In what steps can the radiator valve regulate heat? And for the thermostat?

@Chris_topher Not a simple question to answer. Firstly, I am a homeowner and not a heating engineer, but my experience of Tado for over a year has left me with the following opinion....

I think it depends greatly on whether you allow all rooms to demand heat - i.e. all rooms connected to the zone controller. In this scenario I think you can (perhaps) leave things to Tado, without balancing. Any rooms which don't receive enough heat straight away, due to distance from the boiler on the pipe run, will eventually fill the gap as they force the boiler to fire when closer rooms have received enough heat and shut themselves off.

But, if you have your system configured like mine (only one zc room and all other rooms independent), then I think balancing is very much still necessary. Otherwise, when your zc room has enough heat and turns the boiler off, it's game over for the rest. You need to balance the system in order to push water/heat beyond the zc room. Alternative is to make sure that your zc room is the last on the pipe run, so that when it does call for heat the earlier rooms can grab their piece of the action first.

But....

You also want to make sure that you keep return temps low (for a condensing boiler) so you don't want the flow taking short cuts through a wide open, unbalanced radiator and immediately sending toasty water straight back to the boiler. So, depending how things pan out if left to Tado, you might still want to tweak the balance for maximum efficiency.

I do monitor return temps from each radiator and I do find balancing beneficial. Otherwise some radiators will definitely short circuit the water flow and lower boiler efficiency.

@gary333 I have a whole bunch of these....

https://www.amazon.co.uk/gp/product/B07ZN3QTBV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Enough for flow and return on all radiators at once, plus boiler flow and return as well.

The two larger monitors log temps 24x7 in one minute (configurable) intervals. The smaller ones are real time monitors without logging. These are the ones that go on the rads.

I then snugly secure each thermocouple with a Velcro strap, pressing it firmly against the copper pipe and insulating it from cooler air around.

https://www.amazon.co.uk/gp/product/B001RPWPQE/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I would not strive for Delta T 11 or 12 across each radiator. This will be easier to achieve with high flow temps (like 70C) because the rads will be emitting heat at a higher rate, thus losing it faster. It is a bold ambition for flow temps of 50C or less, especially if the house is already warm. Balancing the traditional way needs a cold house and a cold system to be done correctly. Once things warm up it is increasingly difficult to achieve these Delta T targets.

The same thing goes for targeting Delta T 20C at the boiler. With a non condensing boiler and flow temps of 70+ this is again quite easy, for the same reasons. High temps lose heat fast.

When you run the system longer and lower it is unreasonable to expect such huge temperature gradients. Further, if your boiler is range rated to low output, it is even more impossible.

If I run my boiler without range rating then I can see those 20C deltas at the boiler. But range rated down to 9 kW instead of max 24 kW the water doesn't heat fast enough to create such extremes. I'm happy to see 8-9C delta at the boiler. Properly balanced, it is more likely that it'll be nearer to that for each rad as well.

The way I balance, with a live running system, and a warm house, is to compare return temps from each rad with the return temp at the boiler, and also between rads. If any radiator return is hotter than the rest I squeeze the lockshield down just a little more on that rad.

It's definitely not the conventional way of doing things, but it seems to work. Of course, it is far easier to do it my way when every radiator has a monitor attached at once. I can just run around glancing at the numbers without having to detach and reattach a single gauge and wait for equilibrium.

@eezytiger Thanks for that information. What you are saying about balancing makes sense, and explains why I can't ever seem to get more than a 5oC delta across the heating system). A Tomkat Gas training video on Youtube was showing the same issue you talk about (being impossible to balance using conventional wisdom. He by the end was doing something similar by just getting the rads to heat to the same temp when measured in the centre of the rad.

Hi, just saw this thread.

Doesn't the increased firing/stop cycles prematurely age the boiler?

A boiler, and it's constituent parts, have an MTBF that cumulatively set an MTBF for the boiler in terms of number of firing cycles (affected by lots of other factors, to be sure) but nevertheless, doesn't the TADO controller increasing the number of firing cycles 5 fold equate to reducing the MTBF of the boiler by 80%?

And if the boiler is an older mode, and is more fragile, increase the chance of failure sooner rather than later?

Incrementally opening the radiator valves achieves nothing that on off control in a timely way cant achieve and comes with the added benefit of a mortised pin that can easily detect the entire range of movement and then calibrate its self for open and closed positions.

if you just need a small amount of heat then open the rad valve for 2 minutes out of every 15 for instance. This works just the same as being open 13% of the way all the time....

The thermal mass of a radiator full of hot water will mean you would not be able to tell the difference in the real world between a radiator modulated in the time domain rather than in the "percentage on" domain anyway.

My valves for example are Danfoss and the total movement of the pin from fully out to all the way in is about 4-5 mm - I'm 100% sure there is not intended to be any partial opening of this valve and the standard TRV head would have quickly transitioned from open to closed and vice versa at the set temperature point.

The end result is a system that can work with any manufacturer of radiator valve and can easily modulate your radiators based on what it learns over time. I've noticed my heating getting much batter at eliminating over and undershoots of temp over the weeks I've been using it. my room temps are now kept within 0.5degC of my set temps in all 4 zones all the time.

Anyone contemplating leaving the system because it doesn't open the valves part way is quite frankly an idiot and doesn't understand physics or maths.

edit: the only argument I can think of for attempting to partially open a rad valve would be battery life of the smart valve itself as it wouldnt be going all the way from on to off and back each time - but seeing as you'd expect this partial opening to be constantly adjusting its self to match demand I recon this would be minimal anyway.

I'm interested in your reasons... Ive had my own set of issues too that have been really draining to work with support to try to resolve... That said the deep dive Ive gone into this system in order to resolve my issues has given me an elevated perspective on how Tado and my Boiler interact which has left me with an overall "Impressed" feeling about the system as a whole.

I can see how those would be issues for some people, I dont like the idea of it either but in real world terms I dont think it will affect me, my internet is only ever down if the power is down so no heating anyway... if the internet is down you just control your heating manually with the wall stats and/or rad valve dials.

For me the benefits of multizone control over my opentherm combi boiler out weigh those negatives and also out weigh the issues I have been having with opentherm comms errors...

half my home automation is dependent on the internet - ie everything I control with my voice etc so i guess heating being one more thing is not the end of the world for me

can I ask what other systems you considered and what you have ended up using. I came from nest originally which worked fine but had no multi zone functions and i was getting tired of the mrs saying the bedroom was cold when she went up to the room. I was going to go with the Honeywell evohome stuff before choosing Tado, i also have a lot of experience with heatmiser and hive. Im always curious if theres a better solution out there that ticks all (or more of) my boxes.

Looks like they've updated multiple support pages with the same statement, including this one:

I wonder if this is the reason for the recent jump in firmware version numbers (ie 204.1)