Replacing my Potterton EP2000 boiler controller with a Horstmann - wiring question ?

Im attempting to replace my aging potterton EP2000 controller with a Horstmann C27 controller. Now the instructions for the C27 show kindly show a table for converting the wiring for the EP2000 to the C27. However, having opened up the EP2000, the wiring isnt as straight forward as I thought. The Ep2000 is connected to a Potterton NettaHeat conventional cast iron boiler (circa mid-late 80s), both of which are currently working fine.
Now only having very basic electrician skills, it looks as if this is possible to wire (from the instructions), but since seeing the wiring its now clear that I may need assistance from some experienced/wise bod. ( as the EP2000 instructions werent in the house when I bought it. )
I've included a couple of pics to help explanation.
The EP2000 to C27 conversion table and the EP2000 basic-wiring sticker shown here
http://81.106.39.40/boiler/back.jpg
The crazy wiring can be seen here
http://81.106.39.40/boiler/front.jpg
(ive labelled the wries with letters to aid means of description if anyone can shed any light !)
Alas Ive no idea to what each of the 4 cables attaches (as I have precisely zero knowledge of boilers) as I was expecting the wiring to be a tad simpler.
My current visual observations are: 1) The Lives of cables D & B seem to be wired together, but route to via terminal 5, which isnt listed in the conversion table (it only goes 1-4). This doesnt seem to be doing anything. 2) terminals 1 & 2 dont currently have any cables attached, (which according to the conversion table should supply the control signals for HW OFF and CH OFF ). Ive no idea why - perhaps the controller only needs to enable leccy flow when the units it is ON. 3) terminal 3 (which should be HW ON according to the C27 conversion table) has the Earth of cable A connected. Strange ??????
If anyone could advise on how I should wire up the existing 4 cables to the new C27 controller (to L N E, HW OFF, HW ON, CH OFF, CH ON ) then Id be very appreciative.
Many thanks in advance ....
J.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 18 Sep 2004 11:02:24 -0700, JE wrote:

Only a few systems and controls need a powered OFF signal. (mainly those with non Honeywell style zone valves and 3-port valves).

As you can see from the wiring diagrams the two controllers are almost identical.
The wiring for N L 1 2 3 4 is the same in both cases. The C27 unit does not need the extra wire from L to 5 as its '5' is internally connectd to L. The brown wire from cable B will go to L.
Terminal B is just a spare connector Cales B&D are live as you say.
The person who wired this up committed the great sin of using the green and yellow wire in cable as the HW demand.
To avoid the sort of crap you have here I have just spent 30 on a reel of six core mains cable. It means not only do you not have a stack of blue and brown wires doing several things but often less cables as well...
Read the main FAQ on CH controls. It will help you a lot.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
So basically just to get things clear in my mind
1) The Cable A Earth (green and yellow) isnt being used as earth, but as a live cable to supply terminal 3 (from god knows where)?
2) The join between Cable A Neutral (blue) <->Cable C Live (brown) needs to maintained and permanently connected with connector strip within the new C27 ?
3) Cable D must be the mains supply, (as it's the only cable with all three wires going to the corresponding EP2000 Earth, Line and Neutral terminals. Any idea on what the other 3 cables could be used for by looking at the picture? (note there is also a fused single switch for the controller to the right of the EP2000, but I assume this is just in series and supplies the power to the controller and therefore doesnt supply any other cables in the controller)
If 1 is correct, then Id never had thought that people would use spare wires without at least putting the correct colured insulating tape over them. Good idea on the 6 core - if u do this thing regularly.
Thanks for the FAQ link too - I now know what the 10/16 EP2000 switch is for.
Cheers,
J.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 20 Sep 2004 05:43:55 -0700, JE wrote:

Yes. Better put as terminal 3 supplies the HW demand signal to the G&Y core of cable A (which goes TO god knows where).

Yes. Best practice is not to use the C27 back plate as a mini wiring centre. A wiring centre can be purpose bought or easily made using a single or double patress with a choc strip inside. I suspect there may also be a wiring centre or junction box elsewhere. You actually only need 4 wires + Earth to wire the time switch, L & N and one core from 3 for HW demand and one from 4 for CH demand.

I'm sure the switch (containing 13A fuse should be 3A) runs one of cable B or D.
You cant say if Cable B or D is the supply since both their cores are effectivly connected to LN&E. The other cable of B&D likely goes to the boiler to provide a permanent power supply.

