Potterton performa 28i - too hot water!!

[brian28]

Hi everyone.

This is my first post so i hope you can all help me.

The hot water is this combi is over heating and is being diverted through the heating system (this includes when heating is off).

Phoned a local guy (obviously cant come out ) who thinks it must be a sticking microswitch. I've read some old posts and faulty diverter valves keep being mentioned. Is this the prob with this 'Potty'.

Heating works fine - just the prob with hot water getting too hot

Many thanks

Bri

 

[petit_pablo]

If the diverter was faulty then you would probably find that the hot water wasnt getting hot or the heating wont work. Sticking microswitch is a good place to start but there could be a few other causes.

When you say it overheats, does the hot water get hotter and hotter before running cold then hot again. What does the boiler do when in hot water

 

[Agile]

It may be obvious to you why your local fellow cannot come out but its not obvious to me!

Its not technicaly obvious why the symptoms your describe are apparently the case with a properly set up boiler!

Tony

 

[brian28]

THanks Mr Agile for those wonderous 'pearls of wisdom'.

Upon reading my post i have gotten it a little wrong - i apologise - a long,long day at work prior to my first post.

So. i'll begin correctly again. The hot water actually runs cold. I can get a very hot 'slug' from the preheat store and then nothing.

Heating works fine and the rads are nice and hot.

I've also had a look at the boiler manual and it shows a DHW assembly with a microswitch on the end. Could this be where the fault lies ?

 

[baxpoti]

You need Prt 248734 pressure differential valve,

 

[brian28]

just to update as i've had a better look at the boiler as been off today.

I took both the microswitches off and watched the pins. When i ran the hot tap the top pin came out really easily. Switched the hot tap off and it retracted with no probs.

Tried the same with the heating. Here the pin came out but was fairly sluggish at going back.

Could it be this bottom valve/diverter that is causing the problem with not getting hot water. If the pin on this one does not go back properly, would it let by and allow some of the hot water to creep into the heating side.

What replacement part is needed.

 

[Soggy_weetabix]

Baxpoti has answered this.

Dave

 

[Agile]

I took both the microswitches off and watched the pins. When i ran the hot tap the top pin came out really easily. Switched the hot tap off and it retracted with no probs.

Tried the same with the heating. Here the pin came out but was fairly sluggish at going back.
.

You dont seem to be describing the pins properly! Let me be more clear by calling them the horizontal and the vertical!

If the horizontal one comes out and the boiler does not start to make a noise then the DHW demand switch is failed. Pull the lever forwards and it might cause it to bring the boiler on.

The vertical switch is the system flow switch to prove the pump and water are OK . That will only operate after teh horizontal pin has successfully operated its switch.

From your rather unclear description I think you need a new switch!

Tony

 

[baxpoti]

Let me be more clear by calling them the horizontal and the vertical!

Tony, the post states the boiler to be a 28i (instant).
Both pins are in the vertical plane, top pin is dhw, lower pin is primary (red wires to primary).

 

[Agile]

Oops, its so easy to overlook that its an instant.

Notwithstanding that, if the DHW pin come out promptly then it still sounds as if it might be the DHW demand switch which has failed.

OR

if the demand switch is working and bring the burner on then it sounds as if its the lower part of the diverter valve is not following the upper part.

Tony

 

[brian28]

So, are you saying that the bottom pin should retract without any resistance???

Like i said the top pin for the dhw operates freely and hits the microswitch to give warm but not hot water.

The bottom pin operates to hit the microswitch for c/h but is sluggish to return, but is that a symptom of a faulty pressure differential valve??

 

[Agile]

The bottom switch is for all boiler action, both DHW and CH !

As long as it operates when the pump starts then thats fine. Dont go looking for faults that dont exist.

Tony