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Unvented immersion heater

Does what it says on the tin
mc2fool
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Unvented immersion heater

#493473

Postby mc2fool » April 11th, 2022, 1:29 am

Considering replacing my traditional vented 180ish litre hot water immersion heater with a direct unvented one instead.

Suggestions, recommendations, etc, for or against, for makes, models, types, internal vs external expansion, etc, etc, welcome. :)

mc2fool
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Re: Unvented immersion heater

#493474

Postby mc2fool » April 11th, 2022, 1:56 am

P.S. I'm on Economy 7 and currently have two elements, top and bottom, to utilise that and would be looking for the same.

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Re: Unvented immersion heater

#493699

Postby 88V8 » April 12th, 2022, 10:22 am

I presume you mean unvented hot water tank.... as we're not overwhelmed with replies, I direct the member's attention to this older thread in another place https://www.diynot.com/diy/threads/vented-or-unvented-system.440952/#post-3449125

For me, unnecessary complexification, and I dislike mains pressure systems.
But that's just me.

V8

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Re: Unvented immersion heater

#493703

Postby Dod101 » April 12th, 2022, 10:33 am

I inherited my unvented system and it works well, with little or no maintenance over the 16 years I have been here. I see no disadvantage in having it and as has been said in the article no need for a header tank and good pressure. I actually have two systems, the other is traditional and has very poor hot water pressure. I got a pump installed to help but much better to have the unvented system. Mine is a Heatrae Megaflo and it is big. The tank stands more than 6 feet and it has two built in immersion heaters, one in the top half the other in the lower. I never use them as my water is heated by my oil fired boiler.

Mine is in my garage and that would certainly be a limiting factor, space that is, but I presume that we can get smaller tanks as well. I can see nothing to dislike, but I am quite non technical. It just works.

Dod

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Re: Unvented immersion heater

#493710

Postby Mike4 » April 12th, 2022, 11:47 am

I'd suggest a MegaFLO too.

There are loads of brands on unvented cylinders on the market but most use a separate expansion vessel which can be trouble, and the MegaFLO runs at 3.0 bar pressure rather than the 2.0 bar of the also-rans. The MegaFLO uses an internal air cushion to accommodate expansion on heating.

All unvented cylinders should be serviced annually by a plumber qualified to work on unvented (a separate, specific exam) to check the safety devices are in working order.

Dod101
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Re: Unvented immersion heater

#493717

Postby Dod101 » April 12th, 2022, 12:24 pm

Mike4 wrote:I'd suggest a MegaFLO too.

There are loads of brands on unvented cylinders on the market but most use a separate expansion vessel which can be trouble, and the MegaFLO runs at 3.0 bar pressure rather than the 2.0 bar of the also-rans. The MegaFLO uses an internal air cushion to accommodate expansion on heating.

All unvented cylinders should be serviced annually by a plumber qualified to work on unvented (a separate, specific exam) to check the safety devices are in working order.


Yes my label says 3 bar. I had not heard that they should be serviced annually but will ask the guy who comes to service my boiler about that.

Dod

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Re: Unvented immersion heater

#493720

Postby Mike4 » April 12th, 2022, 12:50 pm

Dod101 wrote:
Yes my label says 3 bar. I had not heard that they should be serviced annually but will ask the guy who comes to service my boiler about that.

Dod


Or...

RTM!

Dod101
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Re: Unvented immersion heater

#493727

Postby Dod101 » April 12th, 2022, 1:31 pm

Mike4 wrote:
Dod101 wrote:
Yes my label says 3 bar. I had not heard that they should be serviced annually but will ask the guy who comes to service my boiler about that.

Dod


Or...

RTM!


RTM?

Dod

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Re: Unvented immersion heater

#493728

Postby ReformedCharacter » April 12th, 2022, 1:34 pm

Dod101 wrote:
Mike4 wrote:
Dod101 wrote:
Yes my label says 3 bar. I had not heard that they should be serviced annually but will ask the guy who comes to service my boiler about that.

Dod


Or...

RTM!


RTM?

Dod

Read The Manual.

RC

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Re: Unvented immersion heater

#493731

Postby mc2fool » April 12th, 2022, 1:47 pm

Mike4 wrote:I'd suggest a MegaFLO too.

