help!!
I am working with a made plumber, he has installed a S PLAN SYSTEM, but with a diverter valve ( witch is a two port eebszone valve ) near the cylinder. so in total there are 3 zone valves apparently this gets wired to the cylinder stat???
cant find any wiring diagrams to follow, they all say two zone valves not 3?
many thanks
feebs73
"Hello feebs73",
Please don`t be offended by the `Tone` of this message - I am trying to prevent You getting into a VERY Serious situation.
Please be VERY Careful what You do regarding wiring this Heating and Hot Water System !
IF this Third Zone Valve is installed on the Primary Heating Pipework [Flow and Return] to an
Unvented Hot Water Cylinder the following applies:
The additional Zone Valve is part of the
`EMERGENCY CUT OFF` Process for an Unvented Hot Water Cylinder it operates in the event of the Cylinder becoming Overheated to prevent Over-pressurisation and possible `Exploding` of the Cylinder IF the Pressure Relief Valve was Faulty.
The Unvented Hot Water Cylinder`s `Safety Zone Valve`is controlled by the EMERGENCY `High Limit Thermostat` on the Unvented Hot Water Cylinder
ONLY -
Nothing at all to do with the Heating System Controls.
I am a Heating Engineer - But I would not be prepared to advise You on wiring the Zone Valve on this Forum even if I was Electrically Qualified - as it is VITAL that this is done correctly -
as will be shown in the Unvented Hot Water Cylinder Installation Instructions.
The Instructions for the Unvented Hot Water Cylinder MUST be followed `to the letter` for wiring the Unvented Cylinder`s Safety Zone Valve.
THIS IS A VERY SERIOUS MATTER - THESE UNVENTED HOT WATER CYLINDERS CAN BECOME `BOMBS` OF RAPIDLY EXPANDING STEAM IF THEY RUPTURE BECAUSE OF BECOMING OVER-PRESSURISED DUE TO OVERHEATING !
IF AN UNVENTED HOT WATER CYLINDER WERE TO OVERHEAT TO ABOVE BOILING POINT [POSSIBLE BECAUSE AT HIGHER PRESSURE THAN ATMOSPHERIC PRESSURE] AND THEN RUPTURE BECAUSE OF THE VAST INCREASE IN PRESSURE THAT COULD OCCUR [IF THE PRESSURE RELIEF VALVE FAILED TO OPERATE] THE RESULT WOULD BE THAT THE WATER WOULD INSTANTLY TURN TO STEAM AND `EXPLODE` / EXPAND RAPIDLY TO 1600 TIMES THE CYLINDER VOLUME !
THIS HAS OCCURRED IN THE PAST DUE TO THE `SAFETY CONTROLS` EITHER NOT BEING FITTED - OR NOT BEING WIRED CORRECTLY - OR A COMBINATION OF BOTH.
Unvented Hot Water Cylinders have at least TWO forms of `Emergency Controls` - these are a Pressure Relief Valve AND an Overheat Protection System - an High Limit Thermostat controlling a `Safety Zone Valve` to prevent Overheating of the Hot Water and Over-pressurisation of the Unvented Cylinder.
If an Immersion Heater is fitted these MUST have a `High Limit` `Cut Off` Thermostat - for the same reason as above - and should be supplied by the Manufacturer of the Unvented Hot Water Cylinder.
I should mention that the Plumber who has installed this System / the Unvented Hot Water Cylinder should be Registered - Trained and Assessed for `Unvented Hot Water Systems` - otherwise He should NOT be Installing them - this is a requirement of the Building Regulations.
If He is `Trained - Assessed and Registered` - He should certainly have been able to let You know that this `Zone Valve` / `Safety Zone Valve` was ONLY to be operated by the Unvented Hot Water Cylinder `High Limit Thermostat` !
And He should have been able to let You read the Installation Instructions regarding the Electrical wiring of the `Overheat Safety Zone Valve` - it would definitely be shown.
Just as a matter of interest could You let Us know what You mean by a `made Plumber` ?
I hope that this is helpful to You and other Members - as I mentioned Please don`t be offended by the tone of My message - I am NOT trying to be pedantic - but this is a VERY serious issue IF the wiring of the `Safety Zone Valve` is not done correctly.
Regards,
Chris - Heating Engineer and Registered Gas Engineer [Plus Registered for Unvented Hot Water Systems].
