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Can the breakers be tested? Or is it just replace the breakers & see if the problem returns?
Neither the breakers or the fuses are (likely to be) bad.
There is "something else" going on inside the machine making it spike occassionally.
Still, that's no reason to not verify some basics in advance of...
The amprobe to check load with known good fuses of equal rating does that.
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The motor winding might be it or maybe the capacitor I mentioned.
It could still be a time of day ambient heat related issue too.
All is conjecture until someone familiar with that model and with hands on the machine gets there.
And it's all still academic with 19yo equipment in Orange County CA
Can the breakers be tested? Or is it just replace the breakers & see if the problem returns?
Just try replacing breakers. It is also possible the compressor starting capacitor is intermittent. Since lights dim in house when it fails I doubt if breakers will fix it but worth a try. Intermittent problems like this require trial and error troubleshooting. If breakers don't solve problem next thing I would try would be a compressor starting capacitor. You might need to consult a known expert's opinion. I am no expert but I have solved a few AC problems which involved weak breakers, bad starting capacitors, burned slip on spade type connections. Be careful.
Alright, I'll try replacing the breakers. They're inexpensive and I can use some extra ones for my new sub-panel. Upon further research with my specific model, it looks like the two most common issues for my problem are related to a faulty contactor (2-pole, 24V, 30A) and run capacitor ($6 part). I'll test the contactor and I'll visually inspect the run capacitor.
I have no shame in having a pro take a look if I can't figure it out. While the AC unit is pretty old, I recently had the furnace, coil, and ducting replaced. The old system was pretty much exhausted and the location, long return line, and poorly joined ducts were reason enough for a new system. I also added a Quietcool whole house fan myself. If anyone decides to install one, I'd recommend adding an attic exhaust vent or two and plugging the fan into a smartplug so you control it remotely via Wi-Fi. You can also setup schedules and "if this then that" logic programming.
it would not run if the contactor was bad . a bad contactor would not cause higher amperage . a flukey run cap would not trip the breaker on start up so you can rule that out . a run cap only comes in to play when running .
it could be a starting relay that sticks or start cap acting up if you have one. there was a start assist package that was offered on that unit .
do you have a start cap and relay ? . or it could be just a compressor starting to go bad . i have seen breakers give nuisance tripping over and over so i would start there .
do you have low voltage issues at times ? that will cause excessive amperage draw .
because you are saying it is on start up only there is not a whole lot it can be and fuses are definitely out of the picture .
there is likely a compressor short cycle protector in that unit that prohibits more than 4 starts an hour if the thermostat calls for cooling more frequently than that .
the 38kc series had one of those if i remember . but that would cause it not to start at times , not trip a breaker .
my vote in order is
weak breaker tripping .
bad start cap and or starting relay
low voltage issues at times
compressor going bad .
Last edited by mathjak107; 06-19-2017 at 03:28 AM..
(Note: only attempt if you are knowledgeable/experienced on 240v circuits; 240v can kill you.)
REPLACE the contactor (DONT reuse old one if 5yo or older) and compressor capacitor (these two components are the main cause of start problems after 5 years of age on them).
TIGHTEN breaker lug connections, and lug connections on contactor, and any pullout lug connections; these can loosen/corrode over time, and cause start problems.
IF these two don't resolve, you can purchase a HARD START KIT, which will help, if the above are all working perfectly.
in his case the contactor clearly is not the issue nor would a run cap be . that is not to say it is a bad idea to replace them after a while down the road as they age but they are not going to be the issue in my experience .
I believe there is also a start capacitor. This would be the one that would cause high current and failure to start. I have seen capacitors intermittent because of eyelet that fastens tap connection on top of capacitor during manufacturing develop an intermittent connection. A run capacitor would not likely cause this problem. Either the breakers or a start capacitor would be all I would try changing and I would be careful doing that.
I ended up replacing the run capacitor but it still randomly tripped the breaker. I hired an AC pro to poke around and they concluded the following:
1) 5-ton AC unit is 18 years old.
2) HVAC is designed for a 4-ton AC unit, limited by the evap. coil.
3) AC is overcharged with R-22
4) No hard start kit.
They gave me a couple of options to consider:
A) Keep the system as is.
B) Recover R-22 to the proper level: $585
C) In addition to the above, they will install a hard start booster: $910
D) Replace unit with 4-ton 14 SEER R410A unit with new disconnect, 12yr parts/1yr labor warranty: $4,450.
I appreciated their service, but their prices seem high. I'm thinking going with option A, but installing the hard start kit myself. There's no way I would have known all of these issues without a professional evaluation.
I believe there is also a start capacitor. This would be the one that would cause high current and failure to start. I have seen capacitors intermittent because of eyelet that fastens tap connection on top of capacitor during manufacturing develop an intermittent connection. A run capacitor would not likely cause this problem. Either the breakers or a start capacitor would be all I would try changing and I would be careful doing that.
i guess there was no start cap then .
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