Unit heater install questions - Check my work??

[Andy_GTS]

I'm installing a Beacon Morris 75k BTU unit heater in my 24x30 garage. I haven't committed to a location yet, thats what I'm looking for advice on. Using an old drywall lift, I put in one location I'm considering.

On the back wall pointing straight ahead towards the overhead/man doors.: Offset

The advantage for this is I can run the vent pipe farther up the slope of the roof. Also simplifies hanging since I can mount directly to the trusses. My concern is that it won't distribute heat well and may block light in that position.

My other idea is to mount it in the corner:

This may distribute heat better?? I'm concerned that if I mount in the corner, the vent pipe will be right at the edge of my roof. Considering the minimum rise of 5ft per installation instruction, that will stick out quite far from the roof.

What is the general consensus on which of these two positions would be better?




Also, in regard to the vent pipe, is a 90* elbow directly out of the heater a problem. The installation instruction states to use as few elbows as possible. I've attached two pictures showing the options.

90* directly out of the heater:

12 inch pipe and then the elbow:

What would be the best of these two options? I like having the exhaust vent closer to the heater (no 12 inch pipe) so that the vent isn't as close to the edge of the roof. Thoughts?

Thanks,
Andy

 

[D45]

My heater stated a specific amount of straight pipe that should be used, before the 90 degree

Check your manual............mine said 12" min

I think the corner location will be the best choice, like you have shown.........the fan should blow 25' so it will cover the area nicely

A 75k heater will heat that garage up FAST......I am running a 45K in my 1000 square foot shop and its decent, maybe a 60k would have been better though

Here is my heater install:
http://www.garagejournal.com/forum/showthread.php?t=325943

 

[D45]

This may distribute heat better?? I'm concerned that if I mount in the corner, the vent pipe will be right at the edge of my roof. Considering the minimum rise of 5ft per installation instruction, that will stick out quite far from the roof.

Follow suggestions in your manual to match your roof pitch

Thankfully, I have a pretty flat roof like so my vent stack did not have to be that tall

What is your pitch?

 

[Andy_GTS]

Follow suggestions in your manual to match your roof pitch

Thankfully, I have a pretty flat roof like so my vent stack did not have to be that tall

What is your pitch?

My pitch is 5/12.

The manual states "A minimum vertical rise of 5 feet (1.5m) is required for Category I venting. The top of the vent pipe should extend at least 2 feet (0.61m) above the highest point on the roof. Consideration should be made for anticipated snow depth. Install an Amerivent Americap or Metalbestos vent cap over the vent opening."

Now does the highest point of the roof mean above the shingles at the exit location or does it mean the very peak of the roof. If it means the peak and I put the heater in the corner, the flue pipe will protrude a lot above the roof.

 

[Andy_GTS]

My heater stated a specific amount of straight pipe that should be used, before the 90 degree

Check your manual............mine said 12" min

I think the corner location will be the best choice, like you have shown.........the fan should blow 25' so it will cover the area nicely

A 75k heater will heat that garage up FAST......I am running a 45K in my 1000 square foot shop and its decent, maybe a 60k would have been better though

Here is my heater install:
http://www.garagejournal.com/forum/showthread.php?t=325943

My manual (in the box with my heater) does not specify a minimum horizontal run. However, if I download the PDF from Beacon Morris, its specifically states 2ft minimum (which seems like a lot). I've been in contact with their Tech agent and he stated I can use a 90* within the 2ft if absolutely required but warned it may cause the blocked vent pressure sensor to trip. Has anyone experienced that?

Also, the reason for the 75k TU over the 45K was that with a rebate and sale at Menards the price difference was $44. I felt it was worth it. I also have a vaulted ceiling so the volume is a bit larger for the footprint.

Thank you for your help so far!

 

[dave*99]

I have a similar size garage and layout. Also with a vaulted ceiling. The ceiling inside peak is around 15 feet.

I put my 45K BTU Dayton heater in the corner as you show in your sketch. Works great.

I think 75K BTU is too large for that space.

 

[Andy_GTS]

I have a similar size garage and layout. Also with a vaulted ceiling. The ceiling inside peak is around 15 feet.

I put my 45K BTU Dayton heater in the corner as you show in your sketch. Works great.

I think 75K BTU is too large for that space.

Would the disadvantage be short-cycling? Where is your location? I also should have added that I will have R13 walls and r19 ceiling. Also have a r6 16ft garage door.

-Andy

 

[dave*99]

Would the disadvantage be short-cycling? Where is your location? I also should have added that I will have R13 walls and r19 ceiling. Also have a r6 16ft garage door.

-Andy

I am in NJ and while winters here are not as cold as yours, I do not heat the garage when I'm not working out there, so a Saturday morning will have 3 cold cars in the garage and a cold concrete floor for the heater to deal with.

So think about you usage too. Will you maintain some heat in the garage at all times or will you usually bring the temp up from very cold? What will be your set point when not using the garage?

This type of heater should not be set to lower than 50F as condensation will build up in the heat exchanger.

In about 30 minutes I can warn up the garage from the 30's to 60. I have insulated doors, R13 walls and R19 ceilings.

And yes short cycling would be the result of too large a heater.

