Which is knackered: boiler or timer?

[mr_simonward]

Hi, I've browsed this forum before, but now i'm hoping someone can help me out, cheers in advance...

Basically, our boiler isn't always firing up when programmed to by the timer unit.

The boiler serves both central heating and hot water, and is controlled by a seperate timer unit (Lifestyle LP241). Hot water doesn't seem to be a problem, but I keep coming home to a cold house.

When this happens, the orange light is 'on' on the timer, indicating that the central heating is on, but the radiators are cold, and the boiler is 'idol'. If I turn off the main 'fused switch' (timer lights go off, but time display remains, i presume backed up by battery) and then turn it back on (orange light comes back on, as programmed), within a few moments the boiler fires up and starts heating the radiators.

How do I go about locating the fault?
Is it the timer unit or boiler?
After looking in screwfix, replacing the timer unit seems both cheaper and easier - being a job i would feel comfortable doing. But if it's the boiler it'll mean getting someone in, and without a doubt end up much more expensive.

I was hoping I could call on the experience of others out there to point me in the right direction of at least the problem , so I am better equipped with knowledge if I have to call someone in (I don't fancy appearing on 'rouge traders' just yet...)

Cheers guys.

 

[gasmarkone]

Hi, by saying that the hot water is OK and assuming that you have a hot water cylinder, I would think that the boiler is not the fault [its only a kettle!]. Could well be a programmer fault, but I think you may have a valve in the airing cupboard [ big assumptions] which the programmer sends power to [ via roomstat] and wants power back from. A few more details about the system should help.

Mark

Milk, no sugar ta.

 

[mr_simonward]

Thanks for the fast response Mark,

It's perhaps best you have a look for your self:

Boiler & Timer: http://www.simonaward.plus.com/ch/1.jpg
Timer: http://www.simonaward.plus.com/ch/2.jpg
Airing Cupboard: http://www.simonaward.plus.com/ch/3.jpg
Thermo: http://www.simonaward.plus.com/ch/4.jpg

My knowledge of CH is limited, I'm still just getting my head around all this (last house was a simple on-demand combi). Not sure that it matters, but it's a 3 storey house, boiler and timer are in the kitchen on ground floor, thermo in the hall on ground floor, and airing cupboard is on 2nd floor (top).

In the airing cupboard, am I right by saying that the green object in the top right is a pump, and the white box mid-right is a valve?

Let me know if you need any more specifics.

 

[gasmarkone]

Well, your a wizz on the computer. And don't call combi boilers simple! So first off, switch the timer to CH on, does the roomstat now make a click when you turn it up/down? If it clicks, power is going to it [silent if no power]. So with CH on, HW off, roomstat 'clicked' on, does the indicator on the 'white box' in airing cupboard go to H position?

Mark

Milk, no sugar ta.

 

[mr_simonward]

It was already set to H, could that be the problem?

Basically, before I conducted this little test the settings were:
- Timer HW: Twice (Currently off)
- Timer CH: Twice (Currently off)
- No 'click' from the thermo when turned up or down.
- 'White box' in airing cupboard indicates H (from choices of W M H)

Now, following your instructions:
- I turned CH ON (boiler fires up)
- There is no 'click' from the thermo when turned up/down (but I'm pretty sure I can hear it 'click' as I turn the CH ON. also, does it not 'click' at the current temperature? it pretty cold now, so perhaps it's below 10' downstairs or something and therefore just 'on')
- HW set to OFF
- No change at the 'white box', still set to H.

What exactly is the 'white box' and what do the W M H mean? When should the 'indicator' be on each? (I actually thought it was a switch, but just daren't touch it )

 

[gasmarkone]

OK, this 'white box' is a diverter vavle, directing the heated water to hot water[W], heating [H] or both [M... mid]. It sounds like its sticking. Try some different switching to see if it moves from H to W and back [is you're immersion heater on, you may have to turn up the cylinder stat on front of hot water cylinder to get switching to W position. As the boiler fired up when you switched on, probably not timer fault. The thermostat should give a click at current temp, hope its not so cold as to not register [ roaring log fire down the pub sounds a better bet than trying to fix it!]. Just try to establish if the valve reacts to the timer or thermostats at all.

Mark

Milk, no sugar ta.

 

[mr_simonward]

Right, I think we're getting somewhere (and it is very much appriciated!)

Again, before I started things were set to: CH & HW Both OFF, Valve = H

I then start experimenting:
- HW ON, Valve moved to W (presume good)
- Leaving HW ON, CH ON too, Valve moved to M (presume good)
- Leaving CH ON, and turning HW OFF, the valve stayed to M (presume it should move to H!) and the boiler did not fire up!
I tried turning CH OFF & ON again, but no movement in valve, or fire in the boiler.

I did however then try my usual fix of "switching it off and on at the mains" (the switch to the right of the timer in the first picture above).
(Can't you tell I'm from an IT background?) and the boiler fires up, and the valve moves to H again.

So does that confirm that it is the valve? Is there any further testing of the valve I can do to confirm this?

I don't know if I'm jumping the gun a little now, but presuming it is the valve - how big a job is it to replace it? Or can it be cleaned out/repaired?

Doing my research, am I right saying I need a 3 port valve? And that these would be suitable replacements:
http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=102632&ts=75095&id=53314
http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=102632&ts=75095&id=30424
(presuming mine is 22mm - is that standard?)

 

[DIYIdoit]

Simon,

As the problem resolves itself when you power cycle the programmer it would suggest the problem may lie there (I don't know much about plumbing so don't take my word for it) but it would be cheaper and easier to replace the programmer. Just switch off at the mains as you have been doing, take the programmer off (the back plate will stay connected and on the wall) and replace with a replacement from ebay

As I say I'm not a plumber so please take this on advisement, but I had a similar problem in the past where the CH on contacts had fused together, it could be that you HW contacts are sticking and therefore keep calling for HW thus keeping the valve in mid position when it shouldn't.

