Gas heater shuts down intermittently

My RHFE-551FA Rinnai heater cuts out for no reason. On his first visit a heating technician cleaned it and checked all the specs which didn't help. On the second visit he ran through all the checks suggested by Rinnai tech service and that didn't help either. For another model, Therinnaeguy suggested checking the small harness from the main board to the sparker board (which the tech did) and if the problem continued to replace the wire harness. Failing success with that procedure he recommended replacing the sparker board.

Would this work for my heater? What would a harness and sparker board be worth and where would I locate them? Thanks for any suggestions

Many of the things have a fairly decent troubleshooting section in their manual. Have you been down there when this happens? It is often easier to evaluate if you can see it happen. Once it does happen, do you have to reset something to make it work, or does it self-recover eventually?

Modern systems often have many levels of safety interlocks. Reading and understanding the interlock and start/stop routine of the system can go a long ways towards isolating the problem. A closed combustion system is more complicated than one with an atmospheric flue, for example. There may be flame decectors, pressure sensors, overheat sensors, etc. in the circuit, and any one of those could trigger the system something's not right and shut things down. If there's a circuit board, often there are a series of lights that show you what's going on. Reviewing those and their sequence is critical to discovering what's going on. An intermittent problem is the hardest to diagnose.

A faulty igniter is only one possibilty. Just in that one component, it could be the controller not sending the signal to ignite, the igniter could be dirty and not spark (or glow if it is that type), the gas valve could be dirty and there isn't enough gas, the flame sensor could be bad and even if it did light, it couldn't sense it.

You need to read the theory of operation and then diagnose. Not all techs are capable of this. If you can't do it, it can get expensive finding someone who can. Trial and error in replacing potentially expensive parts is not the best way to fix it, either - you've got to throw some understanding in along with it. Just like yesterday's car mechanic, unless he is smart and willing to learn, today's electronic devices can be hard to understand and old school can't cut it on these high-tech devices all the time.

Thanks Jadnshua for your response and analysis which I appreciate.
When the heater shuts off on its own I have to turn the shut off knob to OFF, move the temperature control to high and turn the knob back to ON. It always starts when I do this.
The Tech I had working on the unit seemed to fully understand the circuitry and sensors. Additionally during his second visit he was in telephone contact with Rinnai technical service. My observation of an involuntary shutdown was as follows:Unit ON but gas burner not lit;temperature cooled to below thermostat setting; unit fan came on for about 10 seconds then clicked followed by shutdown.
The Tech said when the thermostat called for heat the fan came on, followed by the gas valve opening, followed by the sparker attempting to fire up (Click) but failure to light. On his first visit he had cleaned everything including the optical flame sensor which he thought might have been the problem. Unfortunately that wasn't the case.
I drew his attention to "therinnaiguy" comments regarding the wiring harness and possibly sparker and he thought there was some logic in those parts causing the sequence of events I had witnessed during a shutdown. Rinnai's technical service was initially dubious but conceded that they couldn't come up with anything better so thought it was worth a try.
My tech would be quite happy to proceed with harness/sparker idea but each visit costs me about $250 because I'm 25 miles away from the dealer. I can see this costing me $1000 before I'm done with no guarantee that its going to work so I hoped I could buy a harness and or sparker for a reasonable price and install it myself.

Quote:

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Originally Posted by batass

Thanks Jadnshua for your response and analysis
My tech would be quite happy to proceed with harness/sparker idea but each visit costs me about $250 because I'm 25 miles away from the dealer. I can see this costing me $1000 before I'm done with no guarantee that its going to work so I hoped I could buy a harness and or sparker for a reasonable price and install it myself.

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Ouch..... each call costs $250 cause you are only 25 miles away???
Thats really not that far away even by mid-west standards..

if the fellow cant fix the problem,
and he is supposed to be a qualified service tech,
it seems like he should come back for free till he does.

that is one of the pitfalls of tankless heaters, being at the
mercy of whomever claims to be a service tech.......


out of curousity....how old is this unit anyway???....

