Rinnai tankless water heater problem

Old 11-12-07, 04:16 PM
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Rinnai tankless water heater problem

Moved into a brand new house last January equiped with a natural gas supplied tankless water heater (Rinnai model) which also supplies the radiant heating throughout the house.
The vent is a horizontal.No complaints so far either on the hot water supply or with the heating, that is until last week. The warning sensor has now started to go off randomly either when I take a shower or use the diswasher. The error messages are either ''power interruption during bath fill'' or ''flame failure''.... I have to do is a reset, however, this should not be happening. The vent does not seem to be obstructed'. I've read all the info on this sytem but I don't dare taking it apart to investigate the problem since the whole thing is still under warranty by the builder, and they will come and look at it ( after much insistance on my behalf). My question is, (so not to look like a complete idiot when the plumber finally shows up), has anyone experienced this type of problem and what was the probable cause. Because the two error messages seem unrelated to each other this is throwing me off as to what the problem could be.

Old 11-16-07, 11:42 PM
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don't worry about looking like an idiot, all the pressure's on the plumber to look knowledgeable. you're the customer, you're supposed to be clueless. do you have a manual? it has a list of error codes and possible causes. the flame failure is a fairly common code and can be caused by quite a few problems. what size is the gas line supplying the unit? it must be 3/4" or larger. when you say the vent is horizontal, does it just run a few feet and terminate on the outside or does it run for quite a distance? if it runs for a longer distance, was a condensation tee and line installed? there are gas pressure adjustments for high and low fire possitions that can cause this problem if they're not in spec. nothing you should be messing with though. if it's under warrantee just have the plumber come out and politely ask if you can watch. these are a fair bit more complicated than the old style heaters and i'm sure you'll learn a few things.

my service manuals are in my truck. i'll look at them tommorow and see if i can help you any more.


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