Strange and Fascinatingly Peculiar Home Electrical System Malady

Hey All,

Our lovely abode here in exotic Glendale has an interesting problem.  We have a central air conditioning system, powered through a 1955 Federal-Pacific circuit breaker box.  Before you go off a-googling, know there is abundant material on the interwebs proving beyond a shadow of a doubt the disastrous consequences of continuing to use such a box with lurid tales of units exploding like Roman candles and "No-Arc" breakers doing just that.  Oh, the humanity, but I digress.

Anyway, we had the double 20-amp breaker controlling the AC unit die in the middle of a horrendous heat wave.  We do plan on ridding ourselves of this ancient circuit breaker box as soon as funds are available.  For the time being, I replaced the offending breaker with a Chinese copy of the same amperage since nobody makes this stuff anymore.  Replacing the breaker restored operation to the unit.  However, on days where the temperature reaches more than 100 degrees, the unit pops the new breaker every day at approximately 2:40 pm.  Why 2:40 pm?  Because that's when the sun hits the outdoor breaker box (it's a code thang).  I postulate the resultant radiant heat, coupled with the higher-than-normal ambient temperature and the heat generated by the current, causes the breaker to blow prematurely.

My question:  Should I replace the breaker with one of higher current value (dual 30 amps is the next available size)?  Would that cure our problem?  I know the hot legs on that circuit use 10-gauge wire, which should work with a 30-amp breaker maximum. Our AC repairman did comment about 20-amps being a little too light for the circuit.  So we could be a little slim on margin right now, but I only want to change breakers if doing so would cure the heat-related sun problem.

It really sucks coming home to a hot house when the outdoor temperatures are still in the high 90s after sunset.  The AC chugs away happily for hours on end, even in high heat, as long as the sun isn't on it.  Any illumination (see what I did there?) would be a big help.  I'm tired of me-rigging a sunshade over the breaker box whenever we hit triple digits.

Thanks in advance,

Jerry

Is the breaker box a dark gray color? Perhaps a quick spray of white paint applied would help keep the temps down?

I'm not an electrician by trade, but I'd get a couple more opinions before popping in high amp breakers.      Glowing copper wire is something I've witnessed and don't care to again.

While the copper might be rated for 30amp,   is the AC unit?

I'd duct tape an umbrella over the box to give it a bit of shade, but I'm a redneck when it comes to things like that.

No. The wiring from the breaker to the unit is probably not sized for a 30A breaker, so going with a higher rated breaker can potentially turn the wiring itself into your over-current protection.  When that happens, things typically catch on fire.

Replace the breaker. If it still trips, leave it off and get an electrician to figure out why it's tripping (I'm not joking about the "fire" comment above).

I would build some sort of wooden box like thing to shade your outdoor disconnect box. As the temps go up, the resistance in the wite goes up so there is more voltage drop in the wires. The compressor motor now sees a lower voltage, but will still try to put out the same power, so it draws more amps. That increase must be enough to trip your breaker. I would think that you must be fairly close to tripping it normally with little margin. I wonder if there is a high resistance connection in the outdoor disconnect that is making the problem worse. I'd open the breaker then look inside the disconnect box and make sure the wires are terminated properly. Look for a loose connection or signs of heat damage. 

What is the rating of your AC system?

If you are not comfortable doing that, call an electrician. 

Speaking with an electrician just now he said that the 20 amp breaker is undersized and you need to go with the 30 amp unit (good call mentioning the wire gauge).  Also that Federal Pacific parts are available on Ebay. 

I agree on the shade. Maybe also get a sprinkler hitting it, but water costs may make that cost prohibitive. 

Additionally, have you thought about suffering through the heat in most of the house and just running a window unit in 1-2 rooms until the heatwave breaks and you have the funds to really fix it?

mtn said:

I agree on the shade. Maybe also get a sprinkler hitting it, but water costs may make that cost prohibitive. 

Additionally, have you thought about suffering through the heat in most of the house and just running a window unit in 1-2 rooms until the heatwave breaks and you have the funds to really fix it?

Having been a contractor in LA including Glendale, chances are the house is from the 20s and there isn't sufficient wiring in the walls to support enough BTUs.  There is also most definitely not any insulation.  I tore out plaster in many houses up there, and I'm pretty certain you would only find rough-cut 2x4s and then see the back of the shiplap or the lath for the stucco.  Most likely you would also see light pouring through pinholes.

Not dissing your house, Jerry, just postulating why it might not be effective to put window units in.

If the wiring can take the juice, 30A breakers are a possibility, but the big question is about the compressor.  The breaker protects the appliance as well as the wiring.  If the compressor or fan is dying and drawing too many amps, the breaker is shutting it off before it can cause too much damage/fire.  That is to say, if the appliance is rated as an 18A unit and its tripping 20A breakers, something is likely wrong with the unit.  It starts drawing 18A and then creeps up as it gets hot until it trips.  Switching to 30A means you're just allowing it to continue heating up further.  My guess is that installing a 30A breaker will cause the A/C to fail within the week.

+1 for shading the box first. Increasing the breaker rating risks turning something more expensive and/or flammable in the system into a fuse. For a coating, maybe apply aluminum tape to the outside of the box, that's even better than white paint and costs about the same.

Pete Gossett said:

I'd duct tape an umbrella over the box to give it a bit of shade, but I'm a redneck when it comes to things like that.

