Wireless thermostat on an existing bolier?

Phibsboro

Hi,

I recently got a Ferroli Optimax HE18 gas boiler fitted - its a system bolier, heats both water and rads at the same time. It didn't come with an external thermostat nor does the built in timer have a +1 button for an extra hour - the result is that it is eating the gas as I leave it on for longer than intended when its cold.

I am looking to fit a wireless thermostat and use that to control it instead. I am looking at something like :-

http://www.cheapboilers.com/thermostat/honeywell/cm-927-programmable-wireless.htm

My understanding is that the receiver part wires into the mains power (say after the mains on/off switch and the boiler itself) - is that correct? So I would leave the boiler set up in manual mode (i.e. always on) and use the receiver to control the whole thing being turned on? I just have this vision of the whole boiler shutting down and starting up every few minutes as it hits the target temperature - is that the way it should work?

Any advice would be very gratefully received.

Thanks,
c

youtheman

DO NOT use your external thermostat to switch the main power on/off to your boiler. Your boiler must retain the ability to run the pump even when the burner is switched off (so that the system pumps the hot water around the circuit so that it can cool down in a controlled fashion). If you cut the power then the system just stops, you might also find that the existing built-in-timer also stops.

A boiler is normally supplied with no EXTERNAL controls. There will be a link that has to be removed to allow you fit an external control (normally a volt free contact). So you'll have to look at the manual for your boiler and determine where this link is, remove it and connect the new programmable thermostat to it.

The device you propose also incorporates a timer, so you'll have to decomission the existing built in timer. Also, because the device has a receiver you'll have to give it an independant power supply.

Remember that your heating system has a long delay. So if you programme in a temperature set point, when the system reaches it and switches off the burner, the pump will continue to pump hot water and the temp will continue to rise above the set point. It will eventually stop rising and then begin to drop gradually (depending on the level of insulation etc). When the temp drops below the set point the boiler will kick in again. So it won't be cycling on/off every few minutes, more likely every 10 -15 minutes (or greater)

Sorry if the above is confusing, it's just hard to describe.

youtheman

Look at the manual for your boiler here : http://www.ferroli.co.uk/Product_Documentation/Domestic/Optimax_HE_18_S_Manual.pdf

See Figure 14 on Page 14. The link that has to be removed is between terminals 5 and 6. You then connect your new device here. You'll also have to disconnect the existing Time Clock (would appear to be just plugged in).

You're messing with 220 volts here, so don't go near it unless you know what you are doing.

Lex Luthor

youtheman wrote: »

Look at the manual for your boiler here : http://www.ferroli.co.uk/Product_Documentation/Domestic/Optimax_HE_18_S_Manual.pdf

See Figure 14 on Page 14. The link that has to be removed is between terminals 5 and 6. You then connect your new device here. You'll also have to disconnect the existing Time Clock (would appear to be just plugged in).

You're messing with 220 volts here, so don't go near it unless you know what you are doing.

youtheman is correct....just wire the relay unit across pins 5 & 6 of your boiler. I would think the existing time clock could just be put on continuos as the boiler is now controlled by the Programmable unit.

If you are confident, just make sure you switch off the mains and make sure you tighten down on the terminals of the relay and on 5&6 of the boiler with your connections.

That unit is expensive and I'm sure you'd find cheaper ones out there. I'm not condoning it, I work for Honeywell and its a damn fine unit. make sure you read the manual on the placement of the unit.

With regards to your boiler switching all the time with these....it won't happen. These units wont do that. You house will hold the desired temp for a lot longer than you would think.

They can be set for varying ranges around the desired setpoint, but I would stick to +/- 0.5 deg of your desired temp.

These units aswell allow you to program your times to the minute which is effectively what you are paying for. All the other units mostly only allow changes every half hour or every hour.

Phibsboro

Great advice guys, I appreciate it. I'm gonna review all the data and see if I understand it - if I understand it, I'll give it a go myself. If I'm doubtful I'll get someone else to do it.

Thanks,
c

kitser

worth remembering that if you tamper with it and start having problems, your warranty will probably be void.