worcester 28i RSF, No c/h, losing pressure

[livegame]

Hi, Hope someone can help,
I have a worcester 28i rsh combi boiler, about 5 years old,
Got up one morning about 2 weeks ago, had no c/h, the pressure gauge was at 0, let in water and bought up to 1bar, (done this a few times over the past 4 years)

This time nothing happened, turned off the boiler for about 10min,
turned the boiler back on, it made all the normal noises (a couple of clicking noises and pump starting) but no ignition,

turned on a hot water tap, everything worked fine on the hot water side.

If I leave the hot tap on for about 15 minutes then turn it off, the c/h will stay on???

The pressure gauge will increase to almost 3bar, the boiler will then shut down, it will start up again when the pressure drops back to around 1bar,

after this happens a couple of times, the boiler shuts off after reaching 3bar, but drops back below 1bar and will not restart, the pressure will
slowly drop back to 0.

If you monitor the pressure and keep refiling when you see it drop a little the boiler will continue to work.

I was told it may be a faulty prv, I have changed the prv (no difference)


Help
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[Agile]

I think its a faulty expansion vessel and possibly a faulty sensor or PCB !

Tony

 

[livegame]

Thanks for the advice Tony,

Just to let you know, I was wrong about changing the PRV not making a difference,
The pressure is now staying around 1 bar (not dropping back to 0)

What is happening now is, once I get the boiler to stay on (following the procedure I explained before)
It shuts down after about 30 minutes and will not restart unless I go through the same procedure (turning on the hot water tap on for 15 minutes)

When you say it may be the sensor, do you mean the one that is connected to the same pipe as the PRV, If so I will change that one,
If that does not cure the problem,
then I guess I will have to get someone to change the PCB board.

any Idea how much it will cost to change the board?

Tony, I notice you are from London, what part? (anywhere near Wimbledon)

Thanks
John

 

[Agile]

The first thing to do is to check and recharge the expansion vessel. See the FAQ on this site.

Tony

 

[livegame]

I did check and recharged the expansion vessel before and after I replaced the PRV,

I set the pressure in the vessel at 0.5,

the boiler is now only running for about 20 minutes before shutting off,
the pressure seems to be staying just above 1bar (with no loss)

Thanks

 

[Agile]

The FAQ should tell you to set the pressure at about 0.9 Bar and the water pressure at about 1.5 Bar.

Its essential that the procedure is exactly followed.

You have posted about the pressure going up to 3 Bar. But you have not said that this is not happening any more! Whats going on?

Tony

 

[livegame]

Sorry for not being clear about the pressure,
It does not go above 1.7,
Although it does seem to shut off anywhere between 1.5 and 1.7

I have been reading other post as well as the installation and servicing manual, I have got confused about what the pressure settings should be,

The manual says that the vessel is set at 0.5
But after reading your reply
( i now guess this means for the installer to increase that, depending on how many rad's are used)

I have 6 double rad's and 1 towel rail, over 2 floors.

Now just to make things more confusing, the boiler has shut off about 6 times in the last hour, BUT it has restarted each time????

Would you suggest I alter the pressure now or wait until it does not start up again sorry to be a pest.

Thanks
John

 

[livegame]

Update on problem,

The boiler shut down and would not restart,

I increased the pressure in the vessel to 0.9 and the other pressure gauge
to 1.5,
I also changed the c/h sensor (on the c/h flow pipe)

The pressure has not altered over the last couple of hours (although I have not managed to get the c/h to work again)

Is the next step to change the PCB board or is there any thing else I can try before going to that expense?

Thanks

 

[livegame]