Diy unvented install allowed?

John D v2.0 · 12 May 2019

I noticed there are unvented heaters on sale alongside instant ones. Is that right that they're ok for anyone to buy and install?
https://www.toolstation.com/stiebel-eltron-unvented-point-of-use-water-heater/p69906

If the answer is that it's considered safe enough for diy I'll go for that as it saves installing a dedicated circuit for infrequent use. But if there's a danger of 10l of water flash boiling in my ensuite i don't think so!

Newboy · 12 May 2019

G3 regs cover unvented heaters with capacity of over 15 ltrs.

That said, if a 10l unvented heater is installed without the correct safety devices/expansion vessel/checkvalve/PRV/pipework layout then the potential for the installation to fail still exists.

John D v2.0 said:
I noticed there are unvented heaters on sale alongside instant ones. Is that right that they're ok for anyone to buy and install?

In much the same way that I can buy a distribution board but that doesn't mean that I'm qualified to install it.

bernardgreen · 12 May 2019

From the technical spec

"" Only a qualified contractor should carry out the installation, commissioning, maintenance and repair of this appliance. Where applicable and prior to installation the electricity and/or water utility companies should be notified of your intention to install the product. ""

snb · 12 May 2019

you either have to be G3 qualified and registered with a competent person scheme or have applied to building control to carry out the works and for them to inspect it complies with the regs

John D v2.0 · 12 May 2019

bernardgreen said:
From the technical spec

"" Only a qualified contractor should carry out the installation, commissioning, maintenance and repair of this appliance. Where applicable and prior to installation the electricity and/or water utility companies should be notified of your intention to install the product. ""

Oh took me a while to spot that even after you pointed it out! Hidden away in the general footer, presumably that's a catch all as it appears on the hand dryers and even a tap

oldbutnotdead · 13 May 2019

That tech spec looks like the one with every 13A socket, FCU, pendant light fitting ever supplied- don't ignore it but don't get worked up about it. The installation instructions and basic electrical/plumbing competence will be enough to safely install- double check valve on the supply and I'd be amazed if any external PRVs etc were required.
You might be better (if the tap is infrequently used) going for one of the inline instant water heaters (Think they're Polish, can't remember the name, don't buy the 3 phase one unless you have a 3 phase supply)- that 10l tank is going to cost money to keep to temperature. The inline heaters are too puny to run a sinkful to wash the dishes but are spot-on for handwashing in a garage for instance

cdbe · 14 May 2019

We're having a 9.5kw non storage instantaneous fitted in our scout hut. The MI's state that if a non return valve is fitted on the inlet supply to the unit then pressure reducing and relief valves must be fitted - but if not they aren't needed. I'm no expert but assume any excess pressure is otherwise distributed back along the supply pipe.

bernardgreen · 14 May 2019

cdbe said:
I'm no expert but assume any excess pressure is otherwise distributed back along the supply pipe.

Correct. There may however be a non return valve in the water meter.

John D v2.0 · 14 May 2019

oldbutnotdead said:
10l tank is going to cost money to keep to temperature. The inline heaters are too puny to run a sinkful to wash the dishes but are spot-on for handwashing in a garage for instance

Yeah good shout,i thought that too but i think it was going to be about 4p a day, and given the cost of the 6mm cable it might still be worth the standing losses.
I was even considering an inline heater a couple of kw just to take the chill off the cold water for washing vegetables. But it does seem perverse to have a big boiler and use electric at all the points of use, even if it's more convenient.

cdbe said:
The MI's state that if a non return valve is fitted on the inlet supply to the unit then pressure reducing and relief valves must be fitted

Yes we already have a mini ev next to the boiler since getting the water meter for the reasons Bernard green mentioned.

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Diy unvented install allowed?

Newboy

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