HOW RADIATOR VALVES WORK AND HOW TO SET THEM - TRV/Thermostatic 

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Just had new valves fitted so finding this video is quite pertinent. Probably like most people I didn't realise that is how they work, so thank you for the explanation. I will be trying my new valves out with all this in mind!

As a plumber I have had many a discussion on why two radiators in the same room both set the same but one stays hot longer than the other. My explanations range from the valve being in a restricted air space, behind curtains, furniture or other objects like coats hung on the end covering the valve. I also explain that a radiator on a outside wall or under a window may detect cooler air from outside than a radiator on an inside wall. draughts from windows, doors and vents add to this problem. The position and setting the valve can also be a factor, horizontal or vertical will give different readings which is made slightly worse if the valve is feeding the top of the radiator instead of the bottom. A top inlet vertical valve picks up the heat coming off the supply pipe where horizontal valve is not is not in the direct air flow. The last thing is certain valves come setup to be fitted as a horizontal valve and if fitted vertically they don't work properly. On some of these, on the valve body there is an adjuster with arrows showing the direction of flow. (Danfoss valves were the first I noticed set to be used horizontal) A couple of symptoms of this can be knocking and/or premature closing and late opening on temperature rise and fall. I would love to see you set up some experiments to show these effects.

Great info, thanks for the full explanation I learned something here... Also its great to see Bradley Cooper taking time out from filming for this. :)

Very very knowledgeable and eye-opening video.

After having a new boiler and trv fitted I couldn't think why one of my radiators was off all the time (in the room where the gas fire is always on). Now I know, and I can manage it properly. Thanks 👍🏻

Very good demo for those that don`t have the foggiest of how TRV`s function.

I always thought I was physically turning the TRV to open and close the pin in the rad. This morning I woke up and for some weird reason my brain told me that would just slow down the time it taken to fill with water. I had no idea there was a temp sensor and heat related switch in there! Brilliant video, mind blown.

Really Simple and concise way of explaining how TRV works. Well done

Do these TRV's rely on your heating always being switched on? Please clear up any misconceptions I make but if your heating is switched off and the TRV detects the room is cold it will allow more water flow into the radiator, but won't that water be cold if your heating is not already switched on? Would it only benefit once the heating system was in use? I ask this because obviously not many households will have their heating on 24/7. Great video, really helpful

Thank you, very informative. Did not have a clue to use these valves in the past but now I do. Thank you so much.

Genuinely thought our new boiler was overworking and trying to kill us... Turns out my GF wouldn't stop playing around with the TRVs... so helpful thank you dude!

This is an excellent demo. I'll show this to my family if they ask.

Top video mate. How can we work work out how open the Lockshield should be in conjunction with the TRV? Feel like I'm always having to p1ss about with them both.

Hey James. Thank you. I really appreciate this. Well done on a crystal clear explanation.

Messiah!! I've been trying to get the Mrs to understand how these work for 6 Months, never listens. You managed it in 5 minutes😂😭

really good video, thank you BUT in the interest of fairness can you do a follow up video in your cold area but this time with boiling water running through the pipe/ TRV fully open with the heat rom the hot water in the TRV rising to demonstrate /prove the heat from the hot water doesn't cause the wax to expand and close the valve. thanks john. ALSO please comment on; recently in the news there have been an increasing number of occasions where a PEN electrical supply cable has failed, removing the suppliers Neutral conductor so the incoming live connects to the earth to find a return path so everything continues working BUT any metal work now becomes live, in one case a substantial amount of current trying to get to earth, went through the gas meter, the heat caused the gas to ignite and blew up the house. so as well as connecting main bonding to the customers side of the meter we should probably also extend it to the incoming side of the gas meter if the gas supply pipe is not yellow poly

showed this to the wife and kids, next day all the trv's turned to 5...FML

Love it , l am a lady & now understand thankyou 😁

I've leant a lot from this. I'm still a bit unsure about how these TRV's work alongside the main thermostat control. I always keep my thermostat as low as possible to try and save money, and when it reaches the temp the whole system goes off. So, why do you need TRV's? unless you want different temperatures in different rooms. Why does it matter if all TVR's are set to 5, if they'll all switch off when the main thermostat reaches the set temp?

