Takagi ignition

[HANKSTER]

Now my takagi tk3 finally lights up. Outdoor propane unit. It seems to refuse to light when the outdoor temp is at 40 degrees or lower, and the H2O and propane pipes are at 31-35 degrees or so. When the temp rises to 46-48 degrees on both gas and h20 pipes, it will light up eventually.
When the temp outside is 50 degrees or higher, it lights up.
Does anybody out there have any guidance for me on this system? The unit is not sooty, has all the condensation drain and dampers, has the 3/4" propane line from the tank, and the computer surge protector power strip. All the installation tips from the owners' manual have been installed and work ok. The big Rheem gas fired hvac unit on the same gas line works just fine. The overheat control fuse connector melted from white to brown, so I shunted it with a paperclip and the TK3 started right up. This is a white fuse wire wrapped around the back of the copper colored heat exchanger at the top of the unit, and the connector that melts goes between it and the hi-limit switch at the extreme upper left on the output pipe. This tip came from this forum. Thank you!

[Dana]

Takagi America is in your time zone, let their techs talk you through a diagnostic.

(888) 882-5244

Download and read the manual first, and have it handy.

And buy the right part- get rid of that paperclip hack- when your house burns down it'll surely be discovered, voiding some possible insurance claims!

[HANKSTER]

Dana;

as a retired state-licensed auto mech with the specialty of electronics and fuel injection, what i need from takagi is programming and sensor parameter data, and berndt and the guys there won't give me that, because i will uncover all the 'warts' in their little tankless system.
Believe me, i have gone 'round and round' with them, and they don't know anymore than i do, and if they do, they aren't telling me. I sent back a bad controller board for warranty replacement, and they put it back on the shelf for re-issue, and this was when i had told them it was bad and making the commanded gas shut-down and evacuate signal when hot water was signalled by the faucet, or by multiple faucets to go over the gpm threshold. And this in 50 degree outside temperature, no snow at all. Not even cold enough to harm citrus crops!
It was from this forum that i learned of the fuse wire problem, and takagi seems to try to minimize their problems and deny warranty claims.
I will stay away from takagi in the future, because they have such a bad service dept. They would not even tell me which plumbers up in redding
were currently certified to repair their products, and certainly withheld the little fact that their tankless units work poorly in outdoor
cold weather up here. For you yankees, remember the story of the donner party who resorted to cannibalism when they got caught in a california blizzard during the calif. Gold rush era? It ain't all orange groves and surfboards out here, dana. Just because takagi is nice to you, do not presume they are competent. Only results count for score. Kind of like your buffalo bills football team. It doesn't matter how much money you spend, dana. Junk is still junk, lousy engineering is still lousy engineering. That's why billion-dollar space shuttles still crash and burn, not from pilot error.

[Dana]

"..you yankees..."??? Just 'cuz I live in with Yankees doesn't mean I'm clueless, or that I FROM here, eh? I was born/raised in the Puget Sound area, but I've spent sufficient days skiing in the Sierra (even summertime hike-to-ski above Horse Camp on Shasta) to know from Redding CA weather. I've played on the snowy ~13k' summit of my namesake peak overlooking Tioga pass in years past, and would do it again in a heartbeat! I've only XC skied on Donner Pass, but I got hungry enough that I was eyeing my partners with a different kind of interest around lunch time... must be something in the air up there. ;-)

And the Patriots (not the Bills) are my home team, not that I'm a big fan. Ever heard of 'em?

Yours is the first truly negative feedback I've read regarding the Takagi help line. I've never had to deal with them myself. My expectations are pretty low calling any tech line- I don't expect to be talking to the engineer who designed the system.

The whole notion of any outdoor-mounted tankless in places with even a slight freeze potential (as small as it might be in Redding) has always been suspect to me- the heat exchangers on these suckers can freeze up pretty fast (being heat exchangers, and all) and relying on the resistance heater to save them seems like folly. (As if the power never fails when it's below freezing out, say in a 25 year worst-case winter storm?) I'm sorry to hear the Takagi is funky from a control POV even at warmer temps though. There may be weak points in the design, but yours clearly isn't operating as-designed- they run them a 50F in Japan and Florida all the time. I'd suspect something misfunctioning in the pressure regulator were it not for the burnt fuse-wire issue.

