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  1. #1
    Join Date
    Oct 2001
    Posts
    6,942

    Hmm

    had 6 new split units to vac and charge up cycled each copeland scroll(total 2)and was going along charging.went to run both compressors with a(1)condenser fan contactor for 2 fans and the 24v side trips the built in CB 3.2A rated..217 reading on the 3 phase legs TR hooked for 208V with 26 volts out on secondary? each compressor contactors drew 1.2 amps the fan contactor added another 1.1A 75VA rated,i called the factory in Texas they said parallel another 75VA in under warranty the CB is toooo small but it was ok on a smaller (1)compressor unit with exact TR...do those amp readings seem high for the compressor and there is a lp timed jump on start,and a fixed anti-recycle timer per circuit,do they add to the secondary loads when powered

  2. #2
    Join Date
    Nov 2001
    Location
    California
    Posts
    559
    Originally posted by maxster
    the CB is toooo small ... do those amp readings seem high for the compressor and there is a lp timed jump on start,and a fixed anti-recycle timer per circuit,do they add to the secondary loads when powered
    Maxster, from my experience in general (not those exact units) the amperage to the contactor coils sounds pretty high. Since all 3 of the contactor coils have high amps, it may be normal for the brand and size you have. Possibly you could contact the manufacturer of the contactors and ask someone in their application engineering dept if you have normal amp readings.

    As far as sizing the circuit breaker, Ohms Law says the VA divided by the Volts = the Amps, so in rounded off numbers, 75 VA divided by 25 volts = 3 amps, so the circuit breaker is sized properly to protect the transformer. If the equipment manufacturer says to add a transformer, it sounds to me as if they suspect voltage drop (causing higher amps) is causing the CB to trip, and supplying additional power (VA) will correct the problem. However, the way I see it, if you actually have 26 volts while reading those amps (1.2 + 1.2 + 1.1) regardless of the VA, the amps would still be higher than the CB rating, and would trip. You'd have to also use a higher amp rating on the CB or fuse, up to about 6.4 maxster. If the amps you mention are the inrush amps on start-up, it may be due to voltage drop temporarily while the coils are pulling in. Are all 3 coils pulling in at once? I wouldn't think so, but if they are, that would cause higher total inrush amps.

    I'd be interested to know how it turns out for you.

    Regarding the two other components, the additional load would possibly be too small to measure with your meter unless you have a few loops through the amp clamp.

  3. #3
    Join Date
    Jun 2004
    Location
    Richmond Virginia
    Posts
    1,078
    Do you have 26 volts at the contactors or just leaving the transformers? The amp draw sounds high unless these are some big contactors. If you have a long low voltage wiring run, and are losing voltage, you could add some pilot relays which are going to have lower VA ratings perhaps. To answer one of your questions, the common "black box" compressor delay timers do cause a voltage drop. They are "power stealing" as the voltage "trickle" it is using to time out is through the contactor coil. That's why the generic ones sometimes have the little wire to cut for higher voltages (due to the difference in impedence on the high voltage coils).

  4. #4
    Join Date
    Oct 2001
    Posts
    6,942
    tonight another tech added a second 75VA in parrallel on all the units as TEXAS said to do.he did state they couldn't find a TR for that units size 150VA would of been next so they winged it with the 75VA..if that had been a truer 208V then the 217V read on the primary do you think the higher secondary would of held the CB.i hooked it to 240V tap on the primary to see 217V for a 240V tap and it was 21V on the secondary?thanks

  5. #5
    I would first re-tap to the 208 volt tap to get back closer to 24v. Is the transformer in the condensing unit? If so, does the 24 volt wiring go 1/2 a mile on small gauge wire then back to the condensing unit and directly pull in the contactors? If so, check across contactor coils directly to see if large voltage drop due to small wiring is the issue. The coil amps are way too high.

  6. #6
    Join Date
    Oct 2001
    Posts
    6,942

    Hmm

    i thought also on the amps being to high but all six condensers were the same 217V 3 phase read,25V out on secondary...we added a 2nd 75VA TR under warrenty the wiring out was disconnected only R,Y1,Y2 to a generic control sequencer up onto the floor.their is no ucp or solid state within the condenser to pull high VA? 3-contactors,2-LP time delay jumps,2-anti-reccyle timers fixed from the factory...i thought these might be the drain that is pushing the CB to trip.it was running when i left friday time will tell if one of the TRs trip the load will knock the other down running full out!

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