HW and CH timer/programmer issues

[doncorleoni]

I have a quick question regarding the central heating system installed a few years ago....I have recently noticed that I cannot turn on CH independently from the HW. The 3 way Honeywell valve seems to be working fine and is diverting hot water to the rads and HW cylinder (or both) based on input from the thermostats. Hot water works fine if requested from programmer (CH stays off) but if i select CH to be on, the HW comes on too (overrides the off setting on HW and both red lights on programmer light up).

In the Drayton LP55 program manual it mentions a switch at the back of the unit for gravity (g) and pumped systems (p), with gravity it says you cannot have CH without HW being on......great i thought so move the switch to p and problem solved.............. I assumed I had a fully pumped system so moved the switch from G to P After doing this, I could turn on and off HW and CH independently - but boiler does not come on if CH is selected and HW is not (both stats set at max).

I guess something is wired up wrong? System works fine as it is but i would like to separate CH and HW completely if i can to save a few pennies.

Hope this makes sense!

Any help / ideas much appreciated!

 

[mikely]

With a 3 way valve, your wiring should be to the Y plan system. Check to the Honeywell wiring diagram:

http://www.honeywelluk.com/Documents/All/pdf/940.pdf

 

[DeltaT2]

Not too sure why they installed it with the programmer on 'G' as it sounds like you have a fully pumped system. Perhaps they did this to cut corners, who knows?
My advice if you are happy to work on electrical systems safely? Go to the Honeywell web site & download their 'Y' plan wiring details, or indeed check in the FAQ here, as I recall these details are here.

Once you have the wiring details, check if your system has been wired correctly and get back to us. What always helps is some photos; existing controls & wiring etc.
HTH

 

[doncorleoni]

Great many thanks for replies so far had a look at the wiring and it does look like its been wired up as gravity fed. The programmer seems to be missing a connection (hw off) to common (number 1 on control back panel). Possibly as the new heating system was installed in place of an old (25 year) unit the installers used the same wiring which did not have enough wires to make full use of all the hw/ch selections (16) and that's why I am running on 10 and hence why ch and hw must be on at the same time. I guess routing another cable up to the connection box in the airing cupboard from the control panel in the kitchen was too much effort!

So system working as gravity fed - I have room stat and cylinder stat plus hw 3 way valve......had anyone had experience of system set up like this? It's not really a problem and been like this for a few years....but seems a waste to keep heating the water!

Cheers all

 

[DeltaT2]

Yeah, looks like your installer just cut corners with the wiring or just too lazy to do the job right. Certainly you'll need the HW off wired up for a fully pumped system on a 'Y' plan.

 

[doncorleoni]

Yup does indeed look like it but I don't blame them to be honest running another cable up to the valve breakout box from the programmer would have been a bitch of a job behind tiles etc. Found another post saying:


For heating to be on by itself, there must be 240V on the grey wire. This can come either from the Programmer HW OFF terminal or from the cylinder thermostat "satisfied" terminal. If the wire from HW OFF is missing, you will only get CH by itself if the HW is ON but not calling for heat.

So looks like if I want full independence I need to run another cable is there any way I can do something with wiring behind programmer? Cannot see anything obvious from wiring diagrams.


Thanks again all

Read more: //www.diynot.com/forums/plumbing/y-plan-and-frost-stat-wiring-query.296206/#ixzz1bbrWG9td

 

[DeltaT2]

Yup does indeed look like it but I don't blame them to be honest running another cable up to the valve breakout box from the programmer would have been a **** of a job behind tiles etc. Found another post saying:


For heating to be on by itself, there must be 240V on the grey wire. This can come either from the Programmer HW OFF terminal or from the cylinder thermostat "satisfied" terminal. If the wire from HW OFF is missing, you will only get CH by itself if the HW is ON but not calling for heat.

So looks like if I want full independence I need to run another cable is there any way I can do something with wiring behind programmer? Cannot see anything obvious from wiring diagrams.


Thanks again all

Read more: //www.diynot.com/forums/plumbi...at-wiring-query.296206/#ixzz1bbrWG9td[/QUOTE]

Can you not steal a N or E core from the wire that goes from the programmer to the wiring centre to give you HW off to the grey? The E & N are all common connections, perhaps there's a spare core? Failing that, what about fitting a relay/relays at the wiring centre?