Help with unvented cylinders central heating

[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 🙂

 

[Old Account]

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

Thanks shauni, but let me tell you everyone of us, will learn the whole life.

But do t take it wrong as you always do. 😉

 

[tolly]

Nothing wrong with a lever valve on hot outlet at all. Some people will do this where they have a balanced cold coming off a the combination valve so your not turning the hot and cold off together all the time when using the lever valve before the combination valve.

 

[Chalked]

When installing unvented I fit a lever valve on the inlet to combi valve. This enables easy servicing. I then fit one to the balanced cold AND the hot outlet. This enables you to isolate just the hot, or cold for maintenance.

The big mistake I see very regularly, is a valve on the cold feed to the cylinder! Between the combi valve and cyl. This wil cut out the expansion vessel and expansion relief in one go.

 

[1Steven]

Just come across prv after the tundish!

 

[ShaunCorbs]

Do many people fit hotun?

 

[Chalked]

Iv fitted a few hot tuns. They do get around difficult vent runs

 

[ShaunCorbs]

Iv fitted a few hot tuns. They do get around difficult vent runs

Problem is now they can't take the flow, they spill out when blowing off

Twitter

 

[Harvest Fields]

That's bad 😱. Has anyone had a response from hotun? If so what did they say?

 

[Chalked]

You can get a cover

 

[ShaunCorbs]

You can get a cover

Still spills out of it

 

[ShaunCorbs]

That's bad 😱. Has anyone had a response from hotun? If so what did they say?

Yep only tested to 18lpm

 

[Chalked]

Tbh. Something massively wrong if one of the relief valves are passing that amount. I bet the standard ones can't take that either.

 

[ShaunCorbs]

Tbh. Something massively wrong if one of the relief valves are passing that amount. I bet the standard ones can't take that either.

Just fully open and stnd tun should be fine

 

[Adam Perry]

Done my unvented in the end so all qualed now however, before my course i rang gas safe who can advise on building reg G3 who said that as long as your not installing an unvented cylinder, then it is completly fine to work on it and change components!!! This is how companies get around it......although the instrucror on the course said they are talking Rubbish!!! Very grey! Non the less i have the qual now

 

[ShaunCorbs]

Your tutor is correct

If gas safes logic transfers that means you can repair gas appliance eg boilers without needing to be qualified