Modified Y-Plan. Any problems?

[AlexEsser]

Hello, i have an Y-plan heating with an honeywell ST9400 programmer. I would like to use a different programmer having only 2 instead of 3 output wires. Therefore, i would not use the DHW OFF output anymore. Is that possible? What problems would occur?

Thanks a lot. Alex

 

[Agile]

It would not work properly!

Although you can reconstitute a HW off using a relay!

Tony

 

[AlexEsser]

That sounds like a good solution. What kind of relay do I need? How am I supposed to wire it?

 

[D_Hailsham]

Hello, i have an Y-plan heating with an honeywell ST9400 programmer. I would like to use a different programmer having only 2 instead of 3 output wires.

What's so special about the new programmer?

Programmers made for CH and HW will have a HW OFF terminal, so it sounds as if you are trying to use the new programmer in a way which is not intended.

 

[AlexEsser]

I have a programmer with 4 wires. One for Live, one for neutral, one for HW On, one for CH On. so the output wires can be energized, but there isn't a DHW OFF wire. The question ist: can i control an Y-plan using this special programmer?

i mean a S-plan or an W-plan just needs 2 wires....

 

[D_Hailsham]

I was just wondering why you didn't purchase a programmer with a HW OFF terminal. Does the new one have some must-have feature which you can't do without?

If you are stuck with the new programmer the way to wire the relay is as shown in the diagram below (Click image to enlarge):

Untitled

• D_Hailsham
• 31 May 2013
• 1

You need a single pole, single throw (SPST) 3A mains relay with a 240Vac coil, but a SPDT or DPDT will do as well. You will also need a socket for the relay and some form of enclosure to make it safe.

You should be able to get what you need from an electronics component store, e.g Maplins in the UK.

 

[matt1e]

The drawing in this post is now correct

Sorry Dave mate,your drawing is not workable you need to use a changeover relay
connect the relay common to live
connect the n/c contact to the valve grey/cyl sat
connect the n/o to the cylinder stat common
disconnect H/w on from the cylinder stat common and reconnect it to the relay coil


there is a drawing in my album,
View media item 62012
which happens to be the same as Daves
err........ and also wrong ...... I'll adjust it later
( and adjusted as promised )

 

[D_Hailsham]

Sorry Dave mate,your drawing is not workable

Why not?

 

[matt1e]

Sorry Dave mate,your drawing is not workable

Why not?

Because if you are on central heating only and the room stat is calling ie feeding 230v through to the orange via the valve
it will also backfeed your relay coil via the cylinder stat (which will be calling ) and energise it, quickly followed by the valve dropping back which will in turn drop out the relay which will then re-engage the valve which will re-energise the relay
in,out,in,out shake it all about

matt

 

[matt1e]

Like this I mean

no I dont lol hang on
second thoughts
best ignore everything I say , Ive been on the drink all after noon

 

[matt1e]

Right this way will definitely work as intended, I have adjusted daves drawing

View media item 61942
as for using a single pole relay, I'll review it when I'm sober

Matt

 

[harry0harry]

had a fancy new programmer fitted by a large company (Olympic sponsor) who sell contracts,it did not work although the gasman said I can have independent hw or heating.they were unable to correct their fault so I asked an electrician to investigate he was able to adapt an existing wire in the programmer to provide a hw off and it all works very well now.
he also found the boiler was not connected to an earth.well I suppose a gasman is a gasman. very happy with it now.though.

 

[D_Hailsham]

Right this way will definitely work as intended, I have adjusted daves drawing

Thanks for pointing out my mistake. I hadn't thought about the possibility of the cylinder stat still calling when the programmer was on CH only.

Your revision of my diagram will definitely work, but it will need a single pole double throw (SPDT) relay.

I really must get round to copyrighting my diagrams. Then I would be able to sue you for breach of copyright.

 

[matt1e]

Right this way will definitely work as intended, I have adjusted daves drawing

Thanks for pointing out my mistake. I hadn't thought about the possibility of the cylinder stat still calling when the programmer was on CH only.

Your revision of my diagram will definitely work, but it will need a single pole double throw (SPDT) relay.

I really must get round to copyrighting my diagrams. Then I would be able to sue you for breach of copyright.

No probs mate I am guilty of the same mistake myself ( see my earlier diagram above)
As for copyright issues you're right and I should do the same ( but we will have to make sure they are correct first lol)

Matt

 

[DP]

ST9400 does have HW off contact.