I think the difficulty here is there does not appear to be an external input that would work with a traditional stat. The TR2 thingy communicates "stuff" to the boiler including current temperature, but not it seems, ans instruction when to turn on or off.
There must be something that the TR2 can indicate that tells the boiler it is getting a bit nippy in the room though, causing it to turn on. So the next question is how to simulate that.
On Tue, 10 Jul 2007 17:00:05 +0100, Mike Barnard mused:
So what's wrong with the 2 terminals next to the mains input for the external controls?
I have a similar arrangement to this on my boiler (MAN Micromat).
This one, by default, wants to be in charge of the whole show and does not require external controls and sensors, although it does come with an external weather compensation temperature sensor - a semiconductor analogue thing with two wire connection.
There are two switched live *outputs* which can go off to run external pumps or motorised valves. Operation of that depends on settings in the installer menu, hidden from the user. I have it set such that one operates the CH zone valves and the other that for the HW cylinder. The boiler then opens them according to heating/HW demand.
On the input side, there is a set of three connections, similar to the WB arrangement. However, the boiler can be programmed to use them in different ways. One is with a straight and simple set of volt free contacts - in that mode, the boiler is turned on and off in the traditional way.
The second mode uses a three wire connection to a specific room controller. This device has time and temperature settings for the heating (not HW), including night set back, optimised start. It also has a control term to vary the relative influence of it vs. the external temperature sensor as far as boiler operation is concerned.
The boiler is aware of the settings made on the room controller including temperatures. Another aspect of this is that if you turn up the control to increase the room temperature by a small amount - say half a degree - the boiler modulates up a bit. Turn it three degrees and it goes to full power.
A scope indicated what appears to be DC and ground on two of the wires and a digital transmission on the third.
A bit more digging revealed that the controller itself was not made by MAN but by Landis and Staefa (now part of Siemens Building Technologies). They make a range of products that go with various control systems on a standalone and OEM basis. The data sheet describes the interface as being PPS, others in the range as PPS2 - both appear to be proprietary interfaces. The transmission is there the whole time - doesn't disappear out of hours or below the set point or anything like that.
So coming back to Mike's project, I think you are right, from the descriptions in the manual, there is probably more about this TR2 controller than a simple on/off or analogue interface. It may well be using a similar concept to the Siemens controllers or even be made by them - they have quite a product range. Reverse engineering of the interface? Maybe, but decoding an unknown bit stream where even the method of encoding isn't known, is not going to be trivial.
I wonder whether getting one of these TR2s and spoofing its analogue temperature sensing might not be a better proposition. More than likely that will be a thermistor or semiconductor sensor. The manufacturer might even have helpfully marked it on the legend of the PCB. Once the component is identified, it would be reasonably easy to replace it with an appropriate set of resistors, diodes etc. and a relay contact such that the controller is fooled into thinking that the room temperature is very high or very low and stopping and starting the boiler accordingly. Since the TR2 has a rotary temperature control, that may operate a potentiometer inside. If that's the case, then the job is even easier. Whip out the pot, a couple of resistors and a relay and that's it.
These controllers cost about £45, which is not bad for a proprietary thermostat. Dinking with one of these would mean not having to start pulling about the boiler wiring and invalidating the warranty plus whatever other unknowns might happen. For example, breaking into one of the boiler internal wirings to a valve etc. might be detected by the boiler controller and cause a fault lockout on the boiler.
In the worst case scenario with the TR2, the solution wouldn't work and £45 would have been spent. It wouldn't affect the boiler.
Easier solution.
Spend £45 on a TR2 and pull it apart. Either spoof the temperature sensor (probably thermistor or semiconductor) or the rotary control if it's a pot. A couple of resistors and a small relay should be able to have it convinced that the room temperature is changing or being changed.
This avoids needing to break into the boiler and has much lower risk.
"AAAAAAARRRRRRGGGGGGGHHHHHHHHHHHHHHHHHHHHHHHHHHHHHhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh.....
Agreed. There must be a a way to connect a wall themostat to the combi. That is the way you drive the zoning. Some WB models have all the connection for zoning builtin to save you useing a wiring centre (such as the 24 SBi) that's probably what threw the WB techies.
AL you need to do is connect the all the grey wires to one of the thermostat terminals and all the orange wires to the other thermostat terminal.
