Wiring Problem At Heating Programmer

[chris_k]

Evening.

I went to investigate a wiring problem on a domestic heating controller on friday. As i dont really do domestic heating controlls it has me a bit stumped.

The heating timer had apparantly failed sometime ago and the householders son had done a temporary `fix`. He now wants a clock fitting.

What i was presented with was a fused spur output connected to 3 choc block connectors and a mass of wires. When the owner wanted the heating or water on he just turned on the spur.

The previous time clock was a Potterton mini minder E and all the wires below were mounted into the connector plate, now removed.

L-N-E from Spur

L-N-E to pump

4 core flex that disappears behind back boiler.

On the rear of the timeclock there is a dial set to `Fully Pumped`.

The way it was wired into the choc block was-

L - Live to pump & Brown + Black of the 4 core cable

N - Neutral to pump & Blue of 4 core

E - Earth to pump and earth of 4 core

When householder turns on spur he gets heating and hot water.

Looking at various wiring diagrams (s/y/c plan) i cant see how its possible to wire up!

As you can tell im not up on heating system wiring.

Any help much appreciated

 

[NozSpark]

Forget the connections that are currently there,,,, disconnect it all, bell it out and start from scratch

The main things that define the wiring are the zone valves and the time clock so get the diagrams for those and go from there

 

[chris_k]

Im over there tomorrow afternoon so will have a better look. The thing that is puzzling me is having the pump connected directly to the timeclock panel.

On the timeclock wiring diagram -

L

N

1 - HW off

2 - CH off

3 - HW on

4 - CH on

 

[Marvo]

I'm not much of a whizz at the UK heating system layouts but I usually refer to this document if I need info.

http://www.honeywelluk.com/documents/all/pdf/wiring%20guide%20issue%2016.pdf

 

[batty]

If its a gravity system it would be connected into heating on. More info about system is needed.

 

[chris_k]

If its a gravity system it would be connected into heating on. More info about system is needed.

The programmer was set to Fully pumped

 

[batty]

As has been said more info about system is needed i.e. motorised valves ETC. To me it sounds like an old system with no control.

 

[kerching]

The programmer was set to Fully pumped

But if somebody has fiddled with it should it actually be set to gravity instead of fully pumped?

just because it is "set" to pumped does not mean it is correct

just being cautious

 

[NozSpark]

Reading your op back it does sound like gravity hw / pumped ch ,,, however like I said you need to figure out what goes where and how it will connect to your new controls

 

[chris_k]

The guys son just connected the wires up and didnt touch the clock... Apparently!!

The pump is directly below the timer and its wire goes directly into the programmer, not a wiring centre.

From what i can work out from various diagrams is that (assuming it is fully pumped) The pump Live should be connected to the terminals 3 & 4. so when ch or hw is called for the pump runs.

This leaves the 4 core cable that dissappears behind the fire.

For the boiler to run it must have a Neutral - lets assume thats blue core. (currently connected to neutal)

Assume that the green / yellow must be earth (currently connected to earth)

That leaves 2 cores. 1 for CH, 1 for HW.   Which leads me to think its possibly a s plan system?

Its bloody Sunday night. I shouldnt be worrying about this!!!!

 

[Sharpend]

Am I correct in thinking that these connections are in the back of the spur? So how are the connections in the programmer?

I'd guess that the black is the boiler switch live, hence why it's connected to the pump, it's obviously been put to the brown perm live so that when the spur is turned on the boiler and pump kick in.

I'd guess that behind the programmer the switch lives for the heating and hot water are connected to perm live and the thermostats control whether heating is on or off and similarly with the hot water.

As I say it's all guess work without seeing some pictures? As Noz says bell out the cables to get a clearer idea of what's going on.

 

[batty]

The only way it can be a fully pumped system is if you have a motorized valve as said to me this sounds like an old gravity hot water system and pump is for heating. I could be totally wrong but it pointless worrying unless you actually have a proper look at system.

 

[ProDave]

As others have said, you NEED to trace that 4 core cable and see what it connects to. almost certainly a motorised valve, or even another pump.

Then you need to understand how it's plumbed and you can work out how to re connect it.

A classic case of the customer making the job 10 times harder and probably 10 times the cost than if they had just got someone to come and replace the time clock when it stopped working.

BUT be prepared for other faults, perhaps when the heating "stopped working" IT was in fact the motorised valve that has failed? So there's no guarantee when you re connect it with a new time clock that it will all work correctly.

