Should I get a Megaflow?

[pdonalds]

I have a five bedroom three storey victorian semi with two bathrooms. I have just started to convert the cellar which will include a new shower room. I currently have a 17 year old Vaillant combi which has poor hot water flow rate, only one tap at a time. I am therefore thinking of installing a new bolier and maybe unvented system. I have been recommended to install a 300l Megaflow and Worcester 42CDI in the cellar. Any advice on suitability and altermatives? I am concerned that if the Megaflow is sited in the cellar the hot water pressure may be poor on the second floor (attic bathroom) and also have read somewhere that installing a Megaflow in the cellar is problematic due to discharge pipe. What mains pressure/flow rate do I need?

 

[D_Hailsham]

I currently have a 17 year old Vaillant combi which has poor hot water flow rate, only one tap at a time.

You are going in the right direction by not considering a combi. However a Megaflo still relies on the incoming flow rate and pressure. So if it's not sufficient for your combi it may not be adequate for a Megaflo.

I have been recommended to install a 300l Megaflow and Worcester 42CDI in the cellar.

Megaflo recommend a 210l for 4/5 beds, 2 bath & shower and a 250l for 4/5 bed, 3 bath & shower.

How was the boiler size determined? What's the output of your existing boiler?

I am concerned that if the Megaflow is sited in the cellar the hot water pressure may be poor on the second floor (attic bathroom) and also have read somewhere that installing a Megaflow in the cellar is problematic due to discharge pipe.

Se the Megaflo Brochure

As far as flow rates and pressures are concerned, Megaflo say (my emphasis):

Bear in mind that the mains cold water supply to the property will be supplying both the hot and cold water requirements simultaneously. It is recommended that the maximum water demand be assessed and the water supply be checked to ensure this demand can be met.

NOTE: A high mains water pressure will not always guarantee high flow rates.

Wherever possible the main supply pipe should be in 22mm. The minimum supply requirements should be 0.15MPa (1.5 bar) working pressure and 20 litres per minute flowrate. At these values outlet flowrates may be poor if several outlets are used simultaneously, the higher the available pressure and flowrate the better the system performance will be.