worcester35cdi overheating

[pla]

My worcester bosch 35cdi has started tripping out and overheating (2 lights flashing simultaneously) but only when hot water is demanded. CH is fine. It will let me reset it, but happens again straight after.

When it does not trip out, the flame light goes out for 15secs, then it tries to start again, but stops after another 10 secs.

The problem is also partially intermittent. It happened last weds pm but corrected itself thurs and fri am, then started again fri pm. We have have had no hot water since.

Any ideas before I call WB for an engineer?

 

[croydoncorgi]

Yup - it's overheating. But you do not say whether there is any problem with the temperature of the hot water at the taps.

If this is only occurring on HW and not on CH, then there's some reason why the heat is not getting away from the boiler (ie. in the water) OR the boiler is actually creating too much heat for the actual demand. If the HW temperature and volume is OK, there's probably a sensor / control problem. If HW is not hot enough, probably a blocked secondary heat exchanger. Either way, you'd better get a fully-qualified boiler tech to fix it. This is not a DIY job.

 

[doitall]

Not over heating CC.

are the lights flashing fast or slow.

Must likely problem and it needs an engineer to test is the fan/flue or the board, but electrical test will show for certain.

 

[petewood]

Pla apart from the overheating do you think this boiler is ok as I am thinking of getting one.

 

[doitall]

Pla apart from the overheating do you think this boiler is ok as I am thinking of getting one.

Boiler isnt overheating pete, however they are as good as any.

Be warned though, in a few months new laws mean we can only install condensing boilers.

it would not surprise me if The Manufacturers don't take the spares off the maket, thereby making all non condensing boilers scrap.

 

[pla]

Boiler lights are flashing slowly, and as per the instruction booklet it is overheating. But I know nothing more than that.

The water does get very warm (not quite hot, hot) for a short time before the flame goes out. Then it goes cold again.

I have taken your advise and called an engineer.

Thanks for your advice guys, I will let you know how it goes.

petewood - we have been very happy with the boiler since we have been here (it was installed about 9mths before we moved in 4 yrs ago). I do find that the flow rate seems quite low compared to the cold water and it does take a while to get hot water downstairs (the boiler is upstairs in a bedroom). However, I am sure these would happen with any combi boiler especially situated where it is. As far as the heating goes it is pefect.

 

[croydoncorgi]

'scuse me!!! (My handbag's already out and swinging!!!)

2 lights, slow flash = Fail Point G - Primary Overheat.
Possible causes: air in system, lack of primary pressure, pump not turning, sensor fallen off pipe (!), overheat stat stuffed, if none of these, PCB or primary HX fault. Sorry W-B, if the CH is working fine, this rules out ALL of the above and we're left only with a blockage in the Primary flow to the Secondary HX. Which ISTR I suggested in the first place and would produce EXACTLY the same symptoms as a failed pump.

 

[ChrisR]

Have you checked the pump on the HW side? (you have two)

 

[croydoncorgi]

Huh???

Have you checked the pump on the HW side? (you have two)

Double vision?

 

[ChrisR]

No, the 350 had two pumps too.

 

[doitall]

Where do they hide the secong one Chrisr

 

[doitall]

'scuse me!!! (My handbag's already out and swinging!!!)

2 lights, slow flash = Fail Point G - Primary Overheat.
Possible causes: air in system, lack of primary pressure, pump not turning, sensor fallen off pipe (!), overheat stat stuffed, if none of these, PCB or primary HX fault. Sorry W-B, if the CH is working fine, this rules out ALL of the above and we're left only with a blockage in the Primary flow to the Secondary HX. Which ISTR I suggested in the first place and would produce EXACTLY the same symptoms as a failed pump.

I don't have an handbag sweety can I borrow one of your spares

The fault you discribe CC would effect the heating as well

 

[ChrisR]

They don't! Now you ask I think I remember seeing somewhere that there was a version with only one pump - tho I never saw one. I looked on the WB site for pic but I assume the CDi's are obsolete now cos they aren't there any more!

later - looked on hrpc epics thing - the later 35cdi, the Mk2, only had 1 pump. They have a pic of the one with 2 pumps - can send it to you as a pdf if you like!

 

[pla]

Indeed it does have two pumps. And I have to admit that despite being a complete non-expert I did open the cover and check that the pump is not obstructed in any way. It also seemed to be make a noise and vibrating a bit - in a positive way - when I tried the hot water.

I am not brave (or perhaps foolish) enough to try anything else.

 

[croydoncorgi]

Looks like W-B has decided to remove all technical content from its site.
Pity!