Has my neighbour taken over my Drayton SCR?

[DaPanda]

Hi,

I have a Drayton Digitstat+RF thermostat synced with an SCR unit connected to a Worcester combi-boiler. This has worked fine for several years, but for the past few weeks the boiler goes on and off independently of our thermostat.

When the boiler is off, raising our thermostat above room temperature does start it, and lowering it below room temperature does stop the boiler, so the communication and control from our Digistat+RF is still working fine.

However the boiler now goes on at times when our thermostat is below the room temperature and no flame appears. It also goes off on its own.

When this happens, the red light on the SCR flashes before the green light turning on, i.e., the SCR behaves exactly as it had received a signal from a Digistat+RF unit.

Does the syncing of the Digistat+RF and the SCR unit pairs them in any way so that the SCR unit discriminates which thermostat sends controls and only respond to the synched unit, or does it accept control from any thermostat that sends the right command over 433 MHz?

If there's a pairing, what do you think could be the issue?

If there's no pairing, then it is likely that a neighbour recently installed a compatible unit and we're fighting with each other boilers (though as they prefer a higher temperature, they're winning). In this case, can anyone recommend an RF thermostat that has some basic security of the RF communication, if possible with a wiring compatible to that of the SCR unit as it will mean replacing it.

P.S. On which of the 69 channels of LPD433 do these thermostat broadcast? I tried using a radio receiver to check for receiving controls from another controller but going in the middle of the band I get a different noise from when my thermostat transmits (and my thermostat seems to broadcast over all the channels!)

 

[bernardgreen]

P.S. On which of the 69 channels of LPD433 do these thermostat broadcast?

433.925 MHz sems to be common one for almost all control systems. The other channels are used by amateur radio operators ( 70cm band )

 

[Jackrae]

Isn't there a section in the installation guide that specifically addresses multiple device installation and how to pair your SCR to your transmitter only. It may require your neighbours co-operation (they to de-energise their thermostat whilst you retrain yours)

 

[ericmark]

My 70 cm transceiver is faulty at the moment so can't test, but when running there were two ways of getting rid of white noise. One the squelch and the other a tone superimposed on the signal, I think this is how thermostats work, they send an ID tone and often there are dip switches to change the tone used. But the thermostat transmits milliwatt, I did transmit at around 5 watt, and car units are more likely 45 watt, not sure of limit off hand for 70 cm but most frequencies are around 400 watt. If using EME then one can get dispensation and 1 kW is not unknown to bounce signals off the moon to talk, well not really talk you would need around 5 kW to talk but at least use Morse code to USA.

Now how well do you think your little thermostat will reject signals of that strength?

I have tried scanning for mW signals before my battery gave up, and the transmit time is so short I found near impossible to find with my transceiver.

 

[bernardgreen]

there were two ways of getting rid of white noise.

The problem with domestic wireless controls is not white noise but signals with data that is "valid". The data will include data that is the identity of the transmitter and data that is a command. If the transmitter's identity has been "taught" into the receiver then the receiver will act on the command, otherwise the receive will hear and discard the command. So far so good.

But the reciever may be able to hear more than one transmitter. It may be able to hear several transmitters and several of these may be transmitting at the same time as each other.

It is now like holding a conversation with some one across a crowded room. If every one else stays silent and only one person speaks at a time then the conversation(s) can happen. All the listeners will hear all that is said but only take notice of what their own partner says. ( they may choose to ignore it but they will have heard it ).

In reality there can be several people trying to talk across the rooms to their own partner all at the same time. The listeners now have difficulty hearing what their partner is saying. They may only be able to hear the loudest voice and not their own partner's voice.

Wireless communication using Licence Exempt frequencies has the same problems as verbal communication have in that crowded room.

 

[D_Hailsham]

I have a Drayton Digitstat+RF thermostat synced with an SCR unit connected to a Worcester combi-boiler. This has worked fine for several years, but for the past few weeks the boiler goes on and off independently of our thermostat.

When this happens, the red light on the SCR flashes before the green light turning on, i.e., the SCR behaves exactly as it had received a signal from a Digistat+RF unit.

