Rinnai tankless water heater problem

[markk2]

We have installed a bunch of Rinnai units without problems. One exception has a problem no one can figure out. When a shower is in progress, after about 1 minute the heater shuts down for a few seconds, which delivers a few seconds of cold water (not fun for the occupant) then ramps back up and doesn't do it again. We have checked everything 4-5 times and redone the flue once. Nothing changes. The Rinnai factory guy can' figure it out. Anybody else have this problem?

[beenthere]

When you talked to the factory tech, did he address the safety recall on them.

Sorry, I can't help you with the intermitant hot water problem.
If it happens every time. Have one guy go up stairs and run the showe, and you stay at the heater, and check for what ever device is dropping ouot.

[cfb]

Could be a couple of things. A sudden drop in water pressure or gas pressure is most likely.

The rinnai wants a certain water pressure level to run, could be your supply has erratic pressure and at some points you're dropping below its level to stay on.

A gas blockage or drop in gas pressure could produce similar results.

I also heard that some of the Rinnai's have problems with condensate from the duct backing up into the unit and when it senses that, it temporarily cuts the flame. Theres supposed to be an integrated system to eliminate excess condensate, but it may not be functioning properly.

You've discovered some of the many issues with a real-time system...

Get a water pressure gauge (ten bucks) hook it to the end of a hose and drag it over to the WH. Have someone turn the shower on. See if the flame drop is accompanied by a water pressure drop on the gauge.

[Dog]

had that problem with the shower going cold , customer had temp of water to high triggering scald guard in the mixing valve in shower causing it to go cold for a few seconds turn temp down

[weber]

When you talked to the factory tech, did he address the safety recall on them.

Sorry, I can't help you with the intermitant hot water problem.
If it happens every time. Have one guy go up stairs and run the showe, and you stay at the heater, and check for what ever device is dropping ouot.

What saftey recall?

[beenthere]

http://www.cpsc.gov/cpscpub/prerel/prhtml08/08199.html

[weber]

http://www.cpsc.gov/cpscpub/prerel/prhtml08/08199.html

Those are wall furnaces, not water heaters?

[Dog]

Yes I thought it was just the wall furnaces also

[beenthere]

Sorry, just caught the name.
Never read the article.

[markk2]

I thought it might be the shower mixing valve but we tried turning the temp down and that affected nothing. I even changed out the Rinnai. It worked OK for a couple of days then same thing. The plumber says its not in the pipeing so everyone points at the Rinnai. Something in the house is causing the fluctuations, not gas or water pressure, we checked that. Not the flue, we replaced that. I'm HVAC not plumbing, how do you check a house?

[gsilcox]

Washing machines have internal mixing valves that have been known to cause problems with Rinnai's. Try shutting the water to the washing machine off and see if that fixes the problem.:rolleyes:

We've had similar problems and found that to be the issue:eek:

[cfb]

Where's it mounted? Inside the house or outside somewhere? Whats the intake venting look like?

Is this just a problem with the shower or with any h/w usage?

[weber]

Ok, I had a same problem reported yesterday.

Complaint, durring shower loss of hot water a slight pressure problem. Also noticed that they are not saving as much as expected.

Here is what I found was the problem:

Sorry, I just remembered what forum this is, and cant post technical information.

[Moose]

:eek:

[natchagas]

We have installed a bunch of Rinnai units without problems. One exception has a problem no one can figure out. When a shower is in progress, after about 1 minute the heater shuts down for a few seconds, which delivers a few seconds of cold water (not fun for the occupant) then ramps back up and doesn't do it again. We have checked everything 4-5 times and redone the flue once. Nothing changes. The Rinnai factory guy can' figure it out. Anybody else have this problem?

We had this problem and what we had figured out was that the customer was not turning the shower valve wide open at the start and during her shower. She was also trying to consvere on water usage. What we figured was that the restriction of not having the valve full open was causing a lack of the minimum flow rate that the Rinnai needs. The way we found this out was the husband was not having any problem when he showered We had the wife turn on the water and we checked where she positioned the valve. We told her to try it wide open and we have not heard from her since.

Good Luck

[markk2]

Thanks for the reply. We found another problem that affects tankless water heaters. Some higher end showers and appliances have a built in mixing valve that is adjustable. If its not set properly it cuts the hot water pressure down below what the Rinnai needs so it cuts off. I'm not a plumber so I am not familiar with which brands or models do this but I'm learning to look there after I verify gas pipe size and gas pressure. Unfortunately, learning this way cost money. The manufacturer should have let everyone know this could happen.

[Dar Oruen]

I have this problem with hot water cutting out, during a shower. Hot water recovers ~15 seconds. Happens when others turn on another shower in the house, or the irrigation system turns on.

Not a high-end shower fixture, ~15 years old.

I'll contact Rinnai, and post back.

thanks all

[cood60]

I experienced a similar issue when i first installed my unit. Ended up being the shower head in my shower. It was a swater saver type that sufficiently reduced the pressure to cause shut downs of the rinnai.