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My issue with thermo rad valves

Discussion in 'Plumbing and Central Heating' started by rt18, 18 Jan 2021.

  1. rt18

    rt18

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    In my home I have one radiator that rarely gets hot and unfortunately it's in the lounge. When the heating comes on there are some radiators that heat up immediately, others take a bit more time but do get there, and this one in the lounge never seems to get hot. It gets warm, but that's it. It's practically useless, and the lounge stays cold.

    The thermostat is in the dining room, next to the lounge, and that's set to 21. The house never gets above 19 when it's really cold outside, so the heating is practically constantly on during the day when it's the coldest of winters, like now.

    So my conundrum is - how do I get the lounge radiator to get hot without entirely compromising on the other radiators?

    I've opened the TRV on the lounge radiator to max, and tweaked and adjusted the rad valves on the other radiators to try to get them to close off when just warmed, so that the lounge radiator will get the lion's share of the hot water, but the end result is usually lots of screaming/squealing from all the closing thermo rad valves. The sound is like torture, it reverberates through the plumbing and vibrates your head like the famous shower scene from Psycho at full volume. So consequently the rad valves are pretty much all at max everywhere. If I completely close the TRVs to the other radiators, forcing the central heating to go through the lounge radiator only (which does work), then the rest of the house isn't heated. So that's impractical.

    I've checked the manual valves on the opposite side to the TRVs to ensure they're open, and they all are. But I've heard of something called load balancing, which I thought was an outdated concept since the introduction of TRVs, so I've not considered it - might this solve my problem?

    Could the TRV be malfunctioning? If I take it off, that effectively opens the radiator valve fully, right?

    I had the system flushed about 3 years ago, all radiators were cleaned out to remove gunk, brand new combi boiler and the usual inhibitor, and these new thermo rad valves fitted throughout.

    Desperately looking for advice before I go out and by electric heaters for the lounge!
     
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  3. sxturbo

    sxturbo

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    System needs balancing,
     
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  4. rbranco

    rbranco

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    Balance the system.
    For now close all the lockshields on radiators and open them up half a turn and see how they all warm up. They should all work but you will still need to fully balance the system to get best effect. Normally the rads closer to the boiler (in pipe run, not linr of sight) will have the lockshields progressively less and less open.
     
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  5. ericmark

    ericmark

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    OK method 1, 2, and 3.
    Method 1 is measure the water temperature in and out of each radiator and set lock shield valve so 20°C between the two.
    Method 2 turn off each radiator, allow to cool, then turn back on ¼ turn at a time on lock shield until you just feel one pipe getting warm.
    Method 3 fit TRV heads which show target and current temperature and tweak the valves until they match.
    Flat Battery TRV.jpg
    All have their plus and minus, the problem is any modulating boiler will modulate, (turn down output) it is after all what they are designed to do, so any radiator which allows water to return not cooled, will cause the boiler to turn down.

    Years ago, non modulating boiler and no TRV fitted, I tried to adjust the lock shield valves, idea was to balance heat in every room, so one thermostat served all. To be frank it did not work, heat raises and so lower floor heats upper floor but by how much depends if doors open or closed, and leave a bedroom door open and they became roasting hot.

    The TRV was a god save, it stopped the upper rooms over heating, but it did not matter how hot return water was, as long as out water from boiler was hot, and the fan assisted radiator would return hot water when fan speed reduced.

    But then came the boiler which extracted the latent heat from flue gases, for this to work, the return water has to be cool, so the boiler needed to adjust output (modulate) to ensure return water is cool enough.

    Now it takes some time for water to travel through the system, and every thing works slowly, the TRV slowly reduces water flow, the by-pass valve slowly opens, the boiler slowly reduces output, so it takes time for the system to settle to a smooth output, there will be sine waves of temperature as things over shoot then settle down. Often called the Hysteresis.

    So we want to turn off the boiler as little as possible, we what it to have a steady output matched to the conditions. Clearly when we start to use a room, or leave the house, or go to bed, what we want changes, and we tend to use a programmer (time switch) to control when the boiler runs.

    However there is a problem, when the sun comes out, and we get warm weather, the system as described starts to cycle off/on as boiler can't turn down enough, but can't turn off.

    So we fit a thermostat in the coolest room (so warm weather will affect it soonest) with no outside door, on ground floor, with no alternative heating. Quick thought and you realise that room rarely exists, so a compromise, but the aim is still the thermostat only switches when we get warm weather, only exception is the analogue thermostat which does not switch, but turns boiler down or up.

    So today the main controls are the TRV heads and the lock shield valves. The heating guy can try setting 20°C but only approximate in the time he has to commission, and not really going to work too well if commissioned in the summer, I as an electrician have been called to change thermostats etc. And often find the lock shield valves wide open, as to if that is how the heating engineer left them, or if some one has fiddled not a clue.

