Boiler circuit 20A to 15A breaker?

cpaul

I would like to be able to replace a 20A boiler breaker with a 15A breaker, if possible for an approximately 1985 boiler in a cape cod style home. I don't know what the boiler specs or ecectrical requirements are at this time.

The reason I want to do this is so I can install a 15A reliance controls (TF151W) single circuit manual transfer switch on the boiler to be able to run the boiler off a fuel efficient portable 46 pound Honda EU2200i generator during a winter power outage.

Reliance makes a 20A switch (TF201W) as well but then a larger generator would be needed.

A 10 circuit transfer switch will be installed at the panel because the home has a well and an inefficient 6000w generator will power that when the well or kitchen circuits are needed but would like the option to run the boiler through the night on a small, quiet generator.

Thanks for reading.

ratio

A larger generator wouldn't be needed unless you exceed the capacity of the smaller generator, even if you use the larger transfer switch. The wiring would be protected by the breaker in the generator even though the breaker in the transfer switch is rated at 20A.

I would suggest monitoring the current of the circuit you plan on intercepting to make sure the smaller generator will be able to power it, paying particular attention to startup current as that can be significantly higher than run current. This may limit your choice of generator as well as transfer switch.

cpaul

The smaller honda does not accept a 20a plug and is rated 18.333 amps

HVACNUT

Most residential boilers will or should have 15A protection max. Check the rating on the boiler, burner if oil or power gas burner, circulators, any parts that draw power. Since it's now a 20A circuit, it should be #12 wire which is fine. Is this a typical system for a single family home? How many circulators? What brand and model boiler?

ratio

No need for a 20A cordset if the generator overcurrent protection is 15 amps.

@HVACNUT mentioned something that I missed: you may already exceed the nameplate MOCP with a 20A breaker feeding the boiler. Check the boiler nameplate & see what the MOCP is (& note that it may specify different numbers for fuses vs circuit breakers). You may need to change the breaker anyway.

Going down a size on over current protection should be a simple swap—conductors that are sized for a 20A breaker will be fine on a 15A breaker. (The other way isn't possible)

Zman

Just add up the amp rating of your boiler and pumps and you will have the answer.
It is very unlikely that a typical residential setup draws anywhere near 15 amps.

cpaul

Thank you all for your terrific responses, I appreciate it very much.

EBEBRATT-Ed

Unless you have a ton of pumps on the boiler a 15amp circuit is probably fine. A boiler is considered a continuos load so a 15 amp breaker can supply a 12 amp load. A 20 amp breaker can feed a 16 amp load

nicholas bonham-carter

Some newer boilers, and A/C’s are particular about the the quality of A/C current Produced, so try it out first before cutting the check.—NBC

ChrisJ

nicholas bonham-carter said:

Some newer boilers, and A/C’s are particular about the the quality of A/C current Produced, so try it out first before cutting the check.—NBC

It's probably sound advise, but I'd expect a Honda EU2200i to run even the pickiest things.