Thanks for the sympathy Mark. The unit is a space heater not a water heater and is 12 years old.Outside of the present problem it has been maintenance free.
I'm in a small town in central Ontario thus the distance to a dealer.

Regards B---

got my wires crossed on tha tone...sorry

It sounds like it is a closed combustion system. The fan comes on to purge any gasses in the system, then the click is probably the gas valve opening.

Is the igniter a sparker or a glow coil? Is there any way to view the burner while this is going on? The igniter needs to come on before the burner if it is a coil, and about the same time if it is a sparker. You can usually hear a sparker.

In either case, you should be able to verify the igniter is getting power during the cycle. A tech should not have to guess at this, the thing will either have power getting to it or not, and if it has power, it should either spark or glow. A glow coil can be checked for continuity with things off as well. The flame sensor might be able to be bypassed during test to see if the system stays on. You'd need to know if it is a milivolt job or optical and what the output signal when working is, though.

Sometimes you need to learn these things yourself to get good service (yourself).

You may have dodged a bullet, as there has been a recall for potential CO leaks on Rinnai, but apparently not on your model. I would follow up with Rinnai to be sure, though:

Rinnai Recalls Wall Furnaces Due to Carbon Monoxide Hazard

WASHINGTON, D.C. - The U.S. Consumer Product Safety Commission, in
cooperation with the firm named below, today announced a voluntary
recall of the following consumer product. Consumers should stop using
recalled products immediately unless otherwise instructed.

Name of Product: Direct-Vent Wall Furnaces, Models RHFE 431 and RHFE 556

Units: About 52,000

Manufacturer: Rinnai America Corp., of Peachtree City, Ga.

Hazard: A gasket in the unit can fail, posing a risk of poisonous carbon
monoxide gas leaking into the home.

Incidents/Injuries: Rinnai has received 11 reports of carbon monoxide
leaking from the furnace. No injuries have been reported.

Description: The recall involves Rinnai EnergySaver Direct-Vent Wall
Furnaces, Models RHFE 431 and RHFE 556. They are either natural gas or
LP gas (propane) fueled. The following model numbers are included in the
recall:

Model RHFE-431: FAIII-N, FAIII-P, WTA-N, WTA-P, WTA-72B-N, WTA-76B-N

Model RHFE-556: FAIII-N, FAIII-P, WTA-N, WTA-P

The model number is printed on the top of the rating plate located on
the right side of the unit. The recall includes only those units
manufactured from February 2000 through December 2007. The manufacturing
date code is the first four digits of the serial number, written as YY
MM, and is located at the bottom of the rating plate.

Sold through: Wholesale distributors nationwide to contractors and
dealers from February 2000 through December 2007 for between $1,600 and
$1,900.

Manufactured in: Japan

Remedy: Consumers should stop using the furnace immediately and contact
the firm to arrange for the installation of a free repair kit.

Consumer Contact: For additional information, contact Rinnai toll-free
at (866) 746-8344 anytime, or visit the firm's Web site at
www.wallfurnacerecall.com

To see this recall on CPSC's web site, including pictures of the
recalled products, please go to:
http://www.cpsc.gov/cpscpub/prerel/prhtml08/08199.html

jimbo the repair tech has been in contact with them so I would guess that they have the Mod.# and Ser.# and would know if it was part of the recall.

I see that his model # was not listed, but my point was that these recalls often have a tendency to grow. He might call Rinnai and be told "well, maybe there is this problem on your........". Worth the call.

To Jadnashua: Thanks again for your comments. The heater has a closed combustion system ignited with a sparker. When the system ignites I can hear a fan for 10 seconds followed by a click which I assume is the sparke followed immediately by a whoosh which I assume is the flame from the burner. The tech's problem in verifying power to the sparker during an involuntary shutdown cycle is that he hasn't been able to emulate this type of occurrence. He looked critically at the optical flame sensor on both visits and is satisfied its OK.
I use the unit on low heat 95% of the time and the shutdowns have always occurred on low heat (Between 1 and 3 on a 10 unit heat control).

