Choosing a Unit Heater

Sparky49

We have a concrete basement garage and the building has a hydronic boiler. The ceiling is about 8 feet high.

We want a blast of heat to offset the opening of the roll-up door. After the door is closed, just enough heat is needed to be comfortable while working.



What size heater should I choose?



Should it be mounted by the side of the door, or somewhere else?



Additional information:



We have never had to thaw pipes and there is no heat in the garage now. Both the DHW and DCW are in CPVC which is running through the basement . The electric WH is next to the wall away from the roll-up door.

The garage is bermed on the three sides but the door side and half of the adjacent walls are exposed. There is no insulation but the walls are block or stone. The ceiling is concrete panels.

CMadatMe

Modine

Modine makes a nice  low profile unit heater. Info attached..

Sparky49

Thanks for the reference!

That looks like just the ticket.



Now, which one to choose. . .



What would you recommend for BTUH?

CMadatMe

Depends

How long is the door open? What is the heat loss? What temp are you looking to keep the garage at? What type of climate are you in?

Sparky49

We are located in Maryland

The door is usually only open for a few minutes. We will dump most of the heat in the garage in that time though. If we can get a 20 degree F delta in five minutes it should be good enough.







Would it be reasonable to just buy the most BTUH we can afford?

CMadatMe

No

It would be reasonable to purchase the heater that can do the job. Do a heat loss. You then must also make sure the existing boiler can deliver what it needs to deliver to the u it heater. Suggest you call a pro

Sparky49

Does oversizing the unit heater matter?

What's the damage if the unit heater is oversized? The rest of the building is not heated during the few minutes of recovery once the garage warms. 







The rest of the time the garage heater is idling. 

There are no heat loss calculations for overcoming the massive heat loss of opening a garage door AFAIK.

Is the lack of information due to this having been a question for which there is no real answer?

Sparky49

I wish I could call a pro. . .

But, I was told to pick out a unit heater.

Sparky49

answers to questions

How long is the door open? Five minutes or so max.

What is the heat loss? Normally the delta T is about 10 F or so, I have never done a heat loss calculation for a basement much less this one. Since it is partially bermed it has never gotten cold enough to freeze the water or drain pipes.

What temp are you looking to keep the garage at? Fifty or 60F would be acceptable.

What type of climate are you in? "Average annual temperature: 55.1 degrees Fahrenheit. High temperatures occur in July, the warmest month, averaging in the mid to upper 80s. Low temperatures in January, the coldest month, average in the low to mid 20s.



Since 1871, the mean temperature has been 54.6 degrees Fahrenheit, according to the - State Climatologist Office. The highest recorded annual average temperature was 59.2 degrees in 1931, and the lowest was in 1904, at 52.6 degrees."