Megaflo system and boiler choice

26 Apr 2016
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United Kingdom
Hi all, first post here but have read through some of the others and seen some helpful advice so would appreciate any help you can give us.

We are currently renovating our house and need a new heating system fitted. Family and friends have recommended going for a megaflo system as we have 5 bedrooms and 2 bathrooms, and 6 people all rushing to shower in the morning.

We've had two plumbers look at the house and give us a quote.

The space in the utility where we want the boiler and megaflo cylinder to go is quite tight and we have seen the system needs a lot of pipework.

One plumber has suggested a vaillant ecotec-plus 630 system boiler (30kw) with a 210ltr megaflow cylinder. He says the vaillant has an expansion vessel inside so no need for an external red balloon looking one and this would save us some space.

The second plumber has said to go for a baxi system boiler (32 kw) and a 210ltr megaflo cylinder. But he says we have to have an external expansion vessel regardless of which boiler and therefore will take up more space.

Are you able to help advise on which plumber is right. Do we have to have an external expansion vessel.

Any other recommendations on boiler?
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Thanks for your reply. Any particular reason why you wouldn't have those boilers? Reliability issues?
Poor experience of both companies, and although the Baxi is cheap, I won't fit or recommend their products again.

Vaillant you're paying for average quality with frilly knickers.
Largely a matter of personal choice.

But the Vaillant is largely considered to be one of the best three.

The Baxi however, is mostly seen as a middle priced and quality boiler.

One advantage of the Intergas is that it can simply provide advanced weather compensation whereas the Vaillant needs an expensive additional controller.

But to properly compare quotations the installers should be quoting for exactly the same equipment.

Before any unvented cylinder is fitted the mains water dynamic water flow rate needs to be measured. I would be very suspicious of anyone who quoted for an unvented cylinder with measuring this.

Second man is on the money re design. First one is a bathroom fitter or somesuch, and knows nothing about heating design.

I too would not go with the products listed. If you go for a Worcester 30CDi system boiler and a Worcester SC210 cylinder a suitably accredited installer will give you 10yrs warranty via the manufacturer.

However, most installers will like to fit what they are familiar with, and a good finished job in terms of workmanship is worth more than the sum of its parts. Something 'quote hunters' completely ignore, until they see the wonky work afterwards.
With six people all taking showers in succession then I would strongly recommend having a 300 litre cylinder.

If you measure the shower flow rates then you can calculate just how long you would be able to have showers for. Rather less that you might expect.

Even with a typical 10 li/min shower that will only be 6 minutes each even with a 300 litre shower. But ignoring any reheating during showering times which would slightly improve showering times.

I also find that people always underestimate how long they spend in the shower.

Thank you all for your replies! We are going to go with the second plumber I think as from a safety pov if we do need that external pressure vessel it gives us some confidence he knows what he doing. And he comes well recommended.

With regards to boiler he is still insistent on a baxi, most likely because he is baxi accredited and will get the servicing/repairs work in future! I'll suggest the intergas and see what he says

Tony, re tank size. Would a larger boiler improve the reheat times for the water? We have limited space so a 300 ltr tank may be hard to accommodate.

Am I right in thinking the 210 Ltr tank is all hot water? So assuming a mixer shower output of 10lt a minute, based on using a mix of 50/50 hot and cold would use 5 lt of hot water per min.

So 210 Ltrs gives 41 minutes of hot water or roughly 7 minutes each for 6 people.

Still not a lot of time. Does a megaflo refill itself as you use it so providing the boiler is on it continues to fill the tank with hot water.

Or does it wait for the hot water to be finished before the reheating cycle can begin? Prob sounds like a daft question now that I think of it
They will reheat as you go if you set them too. Speed depends on a number of things.

You can use twin coil cylinders too but you're limited by the boiler output too.

Another option is a combi boiler and a cylinder. Combi does one shower, cylinder does the rest.

Ultimately though, if you need the water, make the space.
With that size of house I would recommend one of our Intergas SB24 boilers set up as hot water priority and with a cylinder sensor so the boiler can run at a lower output and flow temp for the heating then a much higher flow temp and kW output to dump lots of energy into the cylinder when it calls for heat. It makes a 210L cylinder perform like a larger one ;)
And I agree with Dan in a house that size you have to have space for the install - even if it's in the loft or garage!

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