Central Heating Wiring help again!

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ive not done many (only 2 in fact) central heating wiring so please dont shout or say you shouldnt be doing it if you dont know, as ill never learn if i dont try:Blushing

basically was going to wire an s plan tomorrow (arranged a couple of weeks ago), which i thought great ive got a diagram for that so was looking forward to it. but just had phone call from the plumber to say its going to need to be wired different as he's not done what he was expecting - but only just let me know headbang .

the set up he's got is an oil boiler feeding 2 seperate pumps, 1 for CH, 1 for HW, a room stat,tank stat and a programmer. hes also mentioned about the pumps needing an over run too.

ill be honest im not sure at all how it needs wiring and what i need apart from programmer, room stat, tank stat and wiring centre, so if anyone would like to help me (i know most will if you know what needs to be done) i would be very grateful.

a paint by numbers diagram would be great:Blushing

ive just signed up for a honeywell course in may so that i can learn the basics better, so hopefully ill be able to help other people in the future.

cheers wayne

 
So he's built it up with 2 pumps but no valves??

Don't think that'll work 'cos whichever pump is on will pump around both circuits.

Ring him now and confirm that he has put in 2x honeywell 2 port valves, one for each circuit. Come back and let us know what he says.

Providing he has, I can tell you how to wire it.

If he hasn't, he's a dipstick and you shouldn't waste your time even going round.

---------- Post Auto-Merged at 19:33 ---------- Previous post was made at 19:30 ----------

Also, confirm that the boiler controls the pump over-run (like the gas ones do).

 
well basically its an adapted s plan you need, but I think it may be tricky to have the boiler fire with only 1 pump run when calling for CH and same again for HW, it is doable though, just haven't got time right now.

 
In that case there's no way you can run each pump seperately to feed the two circuits. the boiler will only have one run signal terminal and one pump run output. You need the switches in the valves to be able to seperate out the signals. Quite simply he should have stuck with one pump and a pair of valves (ie conventional S plan). If it's a large system and needs big pumping power he should use a big pump or two in parallel.

Stoopid plumbers!!

---------- Post Auto-Merged at 19:58 ---------- Previous post was made at 19:57 ----------

And on top of that, even if you could run either pump alone, with no valves to control the flow water will go round both circuits anyway !!!!

 
You could, Noz (with extra faff putting in relays), but this would still be to no avail as the water would still go round both circuits whichever pump was running. There's no valves to control the water flow even if you can 'rig' the electrics. So the system as a whole would not work.

 
I had a 2 pump (4 pipe) setup on an oil boiler just like this with 2 relays (no pump over run) and it worked perfectly... it may have had a very slight trickle through the other circuit, if it did it was very minimal....the extra pump was put in because the gravity HW wasn't convecting due to long pipe runs

 
the tank hes put in is huge about 5 ft as there are 4 bathrooms. from what i gathered theres 2 seperate feeds coming out the boiler (1 each side) then each to a pump. 1 small pump to the tank and 1 big pump for the heating (large house). hes says the over run is needed to get rid of the heat out of the pipes. does this make it any clearer/easier?

im dreading tomorrow now. hes normally pretty good and knowledgable so am sure hes done it a way that work but neither him or me know!

 
Ah ha! Are you saying the boiler effectively has two (water seperate) heat exchangers?

Does it have two run signal inputs?

Link us to the model details and install instructions, please.

I've got to go now. back l8r.

 
Mine was similar to what monkey is on about,,,

4 pipes coming out of the boiler - 2 each side (1 heat exchanger),, but mine didn't have pump over run and all controls were external to the boiler

 
some info ive just got off plumber, Boiler make is fire bird, it has a combined water supply feeding 2 pumps. hes saying the pumps needs to be able to be manually turned off for summer so that the the heating doesnt come on - surely the programmer will do that ie dont turn heating on?!

 
I'm with PC on this, the boiler needs to control the overrun, although it could be done with pipe stats with a bit of thoughtful wiring,

does the boiler deffo have separate HW and CH circuits? it will need to have in order for 2 pumps to work independently, then simply wire the pumps via pipe stats, with the room stat and tank stat calling for heat on each circuit as required by the programmer, you will need the pipe stats/pumps on a permanent live from the programmer though,

its not dead easy simple, but not so overly hard that you couldnt do it I dont think, maybe you will need to come back for a bit more guidance,

or to give us more definate info on the set-up,

but Im thinking this can be done fairly easily as long as the boiler is capable of supplying 2 circuits .

 
thanks for advice so far guys, plumber thinks it can be done so gonna give it a try tomorrow but no doubt ill be back on here tomorrow night!

 
hes found a diagram in a book called Domestic Central Heating Wiring Systems and Controls, which he says has everything we need inc pump over run. one thing he has said is needed (in the book) is a double pole change over relay.

the pumps are on the returns not the flow.

im even more confused then ever now. oh well itll either work or wont.

---------- Post Auto-Merged at 22:20 ---------- Previous post was made at 22:16 ----------

he couldnt remember model but i think its the system one Manfacturing Central Heating Boilers, system boiler

its in an outhouse. sorry PC im rubbish.

 
Enviromax Condensing Boilers

---------- Post Auto-Merged at 22:49 ---------- Previous post was made at 22:46 ----------

the boiler is either on or off according to the manual, so you sre going to need zone valves to sort out the heating and hot water,

I dont see any other way around it, otherwise you are going to circulate water round the whole system.

 
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