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#177564 - 05/07/08 12:32 PM Instant Under counter Hot Water Heaters
Yoopersup Offline
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Registered: 03/04/03
Posts: 822
Loc: Michigan
Instant Hot water heater under the sink Bradford model EFT-28000-4-T-10 208 volt single phase. Draws close to 140 amps.
Theres 45 units that theses are POSSIBLY going to be installed. As far as I see it each one must be rated for condutious duty(X125%)45 x 6075x125% aprox 760 amps ???
Anyone know of any derateing ect in this case?? Seem like a lotta power for Hot water???
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#177566 - 05/07/08 03:03 PM Re: Instant Under counter Hot Water Heaters [Re: Yoopersup]
electure Offline


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Registered: 12/24/00
Posts: 4259
Loc: Fullerton, CA USA

Article 100 defines continuous load as:

"A load where the maximum current is expected to continue for 3 hours or more"

That's one heck of a long time to run the sink.
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#177569 - 05/07/08 04:23 PM Re: Instant Under counter Hot Water Heaters [Re: electure]
Yoopersup Offline
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Registered: 03/04/03
Posts: 822
Loc: Michigan
So Hot water Heaters don't need the 125 % either????
422.13 ?????? come into play


Edited by Yoopersup (05/07/08 04:25 PM)
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#177573 - 05/07/08 05:14 PM Re: Instant Under counter Hot Water Heaters [Re: Yoopersup]
electure Offline


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Registered: 12/24/00
Posts: 4259
Loc: Fullerton, CA USA
The water heater is not a storage type. It is an "On Demand" type.

It heats the water when needed, and only when needed.

Here's a PDF
If you scroll down to "Series Three" you'll find it there.
http://www.bradfordwhite.com/images/shared/pdfs/specsheets/217b.pdf


Edited by electure (05/07/08 05:17 PM)
Edit Reason: I forgot to addlink
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#177575 - 05/07/08 06:01 PM Re: Instant Under counter Hot Water Heaters [Re: electure]
Yoopersup Offline
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Registered: 03/04/03
Posts: 822
Loc: Michigan
So where does it deal with Demand type in the NEC?? and whats to stop it from being on for three hrs or more????
(I knew it was demand type Thus the product #)
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#177576 - 05/07/08 06:04 PM Re: Instant Under counter Hot Water Heaters [Re: Yoopersup]
sparkyinak Offline
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Registered: 07/08/07
Posts: 1307
Loc: Alaska
Insta hots are not considered as storage units per 422.13.
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#177578 - 05/07/08 07:03 PM Re: Instant Under counter Hot Water Heaters [Re: Yoopersup]
renosteinke Offline
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Registered: 01/22/05
Posts: 5316
Loc: Blue Collar Country
Yooper, I might see a few errors in your thinking.

These are single-phase 'whole house' water heaters. I assume that means that these will each be going in a different residence, and different panels.

Does the load seem high? Sure - that's the price you pay for 'instant' heat.

When you do the load calcs for multiple dwellings, there's a multiplier for your "diversity factor." The effect of this is, whether you use the 125% figure or not in each individual panel, I don't think it will change the final total service needed.

Looks like you need 3 two-pole breakers - and they;ll need to be mounted next to each other, so they can be considered as disconnects 'grouped together.'
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#177630 - 05/08/08 04:36 PM Re: Instant Under counter Hot Water Heaters [Re: renosteinke]
Yoopersup Offline
Member
Registered: 03/04/03
Posts: 822
Loc: Michigan
I called the Company your right, Three 2 pole 40 amp breakers for each unit . and thats the Minimin size they say would be required to feed a, Shower, Bathroom sink, Kitchen sink combo. Becta there not going in!!!.
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#177647 - 05/09/08 03:39 AM Re: Instant Under counter Hot Water Heaters [Re: Yoopersup]
SteveFehr Offline
Member
Registered: 03/19/05
Posts: 1195
Loc: Chesapeake, VA
It's insane how much power it takes to heat water on demand, isn't it? I would have had to upgrade my service to put in an in-use hot water heater for my home. Gas isn't much better- the size gas like you need for even a 1-shower-at-a-time tank line that is obscene, too.
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#177655 - 05/09/08 05:53 AM Re: Instant Under counter Hot Water Heaters [Re: SteveFehr]
ghost307 Offline
Member
Registered: 05/09/05
Posts: 900
Loc: Chicago Illinois USA
It doesn't really take more energy to heat the water; it's just that you're trying to heat it in seconds instead of minutes. If you think about the gas versions, you're using 30 minutes worth of a gas flame in a few seconds. That means that the flame will look more like a welding torch than a stovetop burner.

My electric one takes (4) 30 Amp 240V circuits, but it doesn't really show up as a noticable amount on my bill; so I'm not using a LOT of energy, I'm just using the same amount very very quickly.
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