Local disconnect for tankless water heater

[jtinge]

A tankless water heater requiring three independent 40A ckts has been proposed for one of our campus facilities. If the source panelboard does not have provisions to lockout the three 40A breakers, the way I read NEC 422.31, a local disconnecting means is required. Since there are three independent 40A ckts, I'm assuming three local disconnects and the need to add a warning label to indicate multiple sources of power. Anybody dealt with this situation before and how? Is there a multipole local disconnect that will open all circuits at once?

 

[A/A Fuel GTX]

A tankless water heater requiring three independent 40A ckts has been proposed for one of our campus facilities. If the source panelboard does not have provisions to lockout the three 40A breakers, the way I read NEC 422.31, a local disconnecting means is required. Since there are three independent 40A ckts, I'm assuming three local disconnects and the need to add a warning label to indicate multiple sources of power. Anybody dealt with this situation before and how? Is there a multipole local disconnect that will open all circuits at once?

How about a 3 phase disconnect?

 

[Sierrasparky]

I think the OP is refferring to 3 40a two pole circuits.

 

[jtinge]

Correct. (3) 2-pole circuits, 6 conductors.

 

[A/A Fuel GTX]

I think the OP is refferring to 3 40a two pole circuits.

Yeah, you are probably right. One could always use 3ea 2 pole relays with a snap switch to control the coils.

 

[jtinge]

We don't allow use of a control device for LOTO.

 

[A/A Fuel GTX]

We don't allow use of a control device for LOTO.

I don't follow your response

 

[Sierrasparky]

Yeah, you are probably right. One could always use 3ea 2 pole relays with a snap switch to control the coils.

Use of relays do not provide 40 amp overcurrent protection for each element.
What you can do is use a load center with a main breaker. Should work just fine..

 

[A/A Fuel GTX]

Use of relays do not provide 40 amp overcurrent protection for each element.
What you can do is use a load center with a main breaker. Should work just fine..

Would not the OCPD at the branch circuit origination point provide the protection? All we are doing is interrupting the circuit with the relays......

 

[jtinge]

I don't follow your response

Sorry about that. Since the panelboard breakers aren't lockable, we would use the local disconnect to provide a means of lockout/tagout (LOTO) during maintenance. Since the proposed snap switch would be a control device to the relays, it would be unacceptable as a means for LOTO during maintenance. A local load center with main would work but seems extreme. Although I don't agree with it, I noticed the Canadian Electrical Code requires that a single 120A circuit be provided to the heater via an auxilary terminial block located in the heater cabinet used to then feed the (3) 40A circuits. This would allow for a 2-pole local disconnect, but no overcurrent protection for each of the 40A circuits. Still looking for a reasonable option.

 

[cripple]

You might want to install a six (6) ple diconnect check this web page.

http://www.bacocontrols.com/pdfs/DisconnectSwitch/6-134_6-135.pdf

 

[jtinge]

Awesome. Just what the doctor ordered. Thanks for all your thoughts.

 

[benaround]

We have used 6 pole disconnects on motors with a high/low speed, such as cooling

towers for chillers.

 

[Sparky32297]

I am just curious, all of these instant type heaters that I have seen have circuit breakers built into the cabinet. Is this the case??

 

[quinn77]

sub-panel

 

[juptonstone]

Tankless water heater???

Tankless water heater???

Assuming that you have a commercial grade three phase panel, how about installing a sub-panel near the tankless water heater. If you can't directly connect it, then run it off a 125-150 AMP breaker (presumably it takes bolt-ins?) then to the sub-panel.