Low Voltage

[ReefHunter006]

Hi All,

With the heat today came some surprisingly low
voltage which I assume is only going to get worse as the heat persist.

The situation is a bit weird. We bought the house last year, and we were told that the garage is wired with a 100amp sub panel. While technically true, they didn’t mention/might have not known that the sub panel was wired into our main breaker with a 15 amp fuse. So we are gated to the 15 amps (I assume the wire gauge that runs to the sub panel is rated for 15 amps as well).. I unfortunately only came to learn this after the tanks were set up.

Today voltage dropped down to 106 which is quite alarming. I confirmed with a multimeter.

Does anyone else have an issue like this? Is the only solution upgrading the main breaker and running a new line (costly as the structure is surrounded by cement on all sides)?

I’m open to suggestions, because I expect the breaker will trip if if drops any lower and the wire gets hotter.

 

[ZombieEngineer]

An electrician worth their salt can upgrade the subpanel feed to something larger.

You will likely need a master electrician not a journeyman because there are calculations involved that require a masters license to upgrade if possible.

Depending on the cable size used you can either live with a smaller breaker (for example if #10 was run, you could use a 35A breaker to feed this) or have them upgrade the wire and breaker.

If the structure is surrounded by cement, there is a very good chance the wire is run through conduit and if so, that's really easy to pull new wire through.

Unfortunately, this whole process unless it's just a simple breaker replacement is likely to cost at least $400.

 

[ReefHunter006]

An electrician worth their salt can upgrade the subpanel feed to something larger.

You will likely need a master electrician not a journeyman because there are calculations involved that require a masters license to upgrade if possible.

Depending on the cable size used you can either live with a smaller breaker (for example if #10 was run, you could use a 35A breaker to feed this) or have them upgrade the wire and breaker.

If the structure is surrounded by cement, there is a very good chance the wire is run through conduit and if so, that's really easy to pull new wire through.

Unfortunately, this whole process unless it's just a simple breaker replacement is likely to cost at least $400.

I will pay 800 and air travel if that’s true because I was quoted this.

 

[gbroadbridge]

Hi All,

With the heat today came some surprisingly low
voltage which I assume is only going to get worse as the heat persist.

The situation is a bit weird. We bought the house last year, and we were told that the garage is wired with a 100amp sub panel. While technically true, they didn’t mention/might have not known that the sub panel was wired into our main breaker with a 15 amp fuse. So we are gated to the 15 amps (I assume the wire gauge that runs to the sub panel is rated for 15 amps as well).. I unfortunately only came to learn this after the tanks were set up.

Today voltage dropped down to 106 which is quite alarming. I confirmed with a multimeter.

Does anyone else have an issue like this? Is the only solution upgrading the main breaker and running a new line (costly as the structure is surrounded by cement on all sides)?

I’m open to suggestions, because I expect the breaker will trip if if drops any lower and the wire gets hotter.

+/- 10% on rated mains voltage is normal/allowed.

You don't have to worry about extra heat.
If the Voltage drops, so does the current, and power dissipation.

 

[gbroadbridge]

I will pay 800 and air travel if that’s true because I was quoted this.

Get a few more quotes.

That does not seem reasonable.

 

[ReefHunter006]

+/- 10% on rated mains voltage is normal/allowed.

You don't have to worry about extra heat.
If the Voltage drops, so does the current, and power dissipation.

Am I doing the math wrong? 120 +/-10% come out to 108 to 132? So 106 isn’t that concerning?

 

[ReefHunter006]

Get a few more quotes.

That does not seem reasonable.

California rates are higher but I thought that was high even for CA.

 

[ZombieEngineer]

I will pay 800 and air travel if that’s true because I was quoted this.

That's a load of BS right there. If the wire is relatively easily accessible, that is like a 3 hour job at most with like $100 in material unless the two panels are really far away.

I'm an engineer not a licenses electrician, so can't help you with that unfortunately.

 

[ReefHunter006]

That's a load of BS right there. If the wire is relatively easily accessible, that is like a 3 hour job at most with like $100 in material unless the two panels are really far away.

I'm an engineer not a licenses electrician, so can't help you with that unfortunately.

Breaker is on the exterior right of the house, and the garage is detached on the back left of the lot. I would estimate 150ft max, depending where the conduit is under the backyard.

