Unvented/G3 ongoing install sanity check

NoRulesRules · 15 Feb 2021

Hi folks - long time listener, first time caller.

We are currently having our old gravity fed system replaced by a new unvented install. Unvented tank in airing cupboard, new system boiler in garage.

I have a few concerns about the install, despite the installer having good reviews and required G3 cert.

1) The combination valve is positioned very low, this means the tank will need to be drained to service it right? Not a deal breaker, but surely now is the time to get it right?

2) The combination valve does not have a dedicated expansion vessel port on this model (cwic200055). The expansion vessel has been connected to the balanced cold outlet of the valve, is this ok? Every diagram I see shows the vessel T'ed off the pipework after the combination valve if it has no dedicated port

3) They have fitted a blend valve and I'm not sure why. Yes this is a thermal store with secondary solar coil, but the thermostat on the tank will be set at 60-65c anyway. Why do we need to blend cold water to this? I did a little reading and this maybe new G3 regulations to prevent bath scalding with the safe figure 46c now thrown around

4) Even if the blend valve makes sense, its been connected to the balanced cold, and according to the cylinder installation manual, this requires a check valve, which has not been installed

This install is ongoing, scheduled to finish this week. Do I need to kick up a fuss, or am I worried over nothing?

Cheers
AJ

NoRulesRules · 15 Feb 2021

May have answered #4 myself. This is the blend valve AKA TMV:
https://www.altecnic.co.uk/images/products/spec/3b_spec.pdf

Looks like it comes with integrated check valves.

Razor900 · 15 Feb 2021

Not sure why you think the cylinder will need draining to get to the valve when there's a lever valve between it and the cylinder

Of course that also means the expansion vessel isn't connected and things could all go a bit mythbusters

I'd be having serious words.....

NoRulesRules · 15 Feb 2021

Razor900 said:
Not sure why you think the cylinder will need draining to get to the valve when there's a lever valve between it and the cylinder

Of course that also means the expansion vessel isn't connected and things could all go a bit mythbusters

I'd be having serious words.....

Reading between the lines here (Sorry I'm a novice, trying to read up and be as well informed on this one, when parting with large sums of cash).... are you saying that having a lever/isolation valve in that position at all is a big no no? Could you be a little more verbose for a newbie? Thanks

Razor900 · 15 Feb 2021

The expansion vessel is there to allow the water in the cylinder to expand when its heated without causing the pressure in the system to go up.

If that lever valve is shut you can see it will be isolated from the cylinder and you will have to rely on the TPRV valve in the side of the cylinder to prevent bad things happening

Razor900 · 15 Feb 2021

My apologies I'm posting a little tongue in cheek. It's been a very long day but that looks like a very dangerous mistake to me and is something to take seriously

NoRulesRules · 15 Feb 2021

Ok understood. If we leave the lever valve problem to one side for a second (I know its hard too, considering the safety implications), in terms of the other bits, are my concerns valid in terms of current vessel connection point (I.e. on the balanced cold, as opposed to after combination valve).

I'm worried that the combination valve has a check valve inside of it, if that's placed between the balanced cold out, and the cylinder, then that would be in effect making the vessel useless with its current piping. (Come back to original point, about normally seeing diagrams with the vessel T'ed off after the combination valve).

Probably going to push back regardless - kind of concerned for overall system now - what else is wrong if simple mistakes like the lever are being made? Unsure how best to proceed, get it checked by another G3 after install and prior to payment?

Thanks

ScottishGasMan · 15 Feb 2021

The expansion vessels in the wrong position anyway, the balanced cold out almost always has the check valve after it built into the valve assembly so pressure increase in the cylinder wont be absorbed by vessel, it would need to be pipes to the cold inlet to the cylinder.

NoRulesRules · 15 Feb 2021

ScottishGasMan said:
The expansion vessels in the wrong position anyway, the balanced cold out almost always has the check valve after it built into the valve assembly so pressure increase in the cylinder wont be absorbed by vessel, it would need to be pipes to the cold inlet to the cylinder.

Thanks, yes inline with my thinking in the edit above.

If it takes a complete novice like myself to almost work that out with 30mins of googling, and a G3 installer has made two fundamental critical safety errors, then I'm a little shocked. How would you proceed? Should I phone the company and ask for another engineer, or call building control at the council?

