Hydronic Unit Heater Questions

[romoman]

I recently moved and the new house has a 3 car attached garage. At the old house I had a 20x40 detached with a Mr. Heat Big Maxx propane heater. This house has a boiler with sufficient capacity that I could add a hydronic unit heater without too much work.

Does anyone have experience with these? Good choice over a propane heater? Any brands better than others? Any gotchas?

 

[Jackfre]

First Company is probably the largest. There are many others. If you have the capacity in the boiler then, yes, it is a good option for you.

 

[nh_yota]

One of my friends used to live in a house with a Modine hydronic fan coil unit in the attached garage. It was only used when needed and it wasn't running on a thermostat all the time to keep the garage warm. It pumped out a good amount of heat so it was perfect for warming up the garage a bit on a cold day when we were out working in it.

 

[Bondo]

Ayuh,.... No reason it wouldn't work,...

However, when ya shut it down, ya gotta keep some water flowin' through it, or it'll freeze, 'n bust everything,...

 

[ctfjr]

I have a Modine unit in my 3 car garage. The walls are all insulated well and there is a heated space above most of it. The doors are insulated. All that said I installed a unit with ~60mbh output rating (at 190 degs). I keep the thermostat usually set at 48 deg. It is so over sized that when I want to work in the garage I set it up to 60 and can start working in a few minutes. When set at 48 it hardly ever turns on - even in 10-15 deg temps.

 

[rlitman]

Ayuh,.... No reason it wouldn't work,...

However, when ya shut it down, ya gotta keep some water flowin' through it, or it'll freeze, 'n bust everything,...

That, or you get all crazy complicated and add a heat exchanger and then run glycol through the potentially unheated spaces.

Glycol will limit your transfer efficiency (and you'll need an extra pump, and other expenses), but has the benefit that you can completely turn it off without draining if you so choose.

If you think you'll want to treat the garage like a conditioned space, and keep it over 50F, then by all means forget the glycol (and this may make lots of sense if you live in an area with a warmer climate; also depending on how exposed the garage is, and how well the connection between the garage and house is insulated).

If you're only thinking of heating it on say weekends when you're in it, and if you're in a colder location, then you can potentially save a lot on your heating bill by letting it freeze at other times and then glycol may make sense.

Now here's another thought. I have a heat exchanger and glycol loop, but for a completely different purpose. I've got a snow melt zone under my front steps. Once you've gone through the trouble of adding a glycol loop, adding zones to it is much easier. So, if you have bigger plans, this might fit them well...

 

[dogdog]

adding an extra zone might work.... but if the garage is exposed or not well insulated, pipe bursting might be problem in cold frigid weathers, especially if you tends to turn off that zone during times you are not there. Not even adding Glyco or antifreeze, would help in coldest day some times.

 

[Mr onetwo]

Guys....It's an attached garage and he never mentioned unheated spaces.Keep it simple!NO glycol! Be very careful to not oversize the unit heater.I would be surprised if your boiler is sized to accommodate heating the garage, but you may be able to up-fire it. . You need to get an accurate heat loss calculated as a first step...garage doors lose a tremendous amount of heat. Then find a good clean used Modine or Sterling heater or 2, of the appropriate size.Depending on the size of the space, 2 smaller heaters may be better than 1 large one for air circulation.Download a copy of the Modine installation manual "1-550.29 Installation & Service, S/HW Unit Heaters" and read it thoroughly! We need to get more details about your system....boiler size,brand and burner type,pump arrangement, controls, ect. Also garage details. A clear picture or 3 would help. Then we can go from there with some specific recommendations.

 

[romoman]

Thanks guys. I'm in Bedford, NH, so it gets pretty cold (-2 last night). The garage is pretty well insulated with R-13 in 2x4 walls and R-58 in the ceiling with insulated doors with good weather stripping. The 20' front with garage doors and the 30' side are exposed, the other 2 sides are to conditioned space in the house. The boiler has plenty of capacity as it's currently fired for 117,000 BTU/HR and with a nozzle change can get up to 180,000 BTU/HR. It's got a "made" manifold, so adding the zone would not be a problem, though I'll have to add another controller on for it, which won't be a big deal. I've been thinking about adding an outdoor reset anyway and would do it while we are in there.

I'll keep it warm (45ish) all the time and t-shirt weather when I'm working in there. I'm familiar with boilers, zones, and the rest, just never used a hydronic unit heater (plenty of propane ones though!).

Thanks for the confirmation they work well. Now to decide which to get.

 

[Mr onetwo]

A speed control for the fan motor will make it very easy to fine tune things and help with short cycling. These heaters are very noisy at full speed.

 

[Dick in Wisconsin]

How is the existing boiler powered? Propane, NG, wood pellets, or electricity???

I'd recommend putting glycol in the system if you're going to use it in the garage, just to be safe.

 

[dogdog]

just something to consider about.... garage usually is colder and most people won't constantly heat it unless they are there. Other than heat losses from the garage door. Hydronic (water) freezes when the pump is not running. with or without additives. when it is cold enough.

This is happened to my friend not exactly in the garage thing but it's on the addon extension. so it have a zone add to his boiler. Since that was his home office, he decide to shut off the heat to that zone, unless he is in there working. It all works out fine for 2 winters, the third, it was the coldest day of winter....nothing happens. later in the weeks when weather got warmer.. his system started acting weird and the water leaks with the boiler kept constantly refilling water. One of the joints under the floor had cracked/bursted. costed him 6K to rip off the flooring and repair that leak....

Just saying
Might be better with other type of garage heaters than trying to add another zone to the existing boiler, even if the system is capable of it. Because you might not be constantly heating that garage or cost more trying to maintain the temp.

 

[Dick in Wisconsin]

Is there any particular objection to putting some kind anti-freeze in the boiler water?

 

[Denwood]

Adding glycol reduces the heat transfer efficiency significantly as the percentage added increases. That's why plain water is used wherever possible.

 

[Mr onetwo]

Glycol is to be avoided at all costs. It is not permanent and should be monitored yearly and replaced a intervals. Most residential customers are very lax about this and don't want to pay for proper maintenance. Glycol has it's place, just not in this instance.

 

[romoman]

It's an oil fired boiler. I would heat the garage all the time, so I'm not worried about freezing pipes or anything else. I'm very comfortable and used to fhw heat, so that is not a problem. You don't shut off zones completely without draining them in the winter.

There is no need for glycol here - I would be running the heat in the garage all winter at a minimum level of 45F, so there is no concern of freezing. The lines would be run through the basement and through an interior wall up to the installed height of the unit.

 

[Jackfre]

Rik, you should probably begin a new thread for this as you are asking under a different designation of product. The OP, a few years ago asked about "Hydronic UNIT heaters". Your question is about BASEBOARD heating. Different animal.

 

[fitter30]

If your only going to really use the garage heat part time or set at a lower temp than the house then by increasing boiler capacity the boiler would short cycle and boiler really don't like that plus short cycling tend to give uneven heat. Boiler failure in dead of winter you probably have some sort of back up. Now you have to think of the garage.