Getting started with OpenTherm - some basic questions!
Hi all, I’ve got what I’m sure are some very basic questions around a Tado & OpenTherm install that I hoped someone would be able to help me out with?
I currently have the UK wireless starter kit for my combi boiler - my plan is to order the EU wireless starter kit and simply swap out my current UK wireless receiver for the EU wireless receiver.
(I realise Tado also sell the standalone EU wireless receiver, but there’s a reason I’m not planning on getting that - see point 2!)
1. Would this plan work? I guess my concern is whether the thermostat, bridge and receiver from each starter kit are somehow ‘paired’ and will only work with each other i.e. their ‘box buddies’.
2. Semi-related to the above, I plan to gift the new wireless thermostat and bridge from the EU starter kit, along with my ‘used’ UK wireless receiver (having de-registered it from my Tado Home) to my mum - making up a ‘complete’ starter kit I can install for her house. Again, my worry here is whether there is some kind of problem with each device working together if originally from different starter kits.
3. In terms of wiring the new EU receiver to my Ideal Logic+ 30 combi boiler, am I right in thinking the only difference is the addition of the two wires from the OpenTherm terminal in the boiler to the corresponding Digital +/-terminals in the EU receiver? I’ve seen mention of a separate power supply being required - but my current UK receiver is powered from the boiler, so not certain this is required, unless I’m missing something? And do I still require the two wires into CH COM and CH NO?
(Do please excuse any glaring idiocy in any of the above!)
I currently have the UK wireless starter kit for my combi boiler - my plan is to order the EU wireless starter kit and simply swap out my current UK wireless receiver for the EU wireless receiver.
(I realise Tado also sell the standalone EU wireless receiver, but there’s a reason I’m not planning on getting that - see point 2!)
1. Would this plan work? I guess my concern is whether the thermostat, bridge and receiver from each starter kit are somehow ‘paired’ and will only work with each other i.e. their ‘box buddies’.
2. Semi-related to the above, I plan to gift the new wireless thermostat and bridge from the EU starter kit, along with my ‘used’ UK wireless receiver (having de-registered it from my Tado Home) to my mum - making up a ‘complete’ starter kit I can install for her house. Again, my worry here is whether there is some kind of problem with each device working together if originally from different starter kits.
3. In terms of wiring the new EU receiver to my Ideal Logic+ 30 combi boiler, am I right in thinking the only difference is the addition of the two wires from the OpenTherm terminal in the boiler to the corresponding Digital +/-terminals in the EU receiver? I’ve seen mention of a separate power supply being required - but my current UK receiver is powered from the boiler, so not certain this is required, unless I’m missing something? And do I still require the two wires into CH COM and CH NO?
(Do please excuse any glaring idiocy in any of the above!)
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Comments
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All current generation Tado devices work fine with each other. No problem unregistering them or registering to different accounts, especially as you’re not moving the bridge across. Two Opentherm wires plus power needed, use l and n from your current receiver. Don’t connect com and no at all (especially not to the Opentherm terminals on the receiver).1
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Awesome, thanks so much for your help @johnnyp78 👍 - that’s perfect.0
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Righto, so I wired up the new receiver yesterday and, some pairing issues aside, got everything connected - system check using the Pro app all looks good.
The only issue I’m seeing is very frequent pump overrun cycles on my boiler - definitely a huge increase and quite the opposite behaviour I expected when using OpenTherm, but perhaps I’m misunderstanding things (as usual!)
I’ve also noticed these pump overruns almost appear to be triggered in response to very low heat demand from my SRVs… but could be coincidence.
Possible stupid question 1 - is it likely that Tado is switching off the call for heat knowing that the several-minute pump overrun cycle will continue to circulate heat?
Possible stupid question 2 - for low flow temp requests, i.e. maintaining temperature when it’s close to target, could Tado trigger a pump overrun cycle to circulate heat rather than a full-blown firing of the boiler?0 -
Oh, and final possibly stupid question…
I’ve obviously disconnected the COM and NO wires from the receiver end, but these are still in place in the terminal block at the boiler end. I have noted the slightly vague instruction on the Tado Pro system check page that “Some boilers’ relay (on/off) terminals need to be bridged when installing a digital thermostat.”
