Honeywell cm907 in conjunction with a lifestyle lp722

[malcolmallan]

Hi everyone... I wonder if someone can help. I have a fairly old standard gravity fed system. It is a Ideal boiler with a lifestyle 722 controller for hot water and heating with a separate mechanical room stat. Last week i had an electrician replace the room stat with a honeywell cm907 programmable room stat. I noticed a year or so ago (before replacement) that my heating would only come on when the hot water was on. Since replacing the room stat i have noticed that the heating only comes on im this sequence... Put the hot water on... Put the heating on... Then switch the hot water off. Then once he heating is running if i switch on the hot water it wont come on unless the heating is first switched off! The other unfortunate side effect i have noticed is that the boiler spur fuses sometimes when the desired temperature is reached on the programmable room stat.

The electirician was round today with a plumber to look at things.m the plumber is saying the all the zone valves are working and the problem must be electrical. They are suggesting that the lifestyle 722 and the honywell prog room stat are possibly conflicting? Is that possible - i would have thought that the prog thermostat is simply replacing the old mechanical thermostat. They reckon that the lifestyle controller might have to be replaced with one that controls hot water only?

Any advice gratefully received. Thanks.

 

[jackthom]

All it normally needs is for the old programmer to be set to have the heating on permanently, then the new thermostat/prog can control the heating ON/OFF periods.

I can't see how they would conflict, but a few pictures including any motorised valves in the system etc might shed a bit more light.

 

[malcolmallan]

Untitled

• malcolmallan
• 22 Nov 2013
• 1

Untitled

• malcolmallan
• 22 Nov 2013
• 1

Untitled

• malcolmallan
• 22 Nov 2013
• 1

Untitled

• malcolmallan
• 22 Nov 2013
• 1

Thanks for the reply... here are pics of the spur and heating valve, water valve, lifestyle controller and programable thermostat.

I just have the thermostat working on manual - it was the plumber that suggested that this wasnt compatible with the lifestyle controller as he has never seen it before but Im sure that can t be right??

 

[D_Hailsham]

1. The Lifestyle programmer and CM907 are compatible.

2. If you are getting fuses blowing, there is a wiring fault.

3. Can you remove the lid of the junction box and take a clear pic of the wiring?

 

[malcolmallan]

Yes... Il get that uploaded in the next hour or so thanks

 

[Galoka]

Oh right, so I've not seen it before is supposed to be some sort of diagnostic procedure? If they think there was a conflict why did they not investigate? where do these people come from.

In essence they are just switches, why would they conflict?

However, I'm still pondering this one:

Since replacing the room stat i have noticed that the heating only comes on im this sequence... Put the hot water on... Put the heating on... Then switch the hot water off. Then once he heating is running if i switch on the hot water it wont come on unless the heating is first switched off! The other unfortunate side effect i have noticed is that the boiler spur fuses sometimes when the desired temperature is reached on the programmable room stat..

It feels like something not quite wired up properly, but I can't work out in my head what that would be. Did they loo at that do you know?

maybe some pics of what wiring connections there are, or make a diagram.

When you say

once he heating is running if i switch on the hot water it wont come on

What do you mean by doesn't come on? the light on the 722 doesn't switch on, or it does but nothing else happens

 

[malcolmallan]

Untitled

• malcolmallan
• 22 Nov 2013
• 1

Here is the junction box. Yes, when you press the water advance button once the heating has been running, the red light comes on to call for the water to heat but the water valve isnt activated and no water goes to heat the tank.

Its a bit like the opposite of the heating when you click the heating advance button if the water hasnt been on first then it wont activate. so the sequence goes, hot water on (light on).. water starts heating. central heating on (light on)... water is still heating (light on) but central heating valve doesnt then activate until the water goes off (light off)... bizarre. As I say, I dont think it was running perfectly for the last year as I have not been able to get the heating working without the water on first, but I could run them in parallel ok until the room thermostat was added as long as the water went on first.

When I first moved in to the house it all worked fine. My first problem started last year after having had the boiler serviced lol...

 

[D_Hailsham]

As the fault is obviously a wiring one and it will take a long time to diagnose remotely, I think the best solution is to start again with the wiring. That's assuming you can identify what each cable is connected to.

Here is the standard wiring diagram.
Click image to enlarge. Then mouse over image to show the tool bar. Click the square box to enlarge further. Right click to save image.

The wiring of the Lifestyle 722 is not shown so I have given it below.

Untitled

• D_Hailsham
• 22 Nov 2013
• 1

LP722 wiring
L - terminal 1
N - terminal 2
E - terminal 3
1 (HW OFF) - Not used
2 (CH OFF) - Not used
3 (HW ON) - terminal 6
4 (CH ON) - Not used

Wiring of CM907
This is shown in the top half of the page, which is easier to follow. However you need to note the following:

At the junction box identify the wires from existing thermostat.

The wire which links LP722 T4 to thermostat must be moved to T1 in junction box. This wire will connect to Terminal A of CM907.

 

[Galoka]

Though the OP said that they have gravity HW so not the normal S plan, even though they have two zone valves,

so it would need wiring a bit differnetly

 

[twgas]

Though the OP said that they have gravity HW so not the normal S plan, even though they have two zone valves,

so it would need wiring a bit differnetly

OP said "gravity fed" probably meant "open" system, doesnt matter how many times the gravity/fully pumped/open/etc is explained its still "gravity fed" to the masses

 

[malcolmallan]

Yeah sorry... I think i mean open system. Its got a header tank... As you can see im a complete novice!

Thanks very much for this diagram and the advice. I will send this to my electrician and see if he is comfortable with it... If not get a specialist heating engineer in. Will probably take a little time on sunday to check the wiring mysef to make sure nothing obvious is wrong... Obviously disconnecting it first

Its great to know that the devices will work if wired up properly so that i cant be fobbed off with that.

 

[Galoka]

Ah yes, makes sense now

Although it looks complicated, if you are methodical it's easy enough to check the connections are all correct/find the wrong ones.

Still entirely unimpressed that a plumber and electrician between them didn't think to check the wiring, it's basic stuff and should have been staring them in the face.

 

[malcolmallan]

Hi everyone,

A bit of an update on this one... the electrician was out this morning and hard wired the prog thermostat in to the circuit by connecting the LP722 up such that the heating was always on effectively making it a one channel controller on the water. This appears to have solved the problem of the water and heating being able to operate seperately as that seems to now work ok BUT the problem with the boiler spur fusing remains

Still happens either when the desired temperature is reached or you switch the thermostat to off (ie frost protection)... hes coming back Monday!