venting tankless water heater

[lynnbilodeau]

Have a Jacuzzi tankless water heater that is replacing a tank type electric.
The instructions say to mount on an exterior wall so you can run the direct vent set up through the wall.

I would like to mount it in the same closet that the tank unit is in. Long way from a wall. But... it is in the garage, so if I mount the vent so that it draws air from the garage, it isn't an "occupied space".

Am I OK to mount a cone type vent that allows the unit to draw air for combustion from the garage? The cone seals on the inner tube of the pic below. I would still vent the small inner vent (exhaust) air tight to outside.

 

[lynnbilodeau]

One other approach.

I can get this unit on an exterior wall, as it will only be about 10 feet from where the old tank is. Problem is the exterior wall is 17.5 inches thick,,, all brick. The building was constructed in 1893, solid brick with no framing.

So.... if I can't do what I wanted with the vent, and I am forced to go out an exterior wall, how would you go about cutting the hole for the thimble?

 

[Charles (in GA)]

The instructions should give you all the specifics about the allowable length of the vent system, air intake, etc. For insurance and code reasons, you should follow them explicitly.

I recently installed a 90% condensing Noritz unit and it had very detailed illustrations and tables of vent installations, lengths of vents allowed, etc. It used 3" PVC for the exhaust and air intake.

Is it by chance, the model covered by THESE INSTRUCTIONS?

Make sure you have a gas supply sufficient to operate the heater. The gas supply for the old tank type is most likely undersized.

Charles

 

[Charles (in GA)]

One other approach.

I can get this unit on an exterior wall, as it will only be about 10 feet from where the old tank is. Problem is the exterior wall is 17.5 inches thick,,, all brick. The building was constructed in 1893, solid brick with no framing.

So.... if I can't do what I wanted with the vent, and I am forced to go out an exterior wall, how would you go about cutting the hole for the thimble?

Find an ABC cutter business (Asphalt, Brick, Concrete) they can cut a neat hole thru the brick. It will be worth paying them.

Charles

 

[lynnbilodeau]

Yes, those are the instructions.
But they assume the unit is mounted inside living quarters.

I mounted one just like this in the garage of our last house, and we got no flak from the inspector when we sold it. Yes, I understand the inspector might not catch every thing.

I was looking at that part that says: Combustion air shall not be
supplied from occupied spaces.

That made me think about using the cone solution I used at the last house.

If it has to be their vent kit, so be it. Just making sure before I go to that much trouble.

 

[Jackfre]

You are not! That is a DV appliance ONLY. It will fault out if you try to run it on room air. It is designed for a "balanced flue", meaning the induction fan is looking for a pretty even flow on intake and exhaust! I would suggest you install it within the installation manual specs or return it.

 

[Charles (in GA)]

• This water heater is a direct vent water heater and
therefore is certified and listed with the vent
system. You must use vent components that are
certified and listed with the water heater model.

• The vent system must vent directly to the outside
of the building and use outside air for combustion

The Noritz I installed allowed for the use of inside air, provided that it had enough flow available to it. I installed it with outside fresh air so that the closet it was installed in did not have to have louvers installed on the door. As I noted the Noritz used 3 inch solid PVC and fittings for venting, and did not require the special vents like yours does.

Based on what I read above, either install it with the proper venting kit and pipes or as Jack noted, return the unit and get something different.

 

[mires]

That heater needs outside air for combustion. I assume your old heater was gas so there was an existing flue going out of the roof? If so, Just run the vent out of the same hole.

 

[Scott r c]

It looks like you have to use the special double wall vent pipe like on a Rinnai. Edit, I justlooke d it up and it appears you get to buy the pipe I just mentioned above. I think that is the only way to do it.

 

[cj7365]

That heater needs outside air for combustion. I assume your old heater was gas so there was an existing flue going out of the roof? If so, Just run the vent out of the same hole.

THIS


Its says In your instructions, that it MUST use OUTSIDE air for combustion

 

[Scott r c]

Its not quite that simple. There is a special flashing on these, depending on the roof angle. Plus the cap. This pipe is aluminum on the inside and thin wall pvc on the outside.

 

[Hpozzuoli]

Do all tankless units require outside air for combustion? I was thinking of one, but not sure re-routing everything would be worth it. I was hoping to just replace my tank heater in the basement closet.

 

[mires]

Its not quite that simple. There is a special flashing on these, depending on the roof angle. Plus the cap. This pipe is aluminum on the inside and thin wall pvc on the outside.

