I'm about to upgrade my heating system and was all set to get a Magaflo (or similar) but my plumber's now telling me that if the rubber seal goes I need to buy a whole new cylinder and therefore that I'm better off installing an external pressure vessel - in short, does that make sense?? Thanks!
Megaflo or external pressure vessel??
- Thread starter Heddlehead
- Start date
J
johnfox
ok its a short answer,any unvented cylinder fitted needs to be serviced anually.
as per the makers instructions,they do differ.so an extra yearly cost needs to be considered.
personally i would opt for the range tribune unvented cylinders.they have external expansion vessel.
as per the makers instructions,they do differ.so an extra yearly cost needs to be considered.
personally i would opt for the range tribune unvented cylinders.they have external expansion vessel.
I don't think a megaflo has an internal rubber seal.
the internal expansion vessel is just an air pocket that can be easily remade by draining and refilling the cylinder requiring no replacement of parts,most have a guide on how to do this on a sticker on tthe side of the tank so you could do this yourself if req,i would be questioning your plumbers differences in price or see if he is just sticking to what he knows. either way both are good systems its just down to price and what the space available will allow.
Really I thought it had a EPDM membrain in otherwise you would be introducing air into a loop, under presure how is this air bubble controlled as the calorific value changes.
Be aware I am no plumber just have an interest
Be aware I am no plumber just have an interest
calorific value ??? 
You mean temperature?
The megaflo has an internal floating baffle.
You mean temperature?The megaflo has an internal floating baffle.
My version of the story behind Megaflo is thus;
Someone at Heatrae Sadia designed a floating baffle to prevent water and air mixing, and gradual erosion of the air gap.
Until this time separate air membrane expansion vessels had been used.
Unfortunately, the floating baffle didn't stop the problem or work as well as a separate vessel; but someone at Heatrae patented it and then marketed it as an advantage.
Gullible private punters lapped it all up and bought Megaflos in reasonable numbers. After about two years these megaflos started pushing water out of the pressure relief valve, due to the air gap being depleted.
Having duped so many, Heatrae could have either dropped the design and used a sealed expansion vessel like most other (more long standing and experienced) unvented cylinder manufacturers, or printed a label on the outside instructing punters to drain the cylinder of their hot water and refill it when it leaks.
They chose the latter.
It is a prime case of the Emperor's New Clothes. They know the floating baffle doesn't work, but it has worked so well as a marketing gimmick they can't risk destroying the myth.
Europe had unvented cylinders for years before the UK. Ask Heatrae Sadia (Baxi) how many Megaflos they sell outside the UK.
Someone at Heatrae Sadia designed a floating baffle to prevent water and air mixing, and gradual erosion of the air gap.
Until this time separate air membrane expansion vessels had been used.
Unfortunately, the floating baffle didn't stop the problem or work as well as a separate vessel; but someone at Heatrae patented it and then marketed it as an advantage.
Gullible private punters lapped it all up and bought Megaflos in reasonable numbers. After about two years these megaflos started pushing water out of the pressure relief valve, due to the air gap being depleted.
Having duped so many, Heatrae could have either dropped the design and used a sealed expansion vessel like most other (more long standing and experienced) unvented cylinder manufacturers, or printed a label on the outside instructing punters to drain the cylinder of their hot water and refill it when it leaks.
They chose the latter.
It is a prime case of the Emperor's New Clothes. They know the floating baffle doesn't work, but it has worked so well as a marketing gimmick they can't risk destroying the myth.
Europe had unvented cylinders for years before the UK. Ask Heatrae Sadia (Baxi) how many Megaflos they sell outside the UK.
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