Takagi t-kjr error code issue

[Jeffg54]

Hi,
I have an older T-Kjr that has been FABULOUS till I just moved and reinstalled it. It started up right away, heating water for a few minutes THEN the fan started running at different speeds (fast, slow, medium,etc) eratically. The flames were short hot blue as always then just quit. I do not have the remote. The red led flashes 3 times and repeats that code til I reset unit. Here is what I know to this point:
1. Propane tank is half full and uses the same hose to connect to the unit since new
2. Cleaned water filter at base of unit.
3. No leaks or smell of LP
4. Button on upper limit switch is not popped out. (the black one at the upper left of the heat exchanger).
5. I can reset it and it will come back on and heat water but goes out more quickly (3 or 4 minutes).
6. The longest it has operated continuously since 1st malfunction is just over 8 minutes.
Love to get a new one but living on Social Security SUCKS!
Thanks for any help,
Jeff Griffin

[Dana]

According to the table on page 17 of the manual a triple-blink can mean any of:

11 Hi-limit, Igniter
12 Flame Sensor, Hi-limit
55 Main Gas Valve
51 Proportional Gas Valve
72 Abnormal Burning

If you spring for the TK-RE02 remote front panel (about an $85 item typically, sometimes less) it would display the code number associated with the error to narrow it down.

The most common issue on that list for a unit that has been in service a handful of years would be a carbon-varnish on the flame sensor. This can be a DIY remediation with a bit of dissassembly and cleaning the flame sensor with a plastic Fibertex or Skotch-brite type dish scouring pad (not sandpaper, emery paper, or steel wool, which can make the problem recur more frequently by leaving scratches where the build-up can get started.)

Takagi telephone techs are pretty patient and good at talking homeowners through diagnosis and repair. If cleaning up the flame sensor doesn't do it, give them a call as you're waiting for the remote front panel to arrive. You'll save more of your own or a pro's valuable time having one already hooked up then next time there's a glitch, and there will be. Nothing this complex goes forever without repairs, but you should be able to get at LEAST a couple of decades out of a TK Jr with a few minor repairs and maintenance, and having finer insight into the problem detected is going to be worth it- if not this time, 3-5 years down the road.

[Jeffg54]

Thanks,Dana

I should be able to purchase that in a week or so. In the meantime should I put vinegar in to clean the water side? It has never been cleaned.
Jeff

[Dana]

Scale-up is almost certainly not related to the error code problem, even if you happened to have scaling issues. (I'm giving 3:4 odds that it's a dirty flame detector.)

Periodic descaling would only be called for if you have relatively hard water (and no water softener ahead of the tankless). If it's scaling up there is a higher than expected pressure drop across the heater at high flows, or the inability to get high water flows through the thing at 30psi water pressure. If you installed isolating ball valves and ports for hooking up a descaling pump loop when you re-installed it the descaling job is pretty easy with a small pump and a bucket of white vinegar (which you would dilute down at least 2:1, or even 4:1). If you search YouTube for "tankless descaling" you'll find lots of handy videos on how to go about it. This one is a bit long, but a reasonable discussion. I've seen tankless units with 15 years of service behind them going strong without a hint of scaling despite having never been serviced, for other people it's an annual event to keep it flowing, so it's really all about your local water conditions, and the amount of water you're running through it in a year. (A 5 person family will usually use a lot more hot water than a retired single or couple.)

If you are on a well it's a good idea to test the water at least once a decade to keep track of water quality, but if you're on a municipal or county water system there should be publicly available test data which would have hardness data embedded in it somewhere. If you're under 1 grain per gallon fuggedaboudit- it's unlikely you'd EVER have to descale it. If it's something like 5 grains or more it's a good idea to descale it at least every couple of years even if you're a low-volume user, annually if you're a high-volume user.