Good vid, told me something I didn't know. I'm in a new build and one of my rads hasn't got a TRV on it, whys that? is that wot I believe to be a thermostat radiator?? Or that's wot I've been told. Thanks matt

😂😂 nice one. No matter how many times I explain this to customers I know when I leave they turn them all back up to 5!

That was excellent. Just one question our main thermostat is in the hall? What temperature should it be set at to ensure all rooms are controlled properly by the TRVs?

Thank you, you have saved me having to call a plumber, now I know.

Hi James. Loving both your channels! Could you do a video on the perks of being a self-employed plumber rather than working for someone else? I am thinking of taking the step myself but would like to know more of the up and down sides. Cheers!

Brilliant video! Just one question. If you have lots of radiators, (in different rooms,) at different pressures how does that affect the general pressure on the feed pipes from the first radiator to the last?

Thank you pal that’s a fantastic video really well explained , thanks for taking the time 👍👌

Excellent video Sir...Now we understand.

Thank you so much

Very good video 😊

Should the TRV be mounted vertical or horizontal? I've seen both; vertical is neater but nearer the radiator, horizontal is clumsier, but further from the radiator, so it must get a more accurate reading of the room temperature.

Another informative video

love your vids 👍🏼 can I ask....? Ive fitted a TRV to our new bathroom rad but rather than a TRV on one side and a lock shield on the other both valve bodies seem to be the 'pinned' valve type. The TRV can be fitted to either side and the 'blanking' cap can be screwed to the other valve. I take it the blank valve should not be compressing (screwed down) on the other side?

My ex used to regularly wind the room stat up to it's highest setting. Once, I was about to tell her it was fairly pointless, as with the exception of the hall (where the room stat was) the TRVs, which she left set about 3, would cut the radiators off. Thankfully, I thought to shut my mouth in time!

This should be required watching for kids starting high school!

Brilliant got teacher , thanks bro

So what does the other valve do? its either really loose but can be tightened on my radiator? My radiators take up to an hour to warm up and even with 4 turned off the £ per hour seems to stay the same in my flat

Great video

thank you that explains it, but mine is 11 yrs old, I think trv is faulty as it shuts off at 3, and it is very cold. 4 works and my thermostat is on 45c

Frost Protection. The good thing about TRV is that it will protect a radiator against frost by allowing water flow through a radiator if temperature falls below a certain level, even if that TRV is turned off. The bad thing about TRV is that if you have removed a radiator and not yet replaced it TRV will empty heating system fluids across floor during frosty spell. You turned TRV off Frost turned it back on. OUCH.....OUCH.

Great explanation. Could you advise me as I'm not finding my rads get hot for days at a time on 3 unless I set to 5 first for 30 or so mins then set it back to 3. Even then, some don't tend to turn off even when the room temperature is over 21c. I was wondering if TRV's work in that way if connected to a communal boiler. My radiators have been adapted to have the TRV's at waist height with a copper pipe rising from the bottom of the radiator valve to the TRV at the top of the radiator. The water is constantly hot coming through that that extending pipe so I feel it may be sensing that micro climate rather than the ambient room temperature.

So in other words if the room is cold and the radiator is cold, turn it up to 5 to rush the water into it which will heat it up quickly, then turn it back down to4 and then 3 as the room warms up. If the radiator cools off before the room is 68 degrees and the thermostat is at 3 then the thermostat, as you guessed it, doesn't work properly, as they don't 70% of the time.

Good video very useful as usual

My tvr valve is fitted with the arrow pointing up on the it on the outlet pipe instead of down does this matter

My radiators seem to click and make noises when heating is turned on. What could be the issue?

Excellent

You crack me up so much! Thanks for being so informative and hilarious! (Y) Subscribed!

You could have taken the chance to explain that sometimes the pins in TRV's get stuck, and how to fix them. Just a idea. Cheers.

What is with the flight charts in the cat shot? Do you fly?

Is it better to mount TRV's vertical or horizontal, I prefer to mount horizontal if possible for better air flow around them.

Hi wondering if anyone would be nice enough to help. So we had an old ads boiler for ever and only just got a digital thermostat. So what I took from this video is I set my desired heat on the thermostat but just keep the valves on 3 ?

