I need advice on a replacement for my Honeywell C21 Programmer, please

[gold]

It was fitted with the boiler a Potterton Suprima 30L about 21 years ago. Two PCB's later and a new fan the boiler is working perfectly. However, the programmer display is not showing any digits for the clock or anything else so I am unable to program it. It still works the boiler manually setting it to on "all day" or "24 hours" but it is not even displaying the dark squares that move up and down to do that. So it appears only to be the display at fault. Non of the buttons are stuck and I have tried switching the fused spur to the boiler and programmer off and waiting a minute or two then switching back on again but to no avail. Oh yes, and I have had a mandatory prod at the display a few times, again to no avail.

It is not like the more modern C21 programmer in that is only programmable on a daily basis rather than 7 days. I do not need anything sophisticated as I do not have any room thermostats or other valves. I increase the heat to the rads by upping the water temperature by the knob on the boiler and I have a manually operated valve near the hot water tank which I can divert the water to just the radiators or the tank or both. It would appear that the C21 has now been superseded but it would be nice if there were a suitable one that could fit on the same backplate using the same wiring. I intend to have the whole lot ripped out next year and a combi boiler installed with modern rads and all the energy efficient gizmos to go with it.

Any advice would be appreciated.

 

[gpbeck]

Look on Ebay.
There's a nearly new drayton lifestyle LP111Si for £19 delivered.

 

[gold]

That's interesting thank you. Sorry but I am wasting my time as this forum is not allowing me to post a reply.

I tried to post this in reply to gpbeck "
That's interesting thank you. I was erring towards another Honeywell one as I read on a Screwfix comment that the new models were compatible so there is no need to change the backplate or wiring. However, I figured out how to get the front off the C21 and it looks like the backplate which sits on the wall and holds the mains supply cables are compatible for different makes and models of programmer. Is that correct and would the Drayton LP111Si just drop in place on the existing back plate?

What the eff is a matter with this forum! I don't know how many times I have had to get rid of a pop up before continuing to type. This is the message "Oops! We ran into some problems. Please try again later. More error details may be in the browser console." "our content can not be submitted. This is likely because your content is spam-like or contains inappropriate elements. Please change your content or try again later. If you still have problems, please contact an administrator."

OK got there in the end.

 

[gpbeck]

Yes standard backplate straight swap. Thought you should spend minimum if you’re planning an upgrade later.

 

[gold]

Excellent, thank you very much. That was my thinking too as I guess the engineer doing the new installation will need to match up the programmer with the needs of the system and it may not be compatible with the one I obtain now.

I solved the problem, don't hit the reply button. Doing that quotes the previous post and labels me as a spammer!

 

[gold]

Yes standard backplate straight swap. Thought you should spend minimum if you’re planning an upgrade later.

I purchased the Drayton LP111Si as suggested and slotted it into the existing back plate, the wiring being the same as indicated on the Drayton programmer. It lit up when I turned on the fused spur and the boiler (or was it the water pump) made its usual brief noise. I then moved the selection from "off" to "timed" then pressed the "advance" button. The green light lit up on the front of the programmer but the boiler did not come on. I then tried selecting "once" and again the boiler did not come on. Then I moved it to "on" and the boiler did not come on! I put the old Honeywell C21 back in place and I am able to start the boiler manually selecting "24 hours" or "all day" if within the first and last time settings. As said before I cannot see where the setting is on the display so just move the end button until it clicks on. Rear of the Drayton and the old back plate shown below and the rear of the Honeywell. I did note that the earthing spike on the back of the Drayton was missing and the instructions say the following. "The programmer must be set to the type of system it is to control. The link on the back of the unit has two settings - P and G. P = a fully pumped and controlled system - allowing heating and hot water to be set separately. G = a gravity fed hot water system - which does not allow independent setting of heating without hot water, though hot water can be controlled alone. Any idea what the problem is please?

 

[gpbeck]

The feed to your boiler is connected straight onto the power supply, your old programmer was doing nothing and the boiler was permanently powered up. It sounds like the new programmer is working fine but has no conductor to the boiler to fire it up.

The back box needs a wiring modification so that a signal is sent to your boiler to tell it to fire. I note there is a blue conductor cut short from the boiler cable. It is a simple job to rewire this but perhaps you should get a boiler guy to do this safely for you.

 

[gold]

The feed to your boiler is connected straight onto the power supply, your old programmer was doing nothing and the boiler was permanently powered up. It sounds like the new programmer is working fine but has no conductor to the boiler to fire it up.

The back box needs a wiring modification so that a signal is sent to your boiler to tell it to fire. I note there is a blue conductor cut short from the boiler cable. It is a simple job to rewire this but perhaps you should get a boiler guy to do this safely for you.

The boiler and the programmer have been working together perfectly for 21 years both manually, i.e. on "24 hours" and "All day" and the timed options 3 times per day and the wiring configuration has not changed!!

From my original post:

"It would appear that the C21 has now been superseded but it would be nice if there were a suitable one that could fit on the same backplate using the same wiring."

 

[gpbeck]

Is your boiler fitted with an optional controller with time settings, and these are the settings you use to control times?
If so your old controller was doing nothing.

 

[gold]

Is your boiler fitted with an optional controller with time settings, and these are the settings you use to control times?
If so your old controller was doing nothing.

1) If it is, it is not visible without taking the room sealed cover off and if it did have how is it that the boiler has been going on and off each time I have adjusted the timer settings on the programmer in accordance with those settings!

2) It would also appear to follow that if the boiler was fitted with an optional controller then surely this would be working with the new programmer too?

 

[ShaunCorbs]

Link L to 1 on the backplate

Old one passed the live through new one doesn’t

 

[gpbeck]

Got it now the fire line is yellow thought it was an earth.
Terminal L has to be jump connected to terminal 1 with an additional short cable.
Yellow fire line has to be moved from terminal 4 to terminal 3.
But 240V so make sure you feel competent to do it.

 

[gold]

Thank you very much for your input Shaun!

Ok, so I need a small piece of 1mm diameter cable as I think the fused spur is wired into the lighting circuit (the one I will be turning off, including the spur to do the job). Is that correct, and don't worry I will be ensuring the insulation is only being trimmed back to allow for the insertion to the terminals and it will be secured tightly to ensure a good connection.

 

[gpbeck]

You should also have red sleeving on that yellow fire cable to conform with regs. If you move it as I stated it should work. No need to thank me.

 

[ShaunCorbs]

Thank you very much for your input Shaun!

Ok, so I need a small piece of 1mm diameter cable as I think the fused spur is wired into the lighting circuit (the one I will be turning off, including the spur to do the job). Is that correct, and don't worry I will be ensuring the insulation is only being trimmed back to allow for the insertion to the terminals and it will be secured tightly to ensure a good connection.

Yep or 0.75 or 2.5mm tbh anything aslong as it’s rated for 240v and don’t forget to move the yellow over to the left one eg 3 as in keeping with the diagrams