Reznor 50k btu blowing warm not hot

[coppah37]

I bought a used reznor fe50 heater for my garage. My garage is insulated 28x36. The heater is a propane unit. I just got done hooking it all up today. I'm using a 100lb propane tank which is full. I went to fire up the heater and all seemed well but it only seems to blow luke warm air. I let it run for an hour with the same result. Everything seems to work but it only seems to blow warm air. I'm not sure if I did something wrong or if there is something wrong with the heater.

If anyone has any suggestions please let me know.

 

[DEnd]

What's the temp in the garage? Heaters only put so much heat into the air, so if you are starting at say 30º you may be only getting a 90º output temp, which will feel somewhat cool. You start to feel warm air at about 95º and won't start to feel hot until over about 120º (that is output temp of a fan, not general air temp).

The easy way to tell is to measure the input temp and the output temp, subtract the input from the output (the temperature rise, or Delta T), and multiply that by 0.018 That equals the BTU output for each cubic foot of air that goes through the heater. Then multiply that by the CFM rating of the fan. That's BTU per minute, multiply that by 60 gives you the BTU per hour of the unit. compare that to the BTU rating multiplied by the efficiency rating (ie 50K BTU* 0.83 for an 83% efficient unit).

Someone should double check me on that but I'm pretty sure that's correct.

 

[coppah37]

It's certainly cold out recently in NH. I'd say starting temp in the garage today was about 25. Still doesn't seem like it gets hot enough to begin warming up 1,000 sq ft. I have a two stage regulator on the tank that brings the pressure to 11" wc. The heater itself has a regulator on it that brings pressure to 10" wc.

I tested the gas line for leaks And found none. The line is about 10' total run from tank to heater. Could it be possible the distance of the pipe is hurting my gas pressure? It's 1/2" black pipe.

 

[aandpdan]

1/2" is plenty big enough for a 10' run.

Depending upon your insulation your heat loss may be more than 50k.

 

[JCByrd24]

The temp rise through those units is only like 40-50 degrees. 25+50=75 moving as quickly as the air moves through them does not feel hot. It is normal.

 

[James-W]

Does the garage reach the temperature you want it to be?

 

[dave67fd]

It's certainly cold out recently in NH. I'd say starting temp in the garage today was about 25. Still doesn't seem like it gets hot enough to begin warming up 1,000 sq ft. I have a two stage regulator on the tank that brings the pressure to 11" wc. The heater itself has a regulator on it that brings pressure to 10" wc.

I tested the gas line for leaks And found none. The line is about 10' total run from tank to heater. Could it be possible the distance of the pipe is hurting my gas pressure? It's 1/2" black pipe.

My 75k unit will take well over an hour to heat my 1100 sq. ft. from 25 to 60.
Your unit sounds like it's working properly.
Leave it run for a few hours monitoring your temp rise. It will also take alot longer to get all your metal (cars and tools etc..) up to temp.

Your pipe run, size and pressures don't sound like an issue. You should have a maximum of 10" wc "manifold" pressure.

Also If your heater isin't properly located, it can have an effect on how efficient it heats your space.

 

[Kevin54]

I have a 28' x 36' garage with 8' ceilings. R32 in the attic in R13 in the walls. My heater is a 45,000 BTU Hamilton Propane unit running off of a 120 gallon tank. If I want it 80 in here, it will get up to 80. I turn it down to 50 at night and depending on the weather, it may get down to 50, or it may get down to 60. When I am out here, I loke to keep it around 65-70 degrees.

The garage is four sided. meaning that all four sides are out in the open and not attached to the house.

Are you absolutely certain that the jets are correct for propane and you don't have jets in it that is set up for natural gas. There is a big difference in the jets, and if not setup properly, your furnace will not burn properly. You may want to get a furnace person out to look at it. Your garage is the same size as mine, and I can get it super hot in here. My guess is that your jets may be wrong for propane and may be set up for natural gas.

I'm not a furnace person, and a furnace person will be able t tell you whether that may be the problem or not. But a 50,000 BTU furnace should be able to run you out if it is down below zero. We had -10f the other day and I was a very comfortable 65f in just a T-shirt.

 

[dfiler2]

Are you absolutely certain that the jets are correct for propane and you don't have jets in it that is set up for natural gas. There is a big difference in the jets, and if not setup properly, your furnace will not burn properly. You may want to get a furnace person out to look at it. Your garage is the same size as mine, and I can get it super hot in here. My guess is that your jets may be wrong for propane and may be set up for natural gas.

.

The orifice for NG would be larger than for LP and the problem would be the opposite.

 

[zmaxmotorsports]

The orifice for NG would be larger than for LP and the problem would be the opposite.

Unless Ive lost my mind again that is.
Like I said,Wheres my actos and metformin when I need them?
Elvis has left the building and he took my pills with him!

 

[James-W]

I am pretty certain the natural gas orifice is larger.

 

[The Cobbler]

propane higher pressure= smaller orifice

 

[CNGsaves]

If the output heat doesn't feel hot to you, it might be your double regulator setup (ie on tank, plus on heater). Thus, not enough flow so heater is starving for fuel.

That would be first culprit to check if it were me. Any HVAC guru to say whether just one regulator at heater would be better??

EDIT: One other idea . . . OP you sure flue is all clear so heater can "breathe" properly exhaling out flue and drawing in combustion air??

 

[Harix]

Check your regulator.

 

[LS6 Tommy]

Is the entire gas train the same as what the unit originally had? I've never heard of an LP gas train that used two regulators like yours. The people who stated that LP orifices are smaller than natural gas are correct.

Tommy

 

[why worry]

Being a retired sheet metal worker who has installed a few of these DEnd is pretty much spot on. I would check incoming air temp and out going air temp to start with.There are some infared thermometers out there that are pretty cool and inexpensive that you could get for checking the temps. (Always looking for a reason to get a new tool). Then check the burners for proper flame. Since the unit was used you could need to clean the burners as debris can fall out of the heat exchanger and partially obstruct the burner effecting the performance. As other posters have said the orifice would be smaller for propane. Two regulators in series should not be a problem assuming the first one does not reduce to too low a pressure.
As far as the size of the unit goes it should be OK as long as the doors are kept closed and the building is well insulated. Another thing to check is combustion air if the building is to "tight" then the unit could be starving for fresh air this could lead to a unhealthy condition known as carbon monoxide poisoning.
The big thing is recovery time after opening the garage door If your coming and going a lot then it will take awhile to heat back up.

Reznor units are pretty darn dependable and last a long time with a little maintenance.

 

[coppah37]

Just some more background and update. I am a sheet metal mechanic/fabricator for the navy so the one thing I'm 100% on is the exhaust is set up correctly. I'm fairly certain it has the right jets in it not sure how to tell without having one of each to see the difference. I opened up the burners to check for cleanliness and all seemed well. The regulator I have is a 2 stage regulator directly off the tank. It brings the pressure to 11" wc. I got it from Home Depot in the gas grill area. the heater calls for 10" wc. I have it hanging in the back corner of the garage and it's aimed it to the 2' space between the doors approximately a 22.5* angle.

I'm going to get my infrared themometer that I use for nitro rc cars and see where I'm at.

 

[finn]

Is the regulator rated for the gas flow required to run the heater? What is the actual pressure while the heater is firing?