I am a spark and have inherited a central heating system I can't fathom. It has a Greenstar 30 CDi boiler and 2 motorised valves - CH and DHW - there is a Centrestore unvented mains pressure waterheater cylinder and a Heatmiser wireless receiver room stat any advice on wiring this system would be greatly appreciated. can any sparks out there help.
central heating
- Thread starter doakster
- Start date
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You have an S Plan system.Go to Honeywells web site and you can see the standard diagram for that system.
Its a bit more complicated as its an unvented which should have its two port valve wired in series with the over heat stat on the cylinder.
Technically anyone working on an unvented cylinder and its controls should be qualified in accordance with G3.
Tony
Technically anyone working on an unvented cylinder and its controls should be qualified in accordance with G3.
Tony
Normal s plan system would be ok but this boiler has a volt free cylinder stat connection and no live return to open DHW zone valve the CH side seems straight forward - feed out to room stat return to boiler and live return from boiler to zone valve - its the DHW that seems complex
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normal s plan would be ok but this boiler has a volt free connection for cylinder stat and no live return to open DHW zone valve - the CH side seems straight forward feed out to stat and return to boiler and live return to zone valve the problem is the DHW
realise that Tony I'm just in at the deepend here trying to do a favour. This boiler has a volt free channel for the cylinder connection and I can't fathom how I get a live return to open DHW zone valve - the CH side seems straight forward - feed out to roomstat and return to boiler and live return from boiler to open Zone valve - its the DHW side that seems complex and the boiler schematics don't seem compatible with the cylinder wiring schematics
Assuming this is a CDI conventional, only use Ls and Lr on the PCB to turn it off and on.
In fact you only need Lr, which is Worcester's Switched Live.
The motorised valve end switches can be wired across Ls and Lr.
The Cylinder stat and OH are wired from the Programmer HW on, then just turn on the HW zone valve motor when call for heat. When the motor is energised, a microswitch in the valve head joins Ls and Lr.
Similarly, the CH works from the Prog, through the roomstat and to the CH zone valve. The microswitch is commoned to the HW (orange and grey normally used).
Simples! If you are a spark this is easy stuff. Compared to test and inspection!
In fact you only need Lr, which is Worcester's Switched Live.
The motorised valve end switches can be wired across Ls and Lr.
The Cylinder stat and OH are wired from the Programmer HW on, then just turn on the HW zone valve motor when call for heat. When the motor is energised, a microswitch in the valve head joins Ls and Lr.
Similarly, the CH works from the Prog, through the roomstat and to the CH zone valve. The microswitch is commoned to the HW (orange and grey normally used).
Simples! If you are a spark this is easy stuff. Compared to test and inspection!
simon there is no programmer - all works from boiler
Do you have a 30CDi conventional, or a 30CDi system?
You can't use the internal timer/programmer with the 30CDi conventional, only with 30CDi system. And for technical reasons, this is only when the 30CDi System boiler is fitted with the optional internal diverter valve.
Which is incompatible with an unvented cylinder, strictly speaking.
NB: If you have no programmer in the boiler or elsewhere, you should buy one. Honeywell ST9400C is a good place to start, if you also buy a Drayton LWC1 wiring centre that will make your life easier too.
You can't use the internal timer/programmer with the 30CDi conventional, only with 30CDi system. And for technical reasons, this is only when the 30CDi System boiler is fitted with the optional internal diverter valve.
Which is incompatible with an unvented cylinder, strictly speaking.
NB: If you have no programmer in the boiler or elsewhere, you should buy one. Honeywell ST9400C is a good place to start, if you also buy a Drayton LWC1 wiring centre that will make your life easier too.
Simon its a 30CDi system and I'm assuming it has the diverter valve all the eqipment was selected by the plumber who doesn't have a clue about the wiring. Is this incompatible with the unvented cylinder?
This all gets a bit complicated now.
G3 regs state that the HW cylinder needs to have a 2 port spring return valve fitted to an unvented cylinder so that the operation of the OH or temp stat (either) drops the heating source.
