Rheem tankless gas water heater question

[MikeH2022]

Hi there, I stumbled across this place while trying to find some troubleshooting info on an install I did today.

I installed a gas rheem tankless water heater this afternoon and I’m having a little trouble getting it to ignite.

Gas is on, water is on, and when I switch the breaker on, I get pretty much nothing.

When I throw the switch I can put my ear to the unit and I hear a low humming noise that lets about 8-10 seconds, then a pause, then I hear it again for an additional 8-10 seconds, then I hear what I think is the ignition trying to light, but it kind of just gives up.

I bled the gas line to rid it of air, I checked all of my wiring twice, but I’m stumped.

I don’t have my pressure gauge with me today, so I plan to check the gas pressure output Monday.

Is there anything anyone else could suggest that maybe I’m overlooking? I’ve installed about a dozen of these, but it’s been 4 years in between my last two as I went into another profession temporarily.

Any feedback would be greatly appreciated.

Im also not sure if these newer units have some type of delay? When it didn’t ignite I immediately turned everything off each time.

Thanks in advance. I look forward to the replies.

 

[MikeH2022]

I should add, this is a very old building and everything has is plumbed to 1/2”, I had to reroute the line when I relocated the heater and I transitioned it to 3/4” a few feet from the unit and used 5/8” flex line to the unit.

Just wanted to add that in case it matters to anyone.

 

[MikeH2022]

Something else I just thought of and I’ll be quite embarrassed if this is the problem, but I wonder if there was a debris plug in the gas inlet to the unit that I didn’t remove.

If it was there, it’s still there. I didn’t remove one.

 

[Twowaxhack]

You sure you have the correct unit for the type gas you have, natural or propane.

Make sure the gas pressure is corrrect.

 

[MikeH2022]

You sure you have the correct unit for the type gas you have, natural or propane.

Make sure the gas pressure is corrrect.

Yes it’s a natural gas unit. I’m going to check the pressure tomorrow morning.

I’m stumped.

 

[breplum]

If it is a model without a display, then I wouldn't go out without a remote to diagnose anything other than gas pressure.
The Service Manual will usually help but so will the tech service desk

 

[Twowaxhack]

Make sure the electrical is grounded.

 

[MikeH2022]

If it is a model without a display, then I wouldn't go out without a remote to diagnose anything other than gas pressure.
The Service Manual will usually help but so will the tech service desk

Yeah, it has no display on the unit, there is a remote thermostat to adjust the temp.

If all else fails I’ll have to call the company and have them help troubleshoot.

I thank you all for your suggestions and welcome more if anyone has something to add.

 

[MikeH2022]

Make sure the electrical is grounded.

I’ll check that again tomorrow just to be sure.

 

[Tim Whistler]

It sounds like you have a 1/2" gas line going to the heater, most tankless will require 3/4" with full port valves.
Definitely check the gas inlet and manifold pressure with a good manometer. The noise you heard was the ignitor trying 3 times to light up the gas, after that it stops trying. Gas supply could def be the problem.
Let us know -
Tim Whistler

 

[MikeH2022]

It sounds like you have a 1/2" gas line going to the heater, most tankless will require 3/4" with full port valves.
Definitely check the gas inlet and manifold pressure with a good manometer. The noise you heard was the ignitor trying 3 times to light up the gas, after that it stops trying. Gas supply could def be the problem.
Let us know -
Tim Whistler

I’ll update tomorrow either way.

The gas line to the old water heater was 1/2”. I relocated the water heater to the exterior of the building and several feet from the new water heater I transitioned from 1/2” up to 3/4”.

 

[CT18]

I am willing to bet it is a gas supply issue. The old water heater would burn whatever amount of gas was sent to it. It would just take longer to heat the water. The tankless burner will not work that way. It needs a specific volume of gas for that burner.

 

[MikeH2022]

So, yeah, always always check your helps work because we all make mistakes.

Turns out that when we removed the old water heater that was located at the other end of the building, the cold and hot water supply was reversed by mistake. Very simple fix so not a big deal. Took 20 minutes and a few feet of pex to correct the issue.

I checked the gas pressure and it was in the acceptable range. So after sitting there staring at the water heater hoping it would fix itself, I purged the hot water at the relief valve. Right away the unit kicked on. After further inspection and turning on the flush valve on the hot side, while the cold side was off, the water never stopped. That’s when I knew the lines were crossed.

Issue number one fixed.

Now is where I’ve run into another issue. Maybe I haven’t thought about it long enough, but as I sit here I’m at a loss currently.

I added two sink locations for hot and cold water in this building. Everything gets hot water now. Everything except for the existing bathroom sink that I’ve never touched.

The water heater is on the outside of the bathroom wall where the sink is and the drywall is removed, so I suppose I could get hot water to that sink valve and be done with it, but something isn’t making sense to me.

If it were my call I’d cut out the ceiling and get to the bottom of it, but it’s not my building and the owner doesn’t want to go through the cost. No attic, so it’s not accessible unless I cut out the ceiling.

 

[MikeH2022]

That’s probably confusing in itself to read.

Essentially I removed the old water heater and ran the cold water from that spot over to the new location. From the new location I ran my hot water leg back to the original hot water feed that came out of the old tank.

Now the bathroom sink get cold water on both the hot and cold side.

The other 3 sinks which are on the same line as the bathroom sink are getting hot water.

That shouldn’t be and it has me in the fetal position in the corner.