Help with unvented cylinders central heating

[Adam Perry]

simple question but answer not easy to find......

I do not have the unvented qual but what are you actually allowed to work on without the qual. My company thinks that anything apart from the vessel and prv on the vessel cannot be touched but everything else is ok???

 

[Harvest Fields]

I do have the qualification and the reason I have the qualification is I had the same problem. (It baffles me no end) my understanding is that. You cannot work on anything to do with the cylinder/vessel/Controls or safety devices. Can anybody else add anything that should not be touched by someone that does not have unvented?

 

[snowhead]

Sad to say , again, the O.P's company is incorrect.

In my view only the mains cold into the unit and the hot flow out of the unit can be touched by non qualified.

The unvented unit includes;
Multiblock (or Pressure reg, pressure relief, non return assembly) including discharge piping.
Cylinder including Overtemp safety control and wiring, immersion heater, control stat, 2 port valve.
Cylinder pressure relief, including discharge piping.
Expansion vessel and any pipework leading to it if remote.

If any or all of the the above are interfered with then you need the competency to say that the Unvented system as a whole is safe.

 

[king of pipes]

As above anything that comes as a packaged unit or pre plumbed with the cylinder cannot be touched ,only thing you can work on is hot out and cold main before the isolation valve to the combination valve everything after that no cheers kop

 

[Adam Perry]

Cheers all

 

[Best]

Safety devices are -
Cylinder Thermostat,
Cylinder 2 port valve,
Immersion stat and immersion overheat cut off,
Temperature and Pressure relief valve,
Pressure relief,
Discharge pipework.
(All the above are critical safety parts)

Other important parts are -
Pressure Reducing valve (Combination valve),
Expansion vessel, or air gap on some.

Danger with unvented is overheat and obviously anything linked to that or the discharge are critical.
So answer is, nothing you can work on if not G3 qualified

 

[ShaunCorbs]

TBH normal gravity cylinders / hot water systems come under the umbrella of G3 these days

 

[Old Account]

How often you see people installing a lever valve on top of the hot outlet.

You can tell straight away who Installed the cylinder. It's very dangerous as it could act like a bomb.

 

[ShaunCorbs]

How often you see people installing a lever valve on top of the hot outlet.

You can tell straight away who Installed the cylinder. It's very dangerous as it could act like a bomb.

Think about your statement it can't be a bomb and it's ok to do

 

[Old Account]

What's the point of installing a lever on hot outlet if you can turn the mains off ? Trust me it can act like a bomb, I went on German courses where we had discussed this subject. I have seen twice an cylinder explosion and 3/4 of the house were gone. But if you know better that's fine with me.

 

[ShaunCorbs]

What's the point of installing a lever on hot outlet if you can turn the mains off ? Trust me it can act like a bomb, I went on German courses where we had discussed this subject. I have seen twice an cylinder explosion and 3/4 of the house were gone. But if you know better that's fine with me.

You sure your not thinking of a gravity cylinder that has a vent

Unvented have 2 safety valves and an expansion vessel so unless both of these fail at the same time no bomb

 

[moonlight]

How often you see people installing a lever valve on top of the hot outlet.

You can tell straight away who Installed the cylinder. It's very dangerous as it could act like a bomb.

I had to remove one of these last month the whole system etc was installed by someone who was supposed to be qualified or so he told the customer. Not only was that a problem but he had 5 returns into the primary. Good one for me though. Two days putting it all right and finishing his job off.

 

[Best]

How often you see people installing a lever valve on top of the hot outlet.

You can tell straight away who Installed the cylinder. It's very dangerous as it could act like a bomb.

Hi Matchless, hope all well with you? Sorry I can't contact you directly as my pm has been removed on this forum.
On the issue of putting a lever valve on the hot outlet, that would be fine on an unvented cylinder, as outlet is closed when taps are closed anyhow, although pipework volume would be larger obviously when valve open or not installed. The wrong place is if the pressure relief valve and/or any expansion vessel serving the unvented unit is isolated with a valve.
Unvented units just need their expansion, pressure relief, and T&P valve to be unimpeded.
Think of it this way, - You could install an unvented unit that has nothing else but one tap to supply just a metre of pipe away from hot outlet of unit. Nothing wrong with that at all, because the unit still has its expansion and safety valves etc.
Although a valve on the unvented hot outlet seems pointless because a valve fitted to the mains would do same job, however I can think of times where it would be handy for myself.
The test to exploding unvented cylinders on Mythbusters is done by capping off the cylinders outlets, yes, - but it is the relief valve they also capped, together with over pressurising and heating the unit that caused the danger and inevitable explosion.
Installing a valve on a vented cylinder vent pipe would definitely be crazy.

 

[Old Account]

Hi Matchless, hope all well with you? Sorry I can't contact you directly as my pm has been removed on this forum.
On the issue of putting a lever valve on the hot outlet, that would be fine on an unvented cylinder, as outlet is closed when taps are closed anyhow, although pipework volume would be larger obviously when valve open or not installed. The wrong place is if the pressure relief valve and/or any expansion vessel serving the unvented unit is isolated with a valve.
Unvented units just need their expansion, pressure relief, and T&P valve to be unimpeded.
Think of it this way, - You could install an unvented unit that has nothing else but one tap to supply just a metre of pipe away from hot outlet of unit. Nothing wrong with that at all, because the unit still has its expansion and safety valves etc.
Although a valve on the unvented hot outlet seems pointless because a valve fitted to the mains would do same job, however I can think of times where it would be handy for myself.
The test to exploding unvented cylinders on Mythbusters is done by capping off the cylinders outlets, yes, - but it is the relief valve they also capped, together with over pressurising and heating the unit that caused the danger and inevitable explosion.
Installing a valve on a vented cylinder vent pipe would definitely be crazy.

