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#27525 - 07/19/03 11:27 AM Duel water heater feeds
wirecat Offline
Junior Member
Registered: 05/21/02
Posts: 6
Loc: Versailles, KY US
Yesterday I had to wire up a water heater that required two 30amp 240v circuits. This heater is wired to allow the bottom element to stay on when the cold water reaches the top of the tank triggering the top element - both elements on at the same time for a quicker recovery. We ran two 10/2's to two separate cut-offs. Than out of the bottom of the cut-offs two 10/2's to a j-box where we fed the two separate circuits (less one egc) thru flex to the one available KO in the top of the water heater. It looks real neat, but a lot of work to wire up one water heater - two cut offs and all that 10/2!. My questions: Is there a 4 pole cut off box on the market? Our suplier said no such amimal. Why would the mfg not wire the water heater so you could use one 60amp 240v circuit? With 4500w elements you could run one 50amp 240v circuit. I hear the on demand heaters require four 30amp circuits!
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#27526 - 07/19/03 01:57 PM Re: Duel water heater feeds
Bjarney Offline
Moderator
Registered: 04/10/02
Posts: 2527
Loc: West-Southern Inner-Northeast ...
Square-D catalogs 30+amp 4- and 6-pole safety switches, but are "heavy-" {600V} not "general"-duty.
http://www.squared.com/us/products/safetysw.nsf/07a0210021262d45862564b5006e4f84/fa3cba46f7a9519d852566c50073d833/$FILE/3100BR9801R601.pdf
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#27527 - 07/20/03 06:06 AM Re: Duel water heater feeds
pauluk Offline
Member
Registered: 08/11/01
Posts: 7520
Loc: Norfolk, England
I have to ask:

What capacity cylinder is this that needs 14kW of heat?
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#27528 - 07/20/03 09:52 AM Re: Duel water heater feeds
wirecat Offline
Junior Member
Registered: 05/21/02
Posts: 6
Loc: Versailles, KY US
If I get sent back to this same house this week I am going to get the capacity of the tank and size of each element. It was not a large tank, probably about 50 gal. It is simply designed to have a fast recovery time; therefore both elements can be on at the same time. (I guess people who spend 250K for a house don't want cold showers!) Seams to me we could have run only one feed since these elements are wired in parallel. 50amp if the elements are 4500w each or a 60 amp feed if the elements are 5500w. I am going to guess that during rough-in the usual 30amp 240v water heater circuit was run, than the plumbers come and install a water heater with elements that can both be on at the same time. Therefore, boss says, to save time, install a second 30amp feed and j-box with the usual flex to heater connection.
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#27529 - 07/20/03 03:38 PM Re: Duel water heater feeds
Bjarney Offline
Moderator
Registered: 04/10/02
Posts: 2527
Loc: West-Southern Inner-Northeast ...
wirecat, for other readers' reference, there are some example online wiring diagrams of 'non-simultaneous, two-wire' {page 4} and 'simultaneous, 4-wire' {page 6} electric water heaters.
http://www.hotwaterproducts.com/BWC/Parts/Pdfs/Electric%20Wiring.pdf

I don't know if your heater has the exact same wiring, but there can’t be too many variations of two heater elements with two thermostats.
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