Have you tried replacing the batteries in the thermostat?
Are you using rechargeable batteries? If so replace them with normal alkaline batteries.
Are you using good quality batteries, i.e Duracell?

 

[DaPanda]

Thank you all for the responses so far. Some additional information based on some of the responses:

433.925 MHz sems to be common one for almost all control systems.

Tuned it to 433.925, heard the same rattle than when my thermostat sends control, rushed to the SCR unit and it had its red light flashing and then the green light switching on the boiler (when my thermostat is set very low so not to activate).

I think I now have confirmation that another thermostat set at a higher temperature, nearby, is sending commands to my SCR unit which is accepting them.

Isn't there a section in the installation guide that specifically addresses multiple device installation and how to pair your SCR to your transmitter only. It may require your neighbours co-operation (they to de-energise their thermostat whilst you retrain yours)

The only mention of multiple device is for multizone installations: 'If more than one 'wireless system' is fitted within the same property.ie. for controlling 2 or more zones (multi-zone) it is essential that the Digistat RF units are matched correctly to the relevant SCR. This is easily achieved by commissioning each Digistat and SCR in turn.'

This is extracted from http://www.draytoncontrols.co.uk/sites/default/files/Digistat+RF (U.&I. Guide)_0.pdf

That would seem to indicate that some kind of pairing happens. As I mentioned in my original post, I did redo the matching procedure. However my thermostat does control the SCR unit so that is 'matched' fine, but there appears to be another close by thermostat that is also 'matched'. There's no indication about how to lose the 'matchings'. This is why I'm not convinced it is anything more than checking a thermostat is there and in range.

The data will include data that is the identity of the transmitter and data that is a command. If the transmitter's identity has been "taught" into the receiver then the receiver will act on the command, otherwise the receive will hear and discard the command. So far so good.

Are you sure the Drayton system does send the identity of the transmitter. If that's the case, how can make my SCR unit lose the identity of the remote thermostat taking over? Or could it be that both my thermostat and the nearby were shipped with the same identity.

If that's the case does anyone knows how to change the Digistat+RF thermostat's identity? This is not documented.

Have you tried replacing the batteries in the thermostat?
Are you using rechargeable batteries? If so replace them with normal alkaline batteries.
Are you using good quality batteries, i.e Duracell?

I am using Alakaline battery, and in any case the issue is with signals received by the SCR unit *not* sent by my thermostat.

Rgds.

 

[bernardgreen]

Are you sure the Drayton system does send the identity of the transmitter.

If it doesn't then the design of the system is not good. In fact that would be a very poor design. I don't have the details but from the available information I am assuming there are no configuration switches in the thermostat so therefor the identity is fixed at production and cannot be changed.

If there are configuration switches ( or links ) then with 4 switches there would be 16 possible identities, 5 switches then 32

Or could it be that both my thermostat and the nearby were shipped with the same identity.

One would hope not.

 

[DaPanda]

If it doesn't then the design of the system is not good. In fact that would be a very poor design.

I agree, which is also why I'm surprised not to find any similar report.

I don't have the details but from the available information I am assuming there are no configuration switches in the thermostat so therefor the identity is fixed at production and cannot be changed.

I removed the Digistat+RF from its wall support to check the PCB. No switch visible.

The PCB was displaying three sticky labels:

2012

MODEL No: RF6010 (the last digit was cut but is most likely a zero)
MFR Date: 08/09
W.P. : 18
SOFTWARE: V31.0

6309149001 Is nº F
UTRF
5516545 6-09

None of them clearly indicating anything resembling a unique ID.

 

[bernardgreen]

The unique identity is hard programmed into the "chip" in the transmitter, it is not possible that two chips can have the same indentity.

A receiver can be linked to two transmitters, If your neighbour had linked his transmitter to his receiver at exactly the same time as you had linked your transmitter to your receiver ( both receivers in "linking" mode ) then there is a remote possibility that your receiver linked itself to both your transmitter and your neighbour's transmitter.

