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I bought a house with an old Carrier 5-ton AC unit (38CKC060). It's wired to a separate pull-out breaker box with two fuses, a 60A and 50a, which then feeds into a 60A breaker on the main panel (200amp). About every 50 or so startups, the compressor will trip the pull-out switch and/or cause a split-second outage to the house. The blower to the HVAC and everything else seem fine, but the compressor and fan won't do much until I pull the switch and reinsert it. I've checked the connector wires for any signs of burnouts or overheating and everything looks fine. I checked the fuses and while very old, they tested just fine. Before I contact a serviceperson, can anyone give some suggestions as to what my issue might be? Thanks in advance.
It's wired to a separate pull-out breaker box with two fuses, a 60A and 50a,
which then feeds into a 60A breaker on the main panel (200amp).
I checked the fuses and while very old, they tested just fine.
I've checked the connector wires for any signs of...
Before I contact a service person....
Spend $5 for a pair of new fuses. Start with 60A then put an amprobe on the wires.
While everything is off tighten up all the connections.
I'd be surprised though that the running load is over 30Amps.
Quote:
About every 50 or so startups...
Any pattern to time of day when this happens?
Last edited by MrRational; 06-18-2017 at 02:28 PM..
i doubt it is the fuses . fuses are blown or they aren't . in 40 years in the business i never ran in to fuses that were bad and not open . i would look else where for the problem .
i would start with the breakers and if that doesn't do it then you have to have some trouble shooting done on the ac unit
Pretty common with some types of electric motors that you get a short in the windings which gives you a dead spot; if the motor stops in a way that's lined up with the dead spot it'll pull a lot of amps trying to start. Hard to test though, you need a megger, access to the phase windings, and also the specs of what the motor should be.
Thanks for the replies everyone. I feel confident enough replace the fuses, but I think everything I'll rely on a technician. There's no pattern other than it trips only when the thermostat calls for the AC to turn on; it never trips in the middle of its cycle. I believe the AC was installed in the 1998. According to the back information badge, the unit uses a max load of 36amps.
at start up is the hardest point . it can draw up to 5x its running amperage . breakers are designed to allow this . but breakers can become tired and weak which is why i would start with the breakers . the fuses are pretty much out of the loop unless they blew .
At 19 years it is past the 'useful service life' and due for replacement.
A good service tech can probably nurse it along through the season (might even be something as simple as a capacitor)
but even if they can... you need to start stacking the Benjamins for some new R410 AC equipment.
The furnace might be a justifiable replacement at this point as well.
at start up is the hardest point . it can draw up to 5x its running amperage . breakers are designed to allow this . but breakers can become tired and weak which is why i would start with the breakers . the fuses are pretty much out of the loop unless they blew .
Can the breakers be tested? Or is it just replace the breakers & see if the problem returns?
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