Elec Tankless Heaters?

Bjd

Morning Guys;
Not real sure where this belongs, though I would start here.

I have a customer that bought a Tankless water heater, House is all electric.

200 Amp panel for the house Maxed out.

New tankless heater Requires (3) 40 amp breakers,as its 120 amps.

Directions call for a min of 200 amp house service, how in the hell are you going to handle the house and the 120 amps of the tankless?

Sure by pulling the duplex 30 for the current heater drops you some but still not enough.

Does this mean that he needs a seprate 200 amp service for just the tankless, and then upgrade the ouside service to a 400 amp?

Thaks BJD

mdshunk

These electric on demand water heaters can really throw a chink in the electrical service of a house. You MUST DO a proper demand load calculation to find out how much is "left" on the current service. If you do anything at all without doing a demand load calculation for the dwelling, you're doing the wrong thing, period. See this link for a pretty complete article on doing the demand load calculation. This is the bare minimum step#1. Repost if you have questions about performing the calculation or if you need help interpreting the results.

Grumpy

We cover this topic at least once a month.

mdshunk

I was just hoping that someone wouldn't say "Just install the water heater and see if the main breaker trips". I've actually heard so-called knowledgeable people offer that [bad] advice on other sites.

Bjd

Oh no; the home owner purchased this unit, and had me install it a few weeks back. My install does not include the power supply, to this day I think he still has not wired it due to this problem.

BJD

Thanks for your info

mdshunk

It's not as much of a problem as it is an involved project. People just don't realize that sometimes when they gets things like central air, heat pumps (where none was before), hot tubs, and these tankless water heaters that their whole service may need upgraded one size. It's an everyday thing. Regrettably, some homeowners (upon receiving the sad news from a reputable contractor) will get Joe Blow's Handyman Service to install it anyhow, creating a hazard.

boogie

just ran into the same problem sort of
wasnt thinking and trying to absorb what the owners were wanting but just did a quick look thru and was out the door
went back to wire the new furnaces (electric heat , dont know why they have n.g.)
ran home runs wired furnace end started to take panel covers off and dooooooohhhh
60a furnace 60a main in apt panels ooops not going to work
havent got a return call from owners to break bad news yet
but i can already hear it "why didnt you check that "
my reply will be why didnt you ask me before you installed the furnace (what were done weeks earlier)
dont think they will take it well

mdshunk

Well, Boogie, at least you're gauranteed you'll get to do a couple of service upgrades. Admittedly, they won't be very happy with you. I can't come down too hard on you, because similar things myself from time to time. Does make you feel like a screwup for a couple of minutes, even though it's not your fault that the service is too small.

boogie

sure did make me feel foolish for a moment
but then again i thought to myself why would you take out gas then put in electric furnaces one without checking themselves or at least the hvac contractor
silly things have been in for awhile and each apt has its own gas meter i dont get it gas has got to get extremly expensive to come near the price of electric heat
finally got ahold of the owner and they didnt seem to even flinch "well if thats what we need then make it so" got to love to hear that