Trying to be pragmatic, considering our heating system is currently in bits and have sprogs at home. So one way or another, it needs sorting semi quickly

Gasguru · 15 Feb 2021

Slightly confused as you say unvented but then mention thermal store (that doesn't require the safety valves)...what's the cylinder model?
Very poor install..are you sure he's G3 and it's in his name? Check with the organisation he's got it through.
Absolutely no reason not to have the combination valve above the cylinder and best practice to do so.
Vessel incorrectly plumbed in and will do nothing as the non return valve normally sits just upstream of the expansion safety valve.
There's a plastic blanking plug that can be removed to connect the vessel.
Must not have that iso valve on the cylinder inlet. Hot taps should be blended down at the point of use.
Hate to think what a mess he'll make of the TPR and Exp valve pipework.

ScottishGasMan · 15 Feb 2021

If it needs sorting semi quickly then avoid the bulding control/council.

Do you know for a fact the guy working in the house is a G3 register installer? Not that it matters much as its a one day tickbox course like all the rest of them, you cant fail it. But id be inclined to call the company state your concerns and ask for a senior engineer/manager to attend or otherwise invite them to come back and take the cylinder away (assuming they supplied it) shoudlnt take long for them to sort it out. See it all the time unfortunetly.

Gasguru · 15 Feb 2021

And make sure the tyre valve on top of the vessel is accessible for checking/inflating the vessel each year..

NoRulesRules · 15 Feb 2021

Gasguru said:
Slightly confused as you say unvented but then mention thermal store (that doesn't require the safety valves)...what's the cylinder model?
Very poor install..are you sure he's G3 and it's in his name? Check with the organisation he's got it through.
Absolutely no reason not to have the combination valve above the cylinder and best practice to do so.
Vessel incorrectly plumbed in and will do nothing as the non return valve normally sits just upstream of the expansion safety valve.
There's a plastic blanking plug that can be removed to connect the vessel.
Must not have that iso valve on the cylinder inlet. Hot taps should be blended down at the point of use.
Hate to think what a mess he'll make of the TPR and Exp valve pipework.

Thanks, just going to try and unpack your reply, I'm a little slow / playing catch up

0) Sorry I probably used "thermal store" term incorrectly, its just a regular unvented cylinder with solar coil. As part of the work also includes solar thermal panels on roof.
1) I was told G3 when I got the quote etc, I specifically asked, I've not seen the card. It would feel awkward to ask, but will do tomorrow now this has happened.
2) Thanks for confirmation on valve height
3) Thanks for confirmation on Vessel plumbing being incorrect
4) The plastic blanking plug, apparently on this model of combination valve cannot be removed. I'll try and dig out the spec I found
5) Noted regarding iso/lever valve fault
6) "hot taps should be blended down at point of use" >> are you saying that there is no need for this blend valve, and normal mixer taps are fine?
7) Yes agree, there is more to come. There is also solar thermal as per (0) which has more opportunities for cockups

NoRulesRules · 15 Feb 2021

ScottishGasMan said:
If it needs sorting semi quickly then avoid the bulding control/council.

Do you know for a fact the guy working in the house is a G3 register installer? Not that it matters much as its a one day tickbox course like all the rest of them, you cant fail it. But id be inclined to call the company state your concerns and ask for a senior engineer/manager to attend or otherwise invite them to come back and take the cylinder away (assuming they supplied it) shoudlnt take long for them to sort it out. See it all the time unfortunetly.

As per above, on reflection I dont know for a fact, I took it on their word that the installers were G3. Will attempt to confirm tomorrow. Will escalate the issue tomorrow, in parallel with trying to sort in the ground. Not sure how asking them to take the cylinder away would help, reinstalling our old system is impossible now, pipes all cut, and they've even taken the old cylinder away! Not to mention they've installed a new boiler too

Gasguru said:
And make sure the tyre valve on top of the vessel is accessible for checking/inflating the vessel each year..

Thanks for the headsup, did not realise that was even a thing, I just checked and there is about 6" about the vessel, and I can twist the valve (awkwardly) with my hand.

Brilliant forum, you dont know what you dont know!

NoRulesRules · 15 Feb 2021

PS. Almost wished we just went for a combi now, simple life! Ho hum, I'm sure it will get sorted one way or another.

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Unvented/G3 ongoing install sanity check

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