Why Are Your Radiators Getting Hot When the Heating Is Off?

So your radiators are getting hot when the heating is turned off and you don't know why?
Roger explains in his latest Know Your House whiteboard explainer.
#KnowYourHouse #DIY #SBFAQ
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[@tonybowe1266]

Love these SB videos. Amazing knowledge and very clear when explaining how things work. I have this issue so know what to look for now. Thank you.

[@kennethbone5490]

I had this exact issue in house I bought where the plumbing was converted to a pressurised hot water tank for a loft extension with an extra en-suite bathroom. In summer some of the downstairs radiators got warm from the lockshield ends. Four British Gas engineers tried to fix it over 3 days. They changed the motorised valve twice! They couldn't work it out and left it unfixed. I then got in local independent heating engineer out who diagnosed the problem and fixed it with a non return valve on the hot water return as you described in a mornings work. Great video, spot on.

[@mdsween]

I have exactly the same circumstance as you Kenneth! Am about to do the heat check now before I call out the plumber

[@n0vaph0enix]

I think you may be a wizard! This has been bugging me for ages and this was such a simple and clearly detailed explanation that you’ve made it seem completely obvious.

[@descheers2217]

Another invaluable piece of info, thanks for that. I was just re-watching an old video of yours regarding leaking stop taps and again a priceless titbit of info that's helped me out a few times. These sorts of videos that you and Robin do are a great source of information and are superb because of how short and straightforward they are. Many thanks again 👍

[@stevejones9529]

Thanks for your comment on stop taps, I've just stop mine leaving

[@michaelblissett9863]

An excellent teacher, clear and precise and has a way of explaining in detail that is very helpful to many.

[@aspetm3846]

As usual you have done great work and explained your own experience to be helpful for others. Many thanks Roger.

[@mystikal518]

its always a joy to listen to someone who really knows his onions! Brilliant explanation

[@danielgyc8800]

Well explained mate! Nice to refresh on these sort of things when you haven’t been jobbing for a while!

[@daytonamann5618]

Hi Roger, Thanks for the clear explanation. I have that problem and never really found a clear explanation until I saw your video! Thanks

[@adrianodoherty6283]

A decent explanation of a problem most plumbers/heating engineers have come across. Just moved house and it’s happening in mine too! 😀 Need to get round to draining it down and correcting before too much longer!

[@GrahamF]

Absolutely spot on & exactly what was happening to my system! I tried everything to find out why this was happening, and it wasn't until I got rid of my heat only boiler, and changed to a combi boiler. The connection from the HW return was connected to the radiator return pipe under the floor. This was done when the house was built! Lazy plumbing indeed. Thank you 👍

[@donaloconnell5015]

Hello Roger you are a great tutor for me because you speak my kind of uncomplicated language. I think a lot of tradesmen didn't have uncomplicated speakers like you when they were learning so they do their learning at the expense of their customers for many years.

[@SkillBuilder]

Thanks for that. I try to stay clear of BS numbers and all that stuff because I think that is what a lot of lecturers become obssesed with

[@silastetley9643]

Roger job spot on, well explained. The time taken is worth it 👌.

[@SkillBuilder]

Thank you. I watched my previous efforts and thought it was just not clear enough. I am glad it worked in the end.

[@MatSmithLondon]

This is my favourite type of video, simple but really good. I think explaining stuff like this is your forte! (Not to say the other types aren’t good, but really like this format)

[@SkillBuilder]

Thanks Mat. How is the house coming on.

[@jctai100]

Excellent explanation! thank you

[@tobinparsons]

Thanks, exactly the problem iv got! Top man.

[@declanmoran1894]

Great stuff Roger , fully explained 👍👍👍

[@SoledadSolary]

Excellent Roger. Thanks. Well explained.

[@jonathanconway8094]

Another terrific video. Thanks. We have only a towel rail heated in the summer via the boiler and all rads are off but still get warm despite TRVs off. Rads upstairs and UFL down. As soon as it gets warm I shut the lock shield valve down and this sorts the problem. A new installation (including a low loss header (no idea what that adds)) but after watching this I'm getting them back in! Cheers

[@SkillBuilder]

The summer operation towel rail is intentional but I suspect it is reverse circulating. They should be able to feel this on the pipes A non return valve should sort it out

[@RoderickSpoke]

Brilliant as usual, we have just had this happen tonight 1st time in 6 years. Turned off the rads on the control unit and let's see what happens tomorrow.