    But the fault is rarely in the cool room, fault is normally in the hot rooms, where they return hot water so turns down boiler.

    biggest problem is *123456 marked on TRV heads, what is the good of that? I know what 70°F is or 20°C but between 3 and 4 means nothing. I have in the main now heads that show °C and the old heads are in a draw, fitting one to a valve and blowing through it while adjusting and you realise there is 2 to 3°C difference between when it starts to close to when fully closed, so one room 2.75 may = 20°C and another rooms 3.75 = 20°C, as one rooms needs it ¼ closed and another room ¼ open. Which is why I fitted electronic heads.

    So you have two adjustments, and no idea which to adjust, however this is second house with electronic TRV heads, and when I removed them from mothers house, and replaced with heads marked *123456 set to around 3¼ they actually worked nearly as well as the electronic, not programmable of course, but did control temperature well now the lock shields already set.
     
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  6. rt18

    rt18

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    Thanks everyone, especially Eric for the extensive explanation. (Incidentally, I did look at electronic TRVs but only found Tado ones and can't afford those prices.

    So I can confirm the lockshields are all wide open, and that's my doing - and my misunderstanding. I assume the TRVs would control the flow, and the lockshields were purely for isolation when maintenance work was happening etc. I'll follow your guidance and turn off heating, reduce all lockshields to a quarter turn open, let system cool, then start a balancing process. (Quick question - if all lockshields were closed and heating was on, would the boiler be damaged from an inability to circulate water? Or does it have a pressure relief bypass?)

    @ericmark Something you've said, "any radiator which allows water to return not cooled, will cause the boiler to turn down" occurred to me also. And if just one radiator nearest the boiler is passing hot water straight through and back to the boiler then I assumed the boiler would start to modulate down.

    So if all lockshields are set the same, surely the behaviour will be unchanged to now with them all wide open - the radiators all heat up the same and the coldest rooms stay the coldest. Therefore the balancing strategy is to find these colder rooms and open their lockshields slightly to bias the flow of water in their favour? Just a quarter turn more open is enough, then? Or somewhere between a quarter turn and a half turn? @rbranco You suggested to open a half turn then slowly close them on the rads warming first, to reduce their flows, right? So i can assume the final positions for all valves will be between a quarter open and a half open. That surprises me when the valves can be turned a few whole rotations, this is a finely balanced process!
     
  7. rbranco

    rbranco

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    Balancing is to make sure the hot water gets circulated around to the furthest radiators, remember water will take the path of least resistance, so the radiators closer to the boiler will get hot first, but not drop enough water temp which then goes back to boiler too hot and it modulates down until the TRV starts to close, which then reduces flow though the first radiator, then the second starts to get more flow etc etc keep repeating till the last radiator.
    What you want is all radiators to get a portion of the hot water so they all come up to temp at the same time, the water will then return to the boiler much cooler.
    So this is why the locksheilds closer to the boiler (in pipe run) will be closed the most. (eg, 1st rad 1/4, 2nd rad 2/4, 3rd rad 3/4 etc but its not that straight forward as you are also looking for a temp drop between flow and return on each radiator to the same across all your radiators so they are coming up to temp at the same time.
     
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  9. rt18

    rt18

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    Thanks. As I have no way of measuring temp drop, I guess I need to use constant tweaking of the valves until we get a reasonably consistent behaviour from all radiators. If there are radiators that don't seem to get warm, I'll open up their valves another quarter turn.

    I guess it also depends on the pipework - if one branch is feeding the entire upstairs then it has six radiators to feed, but downstairs we have eight radiators, so they'll provide less resistance to the flow as there are more routes to take? Therefore I need to think about opening up the upstairs valves a touch more?

    Another question (because I'm inexperienced with this) - currently all the valves are wide open so the water is flowing as fast as the boiler can pump it round. But if I reduce all the valves to just one quarter open, will that not massively slow down the water flowrate, and thus mean it takes an age for the hot water to travel the pipe lengths to get to the radiators? Obviously I don't know, experimentation will reveal the reality, but I'm wondering if the hot water will go from maybe one minute to reach the radiators, to something much longer like 30 minutes? Let's see....
     
  10. ericmark

    ericmark

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    If the heating is not turned off each TRV will control the radiators with lock shield wide open. But as soon as turned off, on switching on again it will heat home one room at a time.
     
  11. ericmark

    ericmark

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    Oh yes look for Terrier i30 and eQ-3 TRV heads, the latter both with and without blue tooth, were £10 without and £15 with but seems Brexit has caused a price rise.
     
  12. Terrywookfit

    Terrywookfit

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    Try telling customers that a warm room with cold rads is good.
    As soon as the rad starts to cool 90 % of people try to turn things UP!
    I have long since stopped trying to balance systems to achieve max efficiency as you would inevitably get a call saying " Rads are not hot enough".
    The Bill paying Tight fisted ones who are determined to save the planet, seem happy to constantly adjust settings to satiate their obsession whilst spending a fortune on various wifi controls!!
     
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  13. rbranco

    rbranco

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    I rather save my money by making sure its running efficiently to spend on motorbikes
     
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