Two Pump System Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[maxcaddy]

I have a standard vented oil fired system installed in 1971 as pumped CH and Gravity HW, updated in 2006 to (Worcester Greenstar 32-50) running 2 pumps (CH +HW) (2 NRVs) and operating off of two 24hr timers (linked boiler feed), with no thermostats.

Can anyone point me in the direction of a wiring diagram so I can use a controller (EP3002 or similar) and HW & CH thermostats.

Previously I wired a gas sysyem with 2 pumps about 18 years ago using the diagram that came with a Potterton Profile 50 boiler. However thats lost, and Pottertons don't seen to want to 'find' the circuit or any details for me.

I've looked at the 2 wiring diagrams on a link from here, but they are not as clear as I would like, and don't seem to have separate timing control for HW & CH.

Any help will be most welcomed

[plumbbob]

Have you tried the Honeywell website and searched for "Sundial S plan"?

[maxcaddy]

Thanks for that, but I'm not sure why I would want to buy 2 motorised valves, when all I need is to control the switching on/off of the pumps ?.

I already have bought a contoller and the thermostats, and its only identifying the system wiring which will power the HW pump when the HW thermostat is closed, and the same for the CH, off of a timed input that I need.

Twin pump systems were popular a number of years ago, but now seem to be rare ?

[sparx]

Hi Maxcaddy,
If you were running 2 pumps already then there must be a relays calling the boiler otherwise no isolation between ch/hw. therefore all you need to do is break the individual pump lives with the thermostats.

Most room 'stats need a neutral to operate with minimum 'deadband' so run a three core and earth cable from timer/programmer position to room 'stat. pick up neutral at prog./timer using grey (sleeved/taped blue). replace pump outgoing live with brown core, and connect it(red?) in a single connector block to black (sleeve/tape brown).
At room stat end connect 'stat using brn to live in, grey to Neutral, black to 'call' term .

do similar using twin/earth to cylinder 'stat, minus Neutral. ie,replace out going pump live at prog./timer with brown from new cable.
connect pump live to blue(sleeved/taped brown) in small terminal block.
At cylinder connect brown to common term and blue to 'call' term.
earths sleeved green/yellow must be connected to earth at prog. even if stats don't require them, to comply with regs.

suggest doing all this before changing to programmer from timers to ensure system works OK at each step.

However I would suggest running cables from control area to each stat position yourself then get any good local leckie to connect up for you as it's easy to muck it up!!

regards SPARX

[maxcaddy]

Many thanks Sparx, I guessed it would only be wiring the thermostats into the line, with the actual pin to pin contacts being the unknown.

Actually I don't have any relays in the system. Its simply timers onto pumps. Yes I know someone will say there's the issue of differential pressure when both pumps are running, which should make a big problem for the flow rates, but in reality (for the last 3 years) my system will pump both HW & CH with both pumps running and give good circulation, as proven by putting thermometers onto the pipe runs.

In the meantime I have been sent a wiring diagram from Honeywell for a two pump system but this uses two 'zone valves' as well, presumeably in lieu of using non return valves ? However, this system also identfies using a 'typical SPDT relay'. Any idea of which/what one would work best ?

Regards

MC

[maxcaddy]

OK no worries, its all sorted with the help from Honeywell who have provided a drawing of exactly what I needed. Other than......

Where can I buy a cheap SPDT relay ?

thanks

MC

[plumbbob]

Maplin sell online and have stores nationwide.

[maxcaddy]

Thanks for that :D

Seems the N07AW relay on the smaller base (N32AW ?) is the way to go.

Have you, or anyone on here, wired one ?, and if so which of the 8 pins did you use ?, or is there a wiring diagram with the maplin kit which clearly identifies which of the pin-outs matches the 5 contacts which I need come off of ?

Regards

MC

[plumbbob]

I'm not quite sure what you are asking here. If you need advice on how to incorporate the relay into your system, the answer is I have no idea. If you could point to the Honeywell diagram maybe it can be worked out.

If you are asking specifically about the relay, then there will be a wiring diagram supplied that shows which pins do what, and anyway, with the case being clear plastic, the internal works can be easily worked out.