My t r v when I open it from 3 to five the rad does get hotter I’m confused what your saying

GEORGE! Some of my valves squeak when the reach the setting temp, really bloody annoying

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It's a losing battle with my family they turn it back up to 5 as soon as my back is turned! Some things just never get through to people!

Always make sure your TRV is Closed before you start filming Mate ....Button Tight !!

can you change a radiator without draining the system down

1. Thermostatic valve should be mounted horizontally...

awesome

That’s really well explained and well presented, I think we’re all a little wiser, excellent 👍

That's great. Now do a tutorial on how the indicator lights on a car work and how to activate them. This will benefit many drivers.

I was today years old when I figured out how my thermostat (TRV) worked. Thanks for the great explanation!

I’ve always had a understanding how it works roughly but this really set it in stone and it’s great looking how it actually does it’s job for better understanding. Thank you James 🙂

Another great video. I love the quality of your camera and what all you are doing!!!

Love this video! can you now do one explaining how this correlates to the thermostats and main heating controls. Like if i have the digital thingy set to 28 degrees but the TRV's set to '3'. Then which component takes priority?

even knowing how the valve works it's still awesome to see the valve work in action, watching the flow of water slow down till it stops as you are heating it up is very cool. love your videos, as i have just finished learning beside a plumber and now on my way to work solo, your videos are very useful.

Hi. Nice demonstration. If all TRV in rooms have reached lets say desirable temp of 20 degrees, does it mean that boiler will shut off even if the room thermostat is set to.let's say 23 degrees?

It frustrates the hell out of me that folk turn them up full to heat the room 'faster'. Think about it, these valves are so near the hot radiator! Best idea, mount them HORIZONTALLY. If they are vertical I put pipe insulation on the pipe underneath. I also put some insulation between the valve head and the radiator.

This fella is bang on, explains things so easily, which I've just shown a Tennant an she understood straight away

I've just moved from a freezing cold flat to a house that actually stays warm and was wondering why the radiators weren't heating up clearly the rooms are warm enough and don't need to be on. This is explained perfectly now I understand completely

Hi James, thanks for your great vids. Do you have a Pilot's Licence ? I noticed you have an aeronautical chart on your wall.

Please stop being an entertainer/ personality. Your vids are good but the “banter” is a battle to get through

Could do with a follow-up video on TRVs in conjunction with a room thermostat, best placement for a Nest, etc. For instance, my Nest is in my living room which has two big rads and warms up quickly, but my bedroom is usually too cold. When the heating's on, the temp goes up to the Nest setting and shuts off, but the bedroom hasn't warmed up yet, and the air brick cools it down too quickly. So, do I whack up the temperature on the Nest and tweak down the living room TRVs to give the bedrooms a chance? Do I move the Nest? If I put it in the bedroom, the motion sensor will think I'm out all day and put the heating on eco! Confused...

We're an agency and this is such a helpful video to share with our tenants, (especially those in house shares). Keep the basic knowledge videos coming please!

A lot of people get suckered into "smart TRV's" not realising that the TRV's they already have will do the same job. 95% of people just want their radiators to shut off at a set temperature. If that's you, don't buy a smart TRV!

So am I right in saying that if you walk into a room and the room is hot and the radiator is still hot, that means you should turn the TRV down? Also, how do these TRV,s work in conjunction with the wall thermostat in the hallway?? If the wall thermostat in the hallway is set to say 21 degrees but the rooms are still cold, do the TRV,s on the radiators over ride the wall thermostat in the hallway and keep the boiler running until the rooms are warm?? This is what’s really confusing me 🤔

digital ones need 1 minute, only the most expensive analogue danfoss 10 minutes, otherwise 20 minutes

Good vid. My granddaughter's thermo valve is behind her bed. Now I know why the rad didn't work to good.

Great video James, your informal style makes learning fun and demystifies the world of plumbing. Yes please more videos on plumbing basics

Hi but how do you install a trv? Put it on 1 then screw on or set to 5 then screw it on?

But if you have your heating set to manual, and have set your favourite temperature on your zone controllers, the TRVs should all be left fully open, right?

The TRV is so close to the radiator that it can only controll the temperature of the radiator. To sense the room it would need to be a long way from the radiator. The tests done in this video just confirm that it does not sense the room but the temperature in its vicinity which is that of the radiator.

