Safety zone valve to cylinder

[snowhead]

? Do I just choc block it and make safe
thanks feebs73

Yes you only need L,N,E for the safety valve

 

[chris murphy]

Hi Chris
This is my fault, yes there are two jobs that i am talking about
1, is the standard s plan with the extra zone valve (on the hw) fitted to the cylinder, ( so called safety valve) this one is causing the debate.
2, this is another job I have to wire up this is a s plan plus,3 storey house, ground floor is UFH 1st floor has a separate zone valve and stat , 2nd floor has a separate zone valve and stat,

The confusion is I was asking, as they are both s plans pressurised systems, I was woundering why job 2 has not got 2 zone valve attached to the cylinder just the 1, when I asked the plumber he said no you only fit them on a mid position valve Y plan. He than showed me the ( forgive me but It looks like a over flow witch had 2x15mm pipe into 2inch plastic waste pipe) and said that deals with any excess pressure.

I was asking for help as I have never come across this extra zone valve on the hw system (safety valve) before if it is such an important part of the install why cant I find it on any wiring diagram? I would of thought it would of been easy to find it. Even the diagram you posted didn't have the extra have it on there.

I started the other thread to see if I could catch anyone's attention, sorry for the confusion.

I hope this clears things up a bit

I would like to thank everyone personally that is taking time to read these threads and replying to me

Thanks once again all the advise is much appreciated, feebs73

"Hello again feebs 73",


Where You seem to be getting confused here is that there are Not TWO 2 Port Zone Valves required on this Unvented Hot Water CYLINDER - Just ONE which is wired to the COMBINED Hot Water Thermostat AND Thermal Protection / `High Limit Thermostat to provide the Thermal Protection of the Unvented Hot Water Cylinder.

This is usually supplied by the Unvented Hot Water Cylinder Manufacturer and is shown in the Installation Instructions for both the Pipework configuration AND the Wiring Instructions / Diagram.

That Cylinder Zone Valve `becomes` the `Cylinder Thermal Safety Valve` if the High Limit Thermostat has to operate and interrupt the POWER to the Zone Valve which will then CLOSE via the spring return - stopping further Heat circulating around the Cylinder Heating Coil and preventing Overheating and possible Over-Pressurisation of the Unvented Hot Water Cylinder IF the Temperature and Pressure Relief Valve were to malfunction in the CLOSED position.


I also wanted to reply to You again regarding a comment from your post:


QUOTE:


I was asking for help as I have never come across this extra zone valve on the hw system (safety valve) before if it is such an important part of the install why cant I find it on any wiring diagram? I would of thought it would of been easy to find it. Even the diagram you posted didn't have the extra have it on there.


END QUOTE


The FIRST Wiring Diagram that I posted for You was for a Heatrae Sadia Megaflow UNVENTED HOT WATER CYLINDER.

On THAT wiring Diagram the WIRING was shown for the Unvented Hot Water Cylinder Thermostat AND `Thermal Protection` / `High Limit` Thermostat TO the Zone Valve for the Unvented Hot Water Cylinder.


I posted that to show You the `Safety / Thermal Protection` WIRING / Zone Valve for the Unvented Hot Water Cylinder.


It is THAT WIRING that turns the Unvented Hot Water Cylinder`s Zone Valve into a `Safety Zone Valve` IF the `High Limit` Thermostat Operates - by interrupting the Power to the Zone Valve and allowing it to CLOSE via the spring return operation.


You are NOT the only person who seems to have either NOT Understood My explanations OR not read them fully as I can see from some other Members Posts - one of which has duplicated exactly what I was trying to explain although in a much shorter version.

IF they HAD seen / understood what I had written I would be wondering why they would write the same information in a post - especially when they did NOT seem to be agreeing with Me / confirming that what I had written was correct - ?


I hope that You can now work out what the requirements are for the `Thermal Protection` aspect of an Unvented Hot Water Cylinder.

As I have written such a LOT in My messages to You could You please let Me know the Manufacturer and Model of the Unvented Hot Water Cylinder that We have been corresponding about - Thanks.


Regards,


Chris

 

[chris murphy]

On an unvented installation there must be a 2 port valve, spring assisted fail to closed position, (not motored closed) wired via the cylinder overtemp stat to prevent over heating of the cylinder.

