Central Heating Controls

[Geronimo W. Christ Esq]

The wireless stat only controls the CH, not the HW. The HW would still be controlled by the timer (and also a HW stat which is really just there to shut off the boiler, to stop the water getting too hot).

I did exactly what you are describing recently. I got a two-channel clock (Honeywell ST6400C) and a wireless stat (Honeywell CM67). The ST6400C turns the hot water on or off independently of the room stat turning the heating on and off. On the ST6400 timeclock I've programmed the heating to be "always on"; the CM67 is connected in series so the heating is only on when the stat requests it.

The secret to making it all work is to get a mid-position three-port valve.

It would be very handy to have a stat combined with a wireless programmer which would allow you to control everything from one place, but nobody seems to make anything like this.

Yeah, but that's not as efficient as having more precise control, which you can have by marrying a two-channel programmer and a stat as described above.

[roberth1]

I have A CH system with gravity HW with a mechanical cylinder stat. an

the heating controlled by a 2 wire mechanical thermostat. The Controller is mounted near boiler which is not easily accesible. Gas fired boiler replaced in past 3 years.

Wanted to both change the thermostat to a digital one to get mor accuracy and at the same time introduce more flexibility into th system to replace existing controller which is of the conventional H or HW+CH "auto" "twice daily""continuous" type

Thought the anwer would be to get a wireless programmable digita thermostat but on reading all the installation instructions via downloads none of them appear to be able to send a signal to just hav HW on like in the summer time for example. In my case it would jus mean a signal to activate the boiler to "on" as the HW would then b heated. I do not have a problem with the upstairs rads getting hot as these ar all fitted with thermo valves.

Anyone any idea how to arrange this, my thoughts are leaning to the zone type receivers and using the second zone as the hot water on bu think this may still end up calling the pump.

There must be a lot of CH systems like mine and I cannot understand wh the makers of the wireless programmers have not addressed this H problem.

Grateful for any ideas from anyone

-- roberth1

[Billy The Kid ( The Original )]

Lot of talk of what can and can't be done, to make it simple, as you are upgrading the wiring then you have to comply with Part L of the current building regs.

This states you must have a means of controlling your CH & HW seperatley.

If I were you, I would get someone who knows what they are doing and is also certified under Part P of the building regs to do the work.

As you are upgrading the wiring, you would also be liable to upgrade the earthing of the central heating system and also making sure your gas and water are bonded also.

Things have got so silly now, that from the 1st may 2006 you are not allowed toalter or fit a new soil waste or bath without notifying you local building control at your local council, and you have to pay to have it inspected.....

ALWAYS BEST TO GET THE JOB DONE BY A PROFESSIONAL

[Roger Mills]

With a gravity HW system, your options are very limited. In order to have proper independent control of HW and CH - including a boiler interlock to shut the boiler down when both demands are satisfied - you really need to convert to a fully pumped solution.

There *is* an alternative which is nearly as good - but probably doesn't fully comply with the latest regs. That involves inserting a zone valve in the gravity HW circuit, and fitting a cylinder thermostat, and wiring it up in line with Honeywell's C-Plan configuration. That would, indeed, provide a boiler interlock and would be far superior to what you have at present. It would also involve a lot less plumbing and wiring than going fully pumped. The only downside is the HW takes longer to get hot by gravity circulation that it does when pumped - and the boiler is keeping itself hot for all that time, using a bit more energy than it otherwise would.

I would post a URL where you could look at C-Plan (and other plans) - but that bit of the Honeywell site isn't working at the moment. I'm not sure whether that's by design or accident! Here's the URL anyway, just in case it comes back on line.

you have independent control of HW and CH - whether it's by C-Plan, S-Plan or Y-Plan, you can use wireless and/or programmable stats rather than conventional stats if that is more convenient. A solution which works for many people is to have the HW controlled by the main programmer, plus a mechanical cylinder stat - and the CH controlled by a wired or wireless programmable stat so that you can have different temperatures at different times of the day, together with other gizmos likes party and holiday modes.

[Guy King]

The message from "Billy The Kid ( The Original ) " contains these words:

Oh dear. And what do you think the purpose of this group is?

[Michael Chare]

Have you considered using a Danfoss TP9 programmer. This is a two channel programmer, which uses a wired remote room temperature sensor. . The H/W can have two on periods each day. The C/H can have 6 temperature changes per day. There can be separate weekday and weekend programmes.

There is a gravity option. In this case the boiler only gets power when either the pump is running to heat the radiators or during the H/W on periods.

If you have an existing room thermostat, then likely you can replace it with the TP9's sensor and use the existing wiring to connect back to the programmer position.

You can download all the details from the Danfoss web site.

I've not found another programmer which works in the same way.

[Doctor Drivel]

Best he installs a pump in the either the flow or return of the gravity cylinder with a check valve just after the DHW and CH pumps. Minimum pipework interruption. Then a cylinder stat and then a new programmer. The Danfoss, as mentioned, is an excellent choice. Probably a box on the wall to take a cheap £5 relay from Maplin.

[Phil Addison]

[snip]

Shame. You were doing quite well up to here.