There are loads of brands on unvented cylinders on the market but most use a separate expansion vessel which can be trouble, and the MegaFLO runs at 3.0 bar pressure rather than the 2.0 bar of the also-rans. The MegaFLO uses an internal air cushion to accommodate expansion on heating.

I was aware of that but I'd heard the opposite, that the internal air gap in the Megaflo can disappear and need to be replenished, and that doesn't always work. Lots of such reports on the net, FWIW.

Mike4 wrote:All unvented cylinders should be serviced annually by a plumber qualified to work on unvented (a separate, specific exam) to check the safety devices are in working order.

And plumbers say vented system should undergo an annual service too ... :D

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Re: Unvented immersion heater

#493732

Postby Dod101 » April 12th, 2022, 1:50 pm

ReformedCharacter wrote:
Dod101 wrote:
Mike4 wrote:
Dod101 wrote:
Yes my label says 3 bar. I had not heard that they should be serviced annually but will ask the guy who comes to service my boiler about that.

Dod


Or...

RTM!


RTM?

Dod

Read The Manual.

RC


Thanks, I am rather dim with the obvious. I do not think I have a manual but will take a look online. Good idea. For the benefit of anyone who does know about these, I remember being told to look out for a drip and what to do about it if I found one. I have had no need to do anything so far.

Dod

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Re: Unvented immersion heater

#493738

Postby DrFfybes » April 12th, 2022, 2:21 pm

Telford do (or did) a Stainless tank - we had one and it was fine and trouble free for 15 years. Removed the need for shower pumps, and meant we didn't need to go the combi boiler route when we did the loft conversion and lost the header tanks. If we went away for 3 days when we got back the water would still be warm, in summer it was still just OK for a quick shower.

Re : Servicing - they re supposed ot be checked annually. This seems to involve checkingthe pressure on the expansion vessel with a car tire gauge and manually tripping the relief valve so it drips irritatingly in the cupboard in the bedroom for a few days (and niights).

Paul

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Re: Unvented immersion heater

#493754

Postby Neutrino » April 12th, 2022, 3:27 pm

An unvented cylinder requires sufficient mains water pressure and flow.

Building regulations require that an unvented hot water storage vessel (with a capacity of more than 15 l) is installed by a tradesperson with a G3 qualification and that the installation is notified to Building Control, after which a Building Regulations Compliance Certificate will be issued. This certificate is needed when you sell your home.

Most tradespersons do the notification through Gas Safe Register. You can check whether the tradesperson has informed gas safe register that he or she has a G3 qualification at gassaferegister.co.uk. Look for: ‘Hot Water System with Unvented Hot Water Storage’.

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Re: Unvented immersion heater

#493765

Postby Dod101 » April 12th, 2022, 4:20 pm

Neutrino wrote:An unvented cylinder requires sufficient mains water pressure and flow.

Building regulations require that an unvented hot water storage vessel (with a capacity of more than 15 l) is installed by a tradesperson with a G3 qualification and that the installation is notified to Building Control, after which a Building Regulations Compliance Certificate will be issued. This certificate is needed when you sell your home.

Most tradespersons do the notification through Gas Safe Register. You can check whether the tradesperson has informed gas safe register that he or she has a G3 qualification at gassaferegister.co.uk. Look for: ‘Hot Water System with Unvented Hot Water Storage’.


When I bought my current house nobody told me that I needed a Compliance Certificate. Is this something new because I doubt that I have one. I have found my manual and apart from ensuring that the safety stuff is OK you are supposed wash out a filter as well. It sounds more like a safety check than a service. I will try to get the guy who services my boiler to do it whilst he is here, assuming of course that as well as the qualifications for servicing my boiler who also has what is needed for the Megaflo.

Dod

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Re: Unvented immersion heater

#495475

Postby 9873210 » April 20th, 2022, 10:06 pm

Water heaters that work at mains pressure are the standard in much of the world, where they do not need annual maintenance nor particular qualifications to install, and they don't blow up* with any measurable frequency.

Talking about mains pressure as "extreme pressure" is over the top. UK mains pressure is typically quite low, which is one of the reasons for the traditional cold water storage tank.

* There is an episode of Myth Busters where they made an unvented tank blow up. They had to do about a half dozen stupid things. You can make a vented heater blow up if you add "block the vent" to the list of stupid things.


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