Sub Panel Upgrade

[hnsy]

Hey guys,

I had a quick question for the electrical gurus on GJ. I'm looking to add some breakers to my sub panel. The panel has quite a few available slots, the problem is that when the electrical was done on the house, they only used a 60 amp breaker for the sub panel (which I'm convinced is not enough). The sub panel schedule currently has 5 bedrooms, an office, the kitchen/dining /living room lights, the master bath, a dedicated line for a jet tub (which is not installed), a media room, an office, a large central area upstairs, all smoke detectors, general lighting. The real reason I'm looking to upgrade is that I'd like to add a 30 amp 2-pole and a 20 amp single pole breaker for a compressor and a dedicated line for an electrical reel I bought.

So on to my question. I assumed that if they only put a 60 amp breaker for the sub panel, they probably only wired it for that amperage. I opened up the panel to look at the wires used (I'll attach photo). I used an electric caliper to measure the thickness of the red and black wires powering the sub panel. They were 6.3mm including the jackets and insulation. My intention is to upgrade the panel to 100 amps and I'm wondering if the wires need to upgraded as well. For reference the load center is 125amp max, 75 degree, and the current wiring is copper.

Any information would be greatly appreciated.

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[zmaxmotorsports]

Where is the sub panel in relation to the main panel/disconnect?
Id find a new main breaker 100a sub panel and steel the main breaker out of it to install in the existing sub panel to solve the disconnect part of the problem.
As far as refeeding the panel how far it is from the main is going to dictate how to refeed it.

 

[Fixin'Stuff]

Our last place had all of the 240 volt breakers in the main panel, including a single 60-amp breaker that fed all of the 120 volt circuitry in the entire 3,400 sf house. Lights, outlets, you name it. The only time it ever tripped was when the breaker got old and tired. The main panel was on the outside of the house, facing west, in Central Texas. That 60-amp breaker that fed the 120 volt sub panel tripped off a couple of times one summer, but only late in the afternoon when it was 110 degrees outside and the sun was pounding mercilessly on the panel. I checked the current draw with an amprobe and found that each leg was only drawing 20-30 amps. $9 at Lowes Depot for a new 60-amp breaker and it never tripped again.

So you should take a few current readings on the main feeders. You may find that the current being drawn is lower than you expect. CFL and LED lights, Energy Star refrigerators, flat panel TV's, etc. have lowered power consumption quite a bit in the last decade. It's also likely that many of those circuits are either unused or maybe have an alarm clock plugged in to them.

If the numbers look good when the family is home and has all the lights on, I would add the compressor and light circuit and see how it does. If it trips the main breaker, then start looking at an upgrade on the input side. Might save you some coin in the long run.

I expect that Speedy Petey will be along shortly to tell us the real truth according to the NEC.

 

[md21722]

That looks a lot like #6 or #8 wire into the sub. 60A is all you can do with #6 unless you run a new feeder...

 

[hnsy]

Thanks for the input. The main and sub panels are actually right next to each other. Some great suggestions, I think @Finxinstuff has a great point. I might try getting the breakers installed and see if anything trips before going the costly route of tearing apart the panels. Thanks again for the suggestions.

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[theoldwizard1]

What is the make and model number on the sub ? Look it up and see what the actual rating is.

With that many slot, I would guess it is rated for >60A. Maybe all you have to do is upgrade the breaker in the main (90-100A ?) and heavier wire to the sub.

 

[bjcouche]

If by 5 bedrooms, you mean the outlets in those 5 bedrooms, there could be very little load in those, maybe an alarm clock, LCD TV, Laptop computer and cell phone charger.

In the Office, there could be similar loads as I stated for the bedrooms, but there could also be a laser printer which do take enough power to be considered, but the usage is low and the duty cycle even lower.

If by kitchen / Dining / Living Room lights, you mean the lights in those rooms and not the outlets, especially the kitchen outlets, then that load is more than the bedroom lighting, but not huge. Changing those lights to LED is one of the better places to do it because they spend the most number of hours on per day and consume more power than other lighting throughout the house I say this because these rooms are usually more brightly lit than bedrooms.

By master bath, and media room, do you mean the outlets or lighting for those rooms? The bathrooms can have high peak loads when both the wife and the daughter want to run hair driers simultaneously. Tip: when wiring a house, never put the outlets from two bathrooms on the same breaker, this might be code now. Also, try not to put the outlets in the room on the same breaker as the lights, that way if you trip a breaker by overloading the outlets, you aren't left in the dark.


I'd start by doing as suggested and turning on all the lights and everything that you could ever potentially see operating at the same time and measure the current at the black and red wires with a clamp on amp meter. You might find that a 5HP compressor (30A breaker) will not overload the existing panel.
I'm just sayin, that measuring first is a lot cheaper than upgrading it when you don't have to.

 

[hnsy]

Yes, that's a good idea, I think that's the route I go [emoji4]

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