 

[ZombieEngineer]

Am I doing the math wrong? 120 +/-10% come out to 108 to 132? So 106 isn’t that concerning?

106 is low, but they are only obliged to provide +-10% to your metering point. Factoring in extra drop from the subpanel, 106 is barely in the green. If your main panel is reading 106 too your utility is in violation.

 

[gbroadbridge]

Am I doing the math wrong? 120 +/-10% come out to 108 to 132? So 106 isn’t that concerning?

It's borderline, but shouldn't cause any issues.

 

[ZombieEngineer]

Breaker is on the exterior right of the house, and the garage is detached on the back left of the lot. I would estimate 150ft max, depending where the conduit is under the backyard.

150ft is gonna up the price a lot more. That might bring it up to 5-6 hours and the wire alone would be like $800-1200.

I would reasonably expect a quote more like $2500 if that is the case.

 

[ZombieEngineer]

Can you get a look at the label on the wire between them to see what size wire was actually used?

 

[DaJMasta]

Also worth mentioning that there is probably not a specified calibration for your Apex's measurement, so it could also just read lower than actuality. If you've got a multimeter, it is easy to check the voltage, but a tolerance is allowable and it is normal to see some fluctuation.

You could also try testing other outlets in the house and see if the one your Apex is on is actually reading low or its a whole house thing. If it's whole house, there could still be some unreasonable drop in your panel, but it may also just be the delivered power - a drop of that much happening in your panel would heat it up a good bit - while not safe to really feel out, it would show like a sore thumb on thermal.

 

[ReefHunter006]

Can you get a look at the label on the wire between them to see what size wire was actually used?

Between the sub panel and the breaker it is on?

 

[ReefHunter006]

Also worth mentioning that there is probably not a specified calibration for your Apex's measurement, so it could also just read lower than actuality. If you've got a multimeter, it is easy to check the voltage, but a tolerance is allowable and it is normal to see some fluctuation.

You could also try testing other outlets in the house and see if the one your Apex is on is actually reading low or its a whole house thing. If it's whole house, there could still be some unreasonable drop in your panel, but it may also just be the delivered power - a drop of that much happening in your panel would heat it up a good bit - while not safe to really feel out, it would show like a sore thumb on thermal.

Other outlets typically read about 4-5 volts higher when I have checked with the multimeter.

 

[ZombieEngineer]

Between the sub panel and the breaker it is on?

The wire between the main panel and the subpanel.

 

[ReefHunter006]

The wire between the main panel and the subpanel.

I can take a look tomorrow evening.

 

[DaJMasta]

Other outlets typically read about 4-5 volts higher when I have checked with the multimeter.

Provided the measurements were done around the same time, that's not supposed to be. If you've checked them all at different times, that could be normal daily fluctuations. This could also be loading related, so the easiest way to check would be something like:

Get something that draws some power (space heater, blow drier, electric griddle, etc.), plug it into your outlet, and turn it on. If it's the breaker, the module would be heating up when your tank is drawing reasonable current (like lights and circulation on, ideally with heaters running) and you could probably touch the body of the breaker for that circuit itself and find out if it's heating up. Otherwise, you may have a bad connection along the circuit's run (junction box, etc.), a bad connection at the plug (maybe the cables into the screw terminals on the back side of the socket?), or some kind of damage to the cable itself.

Then you repeat this test with another, presumably good, circuit with the same rating. Plug in your power hungry appliance, turn it on, give the voltage at the socket a measure while it's running. If the voltage drops similarly, then it could be voltage drop on the run that may not be out of line (perhaps the tank just heavily loads it), but if it doesn't budge that would point towards an issue with the tank's circuit in particular. It may also be worth adding up the power consumption (Watts) of everything on the current tank circuit and dividing by 120. If that number is close to or more than the breaker's current rating, it could be just that the circuit is being dragged down through excessive loading it wasn't designed to handle, and the solution would be to move some of the tank equipment to a different circuit.

If it acts differently from other outlets and it's not too heavily loaded for its rating, the circuit itself (or the breaker module itself, if it was getting hot) could need to be replaced. The bill for such work should be a lot lower than you were quoted earlier.

 

[csund]

+/- 10% on rated mains voltage is normal/allowed.

You don't have to worry about extra heat.
If the Voltage drops, so does the current, and power dissipation.

Is this accurate?

I was always under the impression for most loads if voltage drops amperage increases.