To jimbo and cass: I called Rinnai and was assured that my model was not on recall. From examining some of the exploded views of the various Rinnai heaters it looks like the heat exchanger was redesigned in 2000 so my '95 model has is OK. Thanks for your interest B---

There is likely a supply vacuum pressure switch interlock that must be closed to enable the burner to stay on. This vacuum is caused by the blower fan. If there is a crack in the intake pipe, the pipe is loose (sort of like a vacuum leak in your car can cause all sorts of problems), or a loose joint, it will not be able to maintain that vacuum, and the system will shut down. Also, double check the outlet and inlet areas to make sure they are not obstructed by snow, ice, a bird's nest, etc. Anything that restricts or unbalances the air flow in the closed combustion system can shut the system down.

To Jadnashua: Thanks again for your suggestions. I examined the intake piping as well as I could and it appears to be in good shape with no sign of leaks. Today I was in contact with my dealer who provided the Technichian I have dealt with. They have presented my problem to Rinnai and are waiting for an answer after which they say they will look at negotiating some form of cost sharing to fix it. If the price is reasonable I'll likely bring them back and present them with all the suggestions given to me on this forum. If not I'll purchase the small wiring harness fro the main board to the sparker board and replace it myself. Regards Batass

Hi!

Batass, did you ever fix your problem?

My g/f has the identical model Rinnai - with the same symptoms. The heater will always start when set to 'on', and the light will come on. Several days later it will be still set to 'on' ...but the light will be off and the unit will be off. By switching off then on it will instantly bring it to life.
So, the issue is that it's either shutting done while firing, or shutting down while trying to refire after the thermostat calls it. Not knowing this is a pretty big hole in my understanding of the problem.

However, what are the interlocks in each case that could cause the unit to go "hard off"?

If the unit is on and running:
Blocked vent? How is this sensed?
Blocked intake? How is this sensed?
Low vacuum pressure?
Is there a room O2 sensor?
Other?

If the unit won't refire:
Igniter problem?
Vacuum pressure problem?
Air flow problem?
Other?

Is there a resource online for these troubleshooting guides? I'd like to resolve this myself if possible ...planning to climb inside tonight! Any advice would be greatly appreciated.

Well I got the heater open last night ...and had printouts of this forum, the heater troubleshooting guide, and fortunately there was some good schematic information on the inside of the heater cover.
I could get the fail consistently if I followed the instructions for turning the heater on.
Set thermostat to low.
Turn on heater.
Bring thermostat up to desired level.

When I brought the thermostat up to just where it kicked in everything looked good. The combustion blower would come on high ...after a few seconds the igniter would fire visibly ...and the flame would light. The combustion fan would then slow to the normal "low" speed and before the main blower would come on the unit would shut down.
I was then informed by my g/f that she'd usually need to adjust the thermostat higher to get it to come on ...which is just what batass said. Hmmm. So I tried this, and sure enough it came on fully ...but the combustion fan did not slow down. I realized there are two levels of fan speeds depending on where the thermostat is set.
This brought me back to jadnashua's critical comment about the pressure switch. This was the first place I looked for issues.... The switch is located at the very top of the unt and has two small plastic tubes connected to it (one blue one clear on my unit). I followed these down to the input and output of the fan housing ...and there was a partial but significant kink in the blue line. I straightened this out and could not get the unit to fail.
Before it was fixed, there was enough pressure making it throught the kink on the high setting to throw the switch. On low, this was not the case.
Unfortunately I did not check the switch before I removed the kink, so I am not 100% sure the problem is gone. However, the fix makes sense given the problems and I could not get a fail after straightening the hose. I'll check it later today to verify it's still running ...fingers crossed!

Thanks for all the good info - hopefully this can help someone else out. The way the hose comes down and is clamped near the output of the fan makes me think this could happen easily on all of these units.