Wow, :,(

Another one good lad got banned to write pm's ... I don't get that why all ppl get banned ... something isn't quite right ."

However, Gary thanks for the explanation and I agree to what you said. I do get the safety valves but trust me I have seen a lot of installation where ppl cap the t&p off and having no expansion vessel installed. I just don't think the lever on a hot outlet is necessary unless you have got an issue with the stopcock I believe that happens also very often hahah ... but I am not wrong with explosion as you know you find a lot of weird installations.

Same as shauni said stopvalves on vent pipes or leaving it capped off .... I've seen it few times though.

However, I am very disappointed that you also got banned for pms :.( you are a very very important person here on that forum and I definitely disagree banning you from PM people.

 

[Best]

Wow, :,(

Another one good lad got banned to write pm's . I don't get that why all ppl get banned . something isn't quite right ."
.......
........
However, I am very disappointed that you also got banned for pms :.( you are a very very important person here on that forum and I definitely disagree banning you from PM people.

Thanks Ron. Note that I think no pms can be sent or received by me. Also I can't begin a new thread.

 

[Old Account]

Thanks Ron. Note that I think no pms can be sent or received by me. Also I can't begin a new thread.

I don't undersTand that seriously, it would be great if anyone could let us knows what's the issue over here @Lou @Dan
I'd be very interested what the reason behind this all is.

It's such a shame and hoping to stay in contact with you Gary

 

[Lou]

I don't know forum politics I'll ask Dan for you guys

 

[Adam Perry]

Who would put a lever valve on the hot on a unvented cylinder??? I have not or ever had the qual but that is the most craziest thing ive ever read!!!! Thanks for the comments though fellas means alot. Ill show it to management and politely say Damn off to fitting components to unvented cylinders without the qual. Thanks again

 

[Best]

Who would put a lever valve on the hot on a unvented cylinder??? I have not or ever had the qual but that is the most craziest thing ive ever read!!!! Thanks for the comments though fellas means alot. Ill show it to management and politely say **** off to fitting components to unvented cylinders without the qual. Thanks again

You are not understanding my point about if a valve is fitted on the hot outlet pipe of an unvented cylinder. The unvented cylinder does not require that pipe to be needed for anything at all. In fact you could install an unvented cylinder and just bleed the air out of it to fill it with water and then never take hot supply to any outlets, and it would still operate perfectly well and safe. (Wouldn't be much use, but will not explode. )
On the subject of G3 qualification, - it can cost approx £200 and does 5 years before needed a refresher exam. Well worth your firm paying it for you

 

[chris watkins]

I specialise in unvented systems both teaching the Part G course & installing/designing them. I often install an isolation valve on the hot outlet from the cylinder, as a lot of the composite cold water valve sets have a balanced cold water port & the expansion relief safety valve built in this means that you can't fit any isolation after it on the cold feed. If I want to have separate isolation of both the hot & the cold then you need to install one on the balanced cold & the hot outlet.
As Best states there is nothing wrong in that at all.

 

[chris watkins]

Just as a point of interest Part G3 is not just concerned with un-vented systems, in my humble opinion if you work on any hot water system, be it vented or unvented, you should hold the this competence, all new installed systems are required to be Notified to BCB as stated below, of course without any enforcement or policing every one just ignores the fact which is why we have so many incorrectly installed systems.

Notice of completion of commissioning
3.77 The Building Regulations (regulation 20C(2)) and the Building (Approved Inspectors etc.) Regulations (regulation 20(1) and (6)) require that the person carrying out the work shall give a notice to the relevant BCB that commissioning has been carried out according to a procedure approved by the Secretary of State, unless testing and adjustment is not possible, or would not affect the energy efficiency of the fixed building service.
3.78 Where the work is carried out in accordance with a building notice, or full plans, or an initial notice or amendment notice, the notice of commissioning should be given not more than 5 days after the completion of the commissioning work. In other cases, for example where work is carried out by a person registered with a competent person scheme, it must be given not more than 30 days after the completion of work.

 

[1Steven]

I would not put an isolation valve after the outlet, it maybe ok when new but if the expansion vessel should fail or the air gap is not right you have a potential problem. Have had my unvented cert. Since 1991.

 

[Best]

I would not put an isolation valve after the outlet, it maybe ok when new but if the expansion vessel should fail or the air gap is not right you have a potential problem. Have had my unvented cert. Since 1991.

What is the difference between an unvented unit with the hot outlet pipe with an open path to the closed outlets, or with an isolating valve, which is then turned off?
Only difference is the pipe outlet will have more volume of water to expand a little to. That won't add any safety
With a valve on hot outlet turned off, then cylinder pressure will be regulated with combination valve and have the pressure relief valve plus the T&P relief valve as safety, should the expansion vessel have failed.
As I earlier posted, what would you do if you had to install an unvented unit where its sole outlet was a shower valve one metre away from unit?

 

[Stigster]

On an Unvented system there is no difference between putting an isolating valve on the hot outlet and having a closed tap on the end of the hot distribution pipe. People seem to get confused about this issue where it would indeed be a dangerous thing to do on an open vented system as you could isolate the vent pipe from the cylinder. This can cause an explosion if the thermostat fails.

Unvented systems, as I said, no different to having a closed tap on the end of the distribution pipe. No safety devices are bypassed or disabled by doing this.

 

[ShaunCorbs]

Thnx Ron, shows you have a lot of learning ahead of you