Mr Heater Big Maxx having venting problem

[Jayhawk714]

I have a Mr. Heater Big Maxx 50000 BTU heater in my garage. And it is not venting right. Normally when I turn it on I used to see the steam coming out of the vent pipe, and now I don't, or at least a small amount once and in awhile. The vent fan runs on start up but the casing where the fan blade is becomes VERY hot but the motor housing does not. Is that normal?? Also, if I leave it running after awhile my eyes start to water so I turn it off for awhile to let the air clear. So there is no doubt there is a venting problem. I am going to run a brush through the vent pipe, however, I can feel a small draft coming out of it. But the hot fan blade enclosure makes me wonder if my problem is there.

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[bczoom]

Welcome to the forum!
First, I'd strongly suggest you get a carbon monoxide detector!!!
You're right to clean your vent. Might have a bee's nest or other obstruction.

 

[Melensdad]

I have a Mr. Heater Big Maxx 50000 BTU heater in my garage.

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I have the same heater hanging in my workshop.

Honestly I've never felt the vent pipe so I don't know if mine gets really hot or not. But I've never experienced the problems you are experiencing.

As Brian suggests above, you might want to run to the store and get a carbon monoxide detector.

It sure sounds like you may have a clog in your exhaust. How many turns does it make? Does it go straight up through the roof? Out a side wall and then up? How long of and exhaust run do you have?

 

[Jayhawk714]

I agree on the detector going to get one ordered today.
The vent comes out on a 90* then a straight run of about 20" to another 90* and then outside. I'm going to run a brush through it and see if that fix's the problem. Also I might go ahead and open up the fan housing and see if there is a problem there. Have you ever felt how much of a draft is coming out of the vent on your heater? Mine is not much of one but that could be normal, time will tell I guess.
Thanks for your reply's and when I find the problem I'll post an update.

 

[Jayhawk714]

I have the same heater hanging in my workshop.

Honestly I've never felt the vent pipe so I don't know if mine gets really hot or not.

What gets really hot is the shroud around the fan blade itself and that just seems weird to me.

 

[Melensdad]

Not much of a draft coming out of mine either.

No clue about how hot the shroud around the fan gets, but that does seem very strange. I still suspect you have a blockage of some type.

 

[waybomb]

Almost sounds like a key fell out or a set screw is loose on the fan hub.

 

[Jayhawk714]

Almost sounds like a key fell out or a set screw is loose on the fan hub.

Very well could be something like that as once in while I do see steam coming out of the vent. Hopefully I'll be able to clean the vent and checkout the fan tomorrow.

 

[Jayhawk714]

Sorry this took so long to answer. I cleaned the vent and there was a lot of soot but really not plugged up. I also use my air compressor to blow out the 3 tubes. After that I turned it on and it worked perfect. No more waterier eyes or bad taste in the air. Thank you all for your help!!!!

 

[Melensdad]

Just curious how long it has been in service.

Mine has been up and running for at least 8 years? No issues. What do you think caused the soot in your exhaust?

 

[Jayhawk714]

Just curious how long it has been in service.my

Mine has been up and running for at least 8 years? No issues. What do you think caused the soot in your exhaust?

Three, maybe four years. I have no idea what caused it. Mine runs on propane, but, maybe the air/gas flow needs a tuneup? Going to contact our propane dealer and have them take a look.

 

[bczoom]

Do you have a propane filter installed?

 

[Jayhawk714]

Do you have a propane filter installed?

There is no filter, that I know of, on the Big Maxx and I have not seen one listed in the parts list in the manual. At one time I thought that also and that's when found out there is no filter.

 

[bczoom]

Pretty sure you can just add one, in-line from the tank to the heater. Look into it more as I don't know if they have a flow rate or other considerations.

 

[Jayhawk714]

Pretty sure you can just add one, in-line from the tank to the heater. Look into it more as I don't know if they have a flow rate or other considerations.

I'll do that. Having a filter is not a bad idea. Thanks!

 

[Big Dog]

I started with 2 - 45000 BM in 2010, God Bless Big Al in helping with the garagemahall. First one made it 10 yrs (replaced the control board after 8yrs). At the time this one started to give me issues I bought 2 more as backup ( son was a Lowe’s employee and good deals 🤣). After that I went into scavenging mode. Pull a card here and yank a fan there. If I used a part from my designated spare scavenge heater, I replaced it, 2 cards and 1 fan. The second made it 13, replaced it last year with a 80000. Still have a new 45000 and a complete spare that I used for scavenge. They all use the same parts and parts are cheap. Awesome heaters, they keep my 2800 sqft garage 64F all year long.

A common issue is the O2 sensor, it needs cleaned occasionally.

 

[Jayhawk714]

Love the garage but makes me jealous!! I will look pull the manual out and locate the O2 sensor for cleaning. Thanks for the information.

 

[Melensdad]

I started with 2 - 45000 BM in 2010, God Bless Big Al in helping with the garagemahall. . . .

View attachment 175358

I prefer the term Toy Castle

 

[Jayhawk714]

 

[Jayhawk714]

I started with 2 - 45000 BM in 2010, God Bless Big Al in helping with the garagemahall. First one made it 10 yrs (replaced the control board after 8yrs). At the time this one started to give me issues I bought 2 more as backup ( son was a Lowe’s employee and good deals 🤣). After that I went into scavenging mode. Pull a card here and yank a fan there. If I used a part from my designated spare scavenge heater, I replaced it, 2 cards and 1 fan. The second made it 13, replaced it last year with a 80000. Still have a new 45000 and a complete spare that I used for scavenge. They all use the same parts and parts are cheap. Awesome heaters, they keep my 2800 sqft garage 64F all year long.

A common issue is the O2 sensor, it needs cleaned occasionally.

View attachment 175358

A common issue is the O2 sensor, it needs cleaned occasionally.

Could not find the O2 sensor on my mhu50. Does it go by another name by chance?

 

[tommu56]

Is there any chance it didn't get propane conversion kit installed properly????
snip from the manual

 

[Jayhawk714]

Had a gas/furnace guy install it so as far as I know it's correct. However, that is something look into. If it's not installed correctly that could explain the heavy soot it produces. Thanks for the suggestion!!

 

[tommu56]

Had a gas/furnace guy install it so as far as I know it's correct. However, that is something look into. If it's not installed correctly that could explain the heavy soot it produces. Thanks for the suggestion!!

Yes if the orifices are NG they are too big and will run too rich causing the soot.
I'd look for the LP stickers id the guy was 1/2 way coherent they should be put on or laying in the unit someplace
If your propane guy didn't install it and they do service I'd get them to take a look.
Nothing I saw in the manual said orifice size to gauge it to see.
It's important to check the gas pressure too make sure its 11" of water at the valve.

 

[Big Dog]

Could not find the O2 sensor on my mhu50. Does it go by another name by chance?

There is a wire that runs from the sensor to control board (remover left side cover and it will be rear, lower corner). Follow it from the board to the front of the burners and clean.