Hanging heater help

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nate379

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This pertains to my nat gas boiler system, but I don't think it really matters how the heat is being made.

I installed a Modine hanging heater in my garage a few weeks ago. I have slab heat, but I was not satisfied with the response time of the slab. It maintains the air temp just fine, but open the door and pull in a cold vehicle (lets say -10* outside) it would take hours to get the garage back up to temp.

My system has a primary/secondary loop, the floor heat runs off the secondary loop. I T'eed into the primary loop to run this heater, that way I should get 160*+ water to it. The problem I'm having is the heater is blowing just lukewarm air. With the boiler at 170* I am seeing only about 120* supply and 95* return off the heater. I am confused on what is going on.

Before I did the plumbing work on it, I had an HVAC come by and let me know the best approach to it (he was doing other work for me at the time). I piped it just like he suggested.

I'll get some photos later this morning when I get home, but maybe someone would have ideas?
 
So is the Modine plumbed in as a secondary off the boiler primary? I.e. it has its own pump and closely spaced tees in and out of the primary loop?

How long is the connection from the primary loop to the Modine? What material? Insulated?

And the boiler primary continues to be 160? Sounds like you aren't getting the hot water to the Modine....a plumbing diagram would really help.

Slabs respond very slowly...but I'm surprised to hear once the car comes into the garage, it takes a long time for the garage to get warm again? I wouldn't think that would be the case with a warm floor. How warm is the floor? In any event, the Modine should certainly allow you to raise the temp in the cold garage much faster than the slab heat will....I agree with that!
 
Once a slab is up to speed it stores a lot of energy. This is why they are som popular for maintenance shop. Road garages, airplane hangers are ideal radiant jobs. Radiant heat is a long wave radiation, the output travels at the speed of light. As soon as something sees the slab it will recieve that energy. It's like steeping out into the sunlight on a cold winter day. as soon as the sun strikes your body you feel the energy. Same with a radiant slab.

Now if you pull a 8,000 lb truck into the shop that is 0F, then that mass will need to be warmed by the energy in the slab. It all about the mass and the temperature. Hot goes to cold, the rate of that heat transfer is based on the ∆T of the objects.

When you heat with a forced air emitter like a Modine you may discover most of the heat energy is up near the ceiling. Fo large shops we would use the Modines that blow straight down. That way they blanket the floor with the heat energy first.

It takes energy and time to bring the slab up to temperature on first start. Consider a yard of concrete, about 81 square feet at 4" thick weighs about 4000 lbs. It takes time to raise that mass temperature. Calculate how many yards of concrete is in your shop slab and run the numbers. It could take a few days to bring the slab up depending on tube spacing and boiler input. Once you have it reved up it should be the most comfortable and least expensive means to warm a shop. I find 60F is plenty warm in my shop if the floors are warm.

hr
 
Floor is usually a few degrees above the air temp. Like right now I have it set to 55* and the floor is 58-60*


bpirger said:
So is the Modine plumbed in as a secondary off the boiler primary? I.e. it has its own pump and closely spaced tees in and out of the primary loop?

How long is the connection from the primary loop to the Modine? What material? Insulated?

And the boiler primary continues to be 160? Sounds like you aren't getting the hot water to the Modine....a plumbing diagram would really help.

Slabs respond very slowly...but I'm surprised to hear once the car comes into the garage, it takes a long time for the garage to get warm again? I wouldn't think that would be the case with a warm floor. How warm is the floor? In any event, the Modine should certainly allow you to raise the temp in the cold garage much faster than the slab heat will....I agree with that!
Click to expand...
 
I would be sweating if I kept it at 60*. Usually 50-55* if I am working in there.

The idea with the Modine was to be able to turn the slab heat down to 45* and just turn that on along with the slab heat when I wanted to work out there. If I went from 45 to 55 it would take probably 6-7 hours.

in hot water said:
Once a slab is up to speed it stores a lot of energy. This is why they are som popular for maintenance shop. Road garages, airplane hangers are ideal radiant jobs. Radiant heat is a long wave radiation, the output travels at the speed of light. As soon as something sees the slab it will recieve that energy. It's like steeping out into the sunlight on a cold winter day. as soon as the sun strikes your body you feel the energy. Same with a radiant slab.

Now if you pull a 8,000 lb truck into the shop that is 0F, then that mass will need to be warmed by the energy in the slab. It all about the mass and the temperature. Hot goes to cold, the rate of that heat transfer is based on the ∆T of the objects.

When you heat with a forced air emitter like a Modine you may discover most of the heat energy is up near the ceiling. Fo large shops we would use the Modines that blow straight down. That way they blanket the floor with the heat energy first.

It takes energy and time to bring the slab up to temperature on first start. Consider a yard of concrete, about 81 square feet at 4" thick weighs about 4000 lbs. It takes time to raise that mass temperature. Calculate how many yards of concrete is in your shop slab and run the numbers. It could take a few days to bring the slab up depending on tube spacing and boiler input. Once you have it reved up it should be the most comfortable and least expensive means to warm a shop. I find 60F is plenty warm in my shop if the floors are warm.

hr
Click to expand...
 
If the Modine and the floor are both running, you probably do not have enough boiler "hp' to keep up the temperature.

The Modine spec sheet should show you the performance with different ∆T, and the air temperature it is inhaling will determine the discharge temperature.

With primary secondary, some of the return from the system is mixing with the boiler supply and mixing down that temperature. If you know the flow rate and temperatures you can calculate that mixed temperature. Here is an example with a Hydro Separator, which is essentially a P/S.

With shoes on in a shop, the slab temperature is not as critical as inside your home. If the slab is lower then skin temperature it will feel cold to the bare, or stocking feet. A cold slab really pulls energy from your body and can be un-comfortable to work on all day. Of course raising the slab temperature will raise the room temperature.

If 50 is comfortable to you, just let the radiant handle all the load. Any blower moving air that is lower than skin temperature will feel cold. Inside the home we call that a cold draft, out side the home it's called a chill factor, same concept really.

hr
 

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I have a radiant slab in my garage which 18X20 and 10' ceiling with the stat set @60 °F and with the temp. @ freezing outside I could have my garage door open for ten minutes then shut the door and the room feels warm in a very short time .the slab is 4 to 6". The slab is a huge mass. Best form of heat i've ever had . Maybe 55 °F is a little bit low . turn it up to 60.
 
Garage is 24x26, 9ft ceiling. Garage door is 18ft wide, 8ft tall. Slab is about 6", though tapers down to about 4.5" toward the front (floor has a bit of slope so water will drain)

I checked this morning and with a "meat" thermometer (same one I use for measureing vent temp on car A/C) I have about 100* air coming out of the heater. I checked the spec sheet that that is what is should be.

I don't really understand why it feels cool. My friend has a similar heater in his garage and the air feels fairly hot coming off it.
 
I have a Modine in my attached garage too. Never measured air temp but like in hot water said-----it feels like a cold draft with the blower moving the air. I thought I had an issue too but it works just fine. Radiant off my Econoburn keeps my garage at 60-65 right now with an outside temp of 19. Blowing air vs. emitters on baseboard or radiant feels much different......... What's your temps up there NATE?
 
It's around 2* right now and snowing like crazy. Yesterday it was -10*
 
Teh 2 pipes that go threw the ceilign are the ones for the heater.

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