So this is where the two port valve comes in.
Your Worcester boiler is designed as a packaged system and uses a proprietary cylinder sensor and, by the sound of it has been fitted with an internal optional site fitted 3 port diverter valve.
So in principle it is incompatible with a 3rd party unvented cylinder.
However, you could in theory hook it up whereby the whole system is configured as per Worcester proprietary, if you can get their thermostat into the cylinder dry pocket.
In order to meet G3, you would then fit a 2 port valve on the primary to the cylinder, 230v wired via the mechanical OH and Stat combo unit. The pin switch on the 2 port (orange and grey) could then be wired in place of the Ls and Lr link on the boiler PCB.
This way, the cylinder stat will still cut the water off and knock the boiler off if temperatures get too high, but in the normal operation it will all think it is a Worcester proprietary system.
You need to set the mechanical cyl stat that came with the unvented up to max, so it is normally calling for heat.
This is a complex problem, there are other solutions. Many heating engineers would struggle with this, so you may want to bounce it back to the installer and ask him what he was planning to achieve, I think he has overreached himself and made it your problem.
G3 regs state that the HW cylinder needs to have a 2 port spring return valve fitted to an unvented cylinder so that the operation of the OH or temp stat (either) drops the heating source.
So this is where the two port valve comes in.
Your Worcester boiler is designed as a packaged system and uses a proprietary cylinder sensor and, by the sound of it has been fitted with an internal optional site fitted 3 port diverter valve.
So in principle it is incompatible with a 3rd party unvented cylinder.
However, you could in theory hook it up whereby the whole system is configured as per Worcester proprietary, if you can get their thermostat into the cylinder dry pocket.
In order to meet G3, you would then fit a 2 port valve on the primary to the cylinder, 230v wired via the mechanical OH and Stat combo unit. The pin switch on the 2 port (orange and grey) could then be wired in place of the Ls and Lr link on the boiler PCB.
This way, the cylinder stat will still cut the water off and knock the boiler off if temperatures get too high, but in the normal operation it will all think it is a Worcester proprietary system.
You need to set the mechanical cyl stat that came with the unvented up to max, so it is normally calling for heat.
This is a complex problem, there are other solutions. Many heating engineers would struggle with this, so you may want to bounce it back to the installer and ask him what he was planning to achieve, I think he has overreached himself and made it your problem.
its the boiler connections for the cylinder stat that are volt free
View media item 32897If you are fitting the integral diverter valve then the drawing above should do you
The zone valve is a safety req it does not have to control the temperature in the cyl it only has to shut down the flow to the cyl on overheat
wire it as above and put the zone valve in the cyl primary
if the overheat stat trips then the demand from the control stat will also be removed via the valve microswitch
if you are using the dhw sensor instead of the cyl stat then ignore all orange and grey cables (you wont need them)
wire the rest of the system reg the diverter valve,room stat etc as per MI's
Matt
ps forgot to mention on the drawing that the terminal connected to number
3 in the centre store will not be used
The zone valve is a safety req it does not have to control the temperature in the cyl it only has to shut down the flow to the cyl on overheat
wire it as above and put the zone valve in the cyl primary
if the overheat stat trips then the demand from the control stat will also be removed via the valve microswitch
if you are using the dhw sensor instead of the cyl stat then ignore all orange and grey cables (you wont need them)
wire the rest of the system reg the diverter valve,room stat etc as per MI's
Matt
ps forgot to mention on the drawing that the terminal connected to number
3 in the centre store will not be used
your installer might find this useful (ignore the solar)
http://www.worcester-bosch.co.uk/cache/file/4/ism1-heating-system-diagram.pdf
depends if he wants to put his neck on the line wiring up your installation like this, I would remove the divertor valve and have the boiler as standard , wb should be able to supply the bits to put it back as it was.
http://www.worcester-bosch.co.uk/cache/file/4/ism1-heating-system-diagram.pdf
depends if he wants to put his neck on the line wiring up your installation like this, I would remove the divertor valve and have the boiler as standard , wb should be able to supply the bits to put it back as it was.
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