Worcester Combi Boiler/Radiator Problems - Drayton Digistat

[chrisha]

****I have changed the thread name to assist future searches by people suffering similar problems.******

We had a new central heating system and Worcester Combi boiler fitted by BG in 2009.

It runs on a remote thermostat with a receiver in the cupboard where the boiler is located.

However, Just lately, the central heating has not kicked in when the thermostat notes the temperature has dropped to the point where the heating should be activated. The thermostat shows the signal requesting heat is being sent, and the receiver flashes and lights up green showing 'on' but no heat comes through the radiators.

The remedy this, it was a case of turning the thermostat down, to below a temperature that requested heat, leave it a minute, then switch it right up and the boiler would usually fire after one or two attempts.

Not ideal, especially at night, when it's quite chilly at the moment, as it means I have to increase the original temperature up a few degrees, so when it fails in the night, it doesn't drop too low. Had it been just me, I would suffer it, but 2 kids under 6 means warmth is pretty much a priority.

However, a week or so ago, this method started failing, and the only way to get it to fire would be to switch the receiver off, leave it a minute, then switch it on again, re-pair the thermostat to the receiver and again 'magic' heat.

This led me to believe there is an intermitant fault between the thermostat and receiver, as the fault only usually happened at night, and manual adjustment of the thermostat wasn't a problem.

However, the problem is deteriorating. The last few nights it’s hasn’t fired up (same as always) but getting harder and harder to re set.

The tried and tested methods of switching off the receiver a few times, or dropping the temperature setting on the thermostat then increasing it to max have stopped working.

The only way to fire it up now is to run the hot water for a minute or 2, then when the boiler switches off from heating the tap water, it switches over to the radiators.

Tested the theory a couple of times, when I was in the bath, I ran some more hot water, and the rads switched off, when I stopped the running water, the rads kicked back on again. I can tell they are kicking on, as there is always a creak of pipes underneath the landing floorboards when the radiators kick in, and the boiler sounds very slightly different.

This now leads me to believe there is no problem with the thermostat or receiver, but a problem with the boiler.

Any ideas, as I can’t get my head around that the radiators won’t fire unless the hot water has been running, but was fixed previously by a simple thermostat adjustment.

Strange thing is, we don't seem to suffer any problems during the day.

 

[Agile]

What make and date of fitting are the transmitter unit batteries?

Only Duracell will operate these reliably as they take a high peak current when sending.

There is a very slight possibility that its getting interference from other electronic devices like TVs and computers which you might be using in the evenings!

Tony

 

[chrisha]

My first thought were batteries, as surprisingly enough, I was running on the original batteries going back to installation, although there was no low battery warning light.

However, I replaced these with some pretty decent re-chargeable ones, and at fully charge, they showed 'low battery', indicating, that yes, I did need the juicier batteries.

Final option, was I replaced all the batteries in the thermostat last week, with again, some top notch Duracell, to eliminate batteries as an issue.

When I go to work, I switch the thermostat down, and when I return from work, I raise the temperature back up and it fires no problem. It also fires healthily during the evening if we need to increase/decrease temperature. I have also noticed that if the ambient temperature hasn't dropped to where heating is automatically requested, the thermostat works ok. Hence my reasons for turning it way down in the day.

It only really fails when the thermostat automatically requests heat, due to the ambient room temperature dropping to a level the thermostat wants to send a signal, which baffles me, as I would have thought the signal would be the same to the receiver for an automatic request for heat as opposed to a manual request for heat.

When the thermostat requests heat that isn't forthcoming, then regardless, it will never fire, unless I go through the stages listed above.

It is only really at night we have the issue. No electrical items are operative overnight, such as broadband, routers, phones etc that are not operational during the day.

It just feels like that if the thermostat isn't adjusted either up or down for a while then 'it goes to sleep' which may explain why in the evening it is operational, as it is regularly adjusted, but obviously while we are sleeping, no manual adjustments take place, hence the lack of response.

The thermostat is a digistat 2rf, although I only found this out by internet enquieries, as it is fully logo'd up 'British Gas' if that's any help.

 

[ianmcd]

it does sound as though you have a pairing problem with your digi stat, have a look at the installation instructions with particular regards to the siting of the receiver unit and make sure it is sited properly, the radiators not heating when you run HW is how the boiler works it stops heating the radiators while you are running HW and then starts heating them again when the HW demand stops, this is perfectly normal and not a fault with the boiler

 

[chrisha]

Thanks for that,

Location and interference seem to be the most logical cause, so it seems the boiler is ok, and the problem lies with the thermostat/receiver somehow.

Someone else has also mentioned an interference issue, we have a wireless Yale alarm and this is the only thing that is operational at night that isn't in the day.

If it is the alarm, I am in a mess really, as I can’t see how I can get round it. I don’t think I can change the frequency of the alarm system, and definitely can’t change the frequency of the thermostat.

But if I can pinpoint the problem, at least the solution won’t be as costly as trying to establish a cause first. I would hate to replace the thermostat and receiver at £100+ plus fitting, for this not to be the problem.

