Dave 123
12-12-2016, 06:04 PM
Hi,
I have a customer with a Searle evap paired to a l'unite single phase condensing unit. The control is simple mechanical setup, ie;- 240V switched across mechanical room stat, up to the condensing unit, through the HP/LP then onto the overload then onto L1 of the contactor relay. The compressor and electric pack (Start cap/run cap and potential relay have been replaced) I have tested that the stat switches the 240V many times, I replaced the stat 3 months ago and I'm confident that the 240V reaches the 240V relay on the contactor (hp and lp switches are made, system full of R134a. The system runs perfectly, 6A on the compressor, 25psi/90psi, full sight glass 6 degrees evap superheat and 10 degrees cond subcooling. However, the compressor sometimes doesn't start. Once it hasn't started, it then wont start until either power is turned off and on or the stat fiddled with. If the stat was not making closed circuit, then the compressor wouldn't start if power was turned off and on again, as it is just a switch. The contactor and overload have also been replaced when I fitted the new comp last week. I was sure the stat was OK so I turned the condenser isolator on and off until the fault occurred (this was the old contactor and overload) Eventually, the compressor failed to start so I checked the contactor and found T2-240V L2-0V (the contactor is linked out to spread the load across three poles so it doesn't fail on overload) I replaced the contactor and overload and thought that was the end of that, but the customer has called today and stated the cellar is high in temp again. My question is; - the contactor is wired as follows; L1 240V in T1 link to T2, L2 link to L3 then 240V out to compressor on L3. The condenser fans are also fed from T1. Is the balancing wrong? I know it should be L1, T1, loop should go from T1 to L2, then T2 to L3, could this be the fault? how much difference is the fact that the wiring is looped slightly wrong across the contactor and the fact that the condenser fans are linked into T1. Obviously this will pull slightly more amps across T1 than the T2,T3. I isn't failing on overload as it restarts everytime the isolator is turned on and off. I have checked all wiring for damage and am getting a good neutral. Any help or suggestions with the contactor/overload wiring appreciated?
cheers,
Dave
I have a customer with a Searle evap paired to a l'unite single phase condensing unit. The control is simple mechanical setup, ie;- 240V switched across mechanical room stat, up to the condensing unit, through the HP/LP then onto the overload then onto L1 of the contactor relay. The compressor and electric pack (Start cap/run cap and potential relay have been replaced) I have tested that the stat switches the 240V many times, I replaced the stat 3 months ago and I'm confident that the 240V reaches the 240V relay on the contactor (hp and lp switches are made, system full of R134a. The system runs perfectly, 6A on the compressor, 25psi/90psi, full sight glass 6 degrees evap superheat and 10 degrees cond subcooling. However, the compressor sometimes doesn't start. Once it hasn't started, it then wont start until either power is turned off and on or the stat fiddled with. If the stat was not making closed circuit, then the compressor wouldn't start if power was turned off and on again, as it is just a switch. The contactor and overload have also been replaced when I fitted the new comp last week. I was sure the stat was OK so I turned the condenser isolator on and off until the fault occurred (this was the old contactor and overload) Eventually, the compressor failed to start so I checked the contactor and found T2-240V L2-0V (the contactor is linked out to spread the load across three poles so it doesn't fail on overload) I replaced the contactor and overload and thought that was the end of that, but the customer has called today and stated the cellar is high in temp again. My question is; - the contactor is wired as follows; L1 240V in T1 link to T2, L2 link to L3 then 240V out to compressor on L3. The condenser fans are also fed from T1. Is the balancing wrong? I know it should be L1, T1, loop should go from T1 to L2, then T2 to L3, could this be the fault? how much difference is the fact that the wiring is looped slightly wrong across the contactor and the fact that the condenser fans are linked into T1. Obviously this will pull slightly more amps across T1 than the T2,T3. I isn't failing on overload as it restarts everytime the isolator is turned on and off. I have checked all wiring for damage and am getting a good neutral. Any help or suggestions with the contactor/overload wiring appreciated?
cheers,
Dave