It doesn’t matter. Supply or return. You can’t put it in close proximity to the air gap for the flue.
Oh I certainly agree that the installations really sucks but I still say blowing a little air across a WH draft hood won’t hurt a thing.
Now I wasn’t speaking about solid fuel burning OR VENTLESS fire places.
Hahaha
I have never seen a solid fuel ventless.
Got a link:)
The manufacturer of the water heater will tell you that any disruption in the natural draft from the water heater will cause several problems. 1) Difficult to keep the pilot light lit. 2) Early degradation of the thermocouple. 3) Particular matter (their words not mine) not carried out with the hot flue gas (dust in ports).
Sparks,
So if I understand you, a WH does not inherently produce CO, however, given the right conditions (lack of combustion air) it can?
Like you said…
Wouldn’t that increase to CO2 in the room (we don’t know the room size) and lead to a lack of combustion air?
You must be one of those perfect people that never made a typo hu?
Really FUNNY ? or you just like making fun of other people?
oh well, there’s one or two in every crowd. :roll:
Anyway I was speaking about one thing and fireplaces were brought into the discussion and they have nothing to do with what I was talking about.
OK, I never said this particular instance wasn’t a sloppy installation but In my opinion …well I’ve said it before.
Of course I could be wrong and I understand that Hi’s have to be overly cautious about everything and with that I agree, I would too but I think sometimes people are so scared of things that they can go overboard also.
I saw on another forum (actually more than once) “OMG this furnace is upside down” rather than check the manufacturer’s installation instructions. I’ve also seen folks post that they think ALL 90% furnaces must have their air intake piped outside when some do not require it but again the manufacture’s installation instructions would tell the story.
It would have been so easy to check the flue draft on this WH by simply turning the high speed blower on and firing up the water heater but again I agree that the safest thing for the HI to do is just condemn anything that is uncertain.
Anyway, I was just speaking in general, not necessarily about the register shown in the picture.
I was just trying to correct something that almost everyone seems to be mistaken about which is “gas burning appliances produce Carbon Monoxide” - they do not, under normal operating conditions.
It’s really kind of sad that some of y’all don’t want to know about how a normal gas appliance flue works. 
Sparks,
See #s 25 and 27.
The whole installation is _____ (fill in your own expletive). As far as the supply or return vent that can be put in another position, move it up 8". All of it has to be redone, I think we can all agree on that. 