Unit NG heater vent help

[B&H]

I have been fighting a unit heater vent pipe condensation problem at my auto repair shop.

http://www.garagejournal.com/forum/showthread.php?t=229341

The final resolution was for the contractor to install condensation drip lines in the 3 heater vents that were leaking. One required a pump but it works well.

However, the workmanship is, umm, err, a little err, umm... leaves a little bit to be desired..

I have lost faith I want to fix this myself.

Anyone have any ideas on a solution to the elbow? If the sloppy silicone worked, I would have probably been alright with it, but the condensation seems to find the tiniest of leaks:

[/URL][/IMG]

 

[zmaxmotorsports]

WTF?
Why does he have such a big flue on there?It looks like theres back fall on the pipe.
What does it look like where it comes through the roof?

 

[B&H]

Not sure what "back fall on the pipe" means. The 2 lower vent pipes in this picture are what you see for the 2 unit heaters pictured above:

[/URL][/IMG]

 

[zmaxmotorsports]

The flue pipe coming out of the furnace needs to be the lowest point in the line.
A smaller flue coming from the furnace to the stack going through the roof will have more velocity to help vent the gasses out through the chimney,that 6"
coming off of there is allowing condensation to build up in the system which is collecting in the bottem of clean out/test tee.

 

[B&H]

The condensation occurs when the unit heaters are off, which is most of the time. They very rarely run, as the radiant floor heat is the main heat source. The humid air from bringing in snow-covered cars, washing the floors down, etc, was condensing inside of the cold vertical flue pipe and leaking onto the ground as well as running back into the unit heaters. The contractor put a little "down" in the pipe to keep any condensate that may make it past the elbow from getting into the heater. I am OK with the "design", just need better parts that won't leak w/o having 10 lbs of silicone on the joints.

 

[zmaxmotorsports]

Your still collecting some condensation from the flue gases not being forced out the chimney fast enough.
Its like having a 1/2" water supply feeding a house then dumping it into 1" to feed all of your fixtures.
That fitting that he bootlegged into the bottem of each tee is going to hold water in the bottem of each cap till it atleast gets above the pipe ******,unless he mounted some sort of flange flush with the bottem to screw it in to.
Either way its a seriously hacked up mess that he did.
Id call a different contractor to look at it and give you some ideas.

 

[CNGsaves]

OP . . with not just one, but two highly unusual setups, have you considered moving the heaters??

If they're not really needed for heating shop (ie since you have radiant in floor), could you survive with just one that was moved so it could have horizontal flue?? Ditch both of the cluster'd vertical flues, and sell extra heater on CL.

What is black box to left of man door??

 

[B&H]

Your still collecting some condensation from the flue gases not being forced out the chimney fast enough.
Its like having a 1/2" water supply feeding a house then dumping it into 1" to feed all of your fixtures.
That fitting that he bootlegged into the bottem of each tee is going to hold water in the bottem of each cap till it atleast gets above the pipe ******,unless he mounted some sort of flange flush with the bottem to screw it in to.
Either way its a seriously hacked up mess that he did.
Id call a different contractor to look at it and give you some ideas.

I don't think that the condensation has anything to do with flue gasses - there is warm, moist air migrating up the stack with the heater off (can be off for days), it gets cooled off on the way up, condenses and drools back down.

I agree about the bootlegged fitting not having a flange and holding water. All 3 stacks, however, do build up enough condensation that you can see it draining in the clear lines and the one heater with the sump and pump (not pictured) does fill up and pump.

 

[B&H]

OP . . with not just one, but two highly unusual setups, have you considered moving the heaters??

If they're not really needed for heating shop (ie since you have radiant in floor), could you survive with just one that was moved so it could have horizontal flue?? Ditch both of the cluster'd vertical flues, and sell extra heater on CL.

What is black box to left of man door??

There really isn't a good place to put the heaters in the 10'x80' shed roof storage room that you see. I really wish that I had them run pex in that area, because as it turns out we wouldn't have even needed unit heaters back there. Running an overloaded automotive shop at the same time we planning and having built a sizeable addition (besides the 10'x80' storage area, we also added 2 more bays, waiting room, offices, bathroom, parking, oil/water separator, added employees, lifts, alignment equipment etc.) almost put US into overload.