As an electrical engineer I've designed boards that have gone up on the shuttle (part of the payloads, not the shuttle's systems) and some goods that went on satellites, but I can't say I've ever been impressed with how those projects were managed. I'd take my chances with an earth-bound Takagi with a paper-clip hack first. :-)

[HANKSTER]

DANA;

This tankless mess has really got me frustrated, as you can tell. I am actually not sure that there is a good reliable tankless unit available yet. My only water heater experience with fuel-fired boilers was when I hung around with the 'snipes' when our ship was in the Persian gulf. It was amazing how much plumbing and control equipment went into a 500lb Westinghouse steam plant, and how long it took the Navy to train the Sailors to run that thing. I do understand some of the functions
of an automated demand-triggered unit. I am of the opinion that they still have a lot of bugs to design out, just like the old fuel injection systems on the cars and trucks
of the 1980s we had to repair. A lot of those old bombs really spent a lot of time in the shop while we did all the head-scratching trying to fix them. I am starting to believe this Takagi is similar, and some of the electrical engineering is odd, to say the least. That overheat fuse is a fuse wire, and they function with a current overload, not a thermal overload. Why not just use a thermal snap switch just like the blower controller uses on a pellet stove? Theyre small, and work in a hot environment. Do you see what I mean? Just 'cause it's shiny and new doesn't make it any good. I call bad engineering bad, period. Soichiro Honda used to throw badly designed units at his engineers, just to get his point across. I disagreed with his politics, but his engineering was ok.

Hankster

[Dana]

Not defending the design, but trying to figure out why they might have gone that way...

Fuse wires are only temperature sensitive- they melt when they hit the critical design temp within the range determined by it's alloy. Whether the source of the heat is from current in the wire (as one normally thinks of fuses or fusible links in other systems) or external, it's only the melting temp of the alloy that counts. Using fuse wires in a sensing circuit the sensing current is always quite small, but it detects the open circuit reliably.

Snap discs are mechanical and can fail in either an open or closed position, and thus not as reliable a thermal sensor as fuse. (If the blower on your stove get's stuck either open or closed it's not a fire hazard, is it?) On a critical safety feature the reliable fail-open may have been a driver of the component choice. But the fact that it fused means it had to have overheated to a critical temp at least once.

All tankless HW heaters are Rube Goldberg contraptions on some level, but they've been around for about a century now. The electronic-controlled versions are less than 15 years old though. But there are literally millions of the electronically controlled units out there still providing reasonable service after years of use (and Takagi has a decent market share, if a much smaller slice than Rinnai.) Something is definitely wrong with yours- it's not behaving as-designed (or as thousands of identical units behave) but figuring out exactly what the issue is might not be very easy via web-forum.

[HANKSTER]

What I don't get with this fuse wire design, is why did an overload of some kind burn the connector plastic to brown from the original white, and not blow the fuse wire as well? When I hit it with the VOM, it read 9.5ohms, so it had a measure of conductivity in it. Was it starting to blow? No other burn marks anywhere in the circuit, from what I saw. I'm still toying with the idea of unscrewing the air inlet panel above this because this unit is in a screen porch with a ceiling about 2 feet above the unit. Possibly this will allow heat to escape and reduce the incidence of connector overheating. Also, wouldn't radiant overheating increase the resistance in the circuit and limit current flow that would otherwise blow the fusible link wire?
I believe it still conducts to a degree, but the 9.5 ohms is too much over the resistance threshold for the controller, and it is having the occasional shut down command.

Naturally, this gizmo is well out of the warranty timeframe, so no possibility of returning it to Takagi.

My hillbilly fix of pre-heating the unit with a radiant electric room heater works like a charm, so I'm ok for now, but will listen to any advice or experiences with other and hopefully better brands available now. I bought this about 3 years ago.

Hankster
Redding, Ca.