Unvented tank brands

[Arjay12345]

Hi

I's like to install an unvented cylinder in my new home. I know you get what you pay for, but are there big differences between a megaflow and a Vaillant Unistor?

Seems to be some difference in price.

Am looking at around the 300 litre mark. Any viewed would be helpful

Thanks..

 

[dumbrill]

Hi

I's like to install an unvented cylinder in my new home. I know you get what you pay for, but are there big differences between a megaflow and a Vaillant Unistor?

Seems to be some difference in price.

Am looking at around the 300 litre mark. Any viewed would be helpful

Thanks..

The Megaflow tanks don't have a separate expansion vessel and instead rely on a trapped pocket of air at the top of the tank. Probably the only other important factor is the material which can either be enamelled steel or stainless steel. The stainless needs to be duplex, but I guess they all are or they wouldn't last.

 

[simond]

Both the uniSTOR and Baxi Megaflo are stainless.

Megaflo use an air bubble in the top of the cylinder, Vaillant use a separate diaphragm expansion vessel.

Nearly all unvented cylinder manufacturers favour the diaphragm because the air and water are kept separate. This allows the cylinder to work without the air charge being eroded, and excess pressure thereafter being created.

In the case of Megaflo, knowing that the air charge would gradually be lost in their 'bubbletop' cylinder, they designed and patented a baffle that floats on the water and separates the air.

There are two problems with this design.

Firstly, it doesn't work. The water does take some of the air out and Megaflos therefore tend to start leaking expanded water out of their emergency relief valves after a few years. They have got fed up with taking phone calls on this so now stick a large label on the side telling you what to do.

The second problem is that the cylinder takes up more headroom than the equivalent cylinder with a separate expansion vessel.


You will have noticed that the Megaflo is more expensive. This is because of the large marketing budget they have to spend influencing gullible punters like you that their flawed design gives a technical superiority.

They quote the patent and the floating baffle as an advantage, but when you read carefully you will see that they don't ever state what that advantage might be.

 

[mickyg]

an excellent asessment of megaflos, couldnt have put it better. There's plenty of well priced quality UV manufacturers, Kingspan, Santon, Range Tribune to name a few .

 

[muggles]

OSO Super S every time for me.

Be aware that one major difference between the manufacturers can be the heat up and recovery times, some take much longer than others.

 

[Axel]

They quote the patent and the floating baffle as an advantage, but when you read carefully you will see that they don't ever state what that advantage might be.

And you still have to fit an external expansion vessel when the cylinder starts to lose it's air charge once a month. Mine does, and I've heard of others that do too. Megaflo recommend an external vessel to be added on in this case!

 

[bookahandyman]

i own a 210 ltr gledhill, easy to fit and two yrs so far no problems. have fitted about four others (gledhills) and no problems yet over 3yrs. reasonably priced, made in u.k

 

[Agile]

Most users find the Megaflow only has to be recharged every six months or more.

It was three years until my friend had to ask me about it.

I find the Santon as one of the best value. Its the second brand name of Megaflow.

Tony

 

[tamz]

i own a 210 ltr gledhill, easy to fit and two yrs so far no problems. have fitted about four others (gledhills) and no problems yet over 3yrs. reasonably priced, made in u.k

Easy to fit or not you need a ticket to do it

 

[Axel]

Course is 1 day - 200 quid plus vat. Cheaper than an installer!

 

[ln1234]

We have the Vaillant Unistor (250 litres I think) with a vaillant system boiler + associated controls. Works absolutely fine.

 

[bookahandyman]

the course is a £200 or so and does take a day, but you may need a background or qual in plumbing before they accept you on the course.
depending on which mickey mouse outfit trains you. lol

 

[Axel]

I trained with Disney.

 

[bookahandyman]

some goofy tw*t trained me

 

[GeorgeBainbridge]

A recent thread said that the Collins Plumbing and Heating guide recommends vented DHW only thermal stores over unvented cylinders. I saw this book in the library and it does. They also say you use 15% less fuel. There is no G3, recharging a bubble and all that comes with unvented cylinders. Food for thought.