I haven't seen much information about exactly how and why you'd want either or both of these. I suspect those that don't know just say "...the boiler will use the WC and OT to work more efficiently..". Yeah but how ?
What problem are we solving? Lets deal with that first. So its said that with a traditional on/off boiler controlled by a room stat, the boiler will overshoot and undershoot its target. So in the real world, Mrs Miggins sets the temp to be 21 and what actually happens is that it cycles between 19 and 23. Doesn't sound too terrible to me. Then we get told well the boiler will also by "cycling". Perhaps on and off every 30 minutes? Lets put that into perspective. My old boiler an Ideal 3100 ran for 30 years and was still running fine when changed. However it would cycle every MINUTE - that's right you set the temp to be 21, the boiler was well oversized and so the rad water temperature hit its boiler-maximum and so the boiler would shut down even when the temp of the house was say 15. It was doing that all its operational life - 30 years. Obviously that was all badly specced and configured but if a boiler can last that long cycling every minute of its operation then I can't see how its such an issue for a boiler to cycle every 30 minutes or so once the home has reached temperature.
On to the how to solve this (non existent?) problem. The OT tells the boiler what the stat's target temperature is and presumably tells it what the temp is now. The WC part tells the boiler how long it is likely to take increase the home temperature by say 1 degree - the colder it is, the longer it takes to heat up. Armed with both, presumably the boiler outputs its highest allowed temp until it gets close to the target temperature. It can see how long it is taking to reach that target temperature so I'm not sure how helpful the WC is when OT is in operation. And yet my boiler has connections to both OT and WC but there is zero information about what it does with that info.
Even though I'm obviously a bit sceptical about the whole thing, I'm planning on connecting up the OT to a yet-to-buy-controller like a Nest (anyone have any suggestions on what is a good OT controller?). Then I can look forward to perfectly stable 21 degree temps. Perhaps I'll put an independent digital controller on the wall so I can start shouting at the stat if the temperature exceeds 21.5 . A modern day fawlty towers if you will....
What problem are we solving? Lets deal with that first. So its said that with a traditional on/off boiler controlled by a room stat, the boiler will overshoot and undershoot its target. So in the real world, Mrs Miggins sets the temp to be 21 and what actually happens is that it cycles between 19 and 23. Doesn't sound too terrible to me. Then we get told well the boiler will also by "cycling". Perhaps on and off every 30 minutes? Lets put that into perspective. My old boiler an Ideal 3100 ran for 30 years and was still running fine when changed. However it would cycle every MINUTE - that's right you set the temp to be 21, the boiler was well oversized and so the rad water temperature hit its boiler-maximum and so the boiler would shut down even when the temp of the house was say 15. It was doing that all its operational life - 30 years. Obviously that was all badly specced and configured but if a boiler can last that long cycling every minute of its operation then I can't see how its such an issue for a boiler to cycle every 30 minutes or so once the home has reached temperature.
On to the how to solve this (non existent?) problem. The OT tells the boiler what the stat's target temperature is and presumably tells it what the temp is now. The WC part tells the boiler how long it is likely to take increase the home temperature by say 1 degree - the colder it is, the longer it takes to heat up. Armed with both, presumably the boiler outputs its highest allowed temp until it gets close to the target temperature. It can see how long it is taking to reach that target temperature so I'm not sure how helpful the WC is when OT is in operation. And yet my boiler has connections to both OT and WC but there is zero information about what it does with that info.
Even though I'm obviously a bit sceptical about the whole thing, I'm planning on connecting up the OT to a yet-to-buy-controller like a Nest (anyone have any suggestions on what is a good OT controller?). Then I can look forward to perfectly stable 21 degree temps. Perhaps I'll put an independent digital controller on the wall so I can start shouting at the stat if the temperature exceeds 21.5 . A modern day fawlty towers if you will....
