Vokera 20-80 RS Flowmatic - pressure problems

[depiorate]

Hi,

I suddenly started to have problems with my boiler. At the beginning boiler was slowly dropping pressure, so had to top up once a week.

Recently I have to re-pressurize the boiler every day.

When I get up in the morning bar proudly say 1-1.5bar. When tap is open or central heating is switched on, boiler after making hell of a noise (like it would want to take off) starts, but pressure drops to 0.2bar. After top-up pressure stay as per usual 1-1.5. If central heating is kept longer pressure rises to above 3 bar.

I am I right to assume that the expansion vessel is causing a fault. If so which one domestic hot water or central heating?

http://www.heatingreplacementspares...EXPANSION+VESSEL&ptid=132112|EXPANSION+VESSEL

http://vokera.co.uk/wp-content/uplo...c_installation_and_servicing_instructions.pdf

 

[45yearsagasman]

The larger CH exp vessel at the rear has failed internally or has no precharge, or the communication pipe is blocked.

 

[depiorate]

The larger CH exp vessel at the rear has failed internally or has no precharge, or the communication pipe is blocked.

Thanks, Pete. At least I am looking in the right direction. I have never played with the boilers before, so you need to bear with me.

I looked and the price for the CH exp vessel is £77, so before buying i need to be sure i've checked all other options.

Can you tell me how to check if it has no precharge, also which one would be the communication pipe?

 

[DP]

Rare for vessel to fail on the Flowmatic. Have come across Flowmatics with external vessels fitted but in each case I remove and recharge vessel and never have any complaints. More likely to be little or no pressure. These are the things that get sorted when boiler is serviced. And this boiler if not serviced properly, will catch fire if you run it with little or no water. Once you start to dabble in that area, you will need to carry out other tasks that may or may not be up to your capabilty (not being nasty when I say that- I said MAY or MAYNOT- advisory only). Cracking boiler that can be fixed but not by those who will see a new boiler when they clap their eyes on it.

Stop playing with the boiler and get it sorted by someone who knows what he is doing. You will definately be wasteing £77.00 changing the component you think is defective, not to mention you will get wet, end up with leaks as you will not have seals, even get nasty shocks from various components exposed when outer case removed.

There will be other areas that will almost certainly need attention

Sorry Gasman, communication pipe does not back up on Flowmatics (at least I have never seen one in that state in 20 years I have been playing with these beauties) in Glasgow as water here is at neutral pH

 

[depiorate]

just had a gas/boiler engineer. We drained the boiler, then pump out all the water from expansion vessel.

Seemed to work so far. Dead easy job.

1. drained boiler
2. pump up pressure via air valve in the vessel
3. bleed heat exchanger.
4. Switched boiler on!

20 min job with boiler assessment

 

[45yearsagasman]

Sorry Gasman, communication pipe does not back up on Flowmatics

No apologies necessary, it was only a suggestion and I can't think when I've ever had to unblock one. I respect your expertise on these boilers.

 

[DP]

depiorate, What was outcome of the assesment i.e. what was suggested?

My assesment would have been that the boiler be serviced.

I suddenly started to have problems with my boiler. At the beginning boiler was slowly dropping pressure, so had to top up once a week.

If you were topping up once a week, unlikely to be the expansion vessel that would have been the issue at that stage but a leak somewhere.

Recently I have to re-pressurize the boiler every day.

The leak gets worst

When I get up in the morning bar proudly say 1-1.5bar. When tap is open or central heating is switched on, boiler after making hell of a noise (like it would want to take off) starts, but pressure drops to 0.2bar. After top-up pressure stay as per usual 1-1.5.

Still say there is a leak

If central heating is kept longer pressure rises to above 3 bar.

Do conceed the point the vessel needed charging but that does not resolve the system pressure loss problem, or the "making hell of a noise"