Also the valves natural state should be W not H and when you turn CH off the valve should return to W (it has a spring to ensure HW is default) so it sounds like the programmer doesn't know if its 4r5ehole or breakfast time.

What position is the valve when the programmer is off at the mains? If it's W then it means the valve is acting normally without interference from the programmer so it's got to be a faulty programmer.

But after all that maybe it's me who doesn't know if what time it is , what do the plumbers think?

 

[mr_simonward]

Thanks DIYIdiot, what you say about the valve having a spring and using HW as default is interesting...

So basically, if I cut the power to the timer - the valve should always return to W?

What do you think Mark, does that sound right to you?

 

[EliteHeat]

The only way in which you will resolve this is to check what is happening via the wiring centre. This is located under all of your bottles of cleaning stuff.

You should be able to get a wiring diagram for the 3-port valve, but the programmer has a number of clearly defined states which are easy to check. They are:-

1) Everything off
2) Hot water on
3) Hot water off
4) Central heating on
5) hot water and central heating on

It is important to understand that the switched lives from above are routed via either the room thermostat or cylindert thermostat and the switched output from these powers the motorised valve.

The valve then operates and activates a microswitch which switches power to ...... the boiler and pump. The boiler does not give a monkeys with regard to what is calling for heat, it just fires up - or not in your case.

So, to problem solve this do the following:-

(1) Identify the 2 switched lives from the programmer, make sure they are working properly
(2) Identfy the wiring with regard to the 2 thermostats and verify that they are switching correctly
(3) Identify the single wire from the motorised valve (usually orange) which is reponsible for powering the boiler and pump and check the voltage.

If your valve is like a Honeywell 4073 (which most of them are) then you should find the following states on the wires TO the valves:-

CH+HW 230V to white - 230V on orange
CH 230V to white and grey - 230V on orange
HW off / satisfied 230V on grey - approx 100V on orange

So it's a case of switched lives, switched lives and err, switched lives.

You will need a multimeter to check these voltages out. Unless you are confident about what you are doing I don't recommend that you dfo any of this!

 

[DIYIdoit]

Here is a link to the post that cured my problem.

It was a different problem to yours but there is a wiring diagram attached and it explains the valve operations.

Basically the valve at rest is at W. If only HW calls there is no change as it already is at W. If HW & CH calls the valve starts to move to H but when it's mid point it hits a microswicth (charged from the HW call) which does something with a diode which in turn stalls the motor at mid point W+H. If only CH calls there is no charge to the microswitch therefore no diode action and the motor is free to move all the way to H. When CH stops calling the spring returns to H. Therefore if the programmer has no power it can't call for CH so the valve should be at W.

Also, heed what EliteHeat says, when I was "messing" with my system I connected neutral to a battery operated device and also fused my programmer but it could have been a lot worse. Changing the programmer like for like is simple enough as all wires are connected to the back plate which you don't need to touch, just ENSURE you isolate it at the fused switch first.

Good luck.

 

[mr_simonward]

Thanks again for your help on this, all very much appriciated.
Thankyou for your contribution EliteHeat, but that all seems abit beyond me.

So, we have it down to 3 possible causes:

1) Electronic Fault of Programmable Timer
2) Mechanical Fault of Valve
3) Electrical Fault of Wiring

Now, considering that it did work before, and I haven't changed or added anything at all can I dismiss the idea of wiring fault?

The combinations of ON's, Off's and Indications is starting to get a little cryptic, but here are my observations:

1) -------------------------------------------------------------------
Tonight, after the timer turned both the HW & CH off at the same time, the Valve was on M (should rest at W?)
Turning power to timer off and on resets valve to W.

2) -------------------------------------------------------------------
Turning the Heating on, Valve to H, Boiler Fires.
Turning the Heating off, Valve stays at H (should reset to W?)

Now this doesn't stop the Boiler from firing if I turn the Heating back on, but this is not what should happen. So basically when the timer turns the heating off, it's turning the Boiler off, but power is still going to the Valve to keep it at H (I presume, unless valve is just 'stuck' at H)...

3) -------------------------------------------------------------------
after resetting, both off, valve = W
Water = on, valve = W
Heat = on, valve = M
Heat = off, valve = W
Heat = on, valve = M (all good til now, with boiler remaining fired)
now, with both on, If I turn Water off, the valve stays at M, and the boiler cuts out.....

So, when switching the water off, the timer should should stop sending power to the microswitch, allowing the indicator to move to H, but it's not.

-------------------------------------------------------------------

So, in all these cases, when the timers decides to turn anything off, it is stoping power to the boiler & turning the boiler off, but the valve is not changing with this.


GGGRRRRR - RAAAR!


I think I'm gonna try my luck with a new programmable timer. If that doesn't fix it, i'll ebay it and get some one in to have a look.

Feel free to comment in the mean time, I'll let you know how I get on with it. (any one want to start placing bets wether swapping the timer will fix the problem?)

 

[ollski]

You don't need to buy a new timer to check it, simply take the front off and link across to check operation. My money is on the valve which is the worst scenario really as you will need a complete valve as the heads aren't interchangable on these.

 

[EliteHeat]

You cannot diagnose the problem by looking at the mechanical behaviour of the 3 port valve.

You must look at the electrical state of the system - this will tell you what the problem is without a shadow of a doubt.

 

[mr_simonward]

Bugger - new timer didn't make any difference. Now going to concentrate efforts on the valve...

I've started a new thread here: //www.diynot.com/forums/viewtopic.php?p=314832#314832