Rinnai EX38C Direct Vent Wall Furnace - Propane

Rightsaidfred

Had a professional install a Rinnai heater in my upstairs shop/garage a few years ago.

About 4-6 weeks ago while we were getting -30C temps (The propane tank was at about 70% full), I was repeatedly seeing a Code 11 ignition failure every morning when I went out to the shop (propane was ~70%). After a few manual attempts to cycle, the furnace would fire and run fine. Fast forward a week or so later, no more code 11's, and the furnace ran great for the last month.

Then...Yesterday I had my propane tank filled again to 80% and since then the unit is throwing the code 11 ignition failure almost every time it tries to turn on.

Im not certain on how these fire up but there appears to be a dual stage burn/ignition (?). Initially the bottom 2 burners fire up ok, then when the top 3rd burner attempts to light, it will fail to light and throw the code 11. Note that this dual stage light ups asi call it has been thing form day 1, you can audibly hear the 3rd burner come on after about 15 seconds (think its called "forced combustion" ?)

Now with the code 11, If I repeatedly try to recycle the unit it will eventually fire on all 3 burners after 5-10 attempts.

Ignitors/flame rods are all clean, Propane is ~80%, filters are clean.

I have a Reznor heater down stairs in the same shop and its running off the same propane source and I have no issues with it.

Thoughts ?

Daveinscranton

My first thought would be to check your propane pressure going to the unit.  Pressure just before the unit.  And see how much it dips when it tries to fire.  Should be some guidance in the manual as to what your unit would like to see.  

Best wishes 

Rightsaidfred

Thanks Dave. My initial thought was propane gas pressure maybe low if temps are very cold and tank is full. I guess I need a professional here with the correct equipment to check the pressures.

Rightsaidfred

Min supply is 8.0 (203mm) W.C. Max supply is 13 (330mm) W.C. for propane. As far as I know most regulators here are typically set to 11WC at the furnace. Ill have to get mine checked by a pro, I dont have the means to test it myself.

Flames are nice blue and strong.

Daveinscranton

If you are comfortable, you can check with a water manometer made from some plastic tubing and a ruler.  Some fittings, a bit of sealant, and some cautious attention may bring some clarity on a Sunday morning.  

Best wishes.

Rightsaidfred

I think ill leave it to a pro, I exhausted my furnace skills & knowledge removing the 3 flame rods and ignitor to check & clean them, they were spotless.

Rightsaidfred

Strange thing is, once I get it to run ok for a while, if I shut it off and then re start it right away, it will fire up fine. If I shut it down and let it cool for a few minutes, the problem occurs - only the bottom 2 burners ignite and when the top one goes to fire up at about 8 seconds later, it fails. then im back to multiple re -starts before it fires again. got some calls in to furnace repair places but likely Tuesday before I hear as its a stat holiday tomorrow here in Canada.

Rightsaidfred

im now leaning towards a solenoid failure or sticking solenoid valve. there appears to be 4 of them, a master and unit that has 3 for the 3 burners..

Update :: Not the Solenoid Valve - the upper burners will go on and off ok when the unit is hot, I can hear the solenoids clicking on and off.

Rightsaidfred

There is also a very detailed and somewhat complex procedure in the Manual for setting the high and low gas settings on the unit -- says you cannot change the pressures on the tank regulator for this appliance.-- depends on altitude, length of the vent pipe, and if its propane or gas. Then you connect the manometer to the high and low pressure ports and compare to the settings and adjust if needed. ---- definitely need a Renai service tech. but my $ is on Solenoid Valve #3 (which controls the burners 3 and 4 which are the 2 that fail to ignite).

Rightsaidfred

So, I fired the 2 guys that showed up to fix my Rinnai wall furnace today, I specifically asked the company for an experience guy that had worked on one of these before and they sent me 2 guys that knew less than me. They were reading my owners manual to figure our what they were looking at (I called the company and gave them a taste of my disappointment).

I have a different company coming tomorrow.

On the good news front, I know kinda what the problem is.

The upper 2 burners dont light when the unit is cooled off. The upper burners ignition via some sort of flame track (not an electrode like the lower ones are lit by). I took the cover off the burner, you cant see the face of the burners much, but I used a brush and cleaned the face of the burners and vacuumed out the area (few bugs and a bit of rust) made sure that flame track was clear.

Now will light OK in only 2 or 3 trys (it was taking me 10 manual on/off tries before I cleaned it).

The upper burners will light every time when its hot, and it always gets ignition failure code when its cold.

Further, the upper burners will go off ok as the room gets close to temperature, and will come back on OK if I increase the temp setting. So..... all this to say, something related to the Cool/Room temperature of the unit is causing the flame to Not Track up to light the upper burners. Once hot either by a couple of start up attempts or when its been running a while and that flame tracks up no problem and they light. there is no debris in there that I can tell, I did fish inside it with a wire guitar string to be sure.

Bri5678

Hi. I'm sitting in my very cold dining room, staring at my Rinnai EX38CT, wondering if you ever resolved this issue? It sounds exactly what my heater is doing. The gas company installed it about 5 years ago. They've been called out to service it a couple times since it started giving the code 11. The technicians have no idea what they're doing.

FrankB

Hi, I had the same issue. I cleaned the electrode and started it. I could see the spark in the window and the flames lit, however on occasion it would shut down. It appears to be one of the flame rods. I focused on the lower rod and noticed that the connection was a little loose. I pulled it off and reconnected it. Has been working well now. The flame rods are like safety switches and will not allow the furnace to start if there is no flame. If grounded out, cracked, or dirty they will act like there is no flame and shut you down. It worked for me. Hope it helps. (In the manual for the ex38ct they are part numbers 118 on page 41)

_JDL_

Check that the burner offices are not dirty clogged at all. If the are you won't have proper amount of gas through the office and not enough heat on the flame rod to keep the unit running.

FrankB

As a follow up, I noticed that the upper flame rod configuration appeared to be incorrect. The rod end is facing away from the actual flame. I bent the flame rod so that the tip is now closer to the actual flame. Have not had any issues since. I'm just wondering if when some were manufactured an incorrect flame rod was installed.

pecmsg

FrankB said:

As a follow up, I noticed that the upper flame rod configuration appeared to be incorrect. The rod end is facing away from the actual flame. I bent the flame rod so that the tip is now closer to the actual flame. Have not had any issues since. I'm just wondering if when some were manufactured an incorrect flame rod was installed.

doubtful