Unvented/G3 ongoing install sanity check

NoRulesRules · 18 Feb 2021

Hi thanks for all the advice. Current state below, I've tried to pull together a diagram to 1) understand whats going on, and 2) make it easier for you fine folks to follow the pics. How are we looking now? (Ignoring how we got here!)

Based on my armchair expert googling I cannot spot any errors, but I'm sure you can

Click the diagram to view full size

ianmcd · 18 Feb 2021

Is the HW zone valve wired via an over heat cut out at the cylinder ?

NoRulesRules · 18 Feb 2021

ianmcd said:
Is the HW zone valve wired via an over heat cut out at the cylinder ?

Assuming you mean the 2-port honeywell valve that is between the boiler flow and cylinder right?

This has a wire coming out of it, that goes in to a 10-way wiring box on the floor. I assume, rightly or wrongly, that this valve is therefore controlled via the Thermostat that lives in the cylinder that is currently set at 65c. The thermostat, according to the supplied docs, is a dual unit for "control and energy cut out".

Mottie · 18 Feb 2021

May be a silly question but why does that 22mm pipe going up through the ceiling have a 15mm restriction valve inline? Surely that defeats the object of using a 22mm pipe?

NoRulesRules · 18 Feb 2021

Mottie said:
May be a silly question but why does that 22mm pipe going up through the ceiling have a 15mm restriction valve inline? Surely that defeats the object of using a 22mm pipe?

Because that pipe is the balanced cold to the mixer shower, and originally did not have an isolation valve. I asked them to fit one, in case the shower has issues with new pressure (the hot has an isolator). They cheaped out and fitted a 15mm that they had, rather than buying a 22mm. It goes to 15mm in the loft anyway via plastic.

I'm glad that's the only thing that is jumping out to you

ianmcd · 18 Feb 2021

NoRulesRules said:
Assuming you mean the 2-port honeywell valve that is between the boiler flow and cylinder right?

This has a wire coming out of it, that goes in to a 10-way wiring box on the floor. I assume, rightly or wrongly, that this valve is therefore controlled via the Thermostat that lives in the cylinder that is currently set at 65c. The thermostat, according to the supplied docs, is a dual unit for "control and energy cut out".

yes that is the way it has to be wired, so if the thermostat fails the OH will cut the power to the valve and remove the heat source to the cylinder

Gasguru · 18 Feb 2021

Sorry to p1ss on the parade again but theres still issues...
Can the T&P relief valve be accessed for replacement...it's stuck round the back of the cylinder by the look of it.
The heating zone valve needs swinging round...how are you supposed to replace the head or motor in that position? And it looks like they shoved a 28mm valve on as they didn't have a 22mm.
What's that stoopid 15mm vent pipe doing...asking to get snagged. 150mm of 22mm and a coupling to a manual rad vent would be so much better.
15mm service valve...been mentioned before.
What's the white thing near the bypass valve?
Is there sufficient clearance for the immersion heater to be replaced?
None of it's been installed for quick and easy maintainence...a few compression joints here and there, a couple of glycerine gauges make all the difference.

Razor900 · 18 Feb 2021

The question is has it been installed to the regs not is this the best install ever!

It looks much much better now. Can't see anything that contravenes regs

Don't forget they will need to properly lag the pipes when they are finished to comply

NoRulesRules · 18 Feb 2021

Gasguru said:
Sorry to p1ss on the parade again but theres still issues...
Can the T&P relief valve be accessed for replacement...it's stuck round the back of the cylinder by the look of it.
The heating zone valve needs swinging round...how are you supposed to replace the head or motor in that position? And it looks like they shoved a 28mm valve on as they didn't have a 22mm.
What's that stoopid 15mm vent pipe doing...asking to get snagged. 150mm of 22mm and a coupling to a manual rad vent would be so much better.
15mm service valve...been mentioned before.
What's the white thing near the bypass valve?
Is there sufficient clearance for the immersion heater to be replaced?
None of it's been installed for quick and easy maintainence...a few compression joints here and there, a couple of glycerine gauges make all the difference.

Thanks for the attention to detail, on some level I want you to pick this apart, reason for posting etc...

Context would be that this won't be the most service friendly of installs, as its shoe horned in to an airing cupbaord. I wanted it in the garage, but the special lagged solar flow/return could not get there due to building config.

- T&P valve can be accessed, not easily
- Heating 2 port valve, yes I see what you mean about access. Yes its 28mm, good spot, no idea why, those are the 2 honeywell valves that shipped with the cylinder. Is this a big issue or not?
- The 15mm vent pipe, are you referring to the automatic air vent? I've got no idea, why is manual better, why is 22m needed for vent?
- White thing near bypass is Hive reciever
- Immersion heater will come out
- I would have liked glycerine gauges too, I probably should have requested, doh

Razor900 said:
The question is has it been installed to the regs not is this the best install ever!

It looks much much better now. Can't see anything that contravenes regs

Don't forget they will need to properly lag the pipes when they are finished to comply

Install being finished off tomorrow, lagging etc, cheers for help so far

Gasguru · 18 Feb 2021

Airing cupboards get stuffed with crap and I've seen so many long 15mm vent pipes kinked over...22mm can take abuse.
You should avoid any electrical gear on the floor in case of water ingress during maintenance or a leaking auto air vent.
AAVs often leak so screw it shut and release any trapped air from time to time.
Will that Hive receiver work given the proximity to metalwork...certainly is bad practice to install where is, whats the manual say?
Hope you give this lot a crap review...

NoRulesRules · 20 Feb 2021

Doing final snagging and noticed the unvented PRV/TPRV > tundish > drain looks incorrect. It's got the right drop on the D2, but after that its just plumbed in to bathroom waste under bath, and shared with bath, standard pipe. It seems this breaks regs in 3 ways;

- cannot share waste with another outlet
- needs special Hepvo trap thing
- needs to go in to soil pipe

- or scrap the above 3 and take it straight under bath in copper and to outside wall

I'm right to press and ensure this is fixed right?

The risk here I assume is 90c discharge water going in to existing waste pipe and melting through to kitchen below?

sxturbo · 20 Feb 2021

Would it be 90 degrees or 60 degrees?

I would have thought the prv is for the hot water, not the boiler circuit as the boiler has its own prv, or am I wrong?

TimboTwo · 20 Feb 2021

sxturbo said:
Would it be 90 degrees or 60 degrees?

I would have thought the prv is for the hot water, not the boiler circuit as the boiler has its own prv, or am I wrong?

Potentially boiling/steam, could easily be 120 degrees .

TimboTwo · 20 Feb 2021

As gasguru said in post 10, that plastic plug in the combi valve is where the expansion vessel connects.
Get it changed straight away before it goes boom!

NoRulesRules · 21 Feb 2021

TimboTwo said:
As gasguru said in post 10, that plastic plug in the combi valve is where the expansion vessel connects.
Get it changed straight away before it goes boom!

Thanks for the response and if you read the follow-up posts you will see that on this particular model of inlet combination valve, the plastic plug is not removable. You will also see in later posts with updated pics, that the vessel has not being repiped in the correct position after the combination valve.

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Unvented/G3 ongoing install sanity check

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