Four Panels

Hey Guys-

I just wanted to double-check with you on this set-up. This has four panels with the last one ending at a detached garage which was about 75 feet from the house. The set-up went as follows:

Service panel (1) on far side of house > to distribution panel (2) in basement > to disconnect panel (3) on the other side of the house > to the detached garage panel (4).

Does the disconnect box (3) need grounding or bonding? They just used a connector to join the service from the distribution panel to the service going to the garage. And should the detached garage then have it’s own grounding/bonding? Thanks.


Photo #1 has a problem with the locknut/bushing at the bottom.
Photo #2 looks OK with separate neutrals and EGC’s.
Photo #3 appears that the disconnect is not properly grounded.
Photo #4 answer depends on when this was installed and the type of raceway. Is there a GES at the garage, there doesn’t appear to be a GEC?

The disconnect box (#3) between the distribution panel and the garage didn’t have any grounding or bonding. The neutral and ground from the distribution panel were joined with the neutral going to the garage within that connector. Nothing was attached to the box.

The raceway between the house and detached garage was plastic. The house was built in 1995 and the detached garage appeared to be constructed around the same time.

Pictures 1 and 2 below are the disconnect box at the house. Picture 3 and 4 is the raceway to the garage panel.

IMO, way over-loaded for 150 amp main. 8-220’s need at least a 400 amp main service, again, IMO. Document, refer.

The disconnect (#3) should have the egc’s bonded directly to the enclosure.

In #4, the panel needs its own grounding electrode (as Robert mentioned), in addition, the egc’s must be bonded to the enclosure.

Depending on the year it was installed, #4 may have the neutrals also bonded to the enclosure, however, as an HI, you should defer that type of installation for verification of no additional connective (metallic) paths.

So instead of doing a load calculation we assume a panel is overloaded based on a visual count of 240 volt breakers? This could be 8 small units that just happen to be 240 volts. Your statement does not take into account for the possible loading of those circuits, not does it consider load diversity for things like heat and A/C that are not used at the same time.

Glad I didn’t pay for that opinion, and I would have liked it even less if I paid for a load calculation or if the possible buyers backed out because of statements like this.

Unfortunately, it is a common mistake for some home inspectors to “over-think” this issue, and assume the panel is over loaded based on simple (unqualified) observations.

Jim thanks for bringing that up. Out in the field you hear all sorts of crazy thing about adding up the circuit breaker values and they can’t exceed X% of the main’s ampacity. Of course the party making the statement says “it’s right there in the codebook you just have to look for it”.

The true indicator of a panel being overloaded is a load calculation, unless of course you’re tripping the main breaker. :slight_smile:

I had a home one time that had a 100 amp main breaker, and three down-stream panels that all totaled 920 amps. Is that OK?

I turned on all three central A/C units, the electric dryer, all of the burners of the range top and the double-wall oven units, and the main popped.

If you think I am unqualified, then how many amps are allowed on a 150 amp main?

Reporting that the panel is overloaded, based on adding up the total breaker-ratings is an “unqualified” opinion.

Reporting that the panel is overloaded, based on a load calculation of the circuits within the residence is a “qualified” opinion.

Yes. There are wattage of appliances to be figured into the calculations via the labels on them. Even the breakers should be figured at 80% load. Example 15 amp circuit times the 120 volts equals total wattage available times .8 which equals a total of 1,440 watts of usage capacity on a 15 amp breaker. Calculations get technical, but when I see anything over 500 amps of breakers on a 100 amp main, I get concerned.

A Square D Service enclosure rated at 200 amps can support 40 separate circuits. Based on having only 15 amp circuit breakers (which would be highly unlikely), the potential load would be 600 amps. Would you call this overloaded without any supporting data?

How about if had all 20 amp circuit breakers?

How about two 2-pole 40’s, two 2-pole 30’s, and the balance with single pole 15’s and 20’s?

Anyone calling these overloaded, without actually running a load calc, would be giving an unqualified opinion.

Although at times your concerns may be legitimate you really have no way of knowing without doing a load calculation.

Also there is no 80% limit on the breakers. That would only apply if the load was considered continuous which means on for 3 hours or more. This would rarely be an issue in a dwelling.

A water heater is considered a continuous load, but I will show the math. 4500w/240 = 18.75 amps. 18.75 * 1.25 = 23.475 amps, so a 25 amp breaker would work. The 30 amp two pole with #10 is more common and allowed.

Adding up the breaker handles does not take into consideration the load diversity for things that do not run at the same time.

Yep, my 200 amp Square D has a combination of 15, 20, 30 and 50 amp breakers that equal 545 amps. Could easily be much higher.

I can put a 200 amp panel downstream of a 100 amp panel if I want to and be compliant. It all depends on the load.

There is not enough information provided in the message to size the service. You can download a free service size calcualtor from my website. Even with the calculator, more information is needed.


Download my free electrical service size calculator. It will help you gain a better understanding of how services are sized.