This I'm aware of. I have installed more tankless heaters than I'd like to admit. When I said to just use that hole, I meant get whatever material he needs to use that hole. Sure beats moving to a different part of the house to try to get it on an outside wall. If it were me, I would take it back and just put a tank in.

 

[lynnbilodeau]

Old heater is electric, so no vent. Was planning to vent anyway.
I am fine going through the exterior wall. It is just the back of the building that backs up to an alley.
Just thought I would ask before putting a hole in 17.5 inch thick wall.

 

[jonjon1]

When ever possible follow the instructions, I can tell you that I have seen them in commission for a long time with no issues using indoor air so will it be the end of the world- Probably not, you need to decide if its worth the risk of doing it twice...

The best bet would be to do it correctly, but just wanted to let you know I have seen them running with no issues not vented concentric... I have a customer that has one in a closet with a louvered door, its been there for 10 years and never failed or killed anyone... I hate to look at it because its vented out with flue pipe that is tin taped to the exhaust, lol... But its in a closet far from his living area, he has co detectors, and he installed it himself and he even bought it used on ebay, lol...

 

[volleyball]

The double pipe usually means that the outer pipe keeps the hot inner pipe away from combustibles as well as providing makeup air.
Yes you want to use the correct double pipe the entire distance.
You can easily make your own hole with a hammer drill and a long bit. You make a series of small holes around the perimeter.

 

[Jackfre]

That unit is a Rinnai. It is a private label deal they had for a while with Jacuzzi and sold only at Lowe's. It is a .82 EF, 180,000 btu input unit. In order to use inside air, which is not allowed on that unit, NFPA 54, The Nat'l Fuel Gas Code, says you need 50 cu ft of unconfined air/1000 btu of input. That is 9000 cu ft. Figuring an 8' ceiling you need 1125 sq ft of space with nothing in it. Like a gymnasium! While Noritz is allowing indoor air, the code still applies. I can tell you it is not worth doing.

It does require the use of the Uubink concentric vent. The vent is 5" OD. Vertical terminations are available. Long runs of this pipe add up in a hurry. I like this unit on or near an outside wall. When longer runs are required I would suggest going with the .95EF units that do vent with PVC. You pay more for the unit, but recover that in venting savings. Your unit cannot vent with PVC. It will melt.

I was the Rinnai rep in New England for 20 years and have a few tens of thousands of these units in the field. They are exceedingly reliable...when installed according to spec. Get creative and it is an invitation to your own personal twilight zone and I know that is correct because I would have to go out and try to repair them.

Most tankless water heaters are planned purchases. Usually, when the water tank leaks a new tank will be installed. In my trainings I always have told contractors to go ahead and bid the install with the tankless in the original location. That is position 1, but do go for a walk and see if there is a better location for the tankless. One that is going to provide better service and comfort and be a better overall installation. That is position 2. Explain to the customer why position 2 is better. In other words do not perpetuate the mistakes of the original low cost bidder.

 

[volleyball]

I am deciding on where to put mine. The cost of the pipe verses having longer hot water runs is a decision maker.
Maybe luckily there is a pipe mfg near by.
What is the appr. going rate for double pipe?

 

[lynnbilodeau]

The garage (unoccupied) where I am mounting this is about 2500 square feet with 10.5 foot ceiling, or 25,000 cubic feet, so I am not worried about there being enough air.

However, I have located an outside wall and will follow the directions exactly.

Already ordered the vent kit.

 

[jonjon1]

good choice

 

[Charles (in GA)]

See page 12 of the link I posted above, to the manual, it lists the only three approved vent systems for this unit.

Charles

 

[Charles (in GA)]

I am deciding on where to put mine. The cost of the pipe verses having longer hot water runs is a decision maker.
Maybe luckily there is a pipe mfg near by.
What is the appr. going rate for double pipe?

Have you bought yours yet? Some brands/units use two pipes, one for intake, one for exhaust. The Noritz I installed is that way. It uses the 3" PVC pipe, and is a well made Japanese manufactured unit.

Charles

 

[wyliesdiesels]

Wow i never realized that tankless water heaters were so complicated to install.

 

[Jackfre]

Wow i never realized that tankless water heaters were so complicated to install.

They are not complicated. They are different with specific requirements.

 

[volleyball]

Have you bought yours yet? Some brands/units use two pipes, one for intake, one for exhaust. The Noritz I installed is that way. It uses the 3" PVC pipe, and is a well made Japanese manufactured unit.

Charles

Yes, I have it. Got it and then more urgent projects came up that needed to be done first. It is a pipe in pipe model. I think I got it cheap enough that it is still cheaper than a dual single pipe system.