There is but it's a proprietary room controller.
There are a couple of terminals next to the mains input with a link between them, but the manual seems to say nothing about them other than that there is a link. Possibly this is a switched live, but it doesn't seem to say.
controller
boiler to be
controller
That's precisely how my Potterton Kingfisher 150CF is wired up. No electronics in it at all, just a pc based external controller doing zone control on 8 zones. The actual boiler went in in 1985 and is working well, though the controller is a bit newer having run since about 1998.
AWEM
You can.
If the boiler has a way of accepting such input.
This one does not.
Its completely integrated and comoputerised, and the only thing apart from the mains that it takes, is a 'smart' room stat made by the manufacturer ONLY.
Even if you had to set the boiler to be
If the whole boiler is off, then no hot water either..
Its highly UN-obvious. Thats someone has finally produced the plumbers dream and the DIY-ers nightmare. A boiler that doesn't need any electrical installation, beyond hooking up to a switched fused spur and turning it 'on'..
That was my thought too.
Use a little Peltier cooler to chill the temperature sensor? Everything of WB manufacture then remains unmodified, downstream replacements off the shelf, and with all guarantees still in place.
I haven't looked. If the room controller is a resitance type (a temperature sensor) then it is more difficult. If it is 12, 24, 240v then it may be a matter of installing a simple relay. It may be a case of getting at the clock terminals to switch the boiler on and off for zoning. If the clock can be remote then the wires can be got at easily. The existing integrated clock can stay at the 24 hrs setting (always on) and clock stats fitted elsewhere for each zone.
On Wed, 11 Jul 2007 02:42:35 +0100, Lurch mused:
Or 3 if you cont the neutral as well, and being reasonably pedantic I'd say it should be counted as a terminal and not left out.
It would then be a matter of finding out what the actual switching signal consists of. I suppose it might be some form of digital multiplex - how many wires go to this controller?
But no matter how oddball it would be *possible* to intercept this control data and alter it.
Sure. Knock up a pic and some mains relays ;)
If the "room stat" is actually a temperature sensor using a resistance to detect the temp (the usual method), opening the circuit will usually send the thing one way or another. I have done this many times in designs on commercial setups. The boiler fully on or fully off. So inserting a relay in the line will switch on or off the boiler. Then this circuit can go though the end switches of the zone valves. When the zone valves are open the whole circuit is engaged and the temperature control is working well. When closed the boiler is off or on. I would guess than when this temp sensor is linked out (no resistance) the boiler will be full on.
It is worth full linking the stat circuit and opening and observe what the boiler does. Then close and see what happens. I would be leaning to that the circuit is just a low voltage resistance temperature setup and what I describe will easily work.
If so, depending on the zone valve a relay have to be incorporated in the design. Best have a SPDT end switch on the zone valve, if possible.
That is the aim of many makers - fit and forget, no need to design as the experts do it for you. Also getting around Part P using a wireless stat.
Except the boiler uses the same basic layout and controller board as many other WB models that can use the TR2 as an *option*, these other boilers can use zone valves or mid position valves.
In the R30 HE Plus manual
The terminals
L N Ns Ls LR
are identical to those on many other Worcester boilers.
For instance look up the Greenstar R28 HE, a system boiler that can be used with a TR2, and can also optionally be fitted with an internal (24v) diverter valve. When configured like this the R28 HE is,with the exception of the hot water heat exchanger section, identical in almost every respect to the R30 HE Plus.
R28 HE manual
Unplug the TR2 from the main pcb (as it's used for settings and diagnostics access in the R30 this might not be a long term option) remove the Ls - Lr link and wire as per these schematics and the boiler will interface to a whole bunch of standard control plans.
Daft idea.
No need to just open or close a circuit. It "appears" that there is no link on the TR2 connections at the boiler. This means on open circuit the boiler is "on" permanently. Connect it and a resistance appears and the controller acts accordingly to turn on or off, or modulate the burner (haven't looked at this boiler in detail so it may or may not modulate the burner via room temp). So closed circuit means boiler off. Opening and closing this circuit to have the boiler on or off will work. When open the frost aspect will be disabled, but an external frost stat can be fitted if need be. When on, burner modulation is activated if a part of the control system as the circuit and the TR2 is in circuit.
Aha ..looks promising.
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