Hot Water / Central Heating Timer

indiegirl_2

I've got a Honeywell CH/HW timer controlling my boiler at the moment, but it's just a 24hr thing for both.

Does a timer exist that allows 7 day programmable functionality, for the HW and CH independently? Some days I'd like the CH to be on when the HW isn't, and vice versa depending on the day and time.

Would a "normal" 7 day timer allow me to do this? Also, could a competent DIY-er change one of these over?

Thanks in advance.

jennifernil

7 day timers are certainly available, but you need to have a certain lay -out of pipework/pumps/motorised valves for it to work, also more complicated wiring.

There are 2 basic types of 7 day timer, ones that will do what you want and ones that won't.

Perhaps not a DIY job, but it will depend on what your present system is like.

moonrakerz

I fitted one of these myself.

Does everything except make the tea !

http://www.inspiredheating.co.uk/acatalog/TEMPUS_6_7.html

indiegirl_2

jennifernil wrote: »

7 day timers are certainly available, but you need to have a certain lay -out of pipework/pumps/motorised valves for it to work, also more complicated wiring.

Okeydokey, I'm not sure if my system is compatible, but I have a gravity fed conventional boiler with a cold water tank in the loft and a hot water one in the airing cupboard.

I've just checked online and I've got a Honeywell ST699 (the 24hr one) - I can get the ST799 which will do what I want, but will the wiring be different?

jennifernil

It could be. Have you got a motorised valve, or 2 pumps?

You need more controls and hence more wires to have them working at different times.

jennifernil

Looking at the Honeywell stuff, I would not think that the 799 will do what you want. The only difference is that it is 7 days rather than 24 hours. What you want is an ST6400C. £52.97 (+VAT?) from Plumbworld

jennifernil

Having spoken with OH he thinks it is likely it would work, as you can already have one thing on while the other is off. He would know by looking at the wires, but that is not much help to you!

Do you have a thermostat on your HW cylinder?

indiegirl_2

Aha, I see the difference. OK, I have one pump, in the airing cupboard. I have a thermostat on the hot water cylinder as well. The system's about 20 years old.

Indeed, I can currently independently control the HW and Heating (ie keep the heating off whilst the HW's on - thank goodness for when it's summer!), but just on a daily basis (ie on at X hours, off at X, or twice in my case), I just wanted to be able to specify the ons and offs per day really, I'm not sure I need as much control as I said in my original post.

You're right about the 799 - it can only specify the ons and offs over a 7day period. I'm not sure if that's going to be enough or not for me as I might only want the HW on for an hour in the evening, but the heating on for 4 hours, say. I'll investigate the ST6400c, and will check with my plumberycorgiblokey (official term, that!) as to whether I've got enough wires!!

Thank your OH for me as well :T

jennifernil

I love your new official term!!! My OH is always making up words!

We have no specialised knowledge, but built our own house 20 years ago and designed the heating system, chose everything that went into the house, so we learned a lot of useful stuff. And OH is/was a Civil Engineer so that helped too.

Our heating is also 20 years old, we keep expecting it to break down any day! OH's hobby is electronics so he built our programmers (we have a "granny flat" with its own heating system) 20 years ago when ones like the ST6400C had not been invented. Ours does what it does. You would get better/quicker heating of the water if you had 2 pumps. And removed the motorised valve (if you have one).

Do you have thermostatic valves on the radiators? Good idea to have them on all but one. Choose a small rad, it acts as a bypass. We use one of the small ones in the hall. It is deliberately too small so never heats the area enough to be too warm.

I don't see any point in changing your 699 for a 799, you can manually reset it for weekends if necessary. I would rather go for the ST6400C as it is all electronic so no mechanical parts to fail. And there is not much price difference.

mk-donald

Indiegirl

Did you sort it out ?

I had a similar issue with my 20yr old system. Had a Honeywell controller that failed and British Gas replaced it with another similar 24hr controller but it had become noisy and I'd stopped paying BGas' exhorbitant annual "insurance" having a CORGI boiler checkup separately and self-insuring for other fixes.

I got the Horstmann Centaurplus C27 Electronic Programmer from https://www.screwfix.com for £28 Quote No: 11225 .

Horstmann were incredibly prompt/helpful in confirming compatibility and wiring diagrams (as there is usually an 'industry standard' 6 connector backplate behind the controller)

on http://www.horstmann.co.uk/downloads.asp
see Programmer Wiring and Replacement guide (Large)

From a quick look your ST699 is compatible with their simpler/cheaper C21 programmer.

Good luck with resolving it.

Mutton_Geoff

Personally I'd get a programmable thermostat instead. You can set your desired hot water times with the existing unit, and if it's on when it needn't be, if you're tank is lagged OK there won't be too much wastage. The programmable stat is very easy to install (two wires) and you can set heating times/temperatures to closely match your needs and leave the airing cupboard controller on 24hr (the stat now controls on/off times). Honeywell do a decent one for about £45.