The manufacturer has to provide this as part of the kit supplied with the cylinder, the manufacturers instructions will say a 2 port valve must be fitted.

The confusion arises when the cylinder is piped up.

If the heating system already has a 2 port valve on the flow to the cylinder, as long as this is wired via the overtemp stat on the cylinder and is spring closed, it will comply. 2nd 2 port valve is not required.

If it has a 3 port (mid position) valve there must be a 2 port fitted as well because the 3port can fail open.

Plumbers /heating engineers will sometimes not look at the whole picture and just see that a 2 port has to be fitted close to the cylinder.

Tried to make this a simple explanation, but it won't work.

"Hello snowhead",


From what You wrote I take it that You did not read My explanations to the OP / feebs 73 about the Thermal Protection / Zone Valve Wiring for an Unvented Hot Water Cylinder - as I had fully explained all that you wrote and I notice that your post was not worded as `in agreement` with what I wrote.

If You had read what I wrote and were posting a `simpler explanation` I would of course understand - But You seem to have written your reply as if I had NOT already explained what you wrote ?


I don`t want to cause an argument here but I wanted to ask You about this comment:


QUOTE:


Plumbers /heating engineers will sometimes not look at the whole picture and just see that a 2 port has to be fitted close to the cylinder.


END QUOTE


I am hoping that You might mean that in the absense of Electrical / Electrical Testing Qualifications and experience a Heating Engineer / Plumber who was just looking at an existing Unvented Hot Water Cylinder might not know whether the WIRING for the Thermal Protection was done correctly - ?


Heating Engineers or Plumbers who `Hold` / `Have attained` ACS Assessment / Certification [& `Unvented Licence Card`] in `Unvented Hot Water Systems` are the ONLY persons who can LEGALLY Install OR `Work On` Unvented Hot Water Cylinders.


That is required by `Part G3` of the Building Regulations - `Hot Water Safety and Water Efficiency` - and as You know these are `Legally Binding` Regulations.

This is a Mandatory requirement for Unvented Hot Water Systems - it is NOT like some other parts of the Building Regulations where Operatives can carry out Works and then Notify them to the Local Authority Building Control Department as either `One Off` projects or as part of a Building Project for LABC Inspection / Certification.



The Electrical Wiring of the Zone Valve and Thermostatic / Thermal Protection for the Unvented Hot Water Cylinder must then be carried out by a Qualified Electrician / `Competent Person` in order to comply with the Building Regulations G3 for Unvented Hot Water Systems.

IF You are implying in your comment that these Heating Engineers /Plumbers are somehow `confused` on the Requirements / Design and Operation of the Thermal Protection for Unvented Hot Water Cylinders that could easily be viewed as Insulting by Professional Heating Engineers like Me.

IF I misunderstood your comment I Apologise - but it did seem that You were suggesting that regarding the Thermal Protection of an Unvented Hot Water Cylinder `Plumbers and Heating Engineers` don`t know exactly what to do regarding the installation of the required Zone Valve .

We would obviously be writing about `Professional` Heating Engineers and Plumbers - NOT the `Cowboys` and I would hope that ALL of the Professional Heating Engineers and Plumbers would KNOW about the Thermal Protection required for an Unvented Hot Water Cylinder.

And that ONLY those who were Registered and Certified for `Unvented Hot Water Systems` would be Installing or Working On Unvented Hot Water Cylinders - obviously I know that it would be very naive to think that this was the case.

When the OP / feebs 73 asked about the Unvented Hot Water Cylinder Zone Valve in this thread there was NOT exactly a `rush` from Electricians / Members to help Him.

I had thought that this was because Members were awaiting further descriptions of the circumstances and that is when I started to Post replies to the OP / feebs 73.

I am sure that the details that I posted were completely correct - except for the confusion about the Underfloor Heating [now found to NOT be part of that Heating and Hot Water System].

I would have thought that what I wrote would have helped the OP / feebs 73 [?] - But I would admit that the Posts were probably be viewed as far too LONG and might have been `off putting` to wade through.

I had hoped that My descriptions of what was required would prompt a detailed description in `Electrical Terminology` for feebs 73 by an Electrician Member.


Regards,

Chris - Heating Engineer and Registered /Certified for
`Unvented Hot Water Systems`