Megaflo discharging despite new TPRV and PRV

[Vee]

Have a problem in that the homeowner says it's discharging regularly (maybe after hot water use). Have changed TPRV and PRV. Also has new combi valve. System is fed via a break tank with a Grundfos booster pump. He says the tun dish is dry but a pint of water comes out of the discharge daily. It's not doing it in my presence. Your views please.

 

[SimonG]

Recharged the bubble?

 

[Vee]

Yes and customer knows how to too. Anyhow should be able to feel / see moisture at tun dish surely?

 

[jase158]

usually white marks around the tundish. (we do have really hard water round here though)
change bubble is only real choice and see if it is that, test flow rates just to make sure that the new combi valve is working properly!!

 

[SimonG]

Is the cold water being run from the balanced cold or from the mains?

How does cust know its a pint of water?

 

[Vee]

Cold water is run from the same booster pump but not via balanced connection on combi valve. I've asked him to put a container underneath the discharge. I am baffled by the fact there is no discharge through the tun dish as he says it's dry when checking.

 

[Ermintrude]

It's the booster set causing loss of bubble. Fit external expansion and 100% be fixed

 

[Destroyer2813]

Ermi do explain expansion vessel for the megalflow?

 

[kimbo]

It could be the heating prv is teed into discharge pipe after tundish

 

[AWheating]

it could be the bubble is not big enough or being lost? an extra expansion vessel may be needed?

 

[kimbo]

If you are 100% satisfied its not coming from the tundish it cant be anything to do with the cylinder.

 

[Chalked]

I find the ones that need re-charging the most are large megafo's fitted in a multi bathroom house, but with only a couple of occupants.
When a large family regularly use lots of hot water, it's less of a problem.
just fit a remote pressure vessel ( suitable fir potable water) and tee into the cold feed after the combi valve .

 

[Ermintrude]

Just chop a tee in above the multi valve (or after NRV) and fit DHW vessel prob 18l

The pump causes rapid movement within the vessel when filling and if the NRV is kaput (happens) the baffle gets flooded and then the air is just absorbed into water and the rest is history.

 

[kay-jay]

Unbalanced cold supply with mixer taps/showers in the property is highly likely.

 

[Ermintrude]

Unbalanced cold supply with mixer taps/showers in the property is highly likely.

Possible dim enough to fit a megaflow dim enough not to fit nrv on mixers

 

[townfanjon]

Yep you can fit a vessel but I would solve the mystery of the dry tundish first, one piece of toilet roll , roll it up and put it through the tundish, and see if it's gone the day after .