Tankless water heater install question
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Installing a tankless water heater (Bosch 250 NG). Got all the hard stuff done (venting and copper piping to/from). Now I am onto the condensate drain line and the pressure relief valve output. This unit is on a second floor so I have to do something relatively bullet proof with this stuff. Can I combine these two lines into one drop from the unit? I was planning on putting 1/2″ line on the condensate and then using 3/4″ line from the pressure relief down into the floor below, where I would transition to 1 1/2″ and out the house at a convenient point (20′ or so, but lots of pitch). My main question is whether code allows the two lines to be combined. Secondly, I was considering putting a trap on the end of the run to keep cold air from coming back up the pipe. This 1 1/2″ line will also pick up an AC and condensing furnace so trap should stay full year round. Anybody see a problem with this? I live in NC so winters not too bad and the trap will be within the heating envelope. MERC |
Replies
Hey - that's an answer I know, since I just had to add a pressure relief valve to my tankless installation (plumber didn't add one) based on an inspection.
The answer is no, you cannot join the pressure relief with other plumbing - it has to go directly to the outside. My inspector said, "same size as the heater piping, straight to the outside, aimed down, without the outlet between 6" and 24" from the ground. It might be different in your area.
For the condensing furnace, I think I'd use PVC pipe over copper. The condensate is pretty acidic, and I'd be worried that the copper wouldn't like it.
My opinion is that you would lose minimal heat from the pipe, especially if it was PVC.
One more thought - how are you supplying the combustion air for the heater? My guess is that the 250 series takes a *lot* of air.
I'm thinking about using this to supply my combustion air, as I currently have two 8" openings to the outside:
http://www.tjernlund.com/
My unit has sealed combustion so I had to pipe a 3" pvc line to the outside. It's a great unit though because it lets me install it just about anywhere I can fit it.
Does your unit have a condensate line in the vent? And that is piped to the outside seperate from the pressure relief valve? I'm not looking to tie into the DWV system, just combine the lines to the outside. I had some thoughts that a combined line could technically blow out the top from water coming out of the pressure relief valve. I was hoping to take care of that by upsizing the line below the PR valve to 1" and using 1/2" for the condesate drop.
I'll give the inspector a call this afternoon and see.
MERC
You can't combine the PRV piping with other piping, even from another unit's PRV. The output of the PRV on the tankless could be relatively high pressure steam... can't have that going into the vent.
That is a good point. I hadn't thought about steam. Ok, so no problem, I can pipe seperately.
Can I combine condensate lines from different units?
MERC