You have a lot to learn about the depth, breadth and creativity of corner cutting...

Yes the 10/16 is very arcane. 8-)
A wild guess based on what I see form the photos plus experience:
The system is operated in '10' or gravity mode there is just a hint that the photo shows the EP2000 in 10 mode. You can't have HW off when the CH on. There is a zone valve for the CH. The boiler is a modern unit requiring a permanent supply. The earth wire was probably reassigned when the boiler was replaced. It might even go all the way to the boiler as is. Somewhere along cable A between the timer and the boiler the wall thermostat joins brown to blue.
Cable B&D are mains, one is supply likely D, and the other goes to the boiler as a permanent supply. Cable A takes CH and HW demand out on brown and G&Y. The blue cable is likely the return from a wall thermostat. The G&Y operates the boiler demand terminal. Either the boiler works the pump or the G&Y also does that.
Cable C likely goes to the CH zone valve to put the radiators on. The micro switch in the zone valve (cable cores orange and grey) is not used.
Boiler is a Potterton Suprima or Baxi Solo? The EP2000 is an older bit of kit which predates the boiler?
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The cam looks to be in the vertical (16) to me
--
geoff

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 20 Sep 2004 20:40:55 +0000, raden wrote:

OK. In which case there are probably two zone valves.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for the advice.
Erm by "connector strip" I acutally meant chocolate strip. ( Ill get the terminology one day. ) Glad to know that I wasnt going completely crazy with the G&Y wire on Terminal 3. Thanks for making me a little more confident in my elecrical knowledge. BTW, the fused switch I mentioned does contain a 3A fuse.
FYI, the boiler is a Potterton Netaheat 10-16. And the controller setting seems to be set to 16 (and not 10) by my judgement (of both the twisty control on the right and the sliding switch on the bottom).
As im in the middle of refitting my kitchen, Im taking the time to fit the new controller and patch the bad plaster around the old, which prompted this whole thread. With the kitchen stripped bare, now might have been the time to replace and fit a new conventional boiler, but it would cost about 2k to buy and get fitted, which seems alot considering the Potterton Netaheat seems to be working fine.
Ive not had the boiler serviced since i moved in 2 1/2 yrs ago - is this something I should sort out ASAP, in your opinion (and then serviced at what intervals )?
Im impressed with your knowledge and also the effort you've taken to help me stop blowing myself up.
Thanks again.
J.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 20 Sep 2004 15:03:33 -0700, JE wrote:

OK that's encouraging.

OK in which case there is likely two zone valvesa and a cylinder thermostat elsewhere.

Yes I have many customers with a Netaheat The units are fairly efficient and very reliable. The arguments for replacement are ambiguous with only a 10-15% saving likely in gas bills the pay back period is lengthy.

All official sources are going to tell you the boiler should be serviced annually and if you rented your house this would legally be required. I would say an annual safety check and expect to do a major service every three years.
--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
JE Wrote: > Im attempting to replace my aging potterton EP2000 controller with a

> I am unable to get past first base. I can't work out how to remove the > front cover of the Potterton. There are no screw fixings and as far as > I can see no simple clip fixings?

--
AndyG


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sat, 23 Jul 2005 17:27:34 UTC, AndyG

Didn't see the original post, and Andy's appears to have a null reply, but...
These are usually held by two screws UNDERNEATH. The screws are vertical, and probably recessed. You loosen them (two), then pull the front of the controller forward, lift it slightly and it comes off the backplate. There is no front cover to remove - it all comes off at once (apart from the connection backplate).
Isolate the circuit first, of course - there will be largish exposed pieces of metal at mains potential.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Bob Eager Wrote: > On Sat, 23 Jul 2005 17:27:34 UTC, AndyG

> but

> the

> as

> once

Thanks for the reply, this is exactly what I would expect, however there are no screws!
--
AndyG


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
AndyG Wrote:

Update: I have since found some more help and have now been able to remove the timer from the wall.
For info. There is a small slot about 10mm X 3 mm on the lower RH side within the groove that runs all the way round the timer. Insert a flat screwdriver into this slot, push upwards to release the "finger catch" that holds the timer to the back plate. The timer can then be tilted upwards and away from the wall. Regards Andy.
--
AndyG

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.