Ariston genus 27 MFFi help

[pavementpizza]

Hi,

We had a problem with our 8 year old Genus 27 MFFi some time back and, cut a long story short, got someone to tell us the bad news that we needed a new pressue vessel (it had other minor problems mainly with the wiring which were fixed). However the fitter has since ceased trading and the two others we have approached are a tad too keen to supply a new boiler as the only option. At the moment the pressure drops to zero after the system is not used (during the night and parts of the day). It takes around four or five hours to drop from around 1.5-2.0 back to nothing. We have to top it up twice a day normally using the little blue turn screws under the unit and then we start it up.

The rads have all been checked and there are no leaks anywehere. The last engineer put a small 'plug' device on the overflow pipe outside to prevent any possible leak from there but it hasn't altered anything.

A few question:

1. Will a new pressure vessel mean the problem will definitely be fixed (or is it more of a pot luck thing)?

2. How much should a pressue vessel and labout cost for a Genus 27 MFFi or does fitting a new boiler make more sense?

3. Is topping up the system as we are doing now dangerous?

Many thanks

 

[kevplumb]

1 no

2 no

3 no wont do the boiler any good tho

4 YOU HAVE A LEAK

The last engineer put a small 'plug' device on the overflow pipe outside to prevent any possible leak from there but it hasn't altered anything.

remove it sharpish

 

[EliteHeat]

The first thing to do is to determine if you actually need a new pressure vessel - which it doesn't sound to me like you do.

First, remove the aircap on the top of the vessel - if water comes out then you do indeed need a new vessel.

If it doesn't then check the pressure using a car tyre pressure gauge. It should read about 10lbs or so. If it doesn't then veerrrry slooooowly increase the pressure to about 10lbs.

The symptoms of a busted pressure vessel are a marked and rapid rise in operating pressure when the boiler is operating. Leading to the pressure relief valve opening and discharging to a safe point outside. Since there is no evidence of this it is unlikely the the PV is at fault.

Unless you have all surface mounted pipework, then why do you not suspect the obvious fault is that of a leak in the system?

If you cannot locate any leak then it is at least worth trying some leak sealer to see if that makes any difference.

It doesn't do any harm to keep topping the boiler up, but remember that the water is going somewhere. If it's not leaking outside of your property then it must be leaking inside it. You are also continually diluting any system inhibitor that you may have in the system which don't do the boiler any favours.

Replacing a PV isn't a massive job. It would be unusual to replace the boiler PV and would be more sensible and much cheaper to fit an auxilliary one.

 

[kevplumb]

It doesn't do any harm to keep topping the boiler up,

shoemenders mate

 

[pavementpizza]

Just taken the plug off and got wet...very wet!

We don't have surface pipes everywhere so of course a leak may be possible somewhere although our house is on many different levels and only one room has the potential to leak without us physically noticing. Point taken though...time for floorboards to me lifted.

Where can I buy leak sealer and what is the brand name (no-one likes to go to a plumbers merchant without at least pretending to be savvy)?

Thanks

 

[EliteHeat]

Plug? do you mean the aircap? or the external plug?

 

[kevplumb]

Where can I buy leak sealer and what is the brand name (no-one likes to go to a plumbers merchant without at least pretending to be savvy)?

err leak sealer

 

[EliteHeat]

Check the air pressure in the PV as stated. If zero, re-inflate, if water comes out get a new PV. No amount of leak sealer will have any effect on a pressure vessel.

 

[pavementpizza]

Yes, I meant the aircap.

Leak Sealer sounds like a good name for a leak selaer, smartar.se.

 

[kevplumb]

Yes, I meant the aircap.

Leak Sealer sounds like a good name for a leak selaer, smartar.se.

its what it's called gobshite

 

[pavementpizza]

err thanks

 

[kevplumb]

no probs marra

 

[kevindgas]

The last engineer put a small 'plug' device on the overflow pipe outside to prevent any possible leak from there but it hasn't altered anything.



3. Is topping up the system as we are doing now dangerous?

Many thanks

yes it is highly dangerous and i would report that engineer to the HSE as what he has done now makes your boiler a pressure cooker waiting to explode.
most likely cause of problem is diverter valve or heat exchanger failure dependant on what type of combi this is
either way get an engineer that knows what he is doing to come ASAP

 

[ChrisR]

Absolutely DO NOT check the pressure of the Pressure Vessel in the manner stated above - that would not help at all! It is Imperative to release all the pressure from the system.

Also, after simply removing the cap you might well not see any water even from a PV with a rutpured diaphragm. You have to depress the central pin to let out whatever's inside

See the FAQ section - Boiler pressure problems.