Hi all
I have a Worcester 350 combi boiler.
Does that mean the fault lies in the PCB inside; or could someone give us a clue how to sort it?
Thanks in advance.
Regards p.mc
Hi all
I have a Worcester 350 combi boiler.
Does that mean the fault lies in the PCB inside; or could someone give us a clue how to sort it?
Thanks in advance.
Regards p.mc
Not knowing anything about this beast, but such systems usually have a thermostat on the side of the tank which, when it gets hot enough switches over and operates a valve that turns and runs the water through the CH system. The boiler merely looks at the water temp and fires up when necessary.
If the boiler is heating the water correctly then either the tank stat is not working or is wrongly set, or it is working but the divert valve isn't - or of course the pump may have failed. One thing to check is the default setting of the divert valve: does it switch the water to the CH and relax to the tank or vice versa? It should switch to the tank and relax to CH in most systems.
Combi boilers don't have or need tanks.
No there's no tank, it just heats on demand. But thanks anyway for the reply.
Any other ideas anyone?
if this is definately a combi boiler then there are two lots of culprits to check for.
Firstly the heating timeswitch and room thermostat for the radiators...... if both are calling for heating, there should be power at the heating demand terminals in the combi boiler.
Secondly, ther other culprit is the diverter valve, either the motor or microswitch within the actuator has failed or the the diverter plunger has jammed or is leaking internally, due to perished O rings or failed return spring.
Hi Stephen. Thanks for your detailed reply.
Oddly enough, I only have a switched spur feeding the boiler and definitely no room stat, although the rads have temperature control vaves on (if that is what they are called?) and I presume the "time switch! is the clocky thing on the panel
That will be the electrical main on/off switch for the whole system. you clearly have power to the boiler otherwise you would not have any hot water. (a gas valve, gas igniter and pump within the boiler needs to run for either hot water ir central heating.)
lthough the rads have temperature control vaves on (if that
These are referred to as TRV's, thermostatic radiator valves. All they do is regulate the flow of water through each radiator according to the room temperature. Being of a mechanical design, they are not able not tell the boiler to start up when the room is cold.
The round thing is the time switch.for the room heating. you have plastic pins that you pull out for off and push in for on.Each pin is worth 15 minutes.
It appears that the picture was taken at 2.30 am in the morning.
It appears to be a 24 hour timer. judging by your picture, you only have heating on from 6.30 am to 7.30am, then a half hour break, then on again at
8.00am till 9.00am. The dials current settings mean that you have no heating at all for the rest of the day.Does this clocky thing go round at all all the time? The timeswitch has a motor in it. its possible that the clock motor hads failed, thereby not turning the timing disc round. if the dial does not go round at all, then you need a new timeswitch.
I see you have a three position switch for central heating marked Off, Auto and On.
Has it been accidentally knocked to the off position? perhaps cos of the summer? check this.
Try clicking it down to ON. Does the boiler then start to heat the rooms up?
Put it back on Auto, and turn the timeswitch dial clockwise manually by hand ( as if you're trying to change the actual time on it... as the pins go past the white arrow, you should hear a mechanical clicking as a switch within the timer opens/closes and the boiler should respond accordingly.
if it does respond, then you need to set the current time at where the white arrow pointing upwards is, and push in pins for the times you want the heating to come on. (as according to your timer settings, you only have 2 hours worth of heating in the morning.
If there is no response to you turning the timeswitch around, but the boiler does respond when you turn the three position switch to ON, then thats a new timer job.
If turning it to ON does not cause the boiler to respond then there is a fault within the boiler's innards. Without a service manual for the boiler, its hard to suggest where to look next.
Let us know how you get on.....
Regards
Stephen.
P.S is the red low pressure light ON or OFF? its hard to tell from your picture.
If ON, you need to fill the system up with more water. Your pressure gauge's white needle is showing 0.9 Bar thats close to the minimum pressure needed by Combis. Some need at least 0.8 Bar, some need up to 1.5 bar.
Unless someone has fiddled with the red needle, it indicates that you need
1.4 Bar pressure.There should be a braided metal hose with valves at both ends somewhere near the boiler unless the hose has been removed.
These valves will look like washing machine valves.
Open both taps till the red low pressure light goes out. This will be at around 0.8 to 1.0 bar. then turn off both valves
Do not go any higher than 1.5 Bar or your pressure relief valve (PRV) will open next time the boiler runs. (PRV's open at around 3 Bar.)
