Unvented Hot Water Cylinders

I'm looking to buy a new unvented cylinder for my new house. I had a Megaflo in my last place and I was happy with it. Looking arounf the merchants, I see quite a difference in price between Megaflos and equivalent sized Aristons (>100). Another advantage is that the Ariston has a smaller diameter making fitting a little easier. Can anyone tell me if there are any significant advantages to the Megaflo over the Ariston?
Steve
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Steve Benjamin wrote:

The Ariston has all electrical and plumbing connetions made from the front, the capacity is it's true water capacity unlike the Megaflow as the expansion vessel is external on the Ariston, internal on the Megaflow. The Ariston reheat time is ~claimed~ to be about 15% quicker.
Ariston prices are good; you could get a slim 505mm, 210 litre indirect for 453.70, direct 371.80 both plus vat of course.
Toby.
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Steve Benjamin wrote:

The Ariston has all electrical and plumbing connetions made from the front, the capacity is it's true water capacity unlike the Megaflow as the expansion vessel is external on the Ariston, internal on the Megaflow. The Ariston reheat time is ~claimed~ to be about 15% quicker.
Ariston prices are good; you could get a slim 505mm, 210 litre indirect for 453.70, direct 371.80 both plus vat of course.
Toby.
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Steve Benjamin wrote:

Two things to be aware of 1) The incoming main must be 25mm (c. 3/4" ID) all but very new houses have 1/2" lead, 20mm plastic.
2) Is the Ariston really a stainless steel mains pressure _unvented_ cylinder? I would expect that a Megaflow which is say 750 would be 650 if its name is Albion or Telford I would have difficulty beleiving that anything under 400 was the real thing. Also note that the other makes use a added on expansion vessel (25) whcih I think is included in the box.
IMHO this is to be PREFERRED over the Megaflow where the air bubble dissappears over time leading to over pressure dribbles and a reduction in the life of the first pressure releif unit.
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Steve,
Go for a vented heat bank, not a thermal store, which is much better than an unvented cylinder. many local authorities are switching to heat banks as they are fed upo of overflows dripping from unvented cylinders.
http://www.heatweb.com http://www.range-cylinders.co.uk (go to thermal storage)
A heat bank:
- gives higher flow rates. - operates on low pressure. - can be DIYed. Unvented cyoidner have to be installed by a BBA approved fitter. - eliminates inefficient boiler cycling, so cheaper to run. - Fast re-heat - does not have an air bubble that requires reinstating every year - does not require an annual service. If you have a blow out (they make a mess) an insurance company wiil not pay up without the annula service. - Can be DHW only or provide CH and DHW from the same cylinder - Can be packaged all in one unit (you just connect up pipes to the boiler and rads, with no design work involved) - Hot water temp at the taps user selectable - A heat bank does not scale up. - Can have electric backup for CH and DHW when using an integrated heat bank or thermal store. - No complex pressure control and reduction valves. - can be run at full mains pressure. - A DHW only heat bank/thermal store costs less than an unvented cylinder.
To to Google and look at the recent thread: Cylinder v thermal store
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