I have a ceiling fan running at a slow speed up in the ceiling peak to move the heat down. This is very effective.

 

[Andy_GTS]

I am in NJ and while winters here are not as cold as yours, I do not heat the garage when I'm not working out there, so a Saturday morning will have 3 cold cars in the garage and a cold concrete floor for the heater to deal with.

So think about you usage too. Will you maintain some heat in the garage at all times or will you usually bring the temp up from very cold? What will be your set point when not using the garage?

This type of heater should not be set to lower than 50F as condensation will build up in the heat exchanger.

In about 30 minutes I can warn up the garage from the 30's to 60. I have insulated doors, R13 walls and R19 ceilings.

And yes short cycling would be the result of too large a heater.

I have a ceiling fan running at a slow speed up in the ceiling peak to move the heat down. This is very effective.

I was hoping to leave the garage heated in the winter to maintain at least above freezing. I bought a ct50 thermostat that allows temp set down to 35. I was thinking around 40* at least. But I don't want condensation to damage anything either.

I have a ceiling fan going in as well. Its too late for me to return the heater for a smaller model. Is it oversized so significantly that I should just sell it off and cut my losses for a 45k BTU?

 

[dave*99]

I was hoping to leave the garage heated in the winter to maintain at least above freezing. I bought a ct50 thermostat that allows temp set down to 35. I was thinking around 40* at least. But I don't want condensation to damage anything either.

I have a ceiling fan going in as well. Its too late for me to return the heater for a smaller model. Is it oversized so significantly that I should just sell it off and cut my losses for a 45k BTU?

Read the owners manual carefully. This was discussed in another thread- where someone asked about finding a thermostat with a set point around 35. Theirs bottomed out at 50F. It's not the thermostat that is the issue here. Condensation in the heat exchanger will rust out the heat exchanger. My owners manual expressly states not to use this heater to maintain temperatures below 50F.

As for advising you to sell your heater and buy a smaller one, that is really up to you, but I will say if you are going to keep the garage at 50 and heat it up from there when you need to, then 75K is too large.

 

[dave*99]

One note of caution on setting your heat below 50 degrees F when using a gas fired unit heater - and this is from the owners manual of the Sterling tubular propeller heaters:

Unit heaters should not be installed to maintain low
temperatures and/or freeze protection of buildings.
A minimum of 50°F (10°C) thermostat setting must
be maintained. If unit heaters are operated to maintain
lower than 50°F (10°C), hot flue gases are cooled inside
the heat exchanger to a point where water vapor (a flue
gas by-product) condenses onto the heat exchanger
walls. The result is a mildly corrosive acid that
prematurely corrodes the aluminized heat exchanger
and can actually drip water down from the unit heater
onto floor surface. Additional unit heaters should be
installed if a minimum 50°F (10°C) thermostat setting
cannot be maintained.

 

[Andy_GTS]

Thanks for the info. I'll just take my heater back to the store and continue to use my kerosene heater. This is all ending up being too much work.

 

[dave*99]

Thanks for the info. I'll just take my heater back to the store and continue to use my kerosene heater. This is all ending up being too much work.

Don't be discouraged. Getting rid of the kerosene heater and installing the unit heater was the single biggest improvement I made to the garage.

 

[TurnipTruck]

Can you vent horizontally out the wall?
I won't put a flue through a steel roof in snow country if I can help it.

 

[Andy_GTS]

Can you vent horizontally out the wall?
I won't put a flue through a steel roof in snow country if I can help it.

I could but I would need to use Cat III stainless steel piping... which is $$$. Also, my roof is regular shingles, not metal.

 

[D45]

Thanks for the info. I'll just take my heater back to the store and continue to use my kerosene heater.

Wanna trade for a 45k????

 

[Andy_GTS]

Wanna trade for a 45k????

Maybe. How old is yours?

 

[D45]

I just installed it a few months ago........I acquired it from someone else, who said it was 2-3 years old

It looks almost brand new

 

[brewchief]

A 45k or 60k heater would have been a better size for that garage but I wouldn't be scared to use a 75k, it will be a bit oversized but as long as it's not running for just a few minutes at a time it won't be a big deal, it may not hold the temp quite as close to the setpoint but it's not like it's a living room so if it is a couple degrees high or low it's not going to be a big deal.

 

[D45]

How's the install going?

 

[Andy_GTS]

How's the install going?

It's going okay. Sorry I haven't updated or added new pictures. I've decided that I'm sticking with the heater I have. It was a great price and I already own it so... there is that.

So far I have turned the unit to angle towards the center of the garage door. I have a draft hood connector, 90* bend, and a 5ft pipe up through the roof. This puts roof termination about 2ft above the shingles. I ran the setup past beacon morris tech support and they said it should work fine despite they revised the newer instructions. They seemed to think I will have no issues considering how short the system is and the negative pressure created by the hot gas.

Thats about as far as I've got considering heavy rains have kept me off the roof. I'll post pictures when I can.

 

[Andy_GTS]

Here is the almost finished project. I have moved it it to a slightly angled position.

I haven't connected all the b-vent yet. I need to put the firestop in. Is the firestop supposed to be between the drywall and the framing or do I put the drywall up first and then the firestop?