Mixergy hot water tank

tim_p

Does a Mixergy tank / system require an unvented system or can it work with a vented / cold tank in roof scenario?

AntonyTewks

Both I believe. But installer sold us on benefits of an unvented system for better pressure (but neglected to tell us our three showers would no longer work...)

Solarchaser

Why would the difference in storage affect your showers?
That doesn't sound right Antony 😕

AntonyTewks

I had showers with built in pumps, on a vented system they gave better pressure. Now it's unvented two of them were leaking water because they couldn't handle the increased pressure going in. The other one is hanging on for now. We'll be changing to thermostatic mixers so no need for any pumps or electrics anymore. He'd indicated there was one central pump in the lift which he would remove which obviously wasn't the case, they were built into each. I did query and should have twigged really but hell I'm no plumber...

Solarchaser

Ahh, I see..strange they can't cope with incoming pressure, but I guess the seals were old perhaps. 
As you say though, no need for pumps now you have unvented 👍

michaels

We have unvented but no danger of any seals failing with the carp water pressure Affintiy Water deigns to supply us with.  We checked the flow rate in the middle of the day and it was just about ok for two showers at once but at 7am even one shower comes out as a piddle.  We asked them to check the pressure over a week and they said it bottomed out at 1.0 bar which just happens to be the minimum that they have to supply.

AntonyTewks

Solarchaser said:

Ahh, I see..strange they can't cope with incoming pressure, but I guess the seals were old perhaps. 
As you say though, no need for pumps now you have unvented 👍

Yes it was the older two that went. I don't think they're meant to take much above 1 bar and the gravity pressure of a loft cold water tank. I think now it's cold mains feed its towards 3 bar.

michaels said:

We have unvented but no danger of any seals failing with the carp water pressure Affintiy Water deigns to supply us with.  We checked the flow rate in the middle of the day and it was just about ok for two showers at once but at 7am even one shower comes out as a piddle.  We asked them to check the pressure over a week and they said it bottomed out at 1.0 bar which just happens to be the minimum that they have to supply.

Wow that's awful. 1 bars got to be worse than a gravity fed tank I would think? I have a few pumped showers going spare if you need... 
Interesting to think off though. Presumably the more unvented systems the lower the pressure will get off the mains at peak times. Guess a lot would have to switch mind but something I'm going to have to be wary of as the kids grow up..

michaels

It is against the law to pump out of the mains so we would have to go back to a header tank, we did used to have a couple of pumps which gave great showers but were noisy.

In theory 1 bar should be a 30 foot head but of course it is spread over both the hot and cold and has to come via a single supply into the house then lots of corners and small pipes before it makes it to the thermo shower valves which take a bit off again....

mnbvcxz

The showeeboosterpump gadget claims it is low powered enough to be legal on mains water. Never tried one.
https://showerpowerbooster.co.uk/ask-alan/

Solarchaser

Your tank shouldn't be more than 1 bar.
It's roughly 0.1bar to 1 meter of rise (or decline from tank) and a typical UK floor to floor height is 2.6m so unless it's 4 floors above the shower, the tank will supply alot less than 1 bar.

Perhaps you would be better with a top fed, bottom outlet tank with solar diversion and a pump Michaels,  as your house uses so much hot water.