Instant hotwater ....help?

[Newcastle George]

Here's something for members to ponder and discuss.

I have a Bosch Instantaneous hot water system in the bus, no power needed just turn on the tap and it fires up, most of the time. It is powered by a water powered turbine which feeds an ICU which in turn operates solenoids to start the pilot flame and main heater.

It will operate perfectly for a couple of weeks but then, seemingly for no reason, it will not even spark to light the pilot flame. Leave it for a few days, maybe two weeks and it will operate perfectly again.

This has been going on for the last 6 months and I have tried to eliminate all posibilities such as replacing the ICU, the two solenoids and checking for resistance at all electrical connections. Luckily I have a plumber contact who has loaned me a new ICU and solenoids for trial, all to no avail. Also, the turbine produces the correct voltage at all times.

HELP

George

[BruceS]

George we have a similar one on the houseboat although it is probably much bigger.
We find ours has a bit of trouble once the gas is nearly exhausted. I'm not sure if there is a certain pressure needed before gas is released for ignition but as you say .... the igniter appears ok. Stands to reason there is no gas to burn??
I wonder if your regulator needs a slight tweaking?

[Newcastle George]

This is mine Bruce, Model WR 325 -8KG. I have had the regulator tested, OK, gas full, when it is working, no matter what I do I cannot make it not work, I can start and stop it as many times as I like over a couple of days without a problem, then a couple of days later no spark no matter how many times I try, try again the next day or a week later and it fires up instantly.

Click to enlarge

100_4276 (Medium).JPG

[BruceS]

I'm guessing you have the manual but .................
https://www.manualslib.com/manual/10812 ... tml#manual
Does yours have the pilot light George?
The one on the boat has no pilot light but relies on 240v being present. (Rinnai Infinity 24)
The one that was on the previous boat had no pilot & no batteries or power at all.

[Newcastle George]

Yes I do have the installation manual and no, it does not require any power by any means, just the water powered turbine which I have tested for output as per the specs wether or not I get the spark which lights the pilot flame. There is an overheating relay which goes open circuit if overheated and is one of the things which may be at fault and I am going to bypass it. Then other is the ICU which may be the culprit. However, I can't see either of those causing the intermitance.

George

[jon_d]

humidity.

[Newcastle George]

humidity.

We have not had any humid days of late and the same applied to Albury Showground on the way to taggerty. However, while at Taggerty it was working.

George

[jon_d]

George,

I guess you need to determine which side is not working


Is the gas flowing out the jet? Or spark sparking?

It needs both. Which one is not working?


Then follow the path until it fails.

[Newcastle George]

When it doesn't work the spark , which is provided via the ICU and the turbine, is absent. The turbine always supplies the correct output and I have previously fitted a new ICU without success. There is a switch which when ON causes power to be supplied from the turbine to the sealed ICU which in turn causes the spark and causes the solenoids which control the solenoids which allow gas for the pilot and main burner flames. It is the intermitency which I cannot understand. I have spoken to a service agent after contacting Bosch and he is still scratching his head.

George

[jon_d]

is there a wire to the spark unit?


or just high voltage out of the icu?