Unvented cylinder in basement - anyone done it?

[RockyBalboa]

I've been informed that it's difficult but doable. I have done a bit of research and been informed that this can be done and a discharge tank (or sump) must be suitable for high temperature water as must the sump pump. The pump must be capable of removing the water at the discharge rate or better (confirmed by cylinder specs).

I’ve been on the phone to Grundfos who state that the following two pumps should be up to the task:

http://uk.grundfos.com/products/find-product/ups2....

or

http://uk.grundfos.com/products/find-product/magna...

Has anyone on here got an unvented cylinder in their cellar/basement?

[Rickyy]

I've only ever fitted one in a basement, but their was drainage down there.

Those pumps in the links are heating circulating pumps. I'm assuming you want some sort of sump pump to empty out the basement in the event of the cylinder 'blowing off'?

You'll need a float operated submersible pump for that, ideally connected to fixed pipe work discharging somewhere that it'll cause a nuisance, so you know that it's discharging.

I'd suggest siting the cylinder in a containment area or tank with a pump, so you have a fighting chance of not flooding your basement.

[RockyBalboa]

Something like this?

http://www.pumph.co.uk/product/ph-5l-hw-temperatur...

[sparkythecat]

I've had an unveiled cylinder in my basement for the past 12 years. My boiler is down there too.

[RockyBalboa]

I know there are specific Building Regs regarding having it in a basement so just want to make sure there are no nasty surprises afterwards.

I suppose I could opt for a thermal store?

[21TonyK]

Am I right in thinking its only in the UK we are so cautious of unvented cylinders? And, should a cylinder vent surely its only to the point that the excess pressure is relieved, it's not like the cylinder drains itself.

[p1esk]

Being an old buffer and a bit slow to move with the times , why is there such enthusiasm for unvented systems these days? Is it so that you have mains water pressure available for the hot water system?

We've always had vented systems with a cold water head tank in the loft, and we've never found this to be an unsatisfactory arrangement.

OK, there you go, guys; I'm listening.

[21TonyK]

Capacity is one factor, 300 litres with a fast restore time. Also mains pressure showers.

[Rickyy]

21TonyK said:

Am I right in thinking its only in the UK we are so cautious of unvented cylinders? And, should a cylinder vent surely its only to the point that the excess pressure is relieved, it's not like the cylinder drains itself.

No idea, but right to be cautious. They are very dangerous if installed incorrectly.

The boiling point of water increases with pressure. If for some reason the water in the cylinder is above 100 degrees C, this will instantly flash to steam and expand rapidly causing an explosion, if depressurised quickly.

Unlikely they would fail unless fitted by a complete moron. They have three safety devices to overcome. Cylinder thermostat, high limit thermostat and temperature/pressure relief valve. All three would have to fail for it to become dangerous.

The risk from flooding is from the temperature pressure relief valve. If the pressure reducing valve fails on the cold inlet or the cylinder overheats, the temperature/pressure relief valve will discharge water until the pressure or temperature falls to safe levels.

Mythbusters blew one up, quite an impressive explosion.

https://www.youtube.com/watch?v=68p4ngS-yME

[RockyBalboa]

Don't suppose anyone knows of of any unvented cylinder that is solar compatible (for the future), indirect (i.e. will be heated by gas boiler), horizontal and 500 L ??

[p1esk]

21TonyK said:

Capacity is one factor, 300 litres with a fast restore time. Also mains pressure showers.

Oh, thank you.

[eliot]

RockyBalboa said:

Don't suppose anyone knows of of any unvented cylinder that is solar compatible (for the future), indirect (i.e. will be heated by gas boiler), horizontal and 500 L ??

Wiesman has a solar coil. I'm sure there's plenty others.

[p1esk]

eliot said:

RockyBalboa said:

Don't suppose anyone knows of of any unvented cylinder that is solar compatible (for the future), indirect (i.e. will be heated by gas boiler), horizontal and 500 L ??

Wiesman has a solar coil. I'm sure there's plenty others.

Hmm, if you use solar heating for a hot water system, does it need to be done in an indirect fashion, i.e. with antifrezze in the primary circuit?