Potteron Suprima 30 Cutting Out When Hot Water On

[ph0u203d]

Dear all,

I have a Potterton Suprima 30 boiler which has started to give me some problems. I have read the many posts on this forum concerning issues with the PCB for this boiler. However, I thought I would write this post in case there is another cause of my problems.

I moved into my house (built around 2000) 18 months ago. About 9 months ago, I noticed the boiler would cut out (red light flashing) quite regularly, meaning I had to manually reset it. At the time I had the control unit set to heat the hot water for 30 mins in the morning, 30 mins in late afternoon and 30 mins at night. I found this was sufficient to give us enough hot water for our needs. I noticed that the boiler cut out almost always during the last 30 min hot water cycle. As such, I changed the programme to run only for 30 mins in the morning and 30 mins in later afternoon. Again, this gave us sufficient hot water, and seemed to almost completely stop the cutting out incidents.

Last week we had plumbers come round to install a heated towel rail in the bathroom. They drained the central heating system (vented) and turned the boiler off during this time. Since then, the boiler has started cutting out quite regularly again. Again, this seems to be related to the hot water, as I left the hot water off for +24 hours and the central heating worked fine. When I tried the hot water this morning, the boiler cut out after about 5 mins, and now the central heating is cutting out fairly regularly, even with the hot water off.

I have noticed a ticking noise from within the hot water cylinder, that I haven't noticed previously. Could this be relevant to my problem?

If anyone could give me some advice on the likely cause of the problem, and the best course of action to resolve it, I would be most grateful.

Thanks in advance.

 

[superdupergasman]

Could be overheating on the hot water cycle??

Try a new thermistor and make sure the balancing valves on the return from hot water cylinder are not shut too far.

 

[ph0u203d]

The balancing valve, is this it...

http://img.photobucket.com/albums/v457/ph0u203d/100_4106.jpg

http://img.photobucket.com/albums/v457/ph0u203d/100_4105.jpg

...if so, how do I know how tightly to shut them?

If this isn't the valve your talking about, where will I find it?

Thanks.

 

[twgas]

you may need to bleed vent, (first pic)

 

[MANDATE]

not too sure if the balancing valve is the root cause of your problem, although do agree if it is closed too far it will restrict the flow of water through the cylinder coil to such a degree that the boiler stat operates because the water can't flow away from the boiler fast enough.
I'd have the valve fully open to see what difference it makes and then try closing it in stages, but never less than 1/3 open
If you say it is also happening with central heating, then that balancing valve is not related.
Do you have a mid position valve in your system
I'm thinking it might point to the pump. I say that because I've removed a non working pump today to find the inlet and outlet holes reduced from something like 14mm down to 4mm with black grud. This also explained why boiler went off before room temperture was reached (this was before pump failure) and finally the boiler was kettling which pointed to pump failure.

 

[ph0u203d]

I've had the balancing valve almost 100% open (it's certainly never been close to being shut), should it be less open than this for optimum performance?

I have bled the vent & shut it tight (that's why I asked if it was the balancing valve, in case I had it too tight!).

The problem with the central heating only seems to occur for a day or so after I've had the hot water on.

I last had the hot water on on Saturday, for about an hour in the middle of the day. The boiler cut out a few times during this period. So in the time since I've had the hot water off completely with the central heating on its normal programme. On Saturday night/Sunday morning, the boiler cut out with the central heating running, but Sunday night/this morning, the boiler seems OK (no cut-outs). Could this 'recovery period' be diagnostic of anything?

As for the pump being blocked, is there any way of unblocking it without removing it? (i.e. is there a good product I can flush through the system?)

Thanks for your help.

 

[ChrisR]

No. Severe blockages can't be flushed out with certainty.
On the boiler - if it locks out due to some pcb fault, nearly always it'll leave the pump OFF. If it goes to lockout on overheat, it'll leave the pump ON. It's usually obvious if the pump's on or not. If not, switch it between speeds and you'll hear it start and stop as you do it.

 

[ph0u203d]

Excuse my incopetence, but is this the pump (arrowed)...?

I actually think that the ticking noise I thought was coming from the hot water cylinder is actually coming from this unit (pump?). Changing the speed dial a few times (from 1-3) seems to cause the noise to go away - does this sound like there is some kind of blockage in there? If so, how easy is it to remove the pump to check?

Also, the valve above the this unit (circled) is almost completely open, so I don't think there is any resistance here.

