Circulator Control for Unit Heater

scottbenent

Hello. I am going to put a hot water unit heater in a garage. The garage is not normally heated (will use heat only intermittently). So the unit heater and piping will be exposed to freezing temps. I don't want to use glycol in the system. I've heard there is a control system that uses a sensor to sensor when the water in the system reaches a set point (some temp close to freezing) and then turns on just the circulator pump and not the fan. That way just the water in the system is kept warm enough not to freeze. The garage is foam insulated so it doesn't get below freezing that much, but I don't want to heat it full time. Is there such a device ? Thanks.

scottbenent

Whoops. Just realized I posted it in the wrong catergory.

scottbenent

Hello. I am going to put a hot water unit heater in a garage. The garage is not normally heated (will use heat only intermittently). So the unit heater and piping will be exposed to freezing temps. I don't want to use glycol in the system. I've heard there is a control system that uses a sensor to sensor when the water in the system reaches a set point (some temp close to freezing) and then turns on just the circulator pump and not the fan. That way just the water in the system is kept warm enough not to freeze. The garage is foam insulated so it doesn't get below freezing that much, but I don't want to heat it full time. Is there such a device ? Thanks.

Zman

The way those heaters are normally setup, first the t-stat tells the boiler system to send hot water to the heater, once the heater is warm, an aquastat tells the fan to turn on and heat the space. It is done this way so the heater won't blow cold air on the occupants as the heat is getting there.

There would be dozens of ways to configure your system so that the pipes won't freeze. The easiest would be to install a low temp thermostat and set it to around 40 degrees. If your building is well insulated, it should not use much energy.

mikeg2015

You might be in the correct category. A garage heater without glycol is a recipe for frozen pipes. At some point the pump will fail or electricity will go out and you may not be there ot drain it. it ALWAYS does on the coldest day, on a Sat. Night or when you aren’t home over a weekend.

How far away is a gas line? The gas fired unit heaters are cheap and work well. Otherwise I think it’s a big risk not to put in a small plate and frame heat exchanger and use glycol on it. The little P&F are pretty cheap. I assume it’s an existing boiler so there’s already a primary circulator.

Tim Potter

Since the garage is insulated & temps rarely fall below freezing, how about a low setpoint freeze protector to run the pump & heater to keep above say 40*? It wouldn't take many BTUs to maintain 40*

This on the pipe wired in parallel with existing thermostat:
https://www.amazon.com/Protech-50313-Freeze-Temperature-Controllers/dp/B009AX7XOO

Or this for the main t-stat:
https://www.amazon.com/Honeywell-CW200A1032-E1-CW200A-Watchman/dp/B00099DG8A

Tim

Zman

Gentlemen,
Can we please just comment on one of these double posts.
@Erin Holohan Haskell can you please delete one?

Jamie Hall

Do not count on just circulating the water to keep it from freezing. First, as noted, if the power goes out on some chilly evening, you're toast. Second, just circulating the water won't keep if from freezing if the building goes below freezing. It will freeze somewhere -- most likely in a lower velocity odd corner of the unit heater, which will then be ruined.

The suggestion of a gas unit heater -- or any one of a variety of other gas (LP or natural) fired heaters -- for this type of application is excellent. Depending on how you are planning to use the space, you could also look into gas infrared radiant overhead heat, such as is commonly used in barns and hen houses and the like. No risk of freeze up when the power is out -- though the building will be cold.

If you really want to stay with hot water, you would be well advised to use the glycol and be safe...

Erin Holohan Haskell

Zman said:

Gentlemen,
Can we please just comment on one of these double posts.
@Erin Holohan Haskell can you please delete one?

I've merged these two posts. Thanks!

GroundUp

Keep it heated or add glycol. Relying on electricity to always be there is not a wise plan.

pecmsg

Why No glycol?

That's just asking for trouble!