Already done except I use paracord in place of duct tape to hold the umbrella because I'm a backpacker.  My name is Jerry after all.

KyAllroad said:

Speaking with an electrician just now he said that the 20 amp breaker is undersized and you need to go with the 30 amp unit (good call mentioning the wire gauge).  Also that Federal Pacific parts are available on Ebay. 

I checked the wire gauge and know it's at least 10.  I know 10-gauge can be used with a 30-amp circuit.  Federal Pacific used to make a dual 25-amp breaker but no one has decided to produce that one anymore.

Speaking of which, Federal Pacific has been gone for a number of years.  Available breakers are limited to Chinese copies and rebuilt original equipment.  They can be had, but the quality is not really up to Federal-Pacific's mediocre standards.

curtis73 said:

Having been a contractor in LA including Glendale, chances are the house is from the 20s and there isn't sufficient wiring in the walls to support enough BTUs.  There is also most definitely not any insulation.  I tore out plaster in many houses up there, and I'm pretty certain you would only find rough-cut 2x4s and then see the back of the shiplap or the lath for the stucco.  Most likely you would also see light pouring through pinholes.

Not dissing your house, Jerry, just postulating why it might not be effective to put window units in.

If the wiring can take the juice, 30A breakers are a possibility, but the big question is about the compressor.  The breaker protects the appliance as well as the wiring.  If the compressor or fan is dying and drawing too many amps, the breaker is shutting it off before it can cause too much damage/fire.  That is to say, if the appliance is rated as an 18A unit and its tripping 20A breakers, something is likely wrong with the unit.  It starts drawing 18A and then creeps up as it gets hot until it trips.  Switching to 30A means you're just allowing it to continue heating up further.  My guess is that installing a 30A breaker will cause the A/C to fail within the week.

 

My neighborhood is full of '20s houses, so good call.  My across-the-street neighbor has some old knob-and-tube in frightening condition.  However, our house is one of three spec houses built in 1955 so the wiring is up to that standard, other than where it's been replaced by either myself or other personages who obviously didn't have the wherewithal to read an electrical wiring book.  The wiring for the AC is intact as far as I know.

As for the AC unit itself, the whole thing has been completely rebuilt.  The compressor was replaced in July and the unit was fully recharged.  There is insulation in the attic because I put it there about eight years ago with all the attendant joys of doing so in the summer under a 2-in-12 roofline.  They say the bad dreams will stop soon.  Only the outer living room wall is insulated because that wall is new.  All other walls are uninsulated.

As you know, if it's a '50s house in LA, it's likely equipped with metal casement crank windows which make AC window units a dodgy affair.

Another thing I would check.  It is possible (depending on the age of your unit) that the compressor and fan are on isolated legs.  Instead of 240v going to each component, they might split and one leg goes to the fan, one leg goes to the compressor.  This is how most electric dryers work; one leg to the motor, one leg to the heater.

If that is the case (and only if that is the case), pull the tie bar off the double breaker and run the unit.  See which one trips.  That's your culprit.

But if they are both 240v components, tripping one breaker will do bad things and possibly damage one or both components trying to handle the load on 120v.

curtis73 said:

Another thing I would check.  It is possible (depending on the age of your unit) that the compressor and fan are on isolated legs.  Instead of 240v going to each component, they might split and one leg goes to the fan, one leg goes to the compressor.  This is how most electric dryers work; one leg to the motor, one leg to the heater.

If that is the case (and only if that is the case), pull the tie bar off the double breaker and run the unit.  See which one trips.  That's your culprit.

But if they are both 240v components, tripping one breaker will do bad things and possibly damage one or both components trying to handle the load on 120v.

Check what I wrote above.  I think you wrote this while I was preparing that post so you didn't see it.  There's nothing in the outside unit that hasn't been replaced.  You are right about the fans.  The whole air handler system is separate because it's shared with the gas heater.  It is on a separate circuit. The AC unit consumes all 220 volts on its own.

Actually, all this wild postulating brings up an interesting point I forgot to mention.  Early this summer, we painted our stucco house a darker color.  I noticed the extra radiant heat from the stucco yesterday when rigging up the umbrella.  There is a separate box cover over the breaker box painted in the new color.  Perhaps painting the box a lighter shade would help.

EastCoastMojo said:

Is the breaker box a dark gray color? Perhaps a quick spray of white paint applied would help keep the temps down?

I'm tempted to try this.  Our new house color is a darker grey so it's obvious you've been watching us with drones and bugging our computers.

I watch all of you scurrying around like ants from the grm satellite  oops I've  said too much 

EastCoastMojo said:

I watch all of you scurrying around like ants from the grm satellite  oops I've  said too much 

You're taking this Mod job pretty seriously, huh?

If it was happy before, maybe when you replaced the breaker, the wires weren't tightened enough. When the box heats up, the wires grow a bit and it might be enough to cause a little short. Maybe. 

akamcfly said:

If it was happy before, maybe when you replaced the breaker, the wires weren't tightened enough. When the box heats up, the wires grow a bit and it might be enough to cause a little short. Maybe. 

It was happy before we painted the breaker box a fairly dark grey after being pale yellow.  However, we also had an original equipment breaker in there before it died.  Now there's a Chinese one.  Too many variables to pin it down.

Yes.  There's a reason why buildings in hot locals tend to be painted lighter shades.  Not only does the dark paint add heat to the disconnect, it's adding heat-load to the house and A/C.  Eventually adding insulation on the south and west facing walls will help as well.