Boiler control

[Adam]

Hi All,

I'm looking for a better way to control our boiler and I'd appreciate advice from the group.

We have a Baxi 133 HE plus (combi), but we daftly thought the cheap manual controller would suffice (a dial on the front of the boiler with radially arranged switches). We'd like to dramatically increase our control over the heating circuit. At the least, we'd like to be able to program two on/off cycles per day, with each day configurable. At best, I'd like thermostatic control too, although I'm not sure where it would be best placed.

Can anyone advise me on controllers, thermostats and whether/how I can fit them to the Baxi?

Thanks - Adam...

[John Rumm]

Assuming the baxi can interface to a standard room stat (I have not checked - but I would surprised if it couldn't), then something like:

do what you want. You set the "programmer" on the boiler to "always on", and let the sat do everything else. You can have different temperatures set at different times of the day (and days of the week).

Install it in a circulation space - hall being typical. Makre sure the rad in the same room does not have a thermostatic valve of its own (if it does, unscrew the head)

[Tim W]

Adam wibbled on Monday 12 October 2009 19:42

There's an infinite choice...

There's loads of electronic 7 day programmers in B&Q (eg Sunvic)

If you want thermostatic (eg a 4 level temperature curve, per day is quite common) you could try Heatmiser (google). Some of those have remote probe options (probably limited to a few metres) but that could allow you to place the controller near the circuit and run the probe to the next room.

Any boiler can be controlled by any timer/stat as there should at least have a pair of terminals marked as demand or thermostat or call for heat or similar (it was common in the old days to put the stat in the hall or main room even if the timer was in or next to the boiler).

As long as your controller can switch mains voltages then it will be fine.

Another option are the Honeywell radio ones (CM Zone), where you put the boiler relay (with radio receiver) near the boiler and the timer/stat can go in any room. With the right model series you can bind multiple (up to 4 IIRC) timer/stats to one relay. I'll look it up if you want more info.

Others also make radio systems - agin, if interested I'll give you some links.

HTH

Tim

HTH

Tim

[Steve Walker]

It all depends how much control you want. One of the radio linked timer/stats is quite flexible, as you can move it to whichever room you're occupying. At the other extreme, we have a motorised valve and a timer/stat in every room, allowing complete control of time and temperature throughout the house. We've even got one in the bathroom (battery powered stats, 12V from a safety transformer and relays to operate the valves - this allows all the stats to be wired with alarm cable too, neatly clipped to door frames, etc and no worries if the kids damage the cables.)

SteveW

[Dave Liquorice]

I'd go for a 7 day programmable room thermostat. This allows different temperatures to set for different times (normal 4 or 6 times/day) independantly on each of the 7 days of the week.

A wireless based one will make installation easier. You just have a reciever that you wire in close to the boiler and the stat/programmer uses RF to tell the receiver to switch the boiler on. You can also move the stat around if you want.

Note that the room with the stat in it shouldn't have any other thermosat trying to control the same room or they will "fight".

[Tom]

I can second that Dave, i had a wireless stat system installed a month or so ago when i had a new boiler put in. I leave the boiler "on" and control the heating from the stat. I have not bothered fixing it to a wall yet as it is great to move it around the house, however the cold weather will be the real test!

Tom

[geoff]

In message , Adam writes

Fit what you like, the pcb only sees it as a switch

[YAPH]

As others have noted a programmable thermostat will probably give you the best control, and there are many makes & models of these. The ones I find easiest to set and program are the Honeywell CM series e.g. CM907 7-day wired or CM927 (or sometimes known as CMT927) wireless stat.

[Roger Mills]

I can't find an installation guide for your exact model - but the electrical connections are likely to be similar to those shown on Page 31 of

the link between terminals 1 and 2, and connect each to one of the switching contacts of just about any wired or wireless programmable stat of your choice. Leave the boiler's manual control set to 'on' - and program the stat to turn the heating on and off, and control the temperature of each 'on' period, several times a day, as required.

[Doctor Drivel]

Your boiler has an integral flow switch to switch out the burner and pump if the flow is below a set rate. This means TRVs can be fitted all around.

Your best option is fit TRVs all around on every rad - then individual and "independent" temperature control of each room. Then fit a Horstman single channel programmer. DO NOT get a stat/programmer or wall stat. This programmer can be fitted anywhere convenient - under stairs, in kitchen, etc.

Use the features your boiler gives - the ability to have TRVs on all rads. A centralised stat means the whole system can be switched off even though some rooms are calling heat. You then have no cables running to stats in halls or living rooms and no ugly stats on the wall.

[Doctor Drivel]

Look at single channel timers:

at No. 12143

[dennis]

So when the boiler flow witch has turned off the pump and there is no flow how does it switch back on? This will happen every time all the TVRs close so what does switch it back on when the valves open but there is no flow due to the pump being off?

[Doctor Drivel]

I believe the boiler periodically turned the pump to test if there is any flow.

[John Rumm]

I would go with the prog stat and one non TRV rad (TRVs elsewhere), since without it you lose the ability to preselect different temperatures during the day, and also the ability to tweak the temperature should you feel too hot/cold.

If the system is well balanced then its not really a problem.

You can get wireless stats if you are afraid of wires.

[Mathew Newton]

Perhaps this is what you meant, but the CMT927 is the wireless version of the CM927. The latter being the updated replacement for the CM907.

Either way I'd agree that they are very good programmers with some useful features.

Mathew

[Mathew Newton]

Oops... Scrap all that - I was thinking of the old CM67 - that's what's been replaced by the CM9## series.

Apologies for any confusion,

Mathew

[Doctor Drivel]

You would, but you haven't a clue about heating.

[YAPH]

No probs. If you want some further confusion there's a (slightly cheaper)

7xx series which is a landlords' version of the 9xx series. It doesn't have the prompt text on the display (so more like the CM67x), I think maybe it doesn't have a backlight(?), is missing some other features (holiday mode maybe? I forget), and I think it has something like a 400-day nag for service (supposed to ensure the system gets looked at annually, e.g. for a Landlord's Gas Safety).

[John Rumm]

Well I guess if the op wants a system with limited functionality he could take your advice.

[Doctor Drivel]

I have explained the stat/progs to you on other threads. Read them again.

To the others. This boiler is one of the few that can cope with TRVs all around and no nuisnace central stat. I doubt he knows that. If Baxi had a good reputation for reliability, they would sell a lot of these boilers. Cheap and quick to install and the customer satisfied as TRVs all around.