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AssuredElectrical, Home Specialist
Category: Home Improvement
Satisfied Customers: 4241
Experience:  35 years home improvement
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I just purchased and installed a 30 gallon low boy hot water

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I just purchased and installed a 30 gallon low boy hot water heater and now the breaker keeps tripping. Actually it trips the main breaker for the townhome and all the power shuts off. Any ideas?

Hello there and welcome to Just Answer. My name is XXXXX XXXXX I will be assisting you today. I am an engineer with over 30 years of electrical and electronic training, repair and installation experience. I will try and answer your question accurately and precisely so that we can get you on your way.

I need some additional information from you in order to fully understand the situation.

Can you tell me the nameplata data on the heater, specifically voltage, wattage, amperage etc?

Please let me know so that we can continue.



Customer: replied 3 years ago.

4500 W



18.8 amps

GE low boy model 30 gallon

Ok, that's great info. Thanks.

Now, what size is your breaker and wiring to this heater?

You should have a 2 pole 30A breaker and #10 wiring. Is that correct so far?

Please let me know so that we can continue.



Customer: replied 3 years ago.

There is a two pole 40 amp breaker. Two pole meaning a double breaker?

The wire is questionable. It comes out of the side wall with no conduit. I think it is aluminum wiring. There is two wires, black insulated. The ground wire is 15-20 thin wires so when you tie them all together is looks like a rope :-). When I first wired the heater and it blew the main breaker the grounding was questionable. I watched the next time we turned the breaker back on and it sparked at the point where the ground was attached to a screw on the heater. I tried to better secure the ground with a metal washer. It still trips the main breaker.

Is this a brand new heater?

Do you have a multimeter or better still, an insulation tester or 'Megger'?

Please let me know so that we can continue.



Customer: replied 3 years ago.

Yes it is a brand new heater. No multimeter :-(.

I have read on-line that maybe it could be the reset on the upper t-stat?

How many wires do you have at your junction box? I assume you have a black and a red and a ground? Is hat correct? Do you have a white neutral?

Please let me know so that we can continue.



Customer: replied 3 years ago.

Junction box meaning on top of the heater? There is a black and red wire coming up from inside the heater. I did not see a ground wire there. no white neutral. The wire leading to the heater has two black and the many smaller ground wires as explained before.

Ok, I am going to opt out of this question which will allow other electrical experts to chime in. I'm not quite sure I understand the situation. I'm sorry.

Hold on and someone should be along.


Customer: replied 3 years ago.

For you or others the situation is that every time I turn the breaker on for the hot water heater it trips the main breaker for the townhome. It is a brand new hot water heater and this was not happening with the old heater. The old heater was replaced because it started leaking. Thanks.

Welcome. My name is XXXXX XXXXX would be glad to assist


I have read the information and postings so fairly familiar with what you have going on at the moment.


Your cable for the water heater sounds like an older SEU cable installation as used in the 70's-80's or even earlier.


It has 2 wires black and the ground is just a group of wires that actually wrap around the other 2 when the cable is unstripped.


That is aluminum and probably #8 awg.


If you can read the outside of the cable insulation it will tell what it is.

#8 should be on a 30 amp breaker and not the 40.


Needless to say, that doesn't trip one so lets look at what the problem may be.


If it sparked at the ground screw, that is a bad sign that wires are shorted somewhere.


So, please do this and post back the results.


Remove the entire cable from the water heater wiring compartment.


The separate the 2 blacks and the ground from each other.


The turn on the breaker and see if everything is fine while it is disconnected.


Do not just unwire the heater, remove the cable from the top where it is connected to the heater going into the wiring section.


Will await the info.




Customer: replied 3 years ago.

Just to make sure because this is at a rental unit 15 min away. You want me to disconnect the wires from the hot water heater and flip the breaker on to see if anything happens. Correct?

How is the cable connected to the water heater?


Water heaters have a whole in the top above the wiring compartment for a connector, then the cable is installed in the connector to get the wires into the wiring area.


How is yours done?


Customer: replied 3 years ago.

Yes sounds similar. The main wire with the 2 black wires and ground runs to the opening at the top of the heater. The ground is attached to a screw outside the compartment and the 2 black wires run into the compartment where they are attached to a black and red wire with wire nuts.

Ok, thanks.


Yes, remove the entire cable up and out of the water heater.


Completely out of the way and separate the wires so they do not touch each other.


Then turn on the breaker and see if it is fine?


What happens with this large cable:


It gets cut by the sides of the entrance hole going into the water and causes a direct short in many cases.


The wire is too big.


Normally what is done, is set a box, then put that large cable in the box and run a smaller #10 copper cable out of the box and into the heater.


That way, there is more room and less chance of a short.


Water heaters are designed for #10 wire, not a SEU cable such as yours.

It is too hard to make connections inside plus the ground on the big cable cannot be made properly to the screw.


The smaller wire is suggested to use by installing the junction box.


Also, you need split bolts for the connection of the big wires and not wire nuts.


Hope that explains it well enough, let me know

AssuredElectrical, Home Specialist
Category: Home Improvement
Satisfied Customers: 4241
Experience: 35 years home improvement
AssuredElectrical and 2 other Home Improvement Specialists are ready to help you

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