Worcester Highflow 400 BF overheating
- Thread starter gcm
- Start date
Sponsored Links
just read your threads again and yours is a problem impossible to diagnose over the internet. I am something of a reluctant expert on the 400 but in your case i would need to be kneeling in front of it watching it taking temps at the gas to water h/exch and plate heat exch etc etc. whether the div valve is energising and sticking in c.h mode etc
Sludge gathering in the plate heat exch is a problem with these boilers. I really think you should get someone who is extremely good on your boiler (rare) or get worcester in. apologies for not being able to help more.
Sludge gathering in the plate heat exch is a problem with these boilers. I really think you should get someone who is extremely good on your boiler (rare) or get worcester in. apologies for not being able to help more.
Good day boilerdoktor, thanks again for the reply,
I agree that "symptoms" appear to be a little odd.
I assume that if sludge build up a problem (I have read about that being a particlar problem with this boiler) then the boiler would not function properly in hot water only mode or in central heating only mode.
There certainly seems to be a problem with something "sticking" (not operating properly) when in hot water/central heating mode, I guess that the diverter valve would be the obvious choice, either the physical valve itself or the solenoid activator.
Regards
I agree that "symptoms" appear to be a little odd.
I assume that if sludge build up a problem (I have read about that being a particlar problem with this boiler) then the boiler would not function properly in hot water only mode or in central heating only mode.
There certainly seems to be a problem with something "sticking" (not operating properly) when in hot water/central heating mode, I guess that the diverter valve would be the obvious choice, either the physical valve itself or the solenoid activator.
Regards
Good day all,
Just been looking at installation/service manual and thinking through my problem. It would appear as if the various thermostats and controls are working correctly as hot water OK by itself and CH OK by itself, the problem comes when both on together.
If both hot water & CH "on" and boiler supplying heat to CH as normal, when hot water tap is opened, the flowmeter detects the hot water demand and control should divert heat output of boiler to hot water system, this is not happening. I assume there must be a thermostat measuring the heat of the hot water being supplied, the only trouble is the heat is still going into the CH system and hot water is infact cold, therefore boiler is being controlled by hot water thermostat because flow meter is telling it that hot water is required, therefore boiler remains lit trying to raise the hot water temperature, this temperature does not go up, but stays cold, so boiler keeps going trying to heat it up, consequently, as the heat output from the boiler is going into the CH system. the CH system overheats and eventually trips boiler due to overheating of the CH system, please note, it is only when drawing hot water (which is in fact cold and doesn't heat up) that the CH system water temperature goes up - when not drawing hot water, the CH runs normally, because flowmeter does not detect hot water draw and therefore the CH system thermostat is controlling boiler firing and controlling temperature correctly.
I deduce from this that the control function that diverts the heat from CH system to hot water system, when hot water tap opened, is not functioning correctly or sticking, or just plain stuck. Am I assuming correctly that I am talking about the diverter valve/solenoid switch.
I now believe that some of the heat is still going into the CH system, even when hot water only is "on" as I have an independant pressure guage external of the boiler on the CH system pipe and the pressure is slowly increasing when the hot water only "on" appears to be functioning correctly, even though the radiators stay cold, this would be because the CH circulating pump would be off.
Understand from further reading that the diverter valve is a diaphragm valve and spindle can get "crusted" and then presumably fails to travel fully or at all.
The only other thing I haven't fully explained (to myself) is the fact that after tripping on overheat, the pilot light will light but unable to make it stay lit. I am thinking that the overheat stat/overheated water takes some time to cool down to normal operating temps/reset, the only thing is I don't know how long this should be, after 15 or 30 mins, it lights but still can't establish the pilot continuosly, however, after 2 or 3 hours, it lights and stays lit OK - if this 2 to 3 hour period is normal, then there is no fault on the thermocouple, it is just doing its job properly (I think this must be the case, as after enough cooling down time has elapsed, pilot operates normally).
