A breaker trips because the circuit drew more than it is rated for, for longer than it allows. Which loads were drawing, and why that morning and not the one before, is written in the current minute by minute. We meter it, name the cause, and write the fix.
The compressor's cold start lands on both kitchen fans and holds the 40 A circuit over its breaker. Started before the fans, with its condenser cleaned, it peaks at 30 A.
A trip that comes and goes is the hardest kind to find by looking, because by the time anybody is at the panel the current that caused it has gone.
Marlow Street Bistro, the specimen restaurant in the scrolled story: 90 covers, an open kitchen and a walk-in cooler. Ckt 12, walk-in cooler, on a cold morning.
The compressor starts at 6:00, the minute the kitchen's exhaust fans come on. Each draw is ordinary on its own. Together, inside the same minute, they sit over the breaker.
On a cold morning the start lasts about 3 times as long and the breaker goes. Mild mornings get through, which is why the trip looked random to everyone who reset it.
Each finding carries its evidence: the minute, the circuit and the reading. A cause that cannot be shown on the meter is not written down as one.
The compressor starts at 6:00, the minute the kitchen's exhaust fans come on. Together they draw 48 A on a 40 A breaker.
On a cold morning the start draw lasts about three times as long, and the circuit stays over the breaker for 3 minutes. Mild mornings get through.
Running, it draws 22 A against 16 A on the plate: a dirty condenser coil, which also lengthens every start.
What to change, on which circuit, and what the circuit should read after. Your electrician makes the repair, and the meter stays on to show it worked.
A timer on the cooler circuit brings the compressor on at 5:15, so its start is over before the fans draw their 14 A.
Serviced, the compressor starts at 28 A and runs at 16 A, which is its nameplate.
No more than 30 A at any minute, on any morning. The meter stays on to show it.
We write down the boards involved and put a meter on the suspect circuit, reading every minute.
We read the week and the worst morning, find what was running when the breaker went, and name the cause with its evidence.
We specify the fix for your electrician: what to change, on which circuit, and what it should read after.
We read the same circuit again after the repair, and a licensed engineer signs the result.
Every minute on each suspect circuit for a week or more, with what was running when the breaker went.
From the meters on the boardThe fault, the circuit it is on and the evidence for it, matched against the faults we have seen before.
Reviewed by an engineerWhat to change, on which circuit, and what it should read after, written for your electrician.
Your electrician makes the repairThe same circuit read again on the same kind of morning, and the fault gone or not.
After the repairTo keep watching the board after the study, see Electrical Watch.
The panel record for the boards involved, and a meter on each suspect circuit reading every minute for at least a week, long enough to include the conditions the trip happens in. A fault that comes with cold weather is studied in cold weather.
The repair is made by your own electrician or FM partner. Wattif specifies it, reads the circuit again after it, and a licensed engineer signs the result under their own licence.