 

[chris_k]

Ive managed to have a better look at the wiring and heres a rough breakdown-

fused spur next to the programmer feeds directly into the programmer.

A 3c from the pump (directly next to the programmer) goes into the programmer

A 4c goes from the programmer and down the back of some cupboards. This terminates to a strip of 4 choc blocks. (L,L,N,E)

This then splits to two 3 core cables. Im assuming that one of the 3c (L,N,E) goes to the boiler to turn it on. And the other 3c (L,N,E) goes to a valve to open the loop for central heating?

I couldn`t get any further to find the valve as the pipework has been totally covered up by the kitchen. One of those kitchens on its last legs. Take it apart and it falls to bits!

The back boiler has no access to trace the cable. There is a great big fire in the way!!

There are no room or tank thermostats.

I spoke to a pumbit mate and he seems to reckon its a gravity hot water and pumped ch. The only thing confusing me is the previous programmer had it switched to fully pumped. Obviously this could have been changed by the client, but he says it wasn't touched.

im thinking, set the new programmer to the  HW / HW & CH setting

Get the spur to feed directly to L,N,E inputs on the programmer

L of the boiler feed goes into terminal 3 (HW demand) This way, whatever is called for HW or Ch the boiler will start

L of the valve goes into terminal 4 (CH demand)

L of the pump goes into terminal 4 (CH demand)

As i said before. at the moment all Lives are connected together and Neutrals are connected together and when turned on does HW and CH together. Effectively what the programmer when wired above would do.

If i were to wire this way and it was incorrect what problems could i encounter?

Ta Muchley.

 

[SPECIAL LOCATION]

You need more than just a L-N-E to work a valve correctlty...

Think of a valve like a relay or contactor...

An activate signal is sent to drive the motor across..

But you don't want to start pumping water into a valve that hasn't opened yet..

so ALL valves have a built in micro switch which operates once the valve body has moved open to let the water flow. 

If you just have two port valves you can think of the basic sequence of the circuit as a load switches:-

Supply--> {supply & MCB}

FCU-->   {manual switch & fuse}

Program/timer-->  {manual or timed output}

Thermostat-->  {temperature controlled output}}

Valve-->  {output only once valve in correct position}

Boiler / Pump   {if passed though all the previous steps then boiler & pump fire away!!!}

Where multiple zones are used some sections will be paralleled up...

You need to sketch out exactly what you haves got..

NOT assume some wire goes somewhere that you haven't proved!

Then it should be relatively easy to figure out what right/wrong/missing/faulty

Guinness

This then splits to two 3 core cables. Im assuming that one of the 3c (L,N,E) goes to the boiler to turn it on. And the other 3c (L,N,E) goes to a valve to open the loop for central heating?

GOLDEN RULE FOR SUCCESSFUL HEATING PROBLEM DIAGNOSIS

Assume NOTHING you haven't proved.

 

[ProDave]

You need more than just a L-N-E to work a valve correctlty...

Think of a valve like a relay or contactor...

An activate signal is sent to drive the motor across..

But you don't want to start pumping water into a valve that hasn't opened yet..

so ALL valves have a built in micro switch which operates once the valve body has moved open to let the water flow. 

Very true, but I was looking at a heating system today where the installer had not bothered to use the feedback contacts.

It strikes mt a very high percentage of heating installers don't really understand what they are doing and a lot of systems are never wired properly.

 

[NozSpark]

The thing is though thst those cables could be connected to anything...

Roomstat, pipe stat, frost stat, valve (incorrectly), pump over run from boiler....

Without further investigation you'll never know... you dont however have to physically trace the whole cable run... just find the ends and bell it out..... you may need a gas fitter to partially dismantle the fire!

 

[chris_k]

In the end i left the job as is. They are getting the fire and boiler serviced soon so ill leave it to the plumbit to sort.

Just to continue the debate, as i dont like to have things beat me.

The long and short of it is there are only 2 lives that control the whole system. There are no room or tank stats. The system looks like its from the ark and was installed by, and i quote ` ..a bloke who used to work at the council...`

What other ways could these two wires be used to operate the system?

Im curious.

 

[steptoe]

simply put,

its one 'live' for hot water,

and one 'live' for central heating

its how they are switched to fire the boiler that makes the difference,

as for leaving it for the plumber to sort,  :slap

 

[Pro spark]

If it's a back boiler the 3 port valve will not be visable. It's all quite easy really as hot water and heating are not seperately controlled. I had to re- wire one of these and it took a while.