Based on the above, I think I should change the diverter valve (+ the expansion vessel) & I think that will solve my problems -----dream on!!!
And save me £3000 aswell (well, in the short term anyway, until the next problem).
Am I on the right track (maybe)?
Just been looking at installation/service manual and thinking through my problem. It would appear as if the various thermostats and controls are working correctly as hot water OK by itself and CH OK by itself, the problem comes when both on together.
If both hot water & CH "on" and boiler supplying heat to CH as normal, when hot water tap is opened, the flowmeter detects the hot water demand and control should divert heat output of boiler to hot water system, this is not happening. I assume there must be a thermostat measuring the heat of the hot water being supplied, the only trouble is the heat is still going into the CH system and hot water is infact cold, therefore boiler is being controlled by hot water thermostat because flow meter is telling it that hot water is required, therefore boiler remains lit trying to raise the hot water temperature, this temperature does not go up, but stays cold, so boiler keeps going trying to heat it up, consequently, as the heat output from the boiler is going into the CH system. the CH system overheats and eventually trips boiler due to overheating of the CH system, please note, it is only when drawing hot water (which is in fact cold and doesn't heat up) that the CH system water temperature goes up - when not drawing hot water, the CH runs normally, because flowmeter does not detect hot water draw and therefore the CH system thermostat is controlling boiler firing and controlling temperature correctly.
I deduce from this that the control function that diverts the heat from CH system to hot water system, when hot water tap opened, is not functioning correctly or sticking, or just plain stuck. Am I assuming correctly that I am talking about the diverter valve/solenoid switch.
I now believe that some of the heat is still going into the CH system, even when hot water only is "on" as I have an independant pressure guage external of the boiler on the CH system pipe and the pressure is slowly increasing when the hot water only "on" appears to be functioning correctly, even though the radiators stay cold, this would be because the CH circulating pump would be off.
Understand from further reading that the diverter valve is a diaphragm valve and spindle can get "crusted" and then presumably fails to travel fully or at all.
The only other thing I haven't fully explained (to myself) is the fact that after tripping on overheat, the pilot light will light but unable to make it stay lit. I am thinking that the overheat stat/overheated water takes some time to cool down to normal operating temps/reset, the only thing is I don't know how long this should be, after 15 or 30 mins, it lights but still can't establish the pilot continuosly, however, after 2 or 3 hours, it lights and stays lit OK - if this 2 to 3 hour period is normal, then there is no fault on the thermocouple, it is just doing its job properly (I think this must be the case, as after enough cooling down time has elapsed, pilot operates normally).
Based on the above, I think I should change the diverter valve (+ the expansion vessel) & I think that will solve my problems -----dream on!!!
And save me £3000 aswell (well, in the short term anyway, until the next problem).
Am I on the right track (maybe)?
Sponsored Links
Good day again,
Can someone confirm correct diverter valve for the Highflow 400 BF?
My manual and one I downloaded from internet has the part number as 8716142482, although I cannot find anything searching for this part number.
Worcester site Hiflow 400 BF spare parts list has part number as 87161207390.
Lokking on internet, sellers have the 87161207390 for sale for the Highflow 400BF.
Is the part #87161207390 simply a modern or updated variation of original/mine?
Regards
gcm
Can someone confirm correct diverter valve for the Highflow 400 BF?
My manual and one I downloaded from internet has the part number as 8716142482, although I cannot find anything searching for this part number.
Worcester site Hiflow 400 BF spare parts list has part number as 87161207390.
Lokking on internet, sellers have the 87161207390 for sale for the Highflow 400BF.
Is the part #87161207390 simply a modern or updated variation of original/mine?
Regards
gcm
there are two types of diverter valve for the 400. The body of the unit is the same for both only the solenoid is different. The black one is probably yours and swithches to c.h and remains usually open for h/w. the purple one is run by low voltage. this was used on the later model.
the diverter valve as i said opens only for c.h energising the solenoid. there is a weep tube running off it that can be blocked and then you would get no c.H.
