Worcester 28i rsf - hot water but no heating

[beesley121]

Got called to a house today, worcester 28i rsf, cyst has hot water but no heating. Pressurised boiler to 1.5 bar, no room stat, mechanical clock bypassed, pump runs and fan remains on. No attempt to ignite.

Cust says had power cut last night and when power came back on, heating wouldn't work


i think its pcb at fault, what do you guys think?

 

[buckley plumb]

any fault lights coming on - does the htg on light illuminate

 

[beesley121]

Unless I've missed something there's only one light on these boilers which is the mains power light

 

[buckley plumb]

- Worcester, Bosch Group UK installer site

is it this one the cdi rsf

 

[beesley121]

No mate, this is the one

- Worcester, Bosch Group UK homeowner site

 

[buckley plumb]

make sure the overheat stat has not tripped - would give you the symptoms you have from memory here is the manual to help

- Worcester, Bosch Group UK installer site

 

[beesley121]

Now that's why I love this forum.

totallymissed that but in the manual.

If I try that and it doesn't work, would you then say its likely to be the pcb

 

[buckley plumb]

possibly - check the resistance of the thermistor on the htg first .been a while since i worked on one of these .let us know how you get on

 

[beesley121]

Thank mate, i appreciate your help

 

[Nostrum]

Interested to here the outcome of this if you could Beasley.

 

[beesley121]

Interested to here the outcome of this if you could Beasley.

I'm back there wed mate so will let you know. Are I having the same problem?

 

[Nostrum]

No mate, but have a few of these we look after, also wondered if OH stat would affect hot water even though these have twin pass heat exchangers so hot water isn't relying on heating as such.

info like this always comes in handy

 

[beesley121]

No mate, but have a few of these we look after, also wondered if OH stat would affect hot water even though these have twin pass heat exchangers so hot water isn't relying on heating as such.

info like this always comes in handy

well from what I have read since, it seems the OH stat will only effect the heating side of things, so hot water would be ok if this had tripped. So on wed, that will be the first thing I will be looking at. Good job it's an empty house for now lol

 

[diamondgas]

You sure the pumps spinning beesley121? Most likely suspect as it only comes on for heating far as i remember

 

[beesley121]

You sure the pumps spinning beesley121? Most likely suspect as it only comes on for heating far as i remember

Yes, definitely spinning. Took the screw out and did the old screwdriver trick

 

[diamondgas]

Yes, definitely spinning. Took the screw out and did the old screwdriver trick

If the burner doesn't light at all I'd be checking the c/h sensor ... Not sure if these were prone to it but the spindles on the control knobs can snap meaning that the boiler may be set to minimum but the knob can show max!

Other possible issue could be a dislodged pump impeller?

Just some thoughts before changing the PCB beesley..

 

[wards]

learn something new everyday.had one of these last week,the p.c.b had gone(dry joints)if you pushed the front casing it would work fine,anyhow changed p.c.b,hot water fine but no ch,called tech line and they suggested o/h stat as when p.c.b interrupted it would throw o/h stat,reset stat and up and running,as said learn something new everyday

 

[buckley plumb]

learn something new everyday.had one of these last week,the p.c.b had gone(dry joints)if you pushed the front casing it would work fine,anyhow changed p.c.b,hot water fine but no ch,called tech line and they suggested o/h stat as when p.c.b interrupted it would throw o/h stat,reset stat and up and running,as said learn something new everyday

had 2 like that

 

[payney1974]

To be honest I thought it would affect DHW too but if the manual says different it has to be OH popped. Power cut probably happened during CH mode which meant alot of heat contained in the HE and no pump overrun.

 

[beesley121]

Well OH hadn't tripped, replaced pcb all if fired up first titime only problem then was I noticed the pressure gauge was increase rapidly and was nearing 3 bar.
I checked the expansion with the view to pumpnit up only to find it was full of water

cust not happy they spent money on a new pcb and fitting only to find its knackerd. Explained that there was no way I could tell the boiler had another fault until the pcb was replaced

Explained to cust not to use boiler and asked th could I turn it off. Getting them a price for a new one and maybe fitting an expansion vessel elsewhere as the cust has no money !!

I'm unsure though if this should have been labeled an at risk. It's not a gas issue, nothing to do with fumes, all other safety features work but is the expansion vessel and prv included in this. All it would potentionally do is either blow off outside or flood the kitchen is they were to carry on using it

 

[Nostrum]

Unlucky but it happens, not at risk so don't worry. Top tip: close rad valves and remove a rad. Empty it, refit but don't bleed and open only one rad valve. Air in rad will act like an expansion vessel for a temporary fix. One closed rad valve will stop circulation so no chance of air moving about.

had a system run like this for 9 months before!

 

[buckley plumb]

Well OH hadn't tripped, replaced pcb all if fired up first titime only problem then was I noticed the pressure gauge was increase rapidly and was nearing 3 bar.
I checked the expansion with the view to pumpnit up only to find it was full of water

cust not happy they spent money on a new pcb and fitting only to find its knackerd. Explained that there was no way I could tell the boiler had another fault until the pcb was replaced

Explained to cust not to use boiler and asked th could I turn it off. Getting them a price for a new one and maybe fitting an expansion vessel elsewhere as the cust has no money !!

I'm unsure though if this should have been labeled an at risk. It's not a gas issue, nothing to do with fumes, all other safety features work but is the expansion vessel and prv included in this. All it would potentionally do is either blow off outside or flood the kitchen is they were to carry on using it

drain a radiator and only open one valve on it and use that as a temp exp vessel customer got heating and hw and is happy at no expense

 

[Nostrum]

And I thought I was a slow typer

 

[buckley plumb]

And I thought I was a slow typer

not as slow as me lol or could be my internet connection. must have been typing at same time