Instant Water Heater with two single pole breakers.

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Alexis Enrique

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I need to install a water heater, the manufacturer call for two single poles (277V), it is a (2) 277V elements, plans call for (1) two pole disconnect mean, shouldn't those breakers have a handle tight or be a two pole breaker? or have 2 separated mean disconnect? Before, when I have a two elements (240V) I use two poles breakers and two poles disconnect, what's the correct installation?
 
Alexis Enrique said:
I need to install a water heater, the manufacturer call for two single poles (277V), it is a (2) 277V elements, plans call for (1) two pole disconnect mean, shouldn't those breakers have a handle tight or be a two pole breaker? or have 2 separated mean disconnect? Before, when I have a two elements (240V) I use two poles breakers and two poles disconnect, what's the correct installation?
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Why wasn't the system voltage included it the OP? Are left to assume that the heater is being feed from a 3ph4w 480y/277v supply with a phase to neutral voltage of 277v 1ph? Again you asked a question leaving for us to fill in the blanks which I will attempt to do.
If what I said is true I am to assume that you are feeding the heater with 2 ckts from the same line to neutral voltage which is different than supplying a heater from a 120/240v 1ph3w system were the heater is actually supplied with L-L 240v in leu of 277 L-N.
Without having any knowledge about why they subject heater requires (2) 277v circuits my reply as only an assumption. Remember that 277v is a L-N voltage of a 3ph4w 480y/277 supply. If you do supply you heater with (2) separate 277 L-N ?kts taken from let's say the 'A' phase and neutral. there will be zero volts between the lines unless one of the lines is taken from another phase, one ckt from the 'A' phase and neutral and the other from the 'B' phase and neutral both of which are single phase voltages but the the line conductors are now 480 apart and not zero volts.
 
For the information given, I take it this unit is designed to be supplied by two 277 volt circuits. That said you could supply it with two ungrounded (same or different phases) and two neutrals, or you can supply it with two phases and a common neutral (multiwire circuit) and it will work just fine either way. The multiwire circuit approach would require multipole breaker or handle ties, where the two completely separate circuits would not.

Of course this is also assuming a 480/277 Y supply system.
 
kwired said:
For the information given, I take it this unit is designed to be supplied by two 277 volt circuits. That said you could supply it with two ungrounded (same or different phases) and two neutrals, or you can supply it with two phases and a common neutral (multiwire circuit) and it will work just fine either way. The multiwire circuit approach would require multipole breaker or handle ties, where the two completely separate circuits would not.

Of course this is also assuming a 480/277 Y supply system.
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Assuming is fun isn't it?
 
kwired said:
So are people that make one post and never return. But I just realized the first post is about 14 days old before there was any reply..
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So true. Its as if they throw a granade in the room and take off to never return. But its fun to watch those who guess what the OP's question was about and not realizing that there were left by the OP to be all tangled up in their underware and the OP simple goes away.
 
Very sorry for not getting back sooner, this is feed from a 3P 277/480Y panel, it is a tankless unit, the unit has two elements, each element as per manufacturer require a single breaker 277V (hot / neutral), it does not matter if the phase for each element is the same (element 1 : Phase A and neutral, element 2: Phase B and neutral or element 1: Phase A and neutral, element 2 Phase A and neutral as long as each element have 277V itself), in both cases each element will have 277V provide by each line (don't want to get into the same or separate neutral, if it was same neutral it need to be double pole) in this case each element have their own hot/neutral, my question is more related when some need to repair or give maintenance to the unit, I would like all the hot lines disconnect at the same time to make sure the unit has not power. The engineer say that as per manufacturer the breakers can not be double pole, it need to be two single breakers and as disconnect for the unit he is proposing two separate 2 poles disconnect, I said 2 pole breaker or just one single 2 pole disconnect for the ungrounded conductors, having the neutral going straight to the unit.
I think the confusion start with the manufacturer recommendations itself of the two "separate breakers" instead of saying "two separate dedicated circuits using 2 hots and 2 neutrals", as of this point I will not do an installation if I think someone may get hurt.
 
Alexis Enrique said:
Very sorry for not getting back sooner, this is feed from a 3P 277/480Y panel, it is a tankless unit, the unit has two elements, each element as per manufacturer require a single breaker 277V (hot / neutral), it does not matter if the phase for each element is the same (element 1 : Phase A and neutral, element 2: Phase B and neutral or element 1: Phase A and neutral, element 2 Phase A and neutral as long as each element have 277V itself), in both cases each element will have 277V provide by each line (don't want to get into the same or separate neutral, if it was same neutral it need to be double pole) in this case each element have their own hot/neutral, my question is more related when some need to repair or give maintenance to the unit, I would like all the hot lines disconnect at the same time to make sure the unit has not power. The engineer say that as per manufacturer the breakers can not be double pole, it need to be two single breakers and as disconnect for the unit he is proposing two separate 2 poles disconnect, I said 2 pole breaker or just one single 2 pole disconnect for the ungrounded conductors, having the neutral going straight to the unit.
I think the confusion start with the manufacturer recommendations itself of the two "separate breakers" instead of saying "two separate dedicated circuits using 2 hots and 2 neutrals", as of this point I will not do an installation if I think someone may get hurt.
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As long as each element connects from a single phase wire to the neutral (grounded conductor, center of wye), then you can use three single pole breakers with a handle tie. No need for common trip (all open when one opens) or anything else. That will be cheaper, IMHO, that two double pole (common trip) breakers and more convenient.
You can use single pole breakers with handle ties regardless of what phases the elements are connected to. But for a standard three phase panel, any group of three adjacent full size single pole breakers (making it easy to do a handle tie) will be from three separate phases.
If you get a good deal on two pole breakers, then using two of them and leaving one pole unused may cost less, but you still need to add a handle tie if you want to use the breakers to disconnect all power to the unit.
If you will be using a single common same-size neutral for all three phases (called a Multiwire Branch Circuit) then current Code requires the handle tie too.
 
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That is the way I see it, it doesn't matter how they get disconnect (handle tie, double pole breaker or double pole disconnect next the unit) but all the ungrounded wires feeding the water heater need to be disconnect at the same time, the engineer does not let me do the handle tie or two pole breaker, instead he draw single breakers with two separate double pole disconnect, if someone turn off only one disconnect then the water heater stay with one element energized with 277V
 
Alexis Enrique said:
That is the way I see it, it doesn't matter how they get disconnect (handle tie, double pole breaker or double pole disconnect next the unit) but all the ungrounded wires feeding the water heater need to be disconnect at the same time, the engineer does not let me do the handle tie or two pole breaker, instead he draw single breakers with two separate double pole disconnect, if someone turn off only one disconnect then the water heater stay with one element energized with 277V
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As you realize, any disconnect setup which could allow someone to turn off one disconnect or one breaker and then think that they had completely de-energized the heater will be either a code violation or just a bad idea.
 
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