Excessive Thimble Gap - Horizontal Venting - Mr. Heater

[Mellotron]

Gents,

Just installed my Mr. Heater Big Maxx 45K. Install went pretty smooth. I purchased the Mr. Heater Horizontal Vent Kit too. Which leads me to my question.

Seems crazy to have such an air gap where the B Vent penetrates the thimble. Is this normal to have pretty much daylight coming through the gap? Do you have any advice on getting rid of this little gap around the pipe? I know not to stuff the thing with insulation etc. But theres got to be something to kill this waste of thermal energy. Super high temp caulk?

 

[krooser]

Silicone.....

 

[blairtruck]

i used the tape that is for the joints.
i pieced together a kit and thought it was my mistake that there was a gap. but if you bought the kit and got the same gap then i am happy with my kit.

 

[TRDon]

Is that not B vent going through the thimble? If not, it should be, if so, wrong one? It should be tight (or relatively) going through it.

 

[Mellotron]

i used the tape that is for the joints.
i pieced together a kit and thought it was my mistake that there was a gap. but if you bought the kit and got the same gap then i am happy with my kit.

You talking the HVAC Foil Tape? Hows that holding up? That stuff is usually only good to about 150 Degrees. I'm certain our exhaust temps are considerably higher. Who knows?

Yeah I'm thinking the thimble gap is just how that kit was made. Totally crazy if you ask me.

Ironic. The very device I was hoping to heat the garage is now the device that causes the most heat loss. I'm researching silicones now...

 

[Mellotron]

Is that not B vent going through the thimble? If not, it should be, if so, wrong one? It should be tight (or relatively) going through it.

Yep it's definitely B Vent. Double wall and heavy.
The B Vent elbow I bought might be throwing you off. If you notice the B Vent elbow has a short length of straight single wall going into it.

 

[RAMBIN]

was there a reason for the big offset you put in? or was that just for the moisture drain back?...

 

[hammlm]

i found stove-pipe sealant in a caulk tube. It's black, and sticky like crazy.

It's been nearly two years, I can't remember if I got it at the hware store or at Home Depot. I remember my dad using it on our wood stove pipes.

My thimble was the same. Before I caulked it shut (inside and out), I made some little metal shims so that the gap was uniform around the circumference.....

 

[Mellotron]

was there a reason for the big offset you put in? or was that just for the moisture drain back?...

Awesome observation. Yes for drain slope and to avoid the framing 2X4s.

I though about flipping the heater and making the hole under the framing but then the slope would be wrong way and my air path would have not been as good.

 

[Mellotron]

i found stove-pipe sealant in a caulk tube. It's black, and sticky like crazy.

It's been nearly two years, I can't remember if I got it at the hware store or at Home Depot. I remember my dad using it on our wood stove pipes.

My thimble was the same. Before I caulked it shut (inside and out), I made some little metal shims so that the gap was uniform around the circumference.....

Aye! Looks like stove pipe goo for me! Great idea using shims first! I'm definitely doing that.

 

[BigChevy80]

That's weird.

I vented my heater through the roof, so naturally I didn't need a thimble. I do remember looking around at the thimbles and pipe at Menards and the 4" pipe in a 4" thimble was a nice tight fit. I actually had to wiggle it around to get it to fit through the thimble. Those kit's must use some kind of bastardized fittings... lol.

 

[Mellotron]

That's weird.

I vented my heater through the roof, so naturally I didn't need a thimble. I do remember looking around at the thimbles and pipe at Menards and the 4" pipe in a 4" thimble was a nice tight fit. I actually had to wiggle it around to get it to fit through the thimble. Those kit's must use some kind of bastardized fittings... lol.

I noticed the same thing at Foam Peehole (Home Depot). The thimbles fit snug with the B Vent. The thimbles were higher quality too. So my guess is this Mr. Heater Vent Kit is not the greatest thimble-wise. The B Vent was good though.

In retrospect I should have hit the box store for my exhaust goods. Ah well. I will make it work with some high temp sealant and shims.

Cheers,
Eric

 

[RAMBIN]

is there a diff thimble for 2*4 and 2*6 walls?,

 

[BigChevy80]

is there a diff thimble for 2*4 and 2*6 walls?,

Nope. The 2 halves of the thimble slide over one another. They should be thick enough for a 2x6 wall.

 

[twostory]

I just installed the same heater and used the Mr Heater horizontal vent kit. My Type B vent pipe fits fairly snug in the thimble. There is some gap, but not anywhere near your large gap.

In your set up, is the Mr Heater Type B pipe what is in the thimble?

 

[dipper]

I tried the foil hvac tape on my vent and it started to burn off after a few minutes of using the heater. I'd stick with a high temp sealant as suggested instead. There will be a slight gap between the B-vent and the thimble. I would just follow the advice already given and seal it up on the inside and outside with some silicone high temp caulk.

 

[Chetter]

I used silicone on mine since I had the gap you are talking about in my vertical kit. No problems with it now and I have had this furnace on line since November.

 

[Mellotron]

I used silicone on mine since I had the gap you are talking about in my vertical kit. No problems with it now and I have had this furnace on line since November.

Yeah I got the silicone done. Turned out great. Daylight is gone! I'm dying to fire this thing up but still need gas pipe work done. Still trying to decide if I want to do that or not.

Thanks everybody for your advice!

Eric

 

[russlaferrera]

They sell galvanized and aluminum metal in the stove pipe section, it's about 1ft square.. Draw a circle the same size of the pipe you are using, cut to fit.

IMO because you have double wall pipe, it does not get too hot, H/T silicone will work.

 

[Mellotron]

They sell galvanized and aluminum metal in the stove pipe section, it's about 1ft square.. Draw a circle the same size of the pipe you are using, cut to fit.

IMO because you have double wall pipe, it does not get too hot, H/T silicone will work.

Awesome idea! I will definitely do this trick if the silicone starts to fail. But I think you're right, the double wall should keep things cooler. I used Black RTV that's good to 500 degrees. I should be good to go.

 

[Ron Lombardo]

Are you sure the thimble is not for ALL FUEL .. or AL-29C a triple wall stainless steel flue pipe ..there should be no gap ....zero ...tight fit .... not a gap to tape or caulk ...call tech support !

Ron

 

[Jasonoff]

Bumping an old thread. Yeah I use the search feature lol.

To the OP, do you have a pic and description of your solution?

 

[Mellotron]

Happy New Year.

Yes, I ended up centering the vent in the thimble with some little bits of metal plumber's tape so the gap was even all around. Then I sealed that gap with high-temp silicone on both the inside and outside. Works great!

 

[Jasonoff]

So, is it safe to assume after 5+ years it's still working great?

I'm having a new house built and they are going to rough in a 6" opening exiting the garage for my future heater install.

I was curious how I would terminate the venting and found this thread.

 

[Mellotron]

Yessir! The heater has been very reliable and a good value. Termination for those heaters are pretty flexible, and you should have one or two options that will work great in your new house. The only thing special I did was plugging in the heater into a high quality line conditioner (not surge strip). It was from Tripp-Lite. I've heard stories of folks losing system boards to transient voltages, so I figured it was a good investment.
Take care.

 

[Jasonoff]

Yessir! The heater has been very reliable and a good value. Termination for those heaters are pretty flexible, and you should have one or two options that will work great in your new house. The only thing special I did was plugging in the heater into a high quality line conditioner (not surge strip). It was from Tripp-Lite. I've heard stories of folks losing system boards to transient voltages, so I figured it was a good investment.
Take care.

Excellent. Thanks for the tip!