Central heating timing question: Is there an easy way to do this?

[Mike W W]

Can anyone think of a way of solving this problem?

I rent part of my house out as a flat. The hot water C/H for the whole house, including the flat, comes from a combi boiler in my part of the house.

The tenant who rents the flat works odd shifts, and they are never the same, two weeks in a row. Therefore, using a programmable timer and a gate valve to time the heating in her zone of the house wouldn't be practical. I couldn't expect her to play around with a programmable timer every time she goes to work. She's probably going to be in a hurry, and think "Ah, to hell with it!" and just leave the heating running while she's at work.

What she probably would be willing to do, though, is just press a single button on her way out of the door. If it's possible, I'd like the said button to switch the heating off in her zone of the house for

7 hours. (Her shifts generally last 8 hours, whether they start in the morning, afternoon, or evening.)

Can anyone think af an easy way of doing this? If it is feasable, I'd also like it so that if she came home early from a shift, she could simply press another button and the heating would come on again until she pushes the 'off' button again.

Ideally, I'd have a third button that would switch the heating to her zone off indefiniteley, until such time as she presses the 'on' button. That's the one she's press if, say, she was going away for a few days.

Thank you,

Mike W

[Andrew Gabriel]

A number of points...

You could use an occupancy detector (as used to switch on lighting) to detect when tenant is in or out, thereby removing the need for the tenant to do anything. (You could use it for the tenant's lighting too.)

One way to disable heating in an area is to fit small heaters to the heads of thermostatic radiator valves. These can be in the form of a resistor attached to a terry clip, clipped on to the phile. The resistor is driven from a low voltage supply for safety, and has the effect of applying a temperature setback which is proportional to the power disssipated by the resistor. I used this technique for years to control a thermostatic gas heater which had no remote switching capability. The resistor was driven by a voltage selectable wall wart which allowed me to adjust the temperature setback, and was switched on and off by a home automation system.

If you will ever want the tenant's part on and yours off, then you are probably going to have to go for a proper 2-zone design and controls.

Cautions about disabling central heating in parts of a house... If parts of a house are cooler than other parts, there will be a tendancy for condensation to form in those areas as air circulates, particulary the colder parts such as on outside walls (depending on building construction) and windows. The heating system in the house probably wasn't designed to leave some rooms cold. You might find heat loss from adjacent rooms to the cold room makes them feel colder than they were.

[Cicero]

============================== One possible solution - I think.

Is the tenant's zone supplied through a standard zone valve? If so a simple light switch could be used to interrupt the current operating the zone valve, which in turn would close the valve.

It would obviously depend on the general state of the heating - it would only switch on /off if other controls permitted.

Cic.

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[Owain]

Does the heating really need to be timed to come on in advance? Especially if you use a programmable thermostat with a set-back temperature, the flat should be tepid enough to warm up fairly quickly if the tenant switches the heating on as she re-enters.

make several versions of a programmable thermostat which boosts the heating for a pre-set time (up to 2 hours): - the 900 with a touch-pad; the 910 which is activated by a PIR.

Owain

[Mike W W]

I guess it's desirable rather than essential.

Do you think the 910 could be used to control a gate valve on the central heating feed to the flat? If so, that would be an option.

Thank you for the sugestion,

Mike W

[Mike W W]

That could easily be arranged. At the moment, it is just a zone within the building, controlled by the main programmable timer.

In that case, a PIR light switch could also be used to control the zone valve, yes?

Understood.

Thanks,

Mike W

[Mike W W]

Thank you for the suggestions,

Mike W

[Cicero]

==================== Since you're prepared to insert a zone valve any switch (suitable for the required current) will do the job including the PIR. You might have trouble finding a suitable PIR which wouldn't need repeated switching like a security light PIR. One possible alternative would be to put in a room thermostat to control the zone valve. This could then be used as a switch by your tenant - turn the thermostat low when exiting and turn it high when returning. Not ideal because of the need to re-set the required temperature every time but it would work. My original suggestion (light switch) seems the easiest solution if a little unconventional.

Cic. ================================

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[Owain]

The terminals on both are 240V Live, Switched Live, and Neutral. 16A resistive, 7A incandescent, 6A fluorescent.

Owain

[Mike W W]

Thanks for the info. So, (excuse my lack of electronic savvy), does than mean it could be used to open and close a motorised gate valve?

Mike W

[Owain]

I see no reason why not.

Owain

[The Natural Philosopher]