tfboy

A little while ago, when redoing my bathroom, had the problem, explained here

Eventually opted for a single pump on the output of the hot water tank, keeping the cold mains-pressured.

To be fair, it works OK, the hot water pressure is now almost equal to the cold so the thermostatic shower is happy.

But, It's a pain if you want just a trickle (sp?) of hot water - the pump kicks in and you put a lot of strain on it by closing the taps only to have a thread of water coming out.

So, I'm back at looking at a proper mains-pressured hot water tank. However, by trawling across the web, I've come across "Thermal Storage" solutions, by Gledhill. I'm looking particularly at the Boilermate system here

These guys claim that it's a big bonus on unvented mains pressure systems because they don't need anual servicing (do they?!) and you don't need to inform your local council that you're having unvented hot water system (did you ?!?)

Also, I can keep my existing boiler which is doing the central heating fine, so this fits the bill quite well as an all-in-one hot-water solution.

Does anyone have any experience with such products / technology or offer any advise?

Ta muchly

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Xavier

bengie

you don't get mains pressure hot water systems other than a combi boiler as far as i know, at least thats what i've been told by the gas engineers at work

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owner of a skoda octavia 4xvrs3

tfboy

According to this you do.
When I first heard it called mains pressure vented system, I thought that didn't make sense at all!

But from what I can figure out, you have a small tank of hot water, that's vented, but with multiple heat exchangers, and the mains pressure goes through it, so it doesn't need an expansion vessel, and it's not as "dangerous" as an unvented hot water system.

The technical installation pdf guide shows how it all works, here (4MB)

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Xavier

bengie

just looked at that an admitidly only scanned it for diagrams but not once did i see a picture of a mains fed hot water system.

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owner of a skoda octavia 4xvrs3

tfboy

A - safety open vent
B - cool feed/expansion
C - Primary flow from boiler
D - Primary return to boiler
E - Central heating return
F - Central heating flow
G - Domestic hot water (mains pressure)
H - Incoming mains cold water
I - Drain valve
J - Primary return for pumped summer towel rail circuit

Attached Images

boiler.JPG (21.2 KB, 4 views)

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Xavier

bengie

thats all well and good xav but as this diagram shows the mains feed goes into a header tank then that feeds the boiler.

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owner of a skoda octavia 4xvrs3

tfboy

But that's just for the heating bit, not the water

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Xavier

Johnnyc

Actually if you read on a bit in the brochure there is a more detailed drawing which indicates the mains feed directly to the boiler. Basically this is a combi boiler except the hot water for the heating is heated in the traditional way instead of instantaneously through a heat exchanger. The domestic hot water is however heated instantaneously via a heat exchanger like it is in a combi.

One of the things you lose with a combi or traditional 4 pipe system over a traditional 2 pipe system is that in summer time you don't get a percentage of the hot-water circulating through the cylinder coil passing through the nearest radiator (usually the bathroom) but this setup has a feed specifically for a towel rail so that you don't lose this facility. Nice touch. I also like the standby electric heater facility for emergencies.

However I notice there's at least 3 pumps in there. That means theres 2 more to go wrong than in a combi boiler. There's a pump dedicated to purging heat from the system and it also circulates water in the boiler if the frost stat kicks in. Then there's a pump for the heating system and one strangely for the hot water which is odd given that it's mains fed. Because there's a common heat exchanger in a combi, 1 pump and a couple of motorised valves does the same job. Also, i'm not sold on the build quality tbh. The PCB should be enclosed and the MCB terminals covered for a start.

Attached Images

Gledhill.jpg (88.4 KB, 3 views)

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Johnny

"Americans have different ways of saying things. They say "elevator", we say "lift" ... they say "President", we say "stupid psychopathic git."