Potterton Suprima (off and on)

[Achy]

I have a Potterton Suprima 100l.

Had the notorious PCB replaced about 2 years ago.

But it's being a bit odd again....

The boiler starts, I can see the flames, the pump is running.
The boiler runs for 45 seconds precisely, the pipes leading from the boiler get hot, then the boiler stops. It sits for about 45 seconds, then does it again.

It tends to do this for about 90 minutes then gets going, and it carries on like nothing has happened.

Needless to say for that 90 mins the radiators and hot water are only barely warm.

But also it doesn't do this every time, just now and again... probably once a week.

Any ideas?

 

[Agile]

Sounds like a sticking pump or sludge in the system.

Tony

 

[rojaca]

When you say Flow pipe getting hot is this just warm or piping hot eg70-80C.

 

[Achy]

Piping hot... I can't keep my hand on it.

After the boiler stops, I can still hear the pump faintly huming, and gradually the water in the pipe cools...

Then it's just warm.

 

[Baxmax]

High Cholesterol.....

Dicky Ticker..........

 

[rojaca]

see agile's post

 

[Achy]

Sounds like a sticking pump or sludge in the system.

Tony

Anything I can do to check/diagnose/fix these?

I'm waiting for local plumber to "fit me in", but would like to have a look/check in the mean time.

 

[robertbentley]

Mine is doing this too. It's on for a few minutes, then just goes off for a bit, even though the hot water is still calling for heat.

I had a bath last night, and the CH was off all evening. (to assist testing). The tank was emptied due to my bath, and so the HW was calling for heat all evening. The boiler was on / off / on / off all evening.

I then turned the HW off and the CH on, and that gave a nice long burn from the boiler, which made me wonder if the HW was passing through the coil in the tank too fast ? (and so the boiler sensed the hot water coming back and so it shut down).

This morning, the CH and HW are fine, and I didn't adjust the valve on the exit of the cylnder coil (which restricts the flow out of the cylnder tank to ensure that the coil doesn't rob all the heat when CH +HW are both in use)

Apologies for badly wording this post !

System is a standard vented HW system, potterton Suprima 70L boiler withthe new PCB fitted 2 years ago...

I wondered if adjusting the temp on the boiler would help ? It's currently on the MAX setting, (to give out hot water to re-heat the tank when I've had a bath)

Rob

 

[Agile]

Robert, you are not meant to hijack someone elses posting.

Your cylinder is obviously unable to adsorb all the boiler's power so it has to turn off. This is called cycling.

Its normal ( and best ) to time your hot water reheat at the same time as the boiler is on for heating.

Tony

 

[robertbentley]

Robert, you are not meant to hijack someone elses posting.

Your cylinder is obviously unable to adsorb all the boiler's power so it has to turn off. This is called cycling.

Its normal ( and best ) to time your hot water reheat at the same time as the boiler is on for heating.

Tony

Apologies - I suspected that my problem could be very similar to the OP. I'll quietly monitor this thread for any developments that could be of interest to me.
Regards,
Rob

 

[Agile]

His problems are caused by a faulty pump or sludge in the system ( or both ).

Luckily for you that is not your problem.

Tony