I will leave the alarm off tonight, or only set the sensors for 'home' which disables the room PID sensors and leaves the door sensors to see if anything changes. Tomorrow, I think I will leave the entire alarm system off, to at least try and eliminate something else.

Funny though as we had the alarm around the same time as the c/h system without issues before, but the way it is at the minute, I am willing to try anything!

The thermostat has never been moved either, so it just seems very strange these problems have only just surfaced in the last few months,

 

[sloaney]

A long shot, but is there anything being stored in the boiler cupboard that could block the signal to the reciever?

 

[hazetimesfive]

move the stat for a few days, see if that changes anything

 

[chrisha]

I think I need to remove a few variables first.

At the moment, it is impossible for me to establish whether there is a fault between the thermostat and receiver, or electrical interference blocking the signal, or whether the signal is being received but the boiler isn't acting on the instructions sent.

My gut feeling is the boiler failing to act on the instruction, as when a signal is sent to the receiver, a green light on the receiver comes on, (which it does, but without firing up)

I will power down as much as I can tonight my other electricals, alarm, routers etc etc. so I can at least remove these from the equation.

Our house has no brick internal walls, there are all plasterboard stud walls, so I can't see this being an issue, but if I have the same problem tonight, my next step will be to move the thermostat next to the sensor.

If I still experience problems, I will know it's not interference or signal. so one step closer I suppose, but still won't know if it's the thermostat or the boiler creating the issues.

Apart from a few kids bath toys, nothing is kept in the cupboard where the boiler is located, not even a towel rack, so I don't think this would be an issue, but clutching at straws a bit now, so will move the few items that are in there just in case.

If it does fire tonight (fingers crossed) I will have to take each night in turn switching one more thing on at a time to see which item is causing the disruption, then go out and burn whatever is causing me sleepness nights!

 

[ianmcd]

The most common cause of signal interference are domestic appliances like fridges microwaves etc are you sure the sender or receiver are not near anything like that? also is the receiver at least 300mm away from the boiler ? (that is the min distance for a drayton RF not sure which one you have but will tell you in the installation instructions what the min distance from the boiler is)

 

[Gaspt]

The relay in your receiver is not switching over, this is a common fault with these stats, I'm afraid you will need to replace it, I would change it for a Honeywell cm921

 

[chrisha]

Thanks, I was thinking I was going mad.

Last night, I switched everything non essential electrical off. I think the only thing left running was the fridge!

I also had another thought, as each night passed with no heat I had been gradually increasing the temperature by half a degree or so to the point it was hitting 25 degrees.

This was to generate enough heat in the early part of the night to make sure there was enough residual heat, so when it shut off, it would take longer to get cold.

My thoughts then followed that perhaps I was overloading the boiler and it was auto-shutting down, as during the day it seems to fire easily at much lower temperatures.

So last night, I reduced the temperature to 20, hoping that I wasn't going to overload the boiler, and it would regularly fire at this temperature.

No luck, at 2am this morning, let's say it was a might chilly, I woke, tried the usual methods to get it working but no joy and way too tired to try and spend half hour to get it to fire.

By the time I finally got up at 6, the temperature had dropped in the house to 13, and it took me nearly 45 minutes to fire it up. Nothing seemed to work, not even the new trick I had learned of running the hot water. I think now, this may have just been co-incidence.

Do I need to replace the thermostat, receiver, or both?

 

[chrisha]

Got back from work, total failure of the heating again!

One hour in, still no heat. Definitely getting harder to re-set now.

 

[BertieGas]

Yep, these are great but over the last few years the only ones I trust now are the Honeywell cm921 or cm927. I use Worcester boilers and fit the Honeywell instead of the Worcester timers as I think they are vastly superior.

 

[chrisha]

Thanks for all the advice guys, especially Gaspt.

Last few days, heating is now getting harder and harder to re-set. The only way I can get it to fire now is completely switch off all power to the boiler/receiver, leave it half hour and then switch on.

It will then fire, but only once before it fails. To combat this, and keep the kids warm, I have moved the thermostat to by the kitchen window (nice and cold there!), turned it up full and turned the rad's down to 2 to prevent us boiling in the night.

This means it fires all night long, and keeps the house reasonable, but dreading the gas bill!!!

Using the advice about a dodgy thermostat, when I reset it tonight, I noticed that when it fired up, I heard a very slight click in the receiver, but when it fails, no click is heard. To me, this definately meant a receiver issue.

A bit of internet seaching resulted in this.....

http://www.draytonrepairs.co.uk/

I have posted this here, so if anyone else ever has this problem, they can find and diagnose the problem quicker than me!

I only stumbled on this site when I was looking to see if receivers could be bought independantly to the thermostat, but it perfectly diagnosed the problem, even down to the click.

End result is a £4 quid fix and hopefully stress free nights!

Bouncing ideas round the forums has definately helped resolve this issue.

Cheers Guys!!!!!!!