Dual 240v Wiring

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  #1  
Old 06-15-00, 07:56 PM
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I have an instant water heater that requires 2 - 240v feeds. I have two separate 10-2 feeds installed each on 2pole 40a breaker. The terminal block is marked "Power Source #1 L1 & L2 / Power Source #2 L3 & L4".

My question/s :

1) Install the two hot leads to L1 & L2 of PS#1 & hot leads to L3 & L4 of PS#2. There is no mention or provision for ground on termainla block.

or

2) Install both hot leads to L1 & ground to L2 of PS#1 & hot leads to L3 & ground to L4.

The manual states to install the PS#1 to L1 & L2 only and the same for PS#2. What worries me is that there is no prvision for a ground.

Thanks in advance for your help

[This message has been edited by frozenokie2 (edited June 15, 2000).]
 
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  #2  
Old 06-15-00, 08:10 PM
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Your directions are very clear. Do it as it says exactly. Your option 2 will create a dead short between the two power legs. A power block if it has a ground lug will be clearly marked either by color, text or both. If your block does not have a ground terminal, then it will have a lug on the frame somewhere inside the electrical enclosure.
Now, I have a question. You do not state what the demand of the heater requires. You have a 10/2 wire on a 40amp breaker which is not allowed. #10 is rated only for 30 amps or 40 amps requires #8 wire size. Make sure you check your specifications on this matter.
 
  #3  
Old 06-15-00, 08:27 PM
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David B. -

Thanks for the responce.

You have confirmed by thoughts on option 1.

As to the wire & breaker.

Unit max amp demand is 37.5 so this is why I choose 40a breakers. The existing old tank type water heater already had 1 10-2 wire on 2 pole 30a breaker. I ran another 10-2 & plan on using 2 pole 40a breaker & replacing the 30a with another 40a.

Do I have the wrong wire or am I over sized on the breaker.

Thanks again.

Almost forgot - As to the ground there is NO ground Lug/Screw/Block that I can find inside the box. Made by Hot Water Generators in Houstan TX some time back.

[This message has been edited by frozenokie2 (edited June 15, 2000).]
 
  #4  
Old 06-16-00, 11:25 AM
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The circuit breaker is there to prevent the wire from getting too hot. As David said, for 10/2 wire you must not use larger than a 30A breaker. My question would be, is that 37.5A rating on your water heater for one or both power sources combined? If it's a combined total, then 2 30A double pole breakers would be enough. If you really need 40A breakers, then you should go the 8/2 wire.
 
  #5  
Old 06-16-00, 03:52 PM
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frozenokie2,
You are definitely oversizing the breaker.
However, Ranck, brings up a good point since you said that the total connected max load is 37+. To verify this just look on each heating element and the wattage will be posted along with the voltage. If these have independent power sources they may also operate independently, that is not on the same thermostat, thus you may be OK with 10.2 wire but use 30 amp breakers or less depending on the size of the heaters they feed.
 
  #6  
Old 06-16-00, 04:51 PM
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David B. & Ranck -

Thanks for your advice & recomendations.

According to the paperwork Max ratings are:

Power Source #1 9K 240v 37.5a 60Hz
and
Power Source #2 9K 240v 37.5a 60Hz

The unit has a heat/power knob that the higher you set it the hotter the water will be. I assume that the higher the dial the higher the amperage usage will be as well.

The unit has the capibility to raise the water temp 123 degrees at a flow rate of 1 gal per min. At 2 gal it raises the temp by 62 deg.

I feel that this will be one electricty eating unit when it is on. The unit will only be on when the water is turned on is the nice part.

Thus in the long run a cost savings.

Thanks again.
 
  #7  
Old 06-19-00, 05:51 PM
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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by frozenokie2:
David B. & Ranck -
According to the paperwork Max ratings are:

Power Source #1 9K 240v 37.5a 60Hz
and
Power Source #2 9K 240v 37.5a 60Hz

The unit has a heat/power knob that the higher you set it the hotter the water will be. I assume that the higher the dial the higher the amperage usage will be as well.
<HR></BLOCKQUOTE>

Wow! That puppy draws some real juice. Now for the bad news. Thermostats and heating elements are pretty much on/off devices. In other words, whenever the heating element is on, it is on all the way. So you need heavier wire and at 40 amp breakers (at least).
 
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