no hot water on a main30he

[Permanent build]

Hello all, I have a problem on my boiler that 2 plumbers can't seem to fix so and ideas? Water started to get Luke warm a couple of months ago then would only work when the heating was on and now all that happens is the rear spindle on the diverter valve pops up and down and the boiler fires then cuts out fires then cuts and so on. I swapped the diaframs same thing happens, swapped the diverter same thing, took out the plate heat exchanger and flushed seemed clean but didn't use any chemicals same thing. The system is 3 years old and seems stupid to put a new boiler in. The fault code is hot water sensor but been told it can't be that. HELP!

 

[Mike Jackson]

Has none changed the hot water sensor?

 

[Permanent build]

Was told by one of my plumbers it can't be that as it wouldn't cause the spindle to pop up and down ps if I hold the micro switch in the closed position it makes no difference, doing my nut in this, one guy says I need a new boiler and the other isn't interested

 

[Permanent build]

Also heating works fine and if its been left on for a good few hours the water works fine?!

 

[Masood]

Was told by one of my plumbers it can't be that as it wouldn't cause the spindle to pop up and down ps if I hold the micro switch in the closed position it makes no difference, doing my nut in this, one guy says I need a new boiler and the other isn't interested

You were told this by someone who couldn't fix it, yet you're happy to assume he's right?

Holding the microswitch open will fire of DHW demand. A faulty sensor will cause the boiler to modulate down prematurely. So the sensor could well be the cause. Although I'd suggest getting in a decent boiler engineer who knows how to use a multimeter, rather than diagnosis by part-swapping...

 

[Permanent build]

That's why I'm here, tbh I thought with that being the cheapest fix and also what the fault was showing. It would be daft not to swap it, il get that tried next, the 2 guys iv had out do all my boiler and gas work (I'm a a builder) and are both gs registered

 

[Masood]

and are both gs registered

GS registration doesn't teach boiler diagnosis and repair, unfortunately. That takes a bit of time and experience (and a few manufacturers' courses!)

 

[Permanent build]

Yeah I can imagine, I'm a electrician by trade I asume the resistance the sensor should be showing will be in the manual?

 

[mountainman]

If the fault code is saying HW sensor then for a tenner I'd be inclined to swap it.
What resistance is the sensor showing when the boiler is cold?

 

[Permanent build]

Il dig the meter out of the van in a bit and test it

 

[Permanent build]

+2000 cold

 

[Permanent build]

002 when hot so I presume it's working fine

 

[Permanent build]

Only thing as a lay man I can think is de scaling the secondary heat exchanger as I just ran it under the tap when I took it out

 

[Masood]

2 KOhm cold is way too low. Normally around 12-15 KOhms. I think you may have found your culprit...

 

[Permanent build]

It's off the scale +2000 is the highest setting on my meter it's not showing a reading, sorry I wasn't clear

 

[Masood]

It's off the scale +2000 is the highest setting on my meter it's not showing a reading, sorry I wasn't clear

Ah right. Well, for a tenner, it's worth a swap I guess. Descaling the PHex won't hurt either. Let us know how you get on!

 

[Dotty]

Have the forum rules changed?

Moving to the gsr private forum out of joe's view

 

[dancinplumba]

Too late I fear, permanentbuild who, first is a builder then a sparks is going to fix his own boiler

 

[Dotty]

But at least it will stop others attempting to repair their own boilers using the information given.

 

[bewsh]

An electrician who's multimeter only reads up to 2kohms?

 

[mountainman]

He probably had it set on the mA range.

 

[Dotty]

scary innit!

And we're advising him to fix his boiler!

 

[Masood]

Sorry, my bad. I saw a couple of earlier replies and didn't even check who the OP was...

 

[Dotty]

Everyone consider their thighs slapped! lol