LS6 Tommy
Well-known member
Went to my BIL/SIL's house yesterday to look at their A/C. BIL tells me the symptoms are intermittant. On some really hot days, when he gets home there is very little airflow and the house is warm. If he shuts it down for a while it seems to recover.
Sounds like a freezing coil to me. I go over, sight glass is clear. Suction line is sweating, condensate coming out of the drain. Gauges read OK. Didn't want to check superheat until I check the rest of basics.
Filters are new. Up into the attic to look at the A/H. Fan speeds are set correctly, evaporator is clean.
The system has one condensing unit, but it's a two zone damper setup. The damper controller LEDs indicate the dampers in both zones should be open, the compressor should be running.
Dampers are closed. I start trying to figure things out with my meter. After I finally think I have things figured out, my BIL tells me he has the installation manual. I grab the manual and start reading. I was right. The damper actuators were wired backwards and the two T-stats were controlling the wrong zones. First floor stat was controlling second floor zone and vice versa. BIL says it can't be because it worked "fine" for years. SIL says it was never really great from the word go. I seem to recall they had other problems right after the installation.
I think it was just getting by with it miswired, but since it was new construction, they didn't have anything to compare it to so they thought it was OK. I figure it this way- the way it was wired, the dampers were going open when not calling instead of closing, and the stats were controlling the wrong dampers. Basically, with the stat wires on the wrong damper actuators and the actuators stroking backwards, when the stat for the first floor called, it ran the condenser and closed the damper for the second floor, but the first floor damper was open because the second floor stat was not calling. This allowed cooling and airflow to the first floor during a call. Same thing happened in reverse for the second floor when it called. The problem was when both stats called at the same time, both dampers would close, the condensing unit would run and eventually the supply duct temp sensor shut down the condensing unit.
Anyway, should be good now.
That will be $2400.00, please.
I wouldn't charge them. They are family...
Tommy
Sounds like a freezing coil to me. I go over, sight glass is clear. Suction line is sweating, condensate coming out of the drain. Gauges read OK. Didn't want to check superheat until I check the rest of basics.
Filters are new. Up into the attic to look at the A/H. Fan speeds are set correctly, evaporator is clean.
The system has one condensing unit, but it's a two zone damper setup. The damper controller LEDs indicate the dampers in both zones should be open, the compressor should be running.
Dampers are closed. I start trying to figure things out with my meter. After I finally think I have things figured out, my BIL tells me he has the installation manual. I grab the manual and start reading. I was right. The damper actuators were wired backwards and the two T-stats were controlling the wrong zones. First floor stat was controlling second floor zone and vice versa. BIL says it can't be because it worked "fine" for years. SIL says it was never really great from the word go. I seem to recall they had other problems right after the installation.
I think it was just getting by with it miswired, but since it was new construction, they didn't have anything to compare it to so they thought it was OK. I figure it this way- the way it was wired, the dampers were going open when not calling instead of closing, and the stats were controlling the wrong dampers. Basically, with the stat wires on the wrong damper actuators and the actuators stroking backwards, when the stat for the first floor called, it ran the condenser and closed the damper for the second floor, but the first floor damper was open because the second floor stat was not calling. This allowed cooling and airflow to the first floor during a call. Same thing happened in reverse for the second floor when it called. The problem was when both stats called at the same time, both dampers would close, the condensing unit would run and eventually the supply duct temp sensor shut down the condensing unit.
Anyway, should be good now.
That will be $2400.00, please.
I wouldn't charge them. They are family...
Tommy
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