Wiring a cylinder stat (unvented cylinder)

[Newbee999]

I have replaced an vented cylinder with and unvented cylinder and am having difficulty replacing the single cylinder thermostat wiring with a dual thermostat.

The original system is a Drayton Bi-Flo Control Packs. The original wiring from the LWC1 wiring centre was:

Terminal 14 Common went to C on the HTS3 thermostat
Terminal 15 Hot water on went to 1 on the HTS3 thermostat
Terminal 16 Earth on the HTS3 thermostat

I disconnected the above wires on the thermostat and linked as follows to the new dual aqua stat cylinder stat that was supplied with the Gledhill cylinder:

Terminal 14 Common went to Common on the overheat stat
Terminal 15 went to 1 on the control stat
Terminal 16 to earth on the dual aqua stat
Then took a link wire from 1 on the overheat stat to C on the control stat

Just kept blowing the fuse...

The instruction manual for the Drayton and the Gledhill unvented both say take the "Hot water on" to the common on the overheat stat. But the other side goes to the two port valve on one instruction manual and the programmer on the other instruction manual.

This is my first install having completed my Part P so need some help since first customer does not have heating or HW and it is getting cold...

Appreciate any help...

 

[doitall]

How can one say this without being rude

I think you're in the brown stuff mate.

First and most important requirement is Not part P, but G3, without it you are not allowed to work on unvented cylinders. Which is also notifiable to the local Building dept.

The valve that came with the cylinder is a safety device that connects to the thermal cut-out (over heat) and turns the boiler off.

If you must work illegally, The manufactures instruction take priority over everything. In this case the cylinder is the Bible, get it wrong and you could make DrDrivel a happy man, as the tank goes through the roof.

 

[matt1e]

Terminal 14 Common went to C on the HTS3 thermostat
Terminal 15 Hot water on went to 1 on the HTS3 thermostat
Terminal 16 Earth on the HTS3 thermostat

hi newbee are you sure that that is an earth condutor connected to an earthing terminal? dont presume because its green and yellow it's an earth

we need more info really

make of stat? i'm assuming it is a honeywell L6191
type of system ie s-plan or y-plan

if its y-plan then I doubt that that was an earth on the original stat connection
did it not connect to number 2?

This is my first install having completed my Part P

you need to have G3 too

 

[picasso]

the unvented cylinder comes with a 2 port valve, go out and buy another and rewire it as an s plan,(you will need a wiring centre as well) at least your customer will have heating and hot water and you can put this one down to experience.

 

[Newbee999]

Hi,

Thanks everyone for such a fast response. I have my G3 ticket and I have notified building control. Unvented cylinders are not something I would play around with having seen the video on utube with them looking like rockets!

The original system is a Y plan - I will check that the earth is actually an earth. The new stat is a honeywell dual stat.

The advice re getting 2 2 port valves also makes sense since this means I can wire it up exactly as the Gledhill cylinder instruction.

I will try both options...

 

[matt1e]

Hi,

The original system is a Y plan - I will check that the earth is actually an earth.

if its y-plan then it won't be as you need three connection on the cylinder stat
common
hot water call
hot water satisfied

The advice re getting 2 2 port valves also makes sense since this means I can wire it up exactly as the Gledhill cylinder instruction.

I will try both options...

wiring diagrams for both systems here the device labeled "energy cutout" is of course the overheat stat incorporated in your duel stat

matt

 

[twgas]

Surely you fitted the 2 port supplied with the cylinder, even if there is already a 3 port it is required. There should be wiring instructions for this in the MI.
Didn't realy understand you comment "I will try both options..." do you intend to alter pipework, then, if you can't get that going put it back again?

 

[doitall]

Surely you fitted the 2 port supplied with the cylinder, even if there is already a 3 port it is required. There should be wiring instructions for this in the MI.
Didn't realy understand you comment "I will try both options..." do you intend to alter pipework, then, if you can't get that going put it back again?

If he has a G3 ticket I'm gonna retire.


And if, he has then one has to wonder how much it cost.

 

[twgas]

Surely you fitted the 2 port supplied with the cylinder, even if there is already a 3 port it is required. There should be wiring instructions for this in the MI.
Didn't realy understand you comment "I will try both options..." do you intend to alter pipework, then, if you can't get that going put it back again?

If he has a G3 ticket I'm gonna retire.


And if, he has then one has to wonder how much it cost.

He says he has - so it must be true

 

[Norcon]

Hi,

The original system is a Y plan - I will check that the earth is actually an earth.

if its y-plan then it won't be as you need three connection on the cylinder stat
common
hot water call
hot water satisfied

The advice re getting 2 2 port valves also makes sense since this means I can wire it up exactly as the Gledhill cylinder instruction.

I will try both options...

wiring diagrams for both systems here the device labeled "energy cutout" is of course the overheat stat incorporated in your duel stat

matt

Why would hw satisfied be needed?
Edit- aaah yes Y plan ,silly me.

 

[doitall]

T1 in the cylinder sat is satisfied.

 

[Newbee999]

You were completely correct about the earthing wire. The earth wire had been used as live by the boiler installer and had not been indicated. It all works now. Also thanks for info about having to put in the two port valve and the y plan valve - I wasn't aware both had to go in. Will have some fun now since it is behind the cylinder! Thanks

 

[TicklyT]

I know it happens, but anyone who uses the CPC ('earth wire') of a cable as anything other than earth should have the hazards they are creating explained to them, preferrably using something large and heavy, with particularly nasty looking pointy bits on it as a teaching aid.

You should use cable with an appropriate number of conductors - that's why they make 4, 5 and 7-core cables!

Imagine removing a suspect head from a difficult to get at 3-port valve, finding you need to take the cable off to free it. Then you put the cable back where you think it went, and twiddle the cylinder 'stat whilst holding the valve head to see if it moves. That would not be a good time to find you've connected a switched live to the case!

Green/yellow conductors should only be connected to earth. It's like driving on the left or stopping at red lights - you might get away with going against the rules sometimes, but things are inclined to get very messy very quickly when it goes wrong, and just about imposible to defend in a court of law