Worcester Greenstar 29HE

[superdupergasman]

This is a conventional boiler on an S-plan sealed system. Its the older style greenstar (not the new cylinder HE style)

The boiler works a treat when under normal operation, however, if it is firing when the demand finishes e.g. the DHW is satisfied, the valves shut pump stops and temp (if its up about 70 under demand) rises up to 99 and the thing boils!!!??

It does not have a bypass however has no pump overrun function so should not need one.

I am wondering if due to poor water (SE london) there is scale causing this problem on the inside of the heat exchanger. but thats just a stab in the dark, going back with a new thermistor but I doubt it, going to change the pump aswell justencase the water is not circulating properly. All rads are heating well so there is no circulation problems.

Any ideas would be appreciated!

Cheers

Mark

 

[nicknox]

Should have a pump overrun and bypass, hence the boiling.

If it didn't have scale before, it has now

 

[swbjackson]

From MI

Note 1: An automatic bypass is required if the controls
i.e. 2-port valves, can result in the closure of the CH and
DHW circuits when the boiler is hot. If mechanically
operated thermostatic control valves are fitted on all
radiators an automatic bypass is required, located at
least 2m from the boiler.

 

[swbjackson]

Should have a pump overrun and bypass, hence the boiling.

No pump connection on boiler according to MI

 

[superdupergasman]

As said NO connection for a pump from the boiler Nicknox!

I read the MI's and it said something different to that quote, i'll look again and perhaps quote the cust for a bypass.

 

[nicknox]

Greenstar 29 HE 41-311-56

'a bypass is generally unnecessary on a sytem using a 3 way div valve as one port will be open to flow at all times. This wil be satisfactory for the PUMP OVERRUN REQUIREMENT'.

 

[superdupergasman]

Greenstar 29 HE 41-311-56

'a bypass is generally unnecessary on a sytem using a 3 way div valve as one port will be open to flow at all times. This wil be satisfactory for the PUMP OVERRUN REQUIREMENT'.

you must have a wrong set of instructions (perhaps there was an amendum)

I phoned worcester tech help to check there was no modification kit available for a pump overrun but there is defo no way to connect a pump to this boiler.

So a bypass it will be.

 

[namsag]

41-311-60 ? (or 56 if you look at sevice book)
Have a look at section 4.2 pump is wired back to boiler.

excellent worcester web site click into 29he discontinued 2003 and it gives you 3 different GC numbers in 3 sections as per worcester clear as mud

 

[nicknox]

In section '3.2 System' it clearly states that an automatic bypass is required if the controls i.e 2 port valves can result in the closure of the ch and hw circuits when the boiler is hot. Hence the pump overrun.

 

[superdupergasman]

41-311-60 ? (or 56 if you look at sevice book)
Have a look at section 4.2 pump is wired back to boiler.

excellent worcester web site click into 29he discontinued 2003 and it gives you 3 different GC numbers in 3 sections as per worcester clear as mud

its the 41 311 56

there must be multiple versions of this boiler with different controls....

This version does not have the pump direct from the boiler, and cannot, it shows it from an external wiring center. Hence as some will not believe does NOT have a facility of pump over run

Was round today and there is a bypass fitted as a towel rail straight after the pump so that is ok however the Heat exchanger has now burst and is dripping down internally and dumping water out the cond drain.

Looks like I will soon find if the cause is scale inside the H/E on friday!

 

[namsag]

If you look at section 4,2 on worcester website for the 29 he it shows a direct connection out of the boiler for the pump to the external wiring centre.
It would not suprise me if worcester have soe sort of amendment sheet for this boiler.
Some of the wiring diagragms for worcesters are feking atrocious, basically for a combi with bits added in on amendments sheets