Big Maxx Heater - Horizontal Venting Slope

[eric.watson]

I've decided to bite the cost of the stainless steel horizontal vent kit for the Big Maxx heater. I know the slope of the vent is 1/4 in. per foot. My question is which way is it supposed to slope?

The manual for the heater states it is supposed to slope upwards toward the termination.

The manual for the vent kit states it should slope downwards to prevent condensation formation or ice buildup.

These manuals are contradicting each other and some expert advice would be greatly appreciated. Thanks in advance!

 

[AlbertaSS]

I just installed a Big Maxx 80000 btu unit. The manual states to slope the vent upward toward termination, so that's what I did. It seems every unit has different instructions for this. I would do what the instructions say for that particular unit.

 

[Choptopjimmy]

I am currently installing the same Big Maxx unit and have the same question as Eric. Why would the manuals contradict each other? There must be a reason for the vent manufacturer to suggest the downward slope, right? Thanks, Jim

 

[PWC Repair]

It's probably just lost in the Chinese translation or something. The poisonous gasses need to rise out. Gas venting ALWAYS rises on it's way to the termination.

 

[manwithtools]

IF you slope upward you need a condensation drain fitting such as this:

The image is a very poor one as this should be installed horizontally, not vertically as shown in the picture. Once you have that piece in place you need to pipe the condensate to an appropriate drain or pump. My unit heater also showed the option of sloping downward toward the outside wall which I did. In that instance no condensate drain is needed. I did not check the Big Maxx web site for their installation guidelines but would surggest you check that as well.

BTW, that Category III pipe is ***** to put together. Watch the rubber sealing rings to be sure they don't get out of position during assembly. I'd recommend shopping around for the correct fittings, the kit's are not necessarily a bargain.

 

[manwithtools]

It's probably just lost in the Chinese translation or something. The poisonous gasses need to rise out. Gas venting ALWAYS rises on it's way to the termination.

Not always, forced exhaust unit heaters don't necessarily need to rise to the termination.

 

[TurnipTruck]

I successfully vented my 75k btu bigmaxx horizontally downward with maybe a 2" fall in 26'. I did have stalagmites of condensate on cold days.

 

[Junkman]

I mounted mine pointed down, but the heater never worked long enough for me to know if there was much condensation running out of the pipe. They sent me some repair parts, but it wasn't enough to get all the tubes to ignite. By the time they sent me additional repair parts, the weather got warmer, and I lost all interest in installing them. The last thing that I want to do is spend a lot of time on a ladder fixing a heater that is 10' in the air. The next fall, I installed all the replacement parts, and when cold weather set in, it still didn't work as it should, but when I called, I was informed that it was out of warranty. It has been hanging on the garage ceiling ever since, and if it were easier, I would have taken it down and put it into the iron pile. It has been hanging there for the past 5 or 6 years, and at this point, when I sell the home, I will let the next owner deal with it. IMHO, the Big Maxx is a big piece of junk...

 

[PWC Repair]

Not always, forced exhaust unit heaters don't necessarily need to rise to the termination.

Wasn't even thinking about powered exhaust.....duh!

 

[toyotadriver]

I installed mine with the pipe slated down to the termination point. Works fine.

 

[ForceFed70]

While I don't think the heater cares, the venting itself is designed to be sloped. Pointing it down is a bad idea unless you are reversing the vent connection directions.

Sloped down causes 2 challenges:
1) Exhaust gases can "rise" through he vent connections allowing exhaust gas to escape at vent connection points.
2) Condensation draining toward the termination won't actually make it to the termination, it'll leak out the 1st vent joint it comes across.

Heaters are designed to have condensation run into them. What do you guys think happens with a vertical vent?

 

[manwithtools]

While I don't think the heater cares, the venting itself is designed to be sloped. Pointing it down is a bad idea unless you are reversing the vent connection directions.

Sloped down causes 2 challenges:
1) Exhaust gases can "rise" through he vent connections allowing exhaust gas to escape at vent connection points.
2) Condensation draining toward the termination won't actually make it to the termination, it'll leak out the 1st vent joint it comes across.

Heaters are designed to have condensation run into them. What do you guys think happens with a vertical vent?

If you are using Category III vent which is now required in most jurisdictions for horizontal venting, it is gasketed and made from stainless steel. It's designed to NOT let condensate accumulate in the heater (which will shorten the unit heater life expectancy due to its corrosive properties).

That's why the pipe section I showed in an earlier post has a condensate drain for use in an upward slope installation - to prevent the condensation draining back into the heater. Downward slope is allowing condensate to drain outside or evaporate.

Take a look at the recommended installation from the particular unit heater manufacturer for the final answer. Be sure you have the latest info as codes have changed over the years.

 

[smalltown]

Pay particular attention to how the CAT stainless pipe goes together. I bought the Duravent fasNseal pipe. After scratching my head I called Duravent, and confirmed that the piping I purchased along with their thimble is constructed so that the piping will slope downwards towards the heater. Otherwise the condensate will pool at the thimble connection which is an adjustable section.

If I had this pipe sloping down and away from my heater Duravent told me the stainless pipe would be OK, but the acidic condensation could ruin the seals.

In my case I needed to buy the Universal appliance adapter with condensate drain to keep any condensate from backing into the heater.

 

[manwithtools]

That's interesting about the Duravent fasNseal, the NovaFlex Z-Vent Category III that I used specifically allows sloping downward AWAY from the heater and my heaters manual also shows the same.

My heater is a Advance Distributors Products brand, but it look like it is exactly the same as the Big Maxx heater. The installation manual even uses some of the same illustrations as the Mr. Heater models.

The following is from the Z-Vent installation manual:

"Any horizontally installed portion of a venting system shall have a slope (upwards for Category II, III, or IV appliances or downwards for Category III or IV appliances) not less than 1/4” (6.4 mm) every 12 inches (305 mm) to prevent collection of condensate at any
location in the assembly. "

The next paragraph is from the heater installation manual:

In areas where authorities having jurisdiction permit, a downward slope of maximum 1/4" per foot is also acceptable. Condensate drainage can be collected in a tee pipe section with drain loop similar to one used for upward slope vent, or allowed to drip through the vent termination, if permitted by authorities

It's all very interesting and I would be sure to follow the recommendations of your heater manufacturer, the vent pipe manufacture and any national and local codes before using my responses. I'm not a heater expert and don't claim to be.

 

[vicegripbloodblister]

Manwithtools explained it all very well. Sometimes it pays to read read read and reread instructions and check out Garage Journal for some very sound advice.