Thread: Electric tankless water heater wiring

Hi Gents,

I came across an electric tankless water heater today for the first time. It was wired with 2-60 amp breakers and was 240 volt. My question is neither run was grounded? both circuit ground wires were just left disconnected. Should they be grounded somewhere?
Thanking you in advance
Rick

Originally Posted by Rick Passero

My question is neither run was grounded? both circuit ground wires were just left disconnected. Should they be grounded somewhere?

Rick,

Yes, the equipment grounding conductors are required to be connected to "ground" (the equipment grounding bar in the panel the equipment grounding terminal in the water heater.

I specified green insulated or bare copper "equipment grounding conductors" to make sure you are not referring to the white color insulated "grounded" neutral conductor.

Thank you Jerry, I didn't open the waterheater to see if or where grounding wires were connected inside the unit itself, maybe I will contact vendor and ask for a return visit

Rick,

No need to return, just write it up as equipment grounding conductors not connected - verify proper grounding connection at all terminations.

It then becomes the responsibility of the electrical contractor to make sure everything is properly grounded at both ends and all locations and terminations.

Originally Posted by Rick Passero

I came across an electric tankless water heater today for the first time. It was wired with 2-60 amp breakers and was 240 volt. My question is neither run was grounded? both circuit ground wires were just left disconnected. Should they be grounded somewhere?

On another note, was it a tandem 60A breaker or two separate breakers? If the latter, did it have a handle-tie such that turning off the one also turned off the other?

Originally Posted by Corn Walker

On another note, was it a tandem 60A breaker or two separate breakers? If the latter, did it have a handle-tie such that turning off the one also turned off the other?

Most likely it was two double pole 60 amp breakers for two 240 volt circuits.

Rick,

Typically, it is not the service size which presents the catch - it is the utility company's transformer which is not rated for those loads.

Give your local electric utility company a call and ask them if they have any concerns with the installation of electric tank less water heaters on their transformers, what you should look for as regards power consumption which may trigger their concerns, and what liability the homeowner may have.

You may find out that the power company will say that the homeowner may be responsible for the cost to change out the transformer to a larger capacity one. In which case you probably would ask (just for your information for clients) what a typical cost for change out might be.

Good information to have and be aware of.

With regards to panel size, I was surprised it was only a 100 amp panel servicing the house. I have attached a photo of what I found, and a pic of his repair, please note I did catch the obvious double and triple taps, after discussing the situation with the owner he called back and said he was thankful I pointed it out to him and that he had corrected. His correction was to ground to the neutral bar right below the breakers in the panel. Am I wrong to disagree that this has solved the safety issue?
Rick

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Originally Posted by Rick Passero

With regards to panel size, I was surprised it was only a 100 amp panel servicing the house.

You didn't mention the model of water heater, but one that I'm familiar with, the Stiebel-Eltron Tempra 24, has a maximum draw of 100A (2 x 50A) and a minimum breaker size of 60A. If the model installed there is anything like that unit, the service is undersized for the demand.

Originally Posted by Rick Passero

I have attached a photo of what I found, and a pic of his repair, please note I did catch the obvious double and triple taps, after discussing the situation with the owner he called back and said he was thankful I pointed it out to him and that he had corrected. His correction was to ground to the neutral bar right below the breakers in the panel. Am I wrong to disagree that this has solved the safety issue?
Rick

Aside from what looks like floating grounding conductors throughout the enclosure (I couldn't tell if they terminated in ground lugs or were just hanging out like the conductors from the water heater), if this panel board is the service equipment AND those bus bars are bonded to ground, then terminating the grounding conductors from the water heater on those bus bars is appropriate. It follows that if this is service equipment then those bus bars MUST be bonded to ground, verification of which would make the repair complete. If this is NOT service equipment then the termination of the grounding conductor on the neutral bus bars is impermissible and the repair is no repair at all.

Originally Posted by Rick Passero

With regards to panel size, I was surprised it was only a 100 amp panel servicing the house.
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Am I wrong to disagree that this has solved the safety issue?
Rick

100 amp panel with 2-double pole 60 amp breakers feeding the tankless water heater? The water heater alone will pull 120 amps when full on (some of the multiple circuit tankless water heaters I've seen sequenced the circuits 'on' in accordance with the water flow, one circuit 'on' for limited hot water flow, both circuits 'on' for high hot water flow).

The tankless water heater itself overloads the panel with only a 100 amp service.

Sure, he grounded that end, but what about the other end in the tankless water heater? And what about drawing 120+ amps through a 100 amp service?

Originally Posted by Rick Passero

With regards to panel size, I was surprised it was only a 100 amp panel servicing the house. I have attached a photo of what I found, and a pic of his repair, please note I did catch the obvious double and triple taps, after discussing the situation with the owner he called back and said he was thankful I pointed it out to him and that he had corrected. His correction was to ground to the neutral bar right below the breakers in the panel. Am I wrong to disagree that this has solved the safety issue?
Rick

I don't see a ground bus in this panel. It appears that all bare ground leads are left floating inside the panel.

Originally Posted by Jimmy Roberts

I don't see a ground bus in this panel. It appears that all bare ground leads are left floating inside the panel.

Rick is in Canada, their panels are configured differently than those here in the US, thus the metal divider between the service equipment part (with the main service disconnect) and the panel part.

The grounds go to the neutral terminal bus which are, as I recall for Canada, also bonded to the service neutral and ground but are done so within the still covered service equipment side.

Originally Posted by Jerry Peck

Rick is in Canada, their panels are configured differently than those here in the US, thus the metal divider between the service equipment part (with the main service disconnect) and the panel part.

The grounds go to the neutral terminal bus which are, as I recall for Canada, also bonded to the service neutral and ground but are done so within the still covered service equipment side.

It looks like most of the grounds terminate at individual lugs bonded to the enclosure, but the picture gives the appearance of others that are left unterminated.

Originally Posted by Corn Walker

It looks like most of the grounds terminate at individual lugs bonded to the enclosure, but the picture gives the appearance of others that are left unterminated.

I think I see what you are talking about - over on the left side of the photo?

Originally Posted by Jerry Peck

I think I see what you are talking about - over on the left side of the photo?

Exactly.
ungrounded water heater.jpg

It is a Canadian Federal PIOneer service panel. Google it.

There are short bus bars for the grounding conductors. There is one in the upper left with 4 terminals, hidden by wiring. There are 2 more top centre and bottom centre (center). All the grounding conductors go to terminals mounted on the back of the panel box, never to the neutral bus, per the Canadian EC

Rick, the stranded copper ground should go to a lug connected to the box, not to the neutral bus. Again, this is a code violation in Ontario, not a hazard.

Re: those double taps, at least 2 of them are due to the sad practice of mounting the doorbell transformers on the side of the panel. This double tapping for the doorbell was allowed for many years. There are numerous discussions to be found regarding this double tap. The transformer does not draw much current, and the wire is usually stranded copper, less likely to cause a loose connection.
It is no longer done that way, but be careful calling it a defect in an older unremodeled home.

Right on with all the conversation, though we should be including the fact that this WH load is a continuous load.... i.e. 125% calc where required. No diversity applicable in regards to continous loads.