Normally, if the system pressure is too low, both hot water and central heating would be affected.
Stephen.
Hi Stephen. Thanks for your descriptive advice.
We had a problem with low pressure a while ago, shutting off the CH and HW but a fellow came and sorted it.
Yeah the timer was at the right time and the settings are for the kids in the morning.(£££'s got to keep the bills down)
---------
1...Yes the timer rotates on it's own.2...The [3] position CH switch was in the off position so I could at least have Hot Water. Because when the CH kicks in it shuts down the boiler alltogether.
3...The timer switch does click when passing the pre-set times.---------
I turned everything off at the boiler and filled to the red arrow indicator.
I then powered up and set the CH timer to on and also auto. Both times the boiler kicked in. I crossed my fingers, but after a few seconds there was a gurgling sound and the whole system shut down. (should have crossed my eyes also)
I then switched the CH timer switch off again and took a screwdriver and held down the red reset button on top of the unit (silly place!)for a few seconds, which powered the unit once more.
So still got HW but no heating. Better than nothing I suppose
Alternatively...JML Snuggies all round (with impressive free open book light)Bargain!!!
This has in fact been your most useful post in helping me to get much closer to the problem...
see replies inline
Aha!. this is the boiler's overheat protection circuit kicking in. Is there an LCD display with a fault code or does a overheat light light up?
There are two thermistors (they measure temperature) on the flow and return water pipes to the gas powered heating boiler cell.
The boiler electronics monitors these two temperatures via the thermistors and calculates the difference between these two temperatures. This is called Delta T.
If Delta T becomes too high, ie return water temp too low or flow water out temp too high, the boiler shuts down, triggering the overheat protection reset switch. This is an important safety feature, as if water was allowed to turn to steam, the PRV (pressure release valve) would open and the boiler would be damaged.
This is the overheat protection cut out, see earlier of how it works.
Baiscally what is happening is when you call for central heating, that the boiler turns on the gas valve, ignites the gas, starts the flue fan and supplies power to the central heating pump.
If no central heating water is flowing at all or is flowing too slowly, Delta T increased dramatically and becomes too high. This forces the boiler to shut down. If water is indeed flowing then Delta T will be low enough to allow the boiler to continue running.
Have you tried opening every single one of your radiator TRV's fully open and then try running the boiler?
If you have all Radiator TRV's shut off completely then the heated water cannot go anywhere.....
you need a minimum of at least 1 radiator fully open (otherwise the boiler shuts down) This is usually the bathroom radiator or the radiator in the same room as a room electronic thermostat. (the latter does not apply to you obviously)
I then looked up the manual for your Worcester 350 RSF. Its actually quite revealing........
The link is
Please don't be offended by my next sentence. It is only mentioned as I have no knowledge of your level of technical competence.
If you are a technically competent person then fine, read on to the rest of my post, but if you have any doubt about your own technical competence, you could cause more problems for yourself and hence cost you more to fix the boiler. So if you feel out of your technical depth, you really should call a boiler engineer in.
My bet is that the central heating pump has failed or seized ( the pump on the left when you take the cover off the boiler the pump on the right is for hot water).
Reading through the manual suggests that if you remove the big screw in the middle of the pump, and then start the central heating, the now exposed shaft should rotate when you set the central heating to ON.
If it does not rotate, use a big screw driver to turn the shaft (its possible the pump has siezed) It should then turn on its own accord. Siezed pumps is actually common after a summer where central heating pumps don't run at all.
On my Combi boiler, there is a programme that runs the internal pump for 5 mins a day every day, simply to stop the pump from siezing up.
As I run the hot water every day via the same pump this is a moot point, and really is only of any value when I am on holiday (My combi has a diverter valve which means it only needs one pump, not two.)
If the pump shaft does not turn, check for power to the pump. There is a plastic cover on top of the pump You can take the cover off this and measure with a volt meter. Warning, this will be at 240 volts AC so proceed with care. There should be 240 volt power to the pump when the central heating is being called for.
Obviously you need to measure after turning Central Heating to ON and before the boiler shuts down due to the overheat protection kicking in.
If there is power to the pump and the pump shaft is not rotating, then pump has failed. You will need to drain down the entire system and swap out the pump along with new rubber "o" rings.. The part codes are in the manual.
If there is no power to the pump, then the fault lies elsewhere. Use the fault finding chart in the manual, it will tell what to do and which part is suspect.
