJQ012-6 in December and from day one this unit has locked out because of cycling on head pressure in defrost. It cycles whether there is ice on the coil or not. Our local Carrier tech support has said the defrost termination switch should open at 65 degrees instead of the 80 degrees that came on the unit, but he can't supply a switch. Has anyone else experienced problems with this particular model?

thanks,
Bobby

[klrogers]

Check out this post: http://hvac-talk.com/vbb/showthread.php?t=453322

Kevin

[dandyme]

just spent 2 quality days cleaning an 016

the defrost sensor looked like the sensor you would see on freezer, it was a 3-wire sensor...............it just struck me as odd

don't know if that was original or not




the only other 50HJQ was a giant POS

[BobbyBJr]

Thanks for the link. We did check to make sure the term switches were on the correct coil and have them in the proper location as best we can tell. I haven't been able to get a definitive answer as to where they are supposed to be located. I haven't been able to find a diagram of the location in the IOM we have for the unit. Our local Carrier folks haven't been able to supply one either. The defrost is set for a 30 minute defrost, which I don't like, but setting it any higher allows too much frost to build up. I have seen the unit initiate a defrost cycle with lots of frost build up and cycle off on head pressure before removing half of the frost. We've checked and rechecked the charge and the air flow and am at wits end as to what is going on with this unit. Our Carrier distributor tells us that they have been some problems with this particular model, but so far hasn't offered any real solutions.

thanks

[buford]

i have got 2 of these same units that had the defrost switch mounted before the metering device on the od coils. also the wiring to the dft and the unloader was swapped in the comp term cover.these units were made the same day. fixed these problems back in dec during a cold spell here.at same time noticed that the dis pressure right before dft,s opened, got to 300 to 310 lbs but both ran fine until last week. went back on no heat from both units and found both rev valves would hang up in cooling when defrost was over.forced into defrost 3 times on each unit and same results.if i tapped on pilot valves, both valves would finally shift over. just finished changing out both valves this week.was told these units mod #50hjq014521qa have not have any reported problems.any one else seen this on these units. ser#s of 3109.

[chshin]

have problem with this Carrier HJQ012 unit blowing cold air in the morning and evrymorning, today I stop by check on the Voltage on the board on the RTU. It has 24 volt on the w1,w2,y2,G, 15 volts on y1 on the terminal board itself, and at the thermostat the fan continously run even after set on OFF mode. start normal after reset by breaker off and on.
Why!

[cb975]

i often run into an issue with commercial h-p units where the thermostat is configured incorrectly and the cooling runs continuosly. the unit is a heat-pump but does NOT use a heat pump stat. the stat should operate as a standard 2-stage heat-cool stat. that means cooling mode will energize y1, y2 and g only and heating mode will energize w1 for heat-pump and fan operation and w1 + w2 for heat-pump operation with electric heat. this often happens because techs don't read the unit literature and assume all heat-pumps use the same type of stat.