( confirmed in a chat with Drayton Tech Help Line )

 

[DaPanda]

The unique identity is hard programmed into the "chip" in the transmitter, it is not possible that two chips can have the same indentity.

A receiver can be linked to two transmitters, If your neighbour had linked his transmitter to his receiver at exactly the same time as you had linked your transmitter to your receiver ( both receivers in "linking" mode ) then there is a remote possibility that your receiver linked itself to both your transmitter and your neighbour's transmitter.

( confirmed in a chat with Drayton Tech Help Line )

I thought of that last point, it is unlikely as our thermostat/SCR had worked fine for years. This remote control of the SCR happened without me re-matching the Digistat+RF and the SCR initially. I did match them hoping this might stop this remote issuing of command, but it didn't. Anyway, to rule out the situation you mentioned I also waited for the invisible thermostat to issue instructions to turn on the boiler and then to turn it off, and just after I went to a match operation between my Digistat+RF and SCR. No change.

If unique identities are truly programmed in the transmitter chip and commands are accepted from the SCR only from the matched identity, then there's no logical explanation for the current situation.

The chances for that remote thermostat to have been in sync mode each and every time I matched mine are impossible odds. The commands are not random, the temperature in our flat is rather nice, the boiler is operated more often to reach a higher temperature that we would normally set, i.e., the SCR/bloiler behaviour is entirely consistent with receiving commands from a thermostat set a bit higher than ours (in normal times, as trying to debug this, I've set our thermostat to 10ºC and the temperature in the room I am in remains approximately 18.7ºC).

So the only logical cause I can think of are, both contradicted by the explanations your provided, are either both thermostats have the same identity or the SCR is not checking for identities.

Annoyingly, it looks like I won't be able to fix this with the current set up, so can anyone recommend an RF thermostat where the identity can be coded and for which the receiving unit is hopefully easy to connect considering the current wiring is for an SCR?

 

[bernardgreen]

and just after I went to a match operation between my Digistat+RF and SCR. No change.

Did you erase the receiver's memory of both identities ?

I do not know what the transmitter sends when in linking mode. If it is a normal command ( such as ON or OFF ) and not s specific " LINK " command then if the neighbour's transmitter sent a command while your receiver was in link mode then it could re-link to your neighbour's transmitter

Maybe contact Dayton directly [email protected] and explain the problem to their technical help staff

 

[DaPanda]

Thank you for your several responses and enquiries.

Did you erase the receiver's memory of both identities ?

There's no documentation about doing this. I do not know if the matching process described by Drayton (in the documentation I linked to in response #7) erases the SCR's memory or not.

I do not know what the transmitter sends when in linking mode. If it is a normal command ( such as ON or OFF ) and not s specific " LINK " command then if the neighbour's transmitter sent a command while your receiver was in link mode then it could re-link to your neighbour's transmitter

I don't either. It is not documented. I do not have access to a protocol analyser and digital receiver to do this reverse engineering and the protocol does not appear to be documented (that would have answered many of these questions).

Maybe contact Dayton directly [email protected] and explain the problem to their technical help staff

I already did. I initially emailed them on 2017-12-03 at 14:18, and again with an update following this discussion today at 13:02, however I'm still waiting for a response.

 

[Jackrae]

Perhaps it's time for a thermostat 'upgrade'. Getting bogged down in problem solving can be extremely frustrating since there may be a simple on-board component failure than no amount of playing about with comms links will resolve. The wiring of most replacement thermostats is pretty much standard and diagrams from installation instructions can be downloaded to ensure you don't end up buying something that cannot be easily installed.

 

[DaPanda]

Perhaps it's time for a thermostat 'upgrade'. Getting bogged down in problem solving can be extremely frustrating since there may be a simple on-board component failure than no amount of playing about with comms links will resolve. The wiring of most replacement thermostats is pretty much standard and diagrams from installation instructions can be downloaded to ensure you don't end up buying something that cannot be easily installed.

I am indeed reaching that stage. Can you recommend any RF thermostat where the identity can be set and is definitely used? This doesn't seem to a be feature listed in the marketing for thermostats and I want to be sure not to end up in the same situation with another neighbour.