Megaflo - loud bangs 3-5 times a day

Hi Forum,

My megaflo (unvented mains pressure water heater) produces seriously noisy "bangs" about 3-5 times a day. Obvioulsy some kind of pressure problem but that's just my guess.

It's been doing this for some 1.5 years now (was installed 3 years ago and worked without noise for the first 1.5yrs) but the bangs do not seem to be following any obvious patterns.

Anyway, none of the (very expensive) plumbers I consulted in the past seemed to be able to suggest either cause or solution.

Something is clearly very wrong but the hot water continues to work and has sufficient pressure. there is occasional modest discharge from the discharge pipe.

The bangs appear to be getting even louder and we've had some at pretty unorthodox times lately (middle of the night, no water used anywhere in the house around the time).

I obviously need to get a decent plumber but so far haven't found one with sufficient experience in these systems and any confidence in their ability to fix it. Heatrae Sadia incidentally not very helpful with locating recommended plumbers for their systems.

Can anyone help?
Thanks
C

cas the only people who should be undertaking any repairs are those who have attended an unvented course and PASSED the assessment. These are issued with a card to so so.

Unvented systems can be dangerous if they are repaired by people who do not know how they work.

Therefore before letting a plumber loose on your megaflow CHECK he is qualified.

As a start I would suggest that you turn off the cold water supply to the megaflow, then turn on hot taps and then drain the cylinder from the drain tap at the bottom.

Finally close hot taps and turn on water supply. This will reform the air pocket at top of cylinder. Check to see if you get any water discharge in the tundish.

Alan
(CITB Unvented qualified)

I seem to have the same problem - wondered if or how you solved the problem (7years ago !!)

If the unvented cylinder is a megaflo there should be a label on it telling you how to re-establish the expansion air bubble.

look into getting an external expansion vessel fitted.

It is best to check/replenish the airgap first.

If this fails to resolve the situation, we had a couple of combi valves changed under warranty a few years back that were making clunking noises.

Stopped fitting Megaflo some years ago, the only thing going for them is that nearly every potential customer knows the brand name.

Customers who have had one a few years know the name AND that they are pony and trap.

The following is from the megaflo manual. Follow instructions to re-establish bubble. If this does not rectify the problem, you must call out a qualified person to check/service the unit.

The air volume within the Megafl o unit will periodically require recharging to ensure any
expanded water is accommodated within the unit. A discharge of water INTERMITTENTLY from
the Expansion Relief Valve will indicate the air volume has reduced to a point where it can no
longer accommodate the expansion. To recharge the air volume :-
i) Turn off the heat source to the cylinder via programmers/immersion isolation switch(es).
ii) Turn off the water supply to the Megafl o unit by turning off the isolating valve on the Cold
Water Combination Valve. Turn the black handle so that it lies at 90o to the direction of fl ow.
iii) Open the lowest hot tap supplied by the Megafl o.
iv) Hold open the Temperature/Pressure Relief Valve until water ceases to run from the tap
and gurgling noise at the valve stops.
v) Close Temperature/Pressure Relief Valve.
vi) Turn on the isolating valve at the Cold Water Combination Valve by turning the black
handle so it lies parallel to the direction of fl ow, when water fl ows from the hot tap, close
tap.
vi) The air volume will be automatically recharged as the unit refi lls.
If after following the above actions water still discharges from the Expansion Relief Valve further
advice should be sought from a competent installer or the Heatrae Sadia Service Department.
User

have a look at the 2 port valve and make sure the arrow on the valve is pointing towards the cylinder.

Hi, thanks for the various inputs - story has moved on.
Megaflo installer called in - reestablished air buble (callout fee + 1 hr ) but thought noise was actually "kettling" from boiler , albeit noise is in airing cupboard where Megaflo / the pump / feeds to vent & from H&E Tank/ plus valves to CH & hot water are - boiler at other end of house.
A differant Gas Safe Plumber called in - Sentinel 200 noise reduction fluid put in system - header tank not flowing to boiler when system drained down to get the 200 in to flowing system.Banging of pipes seemed to loosen some blockage and flow from header tank achieved.
On restart we had flow up the vent through header tank & back - not good!!. Reduced number of radiators being supplied -eventually increased pump speed which seemed to get flow back into main CH loop & not to header tank. Slowly added radiators back in & reduced pump speed to its previouse normal setting.
Flushing noises not heard since (still some loud pipe heating up "ticking".
2nd dose of Sentinel 200 + a dose of 100 added to system .
Now waiting for benefit - no flushing sounds but still some pipe noise.
(Boiler also serviced - no problems seen during that exercise )
Waiting to see whats next!!

There seem to have been some unusual things done here.

My first question would have been what colour is the water in your system.

Tony

A mix of colours - some of the down stairs rads had some black coloured water - the first main drain was said to be "not too bad" but this was from the boiler return pipe drain which is above the level of all the downstairs rads. I tried several downstairs rads after first go with Sentinel to see if still as black and I only got cloudy / brown i.e. just dirty not black. I tried the downstairs rads as the drain of the main system had been done at the higher boiler return pipe drain. System may need a power flush / rads off at sometime time to sort it out but hoping we can do that in better weather if required.

Its always best to drain a dirty system from the lowest point as that helps the dirt to come out.

Tony