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#1
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Worcester Bosch TR2 room stat - reverse engineered
Regular viewers may recall a thread a while back about attempting to
connect a normal prog stat to a WB boiler that was designed to interface only with their proprietary TR2 room stat. I received the following email the other day which looks like it provides a solution: "John picked up your e-mail from a discussion about adding zone control to a Worcester Bosch boiler. I appreciate you are not the poster of the query but I am unable to post a reply and thought you may be able to post/forward/explain how I can post. I have similar problem with this boiler and have reverse engineered the TR2 interface (bit of an exageration for what it is). I came up with what now seems an overly complex solution which fooled the boiler into thinking the tr2 was a) in constant mode and b) demanding max heat. this is done by inserting an 8.95 kohm (a standard 9.1kohm should still work) resistor across pins 4 & 3 of the tr2. The tr2 presents a resistance (my actual measured) to the boiler based on the demand temperature on the rotary dial and the position of the 4 position switch as follows: switch position 30Deg .............0Deg constant 8.95 kohm 11.27 timed 6.22k 8.54k night(econ) 13.96k frost 12.64 From observation of the pcb the rotory dial is a 2.2k pot. in series with a 6.2k (3.5k +2.7k) and a 2.7k which is switched in for constant (i.e un timed operation. it is worth noting that the pot is low for high temp demand and 2.2k for low temp (confused me for a minute did that). The night and frost are fixed 14k and 12.7k resistors. looking back I think a simpler solution is to open/short circuit the temperature sensor, which looks like a thermistor, between pin 4 and pin F to fool the boiler into thinking it was cold. May need to insert a specific value in/across. If there is any interest will look into this option and report back. Craig Nixon" So there you go, it sounds rather like one could introduce a conventional external battery powered stat (programmable if required), by connecting a 8.95K and 2.2K resistors in series across the control pins on the boiler, and then connecting the normally open contacts of the stat across the 2.2K resister. That way as the external stat calls for heat it would bridge the 2.2K out of circuit and change the demand temperature sensed by the boiler from min to max. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#2
Posted to uk.d-i-y
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Worcester Bosch TR2 room stat - reverse engineered
replying to John Rumm, Chris Murray wrote:
Hi John & Craig I wonder if you could help me please. I have just bought a house with a Worcester boiler but no room thermostat is fitted the tr2 is the only suitable one but totally unobtainable now, have read your posts and would like to make one can you advise please on the boiler connections I have the installation instructions but a word of confirmation would be much appreciated.Many Thanks, Chris Murray -- for full context, visit https://www.homeownershub.com/uk-diy...ed-428844-.htm |
#3
Posted to uk.d-i-y
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Worcester Bosch TR2 room stat - reverse engineered
On Thursday, 11 October 2007 03:39:15 UTC+1, John Rumm wrote:
Regular viewers may recall a thread a while back about attempting to connect a normal prog stat to a WB boiler that was designed to interface only with their proprietary TR2 room stat. I received the following email the other day which looks like it provides a solution: "John picked up your e-mail from a discussion about adding zone control to a Worcester Bosch boiler. I appreciate you are not the poster of the query but I am unable to post a reply and thought you may be able to post/forward/explain how I can post. I have similar problem with this boiler and have reverse engineered the TR2 interface (bit of an exageration for what it is). I came up with what now seems an overly complex solution which fooled the boiler into thinking the tr2 was a) in constant mode and b) demanding max heat. this is done by inserting an 8.95 kohm (a standard 9.1kohm should still work) resistor across pins 4 & 3 of the tr2. The tr2 presents a resistance (my actual measured) to the boiler based on the demand temperature on the rotary dial and the position of the 4 position switch as follows: switch position 30Deg .............0Deg constant 8.95 kohm 11.27 timed 6.22k 8.54k night(econ) 13.96k frost 12.64 From observation of the pcb the rotory dial is a 2.2k pot. in series with a 6.2k (3.5k +2.7k) and a 2.7k which is switched in for constant (i.e un timed operation. it is worth noting that the pot is low for high temp demand and 2.2k for low temp (confused me for a minute did that). The night and frost are fixed 14k and 12.7k resistors. looking back I think a simpler solution is to open/short circuit the temperature sensor, which looks like a thermistor, between pin 4 and pin F to fool the boiler into thinking it was cold. May need to insert a specific value in/across. If there is any interest will look into this option and report back. Craig Nixon" So there you go, it sounds rather like one could introduce a conventional external battery powered stat (programmable if required), by connecting a 8.95K and 2.2K resistors in series across the control pins on the boiler, and then connecting the normally open contacts of the stat across the 2.2K resister. That way as the external stat calls for heat it would bridge the 2.2K out of circuit and change the demand temperature sensed by the boiler from min to max. a candidate for the wiki perhaps |
#5
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Worcester Bosch TR2 room stat - reverse engineered
2007, Newer than usual for this stupid portal on Usenet. can we perhaps
kidnap the site writer and get them to make it work as it should, do you think? Brian -- ----- - This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please! "Chris Murray" m wrote in message ... replying to John Rumm, Chris Murray wrote: Hi John & Craig I wonder if you could help me please. I have just bought a house with a Worcester boiler but no room thermostat is fitted the tr2 is the only suitable one but totally unobtainable now, have read your posts and would like to make one can you advise please on the boiler connections I have the installation instructions but a word of confirmation would be much appreciated.Many Thanks, Chris Murray -- for full context, visit https://www.homeownershub.com/uk-diy...ed-428844-.htm |
#6
Posted to uk.d-i-y
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Worcester Bosch TR2 room stat - reverse engineered
On 22/09/2017 08:24, Brian Gaff wrote:
2007, Newer than usual for this stupid portal on Usenet. can we perhaps kidnap the site writer and get them to make it work as it should, do you think? I suspect in this particular case Brian the OP was actually searching for specific information on the TR2 and found the old post, rather than the more typical case where the site shows a list of ancient topics as if they were current. The info from the 2007 post probably ought to be in the wiki anyway to make it more accessible. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
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