We can't ditch any of the heaters. They actually ran this week. The 3rd heater not pictured that has a pump is the make-up for 2 bays, and that ran also this week. The point I was trying to make regarding the condensation is that it is not from burning NG. Matter of fact, if the heaters ran more or had a standing pilot, we probably wouldn't be having a problem.

We also tried a motorized damper in the stack to try to keep warm, moist air out of the vertical flue. It didn't work.

The black box to the left of the man door is a motorized vent door that comes on when we turn a vent fan on. On the inside of that wall is a bench grinder that we use to buff corroded wheels when we're changing tires. Keeps a lot of the dust from going everywhere. The black box above the door is a wall pack light.

 

[bbrz]

Do those heaters have a venter motor (forced) or draft hood (natural flow).
Get rid of the tees? Don't force byproducts into a tee.

 

[55bigblockcid]

and the building is so tight that I rarely

^^^^^ this is what you say in your other post.

The problem I see is you are pulling from the heated space for the combustion air to run those heaters.It has to get air to burn and it is pulling it through the other unit heaters vents to get it causing the building to be in a negative and cold air to come in the other unit heater vents and then condensing,plus the fact the vents don`t seem to be falling towards the heaters and the size of vent pipe seems too big.Also you say you have a exhaust fan in there as well compounding the problem.What you need is a make up air unit not unit heaters. You are pulling more air from the space than what you are putting in with what you have.Interlock a make up air to an exhaust fan if you want things to work correctly,Wrong application for what you are tying to do IMO.

 

[sprntpshr]

You are not going to like what I will suggest but given your situation and the conditions to which the heating equipment/venting is exposed to this will control the air flow out the venting.

This would be an application for infrared tube heater that vents and draws combustion air from outside. This way the heater and venting isn't exposed to conditions and humidity inside. Standard operating procedure here.

Like I say it doesn't use the existing heaters but solves the problem. Very surprised that the heating contractor used that type of heater given the atmosphere in the shop.

 

[brewchief]

Stainless steel class 3 vent might be the answer, it is designed to seal tighter and fittings with condensation drains are available.

Look up Z-flex as one brand.

 

[why worry]

Need a bit more info on the units, IE what size and manufacturer. The manufacture of the units has a recommended vent size and configuration in there installation manual.
Assuming that the sizing is correct then I tend to agree with 55Bigblockcid your problem is a negative building drawing cold air in and condensing in the stacks. You could test this out a couple of ways but I would try opening the damper on the wall a bit and see if air comes into the building or not by holding a dollar bill in front of the opening. If air is coming in then I think you need to put in a MUA system.
As far as workmanship goes it does look a little bit uhm uhm uhm.
The "T's" at the bottom are actually probably OK and would be considered quite acceptable by most manufactures and even required by some for keeping condensation from running back into the burners.
Hope this helps, Good Luck!

 

[B&H]

Stainless steel class 3 vent might be the answer, it is designed to seal tighter and fittings with condensation drains are available.

Look up Z-flex as one brand.

This looks like the solution that I am after. Thanks, going to do some research tonight.

 

[B&H]

Ordered 2 of these from Amazon:

Product Description



Z-Flex Z-Vent 4" Vertical Condensation Drain Tee (2SVEVWCF04). This is the best piece to use as a condensation drain point for all vertical venting installations. This drain tee acts as a 90 degree angle, but it has a reservoir and a drain point to easily remove rain water and condensation that may come down the exhaust system. Z-Flex Z-Vent stainless steel vent pipe is ideal for the Bosch Therm 940ES / Bosch Therm 830ES / Bosch Therm 660EF / Bosch AquaStar 2700ES / Bosch AquaStar 2400ES / Bosch Evolution 500 tankless water heaters as well as the legacy Bosch Pro 715ES / Bosch Pro 635ES / Bosch AquaStar 2400E / Bosch AquaStar 250SX heaters as well as the Bosch AquaStar 240FX, AquaStar 125FX, Takagi TK1, TK2, TKD20, TKJR, TK1S, TM1 tankless water heaters. Z-Flex Z-Vent is rated AL29-4C and is approved for Category I (vertical only), II, III & IV applications and is designed for use with boilers, high efficiency gas and oil heaters and water heaters where cool flue gases are vented under pressure. Z-Vent contains a built-in, fail-safe gasket and locking band connection. No sealant is required.