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



  • So, if the tado valves modulate do we still need to balance the rads via the lock shield?

  • @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.


    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.

  • Could I just ask how you monitor temperature output from your rads? I have tried balancing my system (using probes) but when i do eventually get a 12oC differential the valves are near enough closed down to a fraction of a turn (1/8th or so). However, this then leads to the radiators not heating up and staying near enough stone cold at cooler 35oC - 40oC flow temps as soon as i put the SRT's back on.

    I'm banging my head when it comes to balancing as I just can't seem to achieve anything. From the previous post it looks like my effort to balance is then wasted if it Tado SRT's restrict the flow even more.

  • eezytiger
    eezytiger ✭✭✭
    edited December 2022

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

    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.

    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

    that is interesting, I’m running just the Tado trv’s on 10 rads and using vsmart with its wireless thermometer to fire the boiler and set hotwater tank recharge.

    So all my rads can call for heat but the boiler won’t do anything till vsmart says go.

    i did have it all integrated with the extension kit firing the boiler (I have the correct Vaillent module as had vrc470 before vsmart) but had issues with it not modulating, not heating the tank, or constantly heating the tank with no heating the house & Tado support would do stuff but not explain what they did leading to some days with no heating or hot water in winter which wasn’t fun with a baby in the house.

  • gary333
    gary333 ✭✭✭
    edited December 2022

    @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.

  • @gary333 Ah, yes, I enjoy the Tomkat videos. That guy talks sense.

  • 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?

  • How do you interpret when a TRV calls 1% or 2% heat ?
    What is that supposed to mean ? Such low values…
  • Chapstar37
    Chapstar37 ✭✭✭
    Why not test it using a flow gauge, on the lock shield end.. Reduced flow = reduced aperture, increased flow = increased aperture, no flow = bypassed state