Gas Boiler and Hot Water Heater

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infinity

infinity

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This is sort of a rhetorical question but I have a 15 amp homerun circuit for a hot water boiler that runs all the way to the boiler room in a house. In that room a tankless HWH is being added which requires 120 volts. The boiler draws about 2 amps with the pump running and all the zone valves operating. The HWH draws less than 1 amp. The service will be backed up with a portable generator with an interlock so only certain critical circuits running on gen power. With both on one circuit it would make it simpler than adding the HWH to the existing general purpose circuit. Who would put them on the same circuit? 🤫
 
Is there an NEC section that would require either of them to have an individual branch circuit?

If so, and the load calc works out, you could install a small panel to split your existing 120V 15A supply into two branch circuits, as a fairly pointless exercise in code compliance.

Cheers, Wayne
 
All that WH uses is a small circulator usually the same as the one on the boiler for heat. I see no reason why they all can't be on the same circuit.

-Hal
 
wwhitney said:
If so, and the load calc works out, you could install a small panel to split your existing 120V 15A supply into two branch circuits, as a fairly pointless exercise in code compliance.
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The boiler requires an individual branch circuit. That was one option over trying to get another HR across the basement. Something like an SOY cover with two fuses.

bus-soy-b-12.jpg
 
infinity said:
The boiler requires an individual branch circuit. That was one option over trying to get another HR across the basement. Something like an SOY cover with two fuses.
Click to expand...
Are we confident that the fuses that go in that device are listed for branch circuit protection, rather than just supplemental protection? I recall trying to look that up once and failing to get a definitive answer.

Cheers, Wayne
 
ptonsparky said:
🤔I grew up when fuses were viable. When did it change?
I would prefer an SSU for both.
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I guess if the SSU is using the same fuses as you use in fuse boards, they are listed for branch circuit protection. So the next question is whether the fuseholder assembly (the SSU) requires a listing for branch circuit protection.

Thanks,
Wayne
 
wwhitney said:
Are we confident that the fuses that go in that device are listed for branch circuit protection, rather than just supplemental protection?
Click to expand...
Aren't most plug fuses suitable for branch circuits?

The fuse holders would be protected by the 15a breaker.
 
infinity said:
The boiler requires an individual branch circuit.
Click to expand...

Are you stating that as fact or a what if exercise? If fact I would like to see the wording of the Article. That little circulator is no different than those that would be used in place of zone valves if they did it that way. It's all part of the boiler system. Would a separate circuit be required to supply the circulators if there were a circulator for each zone?

This water heater is not electrically powered which I would agree would require a separate circuit.

-Hal
 
422.12 "CentraI heating equipment requires an individual branch circuit"

I don't believe that the box cover fuse holders are approved for a branch circuit protection but only for supplemental protection, but a two circuit breaker panel would be.

I have an old two pole disconnect with plug fuse holders. I use it when I am upgrading a service I tap onto the wires at the weatherhead or in the meter to get power for lights and a drill while redoing a service. The old disconnect says "suitable for use as service equipment" inside it.

Of course, now with battery tools and lights it's not used much anymore.
 
infinity said:
As Eddie stated a fact. {422.12}
Click to expand...

I just wanted to see if Jersey amended 422.12 to say something else.

422.12 Central Heating Equipment.
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Central heating equipment
other than fixed electric space-heating equipment shall
be supplied by an individual branch circuit.

Exception No. 1: Auxiliary equipment, such as a pump, valve, humidifier,
or electrostatic air cleaner directly associated with the heating equipment,
shall be permitted to be connected to the same branch circuit.

Exception No. 2: Permanently connected air-conditioning equipment
shall be permitted to be connected to the same branch circuit.
Click to expand...



My interpretation is that the boiler with ATTACHED water heater circulator would fall under Exception No. 1 or 2 or both.

A separate water heater, whether gas fired, electric or heat pump, would not because it wouldn't be integral to the boiler and depend on it for operation.

Further, I have NEVER provided a separate circuit for the circulator on an indirectly heated water heater. Most times that circulator is controlled by the same controller that controls the heating circulator(s) and boiler. It has to be because when WH calls for heat it has to fire the boiler and often has priority over the other zones (shuts down the heating circulators until it is satisfied.)

-Hal
 
hbiss said:
My interpretation is that the boiler with ATTACHED water heater circulator would fall under Exception No. 1 or 2 or both.
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If the HWH and the boiler are somehow connected together (like a separate zone on a boiler) and the HWH is dependent on the boiler to operate I agree that the exception 1 applies. In this case other than the cold water the two system are independent.
 
infinity said:
If the HWH and the boiler are somehow connected together (like a separate zone on a boiler) and the HWH is dependent on the boiler to operate I agree that the exception 1 applies. In this case other than the cold water the two system are independent.
Click to expand...

Somehow, I got the impression that this was an indirectly heated water heater (Boiler Mate) which is what I went on to talk about.

After going back to your original post, I see now that you are really talking about a gas or propane fired tankless water heater. :oops:

So yeah, if you can't run a new home run and 15A circuit, I am of the camp that agrees with using a 2 space main lug panel and two 15A breakers to split the (now) feeder into two circuits. It will also double as a disconnect for the WH.

I wouldn't use plug fuses for anything if I could help it.

-Hal
 
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