Rinnai RU98 question

[superduty1]

I have an Ru98 tankless water heater (mounted in garage) that is throwing an error code 11, "NO Ignition."

I saw some stuff via google that folks have cleaned the burners and that fixes the problem. I see in the troubleshooting that debris in the burners could cause this error code.

Most of the other error codes have to do with things that are highly unlikely since the unit has been running perfect for about 5 years.

Can anyone give any guidance on how to remove the burner cover. The inside of the RU98 (like most tankless water heaters) is very compact and crowded with wires and pipes. Looking at the burner assembly it looks very challenging to get in there to disassemble it. Any tips or tricks would be appreciated.

 

[Jackfre]

11 is a failure to fire. I would begin by cleaning the flame rod (use a dollar bill) and sparker. If the gasket gives out order a new one. If you get into the burner compartment again make sure you have new gaskets for the re-assembly. I haven't worked on an RU-98 in quite a while, but I'll dig up a service manual for back-up. Ignition sequence is flow, inducer, spark, gas, Micro-amps proving flame and hot water. Are you getting spark? If so with no ignition it could be the gas valve or pcb.
If you get into the burner tray, yes, there are a lot of screws. Take a picture before beginning Once you get the face plate off (two different length screws) the burner tray will slide right out. There are 16 identical burners in the rack. Look on the back and there is a retainer strap. 4 screws and the burners are loose. The way that unit fires is the 4 burners by the sparker fire every time there is a call. Then the 4 to the right and finally the remaining 8 on the left and it will modulate as it needs to based upon flow and temp rise. Inspect those 4 primary burners and clean them..gently. If there is an issue with the vent and any condensation has come back into the unit those burners can take a beating. I ALWAYS, once in there, swap the 4 left hand burners for the center burners. If you have spark then the gas valve may be a problem. There is a small plastic tube at the bottom of the gas valve. Do you see any moisture in there? If so, new gas valve. PM me and I'll send you the service manual portion for your unit. Exactly what is the model number on the unit. I am assuming REU-KA3237FFUD-US. Oh, on the inside of the cover is a small folded up paper that has a lot of install and service information on it. It may be all you need.

 

[SALIV8]

Wow jackfre

 

[superduty1]

@Jackfre

Please forgive me for not sending you a THANK YOU in December 2019.

I guess I wasn't getting notifications from GJ about replies to posts, as a result I never realized anyone (you) posted a reply.

WOW, great detail and information. Thank you again for taking the time to post.

 

[Jackfre]

Got you PM. Nice of you to say, but I went back and got into the Service Manual and my previous burner info is incorrect. Your unit has the ceramic burner. I cannot send a manual now as I 86'ed the extras upon leaving my work with Rinnai and have only the one manual left. I have emailed the appropriate info on your specific model. You ask about parts and I'll be damned. You may be the luckiest Rinnai KB unit owner on the planet. I got thinking of parts and recalled that I have an old water heater up in the attic of the shop. I just went out and checked it out and it is a KB propane unit. Pretty cool, eh? It is yours for the cost of a piece of plywood to box it up and freight cost from CA to wherever you are. I plugged it in and ran through the start-up sequence with no error codes. I think this unit may have been one I used in my mobile show-room/training trailer. Looking down the vent pipe it looks new but there is indication that it had been hooked up. It is complete and looks about new. I could break parts out of it for you, but think you might better go for the whole thing. It is about 80#, I think. You decide on shipment method and let me know how we proceed.

 

[71Fastback]

Excellent follow up Jackfre

 

[Bigblockyeti]

I have a Rinnai that's ~3 years old and I still have the manual, when I get home I'll see if it's the same as I can't remember the model number off hand.

 

[Bigblockyeti]

Mine is a RUC98i, I don't know what the differences are but presumably it's close to the RU98. I keep getting a code 12 (no flame) and it happens when too much water is flowing through with too high of a set output temperature. It happens much worse in the winter as the output temperature is set at the same and the incoming water is much cooler making the delta t and consequently the required BTU's much greater. That it just quits trying is problematic as the burner goes off, an audible alarm is set but can't be heard outside of the garage. I suspect it's a flow or pressure issue that's the root of the problem but throttling the output via discharge ball valve has worked, though it needs to be fixed correctly.

I have the manual for mine if you need any specific section, I might be able to scan it and send it to you if my scanning is willing to cooperate.

 

[shade]

Mine is a RUC98i, I don't know what the differences are but presumably it's close to the RU98. I keep getting a code 12 (no flame) and it happens when too much water is flowing through with too high of a set output temperature. It happens much worse in the winter as the output temperature is set at the same and the incoming water is much cooler making the delta t and consequently the required BTU's much greater. That it just quits trying is problematic as the burner goes off, an audible alarm is set but can't be heard outside of the garage. I suspect it's a flow or pressure issue that's the root of the problem but throttling the output via discharge ball valve has worked, though it needs to be fixed correctly.

I have the manual for mine if you need any specific section, I might be able to scan it and send it to you if my scanning is willing to cooperate.

Overall would you recommend a tankless?
Debating on it.

 

[Bigblockyeti]

Overall would you recommend a tankless?
Debating on it.

I do, it takes up little room compared to a 50 gallon tank, doesn't cycle when not needed and it's very efficient. The one drawback for our house in particular is 70' of copper buried under the slab to the master bath that sinks a great deal of heat from the water. The output is set at 140° and after 5 minutes (this time of year) I'm only seeing 104° at the shower head, it slowly creeps up to about 118° after 20 minutes but I'm out in 15 minutes unless I have company.

 

[superduty1]

I also recommend it. The initial price is significant, especially if you aren't near the gas meter or dont have large enough gas supply.

Hopefully I can get mine back to working consistently.

I have a recirc pump on mine with a timer, so there is instant hot water.

 

[Bigblockyeti]

I also recommend it. The initial price is significant, especially if you aren't near the gas meter or dont have large enough gas supply.

Hopefully I can get mine back to working consistently.

I have a recirc pump on mine with a timer, so there is instant hot water.

With a recirculation pump does it just run on idle all the time or does it have a lower cut in temperature and a higher cut out temperature? Did you have a dedicated loop or does it backfeed the cold require a wait for cold water to show up? I need something for mine, it's apparent it's costing me $$ pouring cold water down the shower drain while waiting for the warm(ish) water to show up. As an added benefit, in the winter it would loose heat into the slab acting as radiant heating.

 

[shade]

How many btu is your tank less?