One thing I've always noticed ChrisR is that when the boiler has cut out I can hear a humming noise from within the airing cupboard (where the hot water cylinder is located). I take it this is the pump ticking over, therefore suggesting that the boiler is cutting out due to an overheat? Is there anything that would cause the boiler to overheat during a hot water programme & not the central heating programme? Something to do with a difference in settings between the heat dial on the boiler & the thermostat on the hot water cylinder?

Thanks again for your help.

 

[MANDATE]

Yes! that is the pump. And you have two pump isolation valves, one which you circled. There are two types of these valves and it appears you have one of each type. The top one is a 'gate' valve operated with a wheel handle. The bottom one is a 'ball' valve operated with a screwdriver.
Both do the same job. You close these off while 'changing the pump' or 'removing the pump motor', but be warned, the 'gate' type may not fully close if there is any crud or sediment around. I had this problem yesterday and was forced to do a partial drain down to change the pump and also the existing valves could not be cleaned easily so new valves had to be obtained. I think the 'ball' type is better for closing, but tend to get leaks at the spindle sometimes.
You wouldn't need to remove the whole pump, you can leave the body in situ and just remove the head held by 4 allan screws.
Of course you need to isolate the electric to the system and be prepared to do a partial drain down if the isolating valves let water by.
Question is do you have ALL the necessary tools plus the know how, skill and experience

 

[ph0u203d]

Thanks for your detailed reply.

So, on the whole, does it sound like the pump is the cause of the problem?

Out of interest, is there any reason why a problem with the pump would cause the boiler to cut out when heating the hot water but not when only the central heating is on?

Or does any one have any other theories as to why the boiler only cuts out with the hot water on?

Again, thanks for your help.

 

[ph0u203d]

 

[MANDATE]

The other thing that comes to mind is the age of your system and what version of PCB is installed. I think a lot of those installed around 2000 are the ones that gave a lot of problems after 4 to 5 years.
It might be best to start by following the 'potterton fault finding flow chart'.
I'm assuming you may have to download one from potterton
Only problem is that it becomes costly to change the PCB if thats whats required.
I think we changed a 'overheat stat' and a 'ignition lead' (not too dear)
but in the end a new PCB seemed the only other option. It did in fact stop stop all the lock outs.
You may find potterton more helpful these days, it might even be possible to get them to fit one for free. I know 3 or 4 years ago they would not even acknowledge their PCBs were giving problems.

 

[ph0u203d]

OK, thanks, I'll have a look at their website.

Thanks to all of you for your advice/thoughts.

 

[puzzlebobble]

hi ph0u203d,
i'm not a pro but i had similar problems to you and managed to sort in very well with help from this site.

i was having problem with the red flashing light (lock out) on a suprima 100. Like you it wouldn't 'lock out' as much when when heating the radiators as the boiler.

i thought at first this meant it was more likely to be something to do with the circulation than the boiler. I read the instruction manual for my boiler (if you don't have yours google 'interpart' and follow links) which said that the boiler must have a flow of greater than a certain litres per min. If you can find your pump manual it has curves showing how much flow it gives for each resistance. From this you can calculate the maximum resistance of your circuit, above which there is not enough flow to keep the boiler happy .

The only way i found to make sure the resistence doesn't go above this value (and this is actually what you are told to do in the potterton manual!) is to put an 'automatic bypass valve in'. I think in your system this would go where your balancing valve is but hope one of the guys/gals will correct me if wrong. You set the auto bypass valve to this resistance or slightly less. What this does is open if the resistance gets too high and make sure your boiler always gets enough flow (as long as the pump is working ok!).

so now you don't need to worry about the balancing valve as it will take care of itself.

But i still kept getting lock outs!!!! When it wasn't locking out it was a lot quieter though!

i ordered one of the new PCB and installed it (i use pcb quite a lot at work but it isn't too hard to fit if you're used circuit boards and the instructions are nice and clear. i was lucky because all of the rest of the boiler, including seals, were in really good nick- the old one looked fairly rickety by the way). Now it works perfectly even though it was installed in 1996; i'm basking in a nice warm heat . I've had in serviced professionally since and it was fine.

The new pcb comes with new circuitry which allows you to diagnose where exactly the problem is if it breaks down again. I haven't had to use it but I'm glad i've now got the facility.

So I'd say your problem sounds a lot like mine and the combination of a auto bypass and new pcb has done the trick here.

 

[andytheplumber]

you have not got an automatic bypass on your system