[Jeffg54]

I just noticed that I failed to reinstall a 1 foot long x 3/4" capped drop leg on the LP inlet. When I purchased the tkjr a plumber friend told me that I would not have enough volume of LP available to run the unit properly with the hose from the tank directly to the unit (enough pressure, not enough volume. Could this be my problem? would a longer length be better? The unit is 3' above the floor.
When I opened the unit today it is very clean. I will clean the flame detector as you recommend.
Thank you,
Jeff

[Dana]

If the regulator is at the tank but the line is only1/2" and the run is long between the regulator and the tankless, this could very well be the issue. If that's what's going on it would run fine pretty much forever at some low rate, say 1-1.5gpm, then crap out when you open up the flow or some other burner sharing the line kicket on. That should not have changed much just by moving it if the prior installation had been on a similar sized tank & regulator & lines in a similar climate. IS mid-winter, and if symptoms only occur below some outdoor air temp tank size could be playing into it too. This is something like a 140KBTU/hr burner, and 40' of half-inch pipe (or 75' of 3/4") between tankless & regulator could bring it to it's knees. If it's using the same fuel plumbing that had been running a 35KBTU/hr tank it wouldn't be too surprising to find a capacity issue.

Somehow when I read your initial post I'd thought that you had moved the location of the tankless to somewhere else in the house, not to a different house entirely, which opens up these other issues.

By "drop leg" are you talking about the plugged vertical stub on the bottom half of the Tee on the fuel line just be before it enters the unit?



That stub is there to trap any corrosion, condensation, and any fuel-borne crud from getting into the interior fuel valving and burners. If it's burning blue the burners are OK, but if a bit of rust or grit got into the modulation control valving of the unit it could intermittently (or permanently) stick. You DEFINITELY need to put that sort of trap on any fuel line connection, but for the moment I'm going with the fuel line/regulator capacity issue as the prime suspect.

If the fuel lines are too narrow & long to support the BTU-rate at high fire of all burners on the regulator it can cause erratic behavior too. Many pros will use a manometer and measure the pressure drops at high-fire when commissioning a tankless. If a furnace or boiler is teed off from the same line some distance from the regulator as opposed to very close to the regulator there can be pressure interactions that trip codes even if the nominal pipe sizing is adequate. But since it seems to misbehave all the time, not just when some other burner is running, that's just something to keep in mind, it's probably not "THE" problem your chasing right now.

[Jeffg54]

Thanks,
Yes, the drop leg is similar to the one in the pic with the following differences. My T is attached to the fitting coming from the bottom of the tankless and my one foot long piece extends below the T and capped. The hose from my LP tank is 1/4" ID and ties into the lateral leg of the 3/4" T at the unit. The hose is 6' long and has regulater at the tank. My plumber friend suggested the one foot long piece could double as a junk catcher AND A larger manifold to help with volume issue. Propane tank is for Jr only . It performed great like that til I moved. The last time I tried to run it after moving it ran fine far a few minutes with one faucet running, when I added the shower to the load, half of the burner quit and then it switched to the other half, then quit completely. red led blinked three times. As I had misplaced the 1' drop I just installed a plug at the bottom of the T. I'm pretty sure that is my problem. Do you agree?
If you agree would a 2' drop/manifold be better?
Coppers side is very similar to the picture.
I have cleaned the flame detector rods as suggested.
Jeffreha

[Dana]

It's a hack, but yes, the more volume you can add to the near-heater plumbing damps out the pressure fluctuations of the too-skinny/high-velocity propane line. The fatter higher volume local plumbing forms sort-of a low-pressure "tank" for the gas.

It's a pretty marginal approach, but if it's worked for you for years I'm not going to argue- it's not a fire hazard or anything.

[Jeffg54]

Issue resolved!
Cleaned flame detectors, added a 24"x 3/4" manifold and walla, she is working again. Thank you, Dana for the great guidance and advice. So happy to have it working again. Next step is to purchase the remote for any future issues. Thanks again for this great forum.
Jeff