Central heating timer...

[Matthew Ames]

Help :-)

I have an old Randall 3060 in my house that the timer bit has decided not work. The manufacturer tells they don't supply any parts :-( This rather a bummer as I think it is just the motor (or more likely one of the nylon cogs is worn out (it makes a rattlie noise, but when I take it apart nothing looks obviously worn). So that means I have to sell out about £80 for a new timer :-(

SO I thought maybe I'll move into the modern digital age and get someone newer (house is victorian with an old floor standing gas boiler).

The snag is, the house has two thermostats (one upstairs and one downstairs). So heating can be either up or down or both. It has in conjunction with this 2 valves (one for downstairs and one for upstairs heating circuits) and 2 pumps (one for heating that I replaced in feb of this year and one for the h/w cylinder)

However this all means there is a total birds nest of wires everywhere :-(

I would imagine, but I am not 100% there is no thermostat on the h/w tank, and that the pump is just used instead.

What are my options here?!? Obviously Ill try and figure out what wires go where, but there are lot of them and many just vanish into the walls!

I assume as a basic view, the timer switch comes on, and supplies power to both thermostats, if either thinks its location is cold enough to closes to complete a circuit. The returns live feed then goes to the boiler, the appropriate valve. However I have not work out "who" controls the pump yet - is that likely to be the boiler, or will that be driven from the thermostat? Given that with two thermostats it would make sense that they are independent of each other (otherwise why have the valves for up/down stairs?)

Hopefully a mate is going to pop around over the weekend and we will try and figure out the wiring before doing anything, but any suggestions would be a bonus :-)

Cheers, Matt

[The Natural Philosopher]

You are probably up for a 3 zone timer then, plus a nice box to connect all the wires up to.

You SHOULD have 3 motorized valves..one for each zone and one for hot water.

Each timer zone feeds one valve, via the respective thermostats.

the switches on the valves are paralleled and used to run the boiler and pump.

If it ain't like that its worth MAKING it like that.

[Owain]

Usually the thermostat controls its associated valve. A microswitch on the valve then 'calls for heat' to the boiler and pump. If several valves, then the switches would be in parallel so any one could call for heat.

Owain

[Geo]

The timer supplies live to the thermostats - they switch live to their respective valve motors - a switch on the valve (either of them), when it is open, turns on the boiler/pump.

For some coloured pics/discussion look here:-

You only need to consider the cable ends at the timer - which you should be able to identify by getting the manufactures info from their web site. Alternatively this pdf file gives you the connections and you can see the compatibility with other makes:-

use this if word-wrap is a problem

[Matthew Ames]

Arh... thats the did I did not know....

I could not understand how the "call for heat" from the thermostat would not cause all the valves to open

[Ed Sirett]

Agreed. Two pump systems are basically the same sort of controls as the obsolete "gravity". However thought has to be given as to whther a bypass circuit might be needed if you upgrade to a one pump and 3 valve systems.

[Ed Sirett]

Remember on your system you can't have radiators without heating the HW cylinder (even if it's hot enough already). The first pump comes on with the boiler the second pump comes on IN ADDITION if heating is required.

[Matthew Ames]

The how water cyclinder pump has been "built" into a cupboard surrounding the tank to which I have no access (SWMBO will disappove if I destroy it!), so I can't check out the wiring on that side. All I can see is that from the control box side (opposite side of the kitchen) I seem to have a 240volt feed (regardless of what the "control knob" is set to - apart from off) that sends mains over. I assume that maybe the termostat on the hot water cylinder is used to switch the pump on and off? does that seem possible (although rather poor in terms of ethics?)

[Matthew Ames]

Ignore that.... all modes seem to be hot water!!!

[Matthew Ames]

Next bit...

The how water cyclinder pump has been "built" into a cupboard surrounding the tank to which I have no access (SWMBO will disappove if I destroy it!), so I can't check out the wiring on that side. All I can see is that from the control box side (opposite side of the kitchen) I seem to have a 240volt feed (for any of the control knob settings - well they all do water!) that sends mains over. I assume that maybe the termostat on the hot water cylinder is used to switch the pump on and off? Does that seem reasonable?

Cheers, Matt

[Matthew Ames]

I think my boiler seems to have 4 22mm copper pipes that come out of it... or that is what it looks like...... Maybe I need to revisit that bit then :-) Maybe I am going to have a cold Christmas then :-)

Cheers, Matt

[geoff]

In message , Matthew Ames writes

The 3060 is a slightly different timer from all others in the way that it controls the system. It's so long since I had to last think about it, I can't remember exactly what's so special, I'll ask one of my merry men at work tomorrow

I probably have a couple of 3060s around somewhere (having thrown dozens away in the summer) if you are desperate for something to tide you over

[Matthew Ames]

Something to tide me over would be great if you happen to have any spare one around.

I suspect that I really need to update the whole system, but I need to figure out how it all works first, and if I bust it before Christmas I think that I'll be kicked out!!

[Roger Mills]

How about this for a suggestion . . .

Replace each of the two existing room stats with a programmable stat. You can then leave the 3060 on permanently, and do the actual timing - independently for upstairs and downstairs if you wish - with the programmable stats. You can do this without needing to figure out all the wiring - you'll only have to deal with the local wiring to the stats themselves.

When you ultimately sort it out properly, the programmable stats can be part of the final solution - so won't be wasted.

[Matthew Ames]

Mmm yes that could be a good idea. I already have a programmable stat from my last house, but I'll need to get another.... The only downside would be that the boiler would always be re-heating the hotwater tank I assume? rather than just in the two time frames.....

[chris French]

In message , Matthew Ames writes

You just need a to add a 2 port valve controlling the HW circuit circulation.

[Roger Mills]

Possibly, depending on how the HW is controlled. I can't remember what you said about the existence or otherwise of a cylinder stat. What causes the boiler to fire in HW-only mode? [Once you've sorted it, and converted to an S-Plan+ system **, you'll have proper control of the HW, plus a boiler interlock which ensures that the boiler only fires when at least one of the three zones (2 heating and 1 water) is demanding heat.

** See for details of the various standard heating plans.

[Matthew Ames]

From what I can see there is a 240volt feed from the timer for the HW that vanishes into the floor behind the boiler and I assume appears on the otherside of the kitchen with the h/w cylinder. That appears to be wired into a stat on the cylinder and a pump. I assume that when the stat decides it is cold it triggers the pump to run, but there is no feed back to the boiler (and no feedback to the timer unit from the cylinder stat). But to some degree the h/w side is bit of a guess as I can't get to the wiring to see what is actually happening (the cylinder has been built into a cupboard to which if I dismantle this close to christmas I am likely to be killed by SWMBO).

Infact the only wires going to the boiler is the 240 volt feed from the timer unit.

I'll try and source another digi stat 3 (to match my other stat) and take thing from there.....

Cheers, Matt

[Ed Sirett]

Yes, as I said two pumps is the same 'gravity' i.e. "10 mode" i.e you can't have heating without (over)heating the hot water.

[Ed Sirett]

And you might well end up making the vent pipe no longer directly available to the boiler.