What size Megaflo

[soul2soul]

Finally got round to changing to an unvented system but cannot decide what size megaflo to go for.

The house is currently 3 bed but will will be 4 bed with 2 baths in the future.
Trying to decide between the 210 or 250.

The Heatrae guides indicates that the 210 will be fine but some people say the 250 will be better since the megaflo has the internal baffle & hence does not store anywhere near the advertised 210 or 250 litres.

Just trying to ensure that the tank will meet our future needs & that we do not have to upgrade it at a later date.

If anyone can give me an idea of how much shower time a 210 or 250 would give it would be a great way of judging what size to go for.

Thanks

 

[simond]

The time taken depends on the shower volume; if you have a 10 litre per min shower your stored HW will last twice as long as a 20l/m shower.

You need to think about how many people are going to be using those bathrooms and for what purpose, for how long. There are industry metrics but all the unvented manufacturers will guide you. But you must tell them what the flowrate of your shower equipment will be.

Megaflo is best avoided, I don't see how an internal air bubble can possibly be superior to a membrane based expansion vessel. See through the Baxi hype - there are no advantages to an internal bubble, whether they have a patented frisbee inside or not.

 

[toasty]

We've got the 210litre Santon - in a 3 bed house with 4 occupants (2 kids) I would say it could do with being a bit bigger.

If I had my time again I'd get the Santon 300litre, as we have emptied it a couple of times

 

[soul2soul]

Thanks for the quick answers.

Are you kids teenagers or has it been emptied under normal use & how many bathrooms do you have?

So much for the manufacturers guidelines!

Looks like the 250 will be a better option for me then - will also switch to a Santon as it not the first time that I have heard that the megaflo air bubble is hype & not the best way of doing it

 

[BigBurner]

Put one of these in. Stainless, no annual service and can even be DIYed. Run the CH off it too having a Smart pump on the CH loop and then you can have TRVs on all rads and no electric wall thermostat. Put a Magnaclean filter on the CH return pipe to the cylinder. This is not a direct safe replacement for an unvented cylinder, as it offers so much more than an unvented cylinder, a superb CH buffer too, and costs about the same or cheaper. No contest.

http://www.advanceappliances.co.uk/gas_or_oil_thermal_store_systems.html

Unvented cylinders can do nasty things:

http://au.youtube.com/watch?v=pu3FwgIHsQA

http://au.youtube.com/watch?v=GF_Wrm-Ns0I

 

[BigBurner]

We've got the 210litre Santon - in a 3 bed house with 4 occupants (2 kids) I would say it could do with being a bit bigger.

If I had my time again I'd get the Santon 300litre, as we have emptied it a couple of times

A smaller heat bank/thermal store could do even better. The boiler sends it heat directly to DHW use.

DPS have just brought out this:
http://www.heatweb.com/Dublin/index.htm

They use a flue heat recovery unit to preheat the store, clawing back wasted heat.