electronic spares for a top secret plumbing project

[Paul Barker]

Ah you don't always need a circuit board, I am from the thermionic age so I used International Octal bases and the type of relay that fits them, and hard wired it, so there.

 

[ChrisR]

Sure , hence the relays on the din rail. There's always ye olde tag strip I suppose, but these days you'd use i.c's, and the legs won't spread that wide! Then you need a power supply...

You don't "need" a din rail. I came across a relay which was glued inside the lid of a box, and the wires soldered direct to its pins!
At 3 relays and a box for about £12, it would be cheaper than plumbing in a bypass.

[I suppose you're going to tell me you want my Cossor 1035?]

 

[olly_k]

Also look at Farnell (connected with CPC) , RSWWW, Maplin, and Rapid Online, who may be the cheapest.

Relays and solenoids are nothing to do with electronics, I would say.

A quiz for anyone interested :

A CH sytem requires a bypass, but there's nowhere to put one. It has 2 2 port valves, standard S plan, nothing unusual.
SO, using a simple, cheap reliable system, make something which can be connected, such that the HW valve is open when the boiler is keeping the pump on, in overrun, (ie when there's no call for heat.)

Otherwise the system must operate normally.

It's easy with 3 relays on a din rail, can you do it better?
I would say anything electronic, though trivial to design conventionally, would be far too complex to make, for a one-off. For a start you need a circuit board.

I like a challange, now feed me with a diagram of your 2 2 port valve, standard S plan system and I'll have a go

 

[chrishutt]

http://content.honeywell.com/uk/homes/Catalogue/Sundial Plans/3.2 S Plan.pdf

 

[olly_k]

Chris couple of q's please!

Can the wall timer send HW + CH control signal out at the same time - poss not important in this case but may be helpfull...

More importantly, in the diagram you have given me, if I have things correct the pump turns on when either port is energised. I would assume I will need a seperate 'pump on' signal from the boiler which appears to be missing here...? Or have I missed something LOL!

Just a thought - If no signal exists from the boiler could you make use of a tank thermostat strapped to a CH pipe, to allow pump run on until CH water temp reduced to x amount?

 

[olly_k]

is it this simple?

Rl1 switches on whenever it gets a signal from the valves and feeds pump from same supply. when off RL sw1 in normally closed position allows pump feed to come directly from timer htg output via a second relay if required?

Is that what was wanted?

 

[ChrisR]

Actually the diagram is wrong, for a boiler with pump overrun!! The problem comes with boilers which control the pump directly, so when the boiler goes off, the pump stays on for a while.

Skanky S, (oops not Y,) plan sketch

Third para question - answer is yes but no.
Traditional pump overrun control works with a thermosat which has SPCO contacts. Supply to pump, on the common of the stat, comes from permanent live when the pipe is hot, and boiler switched live when the pipe is cold.
That isn't the problem here. The pump power comes from the boiler, and it's important that it's left that way, functionally speaking. You wouldn't want to disable the boiler's self-cooling mechanism.
So the problem is actually that the pump can be on, with nowhere to pump the water to because the valves are shut.

Edit - just seen your diag. Ummm - you've misunderstood the problem!

 

[pannierstan]

Skanky Y Plan.....Looks like an S plan to me Chris

 

[olly_k]

Edit - just seen your diag. Ummm - you've misunderstood the problem!

I just figured that Oh well I might leave it for another day!

 

[ChrisR]

Oh well I might leave it for another day!

Go on have another go. I can't believe it takes 3 relays!