I didn’t do this, as to be honest I couldn’t get specific low-voltage instructions for the Ideal Logic+ 30 combi - so just wondering if this could be connected to the pump overruns?!
(Tado are ‘preparing some customised installation instructions’ for me at the moment apparently, so I guess when I receive those I should at least get an answer to that question!)0 -
If you mean running the pump to circulate heated to temp water, rather than firing the boiler, yes I think this is normal behaviour with Opentherm. It does it on my ideal vogue occasionally. Less so if you lower the max flow temp I think.
Fairly certain you don’t need to bridge com and no, I think the pump over running is more to do with Tado (or the boiler) economising by not firing the boiler unnecessarily.0 -
I'd say the decision is made by the boiler when there is a demand for a small amount of heat. I haven't seen anything that suggests the OT protocol can request a boiler run the pump.
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@Montage my boiler is a Viessmann 100 B1KC(2019 model,not so good at low demand,8kw min) and if I keep my heating on all the time(ex 20C 6am to 12am,19C bedtime) the pump will run all the time after the boiler(or Tado) stop fire at set point(20C) and with 1 wavy line heat demand till the temp drops 0.4-0.5 to set temp will run the pump only….is doing this for hours and hours and maibe if Tado will overshoot 0.1 at least and reduce heat wave to none maibe will stop the pump running,but there is always a heat demand and a pump running the water at 23-30C for nothing. So,I get rid of this by scheduling to start every 2-3 hours and run for 30 min and no pump running unnecessarily cause it is stoped by the time schedules . In order to get 20.2-20.4 C I set the thermostat to 20.5C set point for the 30 min time slot when boiler run. I also calculated how much temp drops in 2-3 hours and don’t have more then 0.7-0.8C drop and the boiler can catch up in the 30 min time to rise the temp close to 20.5C. Usually the boiler fire at heat the water somewhere between 37C to 50C if colder outside and the gap is higher to reach set point. I think twice this winter ramp the water at 61 but was -12C outside and 1.5C gap to set point. No temp limit in Tado Pro,had before limit to 55 but worse outcome with cycling and currently is 80 but never seen more then 61-63.0
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I got my customised installation instructions through from Tado, which did include the step of bridging the Room Stat/Timer terminals on the boiler.
So I did that and guess what? It resulted in pump overrun being permanently on! I gave up after 1hr 45mins and removed the bridge wire - pump overrun stopped after its standard cycle time once I restored power.
The curious thing is, the random/extended pump overrun instances seem to have stopped - the only difference is that there are now no wires in the Room Stat and Timer terminals (I’d left these in place after installing the new OpenTherm receiver, even though I’d disconnected them from COM and NO on the original receiver and obviously not reconnected them to anything.)
Slightly concerned that Tado’s customised instructions are clearly not fit for purpose!0 -
@Montage I wanted to say that my type of boiler connected via digital opentherm wil run the pump all the time,even at a very low heat demand without the boiler to be fired. Therefore my solution was to use schedule,can’t use Tado to same temp all the time.0
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Yes, I understand it happens. What I’m saying is there is nothing in the OpenTherm protocol to command the pump. That means the boiler is doing it. I agree that it is likely when the demand is small.
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@BOG73 Interesting that you have seen less cycling by setting your flow temperature to 80°C. I forgot that I had actually done this too - it was previously 55°C.
I’m not seeing the excessive pump overrun anymore and haven’t seen the flow temp go much above 50°C - and it’s quite cold today where I am in the UK.
I have no explanation for this!0 -
@rampoday maibe Tado is calculating the heat request demand(wavy lines) and percentage of the max heat at one moment acording to max water temp limit and boiler is running longer at low temp....if a boiler can't go lower then 6-7kw min output will leave the pump running till a higher heat request. I also discovered that in my sistem with 13 radiators is better not to follow the radiators balancing by the book(12°C differential flow/return) and allow radiators to heat at the same rate by opening the return valve more at furthest radiators from boiler. I started with 3/4 open return valve at the closest radiators,1/2 to second and so on....I have observed that my rooms are heated more equal and faster (no zoning) and boiler is running mostly at 37C to 45C with -2 C(night) and 10C outside(day time) and ussually is fired for about 15-20 min with 2 hours off(schedule).
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