Your Videos have been invaluable, and gave me the confidence to do some necessary housekeeping on my system. I have found a few tricks, that if you think are sensible to make videos on, would be appreciated: Tip/Vid 1: To find the last RAD, (Which you will drain from), open all Lock Sheer valves and TRV's fully, including downstairs, heat the system up for a 1 hour or so, and the last Rad should be cold. I found this out btw after I had done my work, but doing it before will help I think. I labeled it "Last Rad". Tip/Vid 2: When replacing a 3 port valve, always set the old valve you are replacing to "M" this will make sure you take the top water from the cylinder out of the system when you drain. Use some LS-X silicone around the original olive when replacing, I left it 12 hours to cure , so wrap up warm! and so far...after refilling (touch wood) no leaks. Tip/Vid 3: After you have refilled the system, and you have bleed from downstairs to up, worth advising if you are cleansing the system first before inhibiting, is to close the last RAD valve before refilling contrary to your advice , then follow the bleed process.... that way you don't loose the cleaner. It meant more bleeding, but I'm confident it's in the system for a few weeks before I do the whole process again to then add inhibitor. Lastly add to that, keep the ball cock open in the header tank, as if that drops significantly whilst your bleeding air, you will suck more air in, I heard it filling all the time, but was paranoid about the level going too low. Anyway thanks again for your vids.... they are amazing and will subscribe...I'm no plumber!! but there is NO WAY I would of done this task with out your great vids !!!..

Brilliant demo James, and close to my heart. So many switch between 5 when they are cold and back to 0 when they get too hot! This should be part of the National Curriculum!

30°C ?? Who the hell would heat a room into that temperature ? It's already a nightmare in summer when having 30°C in a room let not speak in winter. I always knew how it works and despite saying it to my office coworkers they keep on pushing all the radiators at the maximum level. A true nightmare.

Do you think having a sofa up against the radiator (and in turn the trv) would stop a trv from being able to accurately gauge the ambient temperature?

Do TRV’s expire/become less effective with age? Just thinking the ones I have are about 20 years old. Are they also interchangeable or do you have to change the valve body as well as the head?

1:40 in and the question has already been answered for me. In all my years I've never known how TRV's worked, Thanks!

One of the best explanation I have ever seen. Well played James

I would have thought it better if the TRVs were projecting horizontally from the radiator. Then they could not be influenced by the convection current of the pipework below them. That would give a better representation of the room temperature.

Excellent video. Acting was first class and the use of extras and props kept this audience member on his toes. The will he/won't he be able to borrow the heater had me on the edge of my seat. My only complaint was the speeding up of the 18 minutes, one of cinema's great losses. Very well explained, thanks.

At last, a thorough explanation of a TRV. Won't forget that now. Thanks.

I had no idea these things were actively sensing room temperature.

Good video had them all on 5 (max) for years hopefully the lower settings will save a little on the bills

So why don't they just print temperature numbers ongo the TRVs instead of an arbitrary scale? EDIT: apparently it's because they cannot guarantee precise enough temps. OK, makes sense.

water in my system is 90C. 4 my valves produce very loud noises, like someone hammering onto pipes. if little turn valve noise gone but return next day. do i need to replace valves?

Brilliant demo. But, you are wasting your time, women are retiles/snakes, got NO blood. My wife says she's cold, so I get a thermometer, place it on the settee where she is laid, guess what? 25 deg C. I'm boiling my balls off in the coolest chair in the room....give me strength!!!! Always love your videos, peace and goodwill.

Great video as normal, but I do have one question/inquiry. While I understand how TRVs actually work, my question is more about the main thermostat itself. I only have one radiator in the property(bungalow) without a TRV fitted, this being the bathroom and I have a wireless thermostat. What is the best set up for this? I currently have the wireless thermostat set to 21c in what we'd say is the coldest/longest room to warm up(the main bedroom) with the TRV opened up to Max (5). All other rooms have the TRVs set to around 2 - 3 depending on rooms. Is this correct, if not what would be a better set up? Any help would be grateful

Great stuff. I've made it to nearly fifty without really understanding how a radiator works. My eyes have been opened, thanks PP :)

I LOVE THE WAY OF TEACHING AND SHOWING US THE MECHANISM OF THE THERMOSTAT. and we can swap the trv and instead this? because my room is very cold. i don't like this trv.