Question for plumber - combi /mega flow

ey143

This is a question for a plumber.

I bought into a large detached house project which is far too big for my current sized family but I believe very good value. Everything needs gutting inc the plumbing. Anyway a house of this size ideally requires a megaflow system, however we are only two adults and a baby for now.

With my parents house we have a condensing boiler which serves a 4 bed semi with about 5 adults and the hot water on demand is fine even with two bathrooms.

I'm against the idea of having hot water stored in a mega flow if we are only two people and at work for most of the day. How best do you recommend we proceed with a water / storage heater whilst keeping in mind that the family will grow in years to come or if we get good value for selling the house, any new buyer will not appreciate a large house with inadequate hot water storage.

Is there a half way solution or a way to get a combi to bypass the filling of a megaflow when not required?

southcoastrgi

I wouldn't fit a megaflow as they are way too expensive to buy, an Ariston unvented cylinder will do just fine & as they have an external expansion vessel you don't lose any capacity within the cylinder, you need to have a site survey with someone who holds the G3 unvented cert, they need to test your incoming water pressure & flow rate, if all is ok I would go with an unvented cylinder over a combi for your house, the heat loss in the cylinder will be min & give you a far better performance

ey143

Thanks. What cost would I be looking at for a site survey? Is it a bad idea to leave this to the builders to arrange or ask the right questions re plumbing as part of a major renovation?

Also could you please elaborate on some of your terms in layman speak? Why would a cylinder be bette than say an ordinary combi? How long can water stay hot for in a cylinder if not used?

Owain_Moneysaver

ey143 wrote: »

Is there a half way solution or a way to get a combi to bypass the filling of a megaflow when not required?

You can plumb a cylinder, whether vented or unvented, into a combi boiler as an additional circuit on the radiator output with its own controls (S Plan Plus). So you can have a mains pressure shower off the combi and a vented cylinder for filling baths.

The thermal loss of a Megaflo Eco 300 litre cylinder over 24 hours is 1.89 kW or about 12 p a day using mains gas. Other manufacturers publish figures for their cylinders.

A Megaflo or unvented mains pressure cylinder will only be suitable if your mains water flow and pressure are suitable.

ey143

We have a renewed mains so blue poly pipe and mains upto the boundary and we will change the copper to blue upto the kitchen tap soon.

Thx.

mandm65

@ southcoastrgi
You seems quite knowledgable so can i ask a question?
If you were to install UFH would you choose combi with HW cylinder or install system (unvented) with HW cylinder? I guess the UFH needs to be run a separate loop (as the desired temp would be lot less).
Assumption for the above is that the flow rate and pressure are suitable.

southcoastrgi

mandm65 wrote: »

@ southcoastrgi
You seems quite knowledgable so can i ask a question?
If you were to install UFH would you choose combi with HW cylinder or install system (unvented) with HW cylinder? I guess the UFH needs to be run a separate loop (as the desired temp would be lot less).
Assumption for the above is that the flow rate and pressure are suitable.

system boiler, with an unvented cylinder, if it's a long distance from the cylinder to the taps a secondary return would also be advantagious to look at (although you would need to make sure the cylinder had this tapping)

ey143

What's a secondary return?

Ruski

ey143 wrote: »

What's a secondary return?

http://www.youtube.com/watch?v=9qWlzJrl3GU

HTH

Russ

Lgas

I'm in a 2 bedroom house with my partner and we're at work all day...I have a megaflo and only heat it for one hour every day, and it stays hot. If we both have a bath/shower after it's timed to go on we'll boost it for another hour. Unvented beats every other system in my opinion!

mandm65

thanks guys for your help/link etc, much appreciated.