Another non-PC application - home furnace

[Anonymous user]

Hello. I'm not going to do anything crazy but I am wondering...
My home has a steam heating system (that is, there is a boiler that burns natural gas to generate steam; the steam wafts up the heating pipes to the radiators; there is no fan or pump used to move the heat from the boiler to the house).

The boiler does use electricity to interact with the thermostat, to turn the gas on/off, and to open/close a chimney damper.

The thermostat has little batteries to send its signal to the boiler, so that's taken care of.

The house wiring runs to the boiler. Once there, there is a Transformer (120 / 24 VAC).
The boiler has a schematic and notes that state: "Electrical input less than 12 amperes, 120 volts, 60 Hz"
The chimney damper has a small electrical motor: "24 VAC, 60 Hz, 80 ma"

Today, if my home has a power failure then we stop having heat.

Would it be possible to use a UPS to keep the home heated during a power failure (i.e., between the house-wiring and the boiler's transformer)?

How could I determine how many watts the system uses, say over one hour?

Thank you.

[Cap1_apc]

Hi,

Use the very simple formula Volts x amps = watts.

If you can get the volts and amps draw off each unit, we can try and size you for a UPS. Do you have a budget in mind? The boiler alone draws 12amps at 120v = 1440w (which would be one of our larger SmartUPS units).

[TheNotoriousKMP_apc]

Gonna need a Smart-UPS regardless.

That DC motor is going to overload any Back-UPS it is plugged into.

[Anonymous user]

Thank you Cap1 and KMP. Even just using the boiler's numbers
...boiler alone draws 12amps at 120v = 1440w (which would be one of our larger SmartUPS units)
and using the APC site's Selector tool, it picks
APC Smart-UPS XL 2200VA 120V, for $1,739
Wow.
That's a lot more power than I would have thought -- I wouldn't think it would take that many watts to open & close a gas switch (though that is an important function! so maybe it's extra-strong/sure); and the chimney damper motor just rotates a 6" circular piece of thin metal a quarter turn.
Thanks again.

Thinking some more, this probably would not be a good application of an UPS anyway. Scenario: we're gone for a few days, power failure hits, and then the battery runs out while the gas valve is in the open position.
Thanks for your help.

Message was edited by: SteveT

Message was edited by: SteveT

[voidstar_apc · Accepted solution]

I'd hope that valve is fail-safe, as the same thing would happen if a power failure hit without the UPS.

The 12A x 120VAC = 1440 W is a conservative estimate... the boiler probably uses less during normal operation. I googled for "boiler current" and [this page|http://www.sheltertech.com/faq.htm] estimates less than 5A under normal operation... or about 600 W. I can find APC SmartUps sold online that supply that for $500-$650... but of course you have other components of this system to power as well. It's probably best to measure the current or power to get a definite answer.