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drobertson517

09:07AM | 04/20/04
Member Since: 04/19/04
5 lifetime posts
Bvelectrical
I am trying to replace an old 40 gal water heater with a tankless model. The problem is that I have a 5 wire line coming in from the sub panel box, 4 black plus a ground. At the sub panel box, I have 2 fuse panels, each capable of holding 2 fuses. Only 1 of the panels has fuses in it (2 30 Amp) and the other is empty. The old water heater was only connected to 2 of the black wires plus the ground. The tankless heater requires anywhere from 3 40 amp circuits to 4 30 amp circuits. I don't know what I can order or how much trouble it is to go from a regular heater to a tankless. Not many electricians in the area the house is in, so I would like to do it myself, if possible.

Thanks!

bcelect

11:17AM | 04/21/04
Member Since: 02/21/04
138 lifetime posts
What sive service is supplying the Dwelling? It sounds like it may be insufficient to power the tankless.

drobertson517

04:32AM | 04/22/04
Member Since: 04/19/04
5 lifetime posts
There is a 150 amp service to the house.

bcelect

01:39PM | 04/23/04
Member Since: 02/21/04
138 lifetime posts
Can you take a picture of the fuses and email it? You will have to add some fuse/breaker capabilitiy there, as you only have 2 available. What kind of fuses are they, screw-in or cartridge?

drobertson517

05:03AM | 04/26/04
Member Since: 04/19/04
5 lifetime posts
I will try and do that, but since I don't get up there very often, it might be a while. Also, the fuses are screw in type. Thanks for the help and I will try and get the additional information to you.

bcelect

06:12AM | 04/26/04
Member Since: 02/21/04
138 lifetime posts
How far from the main panel is it to the water heater? You mentioned a sub panel where is that? The tankless requires 120 amps. The service is 150. that will be a big drain leaving not much left for other loads. Do you have electric heat and/or an electric range?

Tom O

11:12AM | 04/26/04
Member Since: 09/17/02
477 lifetime posts
Unless your house is the size of a shoebox, and you're burning wood or coal for heat in a fireplace, your 150 amp service is too small to support a water heater that will draw 120 amps.

I suggest that you get your hands on a copy of the National Electrical Code and do a load calculation. There are (fairly) easy to follow examples in the back.

Depending on the size of your house and the loads that you have, you could be moving into a service larger than 200 amps.

Tom

drobertson517

05:21AM | 04/27/04
Member Since: 04/19/04
5 lifetime posts
After verifying some additional information and reading your responses to my problem, I came to the conclusion I should not go with a tankless water heater since it simply draws too many amps. Back to a regular electric water heater for me.

Thanks to everyone who responded!!!
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