For what you are now considering (e/v and diverter valve) changing yourself you could get Worcester in for £215 (this includes parts) and at least you know there will be a correct diagnosis.
From what you are now saying I would test the P.C.B is energising the div valve or not. Is there a relay sticking on the pcb ? I have had this once before with the symptoms you mention.
As an amateur this self diagnosis could be costly.
the diverter valve as i said opens only for c.h energising the solenoid. there is a weep tube running off it that can be blocked and then you would get no c.H.
For what you are now considering (e/v and diverter valve) changing yourself you could get Worcester in for £215 (this includes parts) and at least you know there will be a correct diagnosis.
From what you are now saying I would test the P.C.B is energising the div valve or not. Is there a relay sticking on the pcb ? I have had this once before with the symptoms you mention.
As an amateur this self diagnosis could be costly.
Any fully competent DIYer will have a meter and be able to measure voltages applied to components like a diverter valve.
Anyone who does not have that skill is unlikely to have much luck trying to change a complete valve.
Its too long a thread for me to have read everything but isn't there a manual operate lever on the diverter valve which you can activate to obtain CH?
Tony
Anyone who does not have that skill is unlikely to have much luck trying to change a complete valve.
Its too long a thread for me to have read everything but isn't there a manual operate lever on the diverter valve which you can activate to obtain CH?
Tony
Good day boilerdoktor, thanks again for the advise,
Yes, the diverter valve on my boiler has a black top cover (with ZSR printed on it), so mine would be the earlier one.
Understood, the solenoid is energised/diverter valve opened when CH required.
As my CH is working, then I assume it must energise/open and presumably the weep tube cannot be blocked (I had seen this on other notes about this boiler).
Acknowkedged regarding Worcester repair, unfortunately the Worcester approved service centre here was telling me that it could cost £500-£600 to repair boiler and recommended a new boiler at a cost of £3000(Worcester 4.5 - which is also strange as that one is also discontinued and reading up on it, should not be recommended now anyway as it is not very efficient, at least I can't find a new version of the 4.5 now).
I have already bought/received the brand new expansion vessel (£50), as I was sure that was faulty, even if it wasn't causing the problems (if I had known about £215 and let Worcester repair it I would probably have chosen that option - so much for my local Worcester approved service centre!), so I will see what a diverter will cost me and decide then, I could probably either return/sell the expansion vessel if Worcester come in to fix it instead.
You have put into words my last nagging doubt!!! That the PCB control functions are behind the problems, I will get out my multimeter and check what's happening with the solenoid signal from the PCB, but I think I expect to find that the energising/open signal is being correctly fed from PCB to solenoid/diverter valve.
Regards
gcm
Yes, the diverter valve on my boiler has a black top cover (with ZSR printed on it), so mine would be the earlier one.
Understood, the solenoid is energised/diverter valve opened when CH required.
As my CH is working, then I assume it must energise/open and presumably the weep tube cannot be blocked (I had seen this on other notes about this boiler).
Acknowkedged regarding Worcester repair, unfortunately the Worcester approved service centre here was telling me that it could cost £500-£600 to repair boiler and recommended a new boiler at a cost of £3000(Worcester 4.5 - which is also strange as that one is also discontinued and reading up on it, should not be recommended now anyway as it is not very efficient, at least I can't find a new version of the 4.5 now).
I have already bought/received the brand new expansion vessel (£50), as I was sure that was faulty, even if it wasn't causing the problems (if I had known about £215 and let Worcester repair it I would probably have chosen that option - so much for my local Worcester approved service centre!), so I will see what a diverter will cost me and decide then, I could probably either return/sell the expansion vessel if Worcester come in to fix it instead.
You have put into words my last nagging doubt!!! That the PCB control functions are behind the problems, I will get out my multimeter and check what's happening with the solenoid signal from the PCB, but I think I expect to find that the energising/open signal is being correctly fed from PCB to solenoid/diverter valve.
Regards
gcm
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