Let us know how you get on.
Regards,
Stephen.
On my Worcester, it was the motorised diverter valve. After the engineer changed it, I took the old one apart and it was simply slightly burnt contacts which could have been cleaned.
The diverter comes as a complete assembly at about £105 (for me) but it's only the motor switch contacts that go (apparently)
DG
Thankfully I do not have a combi boiler but Stephen you have given nice clear fault finding and system explanations so the OP should have no trouble tracking down the fault. Well done.
Gio
Could this be a blocked condensate pipe? My combi boiler, (not a Worcester), gave similar symptoms when blocked. I know this is usually down to very cold weather freezing the pipe, but it can also occur from sediment etc. in the pipe.
Sorry for not posting back earlier as I've been quite busy. Anyhow "Thanks guys, you've been absolutely amazing" Special thanks to Stephen for your time and effort.
BTW in answer to your questions:
1...There are'nt any lcd displays or light to show overheating unfortunately. 2...Yes there are trvs open and the same problem occurs.I think your guess is the right answer, but I haven't got the time to do the neccesary steps yet. Thanks for that Stephen, I'll let you know how I got on when I get the time.
Hi All
Sincere apologies for my late reply. (Xmas 'n' all) The CH pump was the culprit, there was an electrical feed to the pump so I tried to spin it without much joy. It would turn but wasn't rotating as expected. I'd have had a go at exchanging it, but couldn't find the mains water stop/inline valve anywhere! I looked behind the sink, under the stairs, there were no cupboards or boxing for them to hide in either! (Maybe under floor boards?) So I had to bite the bullet and have a reconditioned pump fitted and...Viola!
Thanks again for all who posted you've been an absolute godsend.
Wishing you all a merry Christmas and happy new year. Regards p.mc
Sorry for not posting back earlier as I've been quite busy. Anyhow "Thanks guys, you've been absolutely amazing" Special thanks to Stephen for your time and effort.
BTW in answer to your questions:
1...There are'nt any lcd displays or light to show overheating unfortunately. 2...Yes there are trvs open and the same problem occurs.I think your guess is the right answer, but I haven't got the time to do the neccesary steps yet. Thanks for that Stephen, I'll let you know how I got on when I get the time.
< snip >
So it's all nicely in tune again...?!! :-))
Best intentions and all that..... :-)
So my diagnosis was correct. It would be a burnt out or gone open circuit motor winding.
Shame you had not posted about boiler isolation valves..... I would have told you the answer. Underneath the boiler you will find several valves that are turned with a flat blade screw driver. There are valves for central heating flow, central heating return, cold water in, hot water out and of course the gas isolation valve. Its also in the manual I posted the link to in a previous post.
Once you close the isolation valves, there is a drain c*ck within the boiler so you can drain just the boiler. No need to drain the radiators or the hot water circuit. You would then be able to replace the central heating pump.
Then you can open the valves, refill via the filling loop, re-pressurise and bleed the boiler, and you're back in business.
Regards,
Stephen.
So I had to bite the bullet and have a
Ouch.... poor wallet. couple of hundred I should think......
Thanks for the comments.
I did see the man shutting the water off at the boiler as you said Stephen. I had to tighten the drain valve after he left though, as it had a slow leak. I then went around the house and bled each rad, the one in the attic released all the air out of the system and I had to get my daughter to keep the rad valve open whilst i filled the system. When all the air was expelled she closed the rad valve and I pressurised the system to 1.5 bar. Just goes to show though how a little bit of extra questioning can make all the difference...my bad :-)
The sharing of knowledge is truly a great gift.
Regards p.mc
Best intentions and all that..... :-)
So my diagnosis was correct. It would be a burnt out or gone open circuit motor winding.
Shame you had not posted about boiler isolation valves..... I would have told you the answer. Underneath the boiler you will find several valves that are turned with a flat blade screw driver. There are valves for central heating flow, central heating return, cold water in, hot water out and of course the gas isolation valve. Its also in the manual I posted the link to in a previous post.
Once you close the isolation valves, there is a drain c*ck within the boiler so you can drain just the boiler. No need to drain the radiators or the hot water circuit. You would then be able to replace the central heating pump.
Then you can open the valves, refill via the filling loop, re-pressurise and bleed the boiler, and you're back in business.
Regards,
Stephen.
So I had to bite the bullet and have a
Ouch.... poor wallet. couple of hundred I should think......
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