Megaflo, lack of pressure-is there any way around this?

[markyc]

I am in the process of getting my entire central heating system replaced and have been recommended a megaflo cylinder. However, the water pressure to my property is 10.5 - 11 litres per minute (1 bar), which I have been told is too low for the megaflo. The British Gas engineer said it needs to be a min of 20 litres and ideally 25 litres per minute for them to recommend fitting.

Is there any way I can get around this? I am having an open vented boiler fitted (I am not replacing the pipework and have therefore been advised that this is what I should go for). I have two power showers currently using a shower pump. The pump was replaced recently (2nd hand via ebay!). Ideally, I would like to get rid of the water tank in the loft and I don't know how long the shower pump will last, which is why I am keen on the megaflo. Otherwise, I will have to retain the shower pump and water tank and use a standard cylinder- not a disaster, but not ideal either.

Any advice would be much appreciated (laymans terms please! My heating/plumbing knowledge is limited).

Thanks

 

[kirkgas]

in laymas terms, it wont work properly and could cost a lot of money to rectify, either by installing a new water main, or a booster pump and/or tank configuaration to store water to give you pressure, but the tank will be as big as the cylinder, who is suggesting fitting an unvented cylinder to such low pressure, you need an expert in to sort it

 

[dcawkwell]

What is important is the pressure you have. You need to measure the static pressure. If you have 2.5 to 3 bar that will
be fine.
You have quoted the low flow rate this can be compensated for by a water accumulator.

Don't get an open vented boiler you want a system boiler that will have pump and expansion vessel in the boiler. Therefore removing the header tank from the loft.

 

[muggles]

Pressure and flow definitely too low, with that kind of poor mains performance you may as well have a combi boiler. If your static pressure is good then an accumulator may well help if you really do want an unvented cylinder, but be warned that these need to be huge to provide the required results

 

[dcawkwell]

Pressure and flow definitely too low, with that kind of poor mains performance you may as well have a combi boiler. If your static pressure is good then an accumulator may well help if you really do want an unvented cylinder, but be warned that these need to be huge to provide the required results

With mains performance like that a combi is completely unsuitable.

 

[Mark Br]

Ask your water board for a quote to upgrade the supply if you really want an unvented cylinder.

Also ask them to measure the flow rate and pressure in the road to see if the problem is there or in the house

 

[Agile]

Don't get an open vented boiler you want a system boiler that will have pump and expansion vessel in the boiler. Therefore removing the header tank from the loft.

Will you take responsibility for any rad which bursts under pressure?

Or any leaking pipes burried in concrete floors?

Or leaking pipes under ceramic tiled floors?

Do you have professional indemnity insurance to cover claims relating to poor quality advice given?

 

[markyc]

thanks for all the replies. A system boiler isn't an option as it will mean replacing all of the extisting pipework. The boiler has to be relocated as there is no external wall to vent it.

It sounds as though I will have to go for a "normal" cylinder rather than a megaflo- I really wanted to find out if there was a way around it. I have already phoned the water co and they have said they only need to provide 1 bar pressure.

thanks for all the advice.

 

[snb]

you can always fit an accumulator with a boost pump to give you 2.5bar for the unvented cylinder. Problem with these setups is the space you need.