[@BusinessButlers]

Thanks for a great explanation, Roger.

[@dskirkpa55]

Thanks, Roger. Indeed very useful information. Continue to keep up the good work

[@lw5944]

Thanks for your video, which is helpful. I have a combit bolier, I can't turn off one of radiators. Could I ask what could be the cause of the problem? Many thanks.

[@grahamshillingford8229]

I had the exact same issue on the same set up but it was the valve that had failed in my case. Another well explained & informative explanation Roger.👍👍

[@SkillBuilder]

I can be the valve but it is easy to feel if it is letting by. I am amazed when plumbers just replace it without doing that.

[@diykhan]

Very informative guide thanks 👍👌

[@stephencrozier396]

Thanks Roger, more content like this please!

[@philtucker1224]

Thanks Roger, that was a great explanation! (I actually have that minor issue with the rad nearest to the hot water tank) Although you explained the “wrong-way flow” and the one way valve solution very well, I think sometimes it’s the convection of the heat that creeps along the pipes, as opposed to an actual flow, so the one way valve may not necessarily function to prevent that…thank you for sharing 🙏

[@jimwoods9551]

I’ve got that too, one rad beside the cistern is heating. No motorised splitter valve. The cistern return is linked upstairs leaving a single return pipe to the lower floor. Going to try an NRV in just that rad.

[@alimusheri8305]

Great lesson. Thank you

[@manofweed1]

Absolutely brilliant explanation, totally correct. As you've probably guessed we have a similar problem, though only a few rads get a bit warm on top. But even if the primary return went closest to the boiler a strong pump action could still make the rads reverse circulate couldn't it ? Thanks.

[@leerolfe5332]

Roger. Been around construction all my life coming from a building/construction family. Decided on plumbing as my profession. If i'd of had you as a mentor I'd of taken half the time to learn the knowledge. Took me a few years to grasp this particular fault find after my apprenticeship! Amazing explanation.

[@TYLERCONSTRUCTION]

I learn a lot from these videos. In fact, I learn a lot from all your videos. Cheers Roger 👍

[@sunegroennebaek5283]

Perfectly understandable. Thank you very much 😊😎🇩🇰

[@williammcgrattan9583]

Excellent Roger👍

[@sleekitwan]

I had this, after I bought a run-down beautiful post-war end terrace in Scotland. It had a turret and spiral staircase, I loved it. Troubles made me sell it after a few years or updating, but the hidden issue was whenever the hot water cylinder was put to use, there was this trend to heat only the lower radiators in the house, not upstairs. I usually believe that once something’s done, I treat it as 100% until I find otherwise, this is one of the three times this has NOT held up! The system had two valves, but once I sketched it out I realised it needed a third. It had been relying on either the house being cold a lot, so some heating downstairs might not be a bad thing (!), or the owners had not noticed, etc. I fitted the third valve, which stopped the back-channel movement of hot water from the cylinder heating circuit, from going at all into the radiators backwards. It drove me nuts, but the present owner benefits as all of a sudden it’s not just a nuisance but an expensive one. As you will understand, the effect mainly was on radiators BELOW the level of the ‘head’ from the hot water entering and leaving the cylinder, which was perched in a corner cupboard of the kitchen, above the fridge. So, a three-motorised-valve system, instead of two, and it was perfect. Quite weird for me. Take care all. PS - have a laugh on me…the cost of the house when I bought it in 2003? £35,000 . 2 bedrooms plus a perfectly serviceable loft bedroom, and in fact this is what scuppered my letting plans - the government introduced a bedroom tax, and suddenly nobody moved because they;d have their benefits and home rooms scrutinised at that point, and this extra room was not ‘legit’. The council man said kindly ‘I am going to forget the request for retrospective approval, and put it in the drawer with the others’. I don;t understand hints, it’s terrible! He meant, I might be asked to return it to how it was, whatever that really means. It can mean, they examine the cables to see what date is stamped on them, but that’s a whole planning and building regs world of pain, let’s not go further.

[@ratchriat1716]

Found this video very informative and useful.

[@shaunglendinning]

Great piece of advice Roger! Appreciated. Cheers.

[@imw4956]

Roger, that might just explain my current problem! I had my combi boiler changed to unvented system and had it relocated in a different part of my house - have some but not all rads getting hot when calling for hot water . Plumber does not now what to do he has changed the 3 way motorised valve so hopefully when I show him your Video it will solve said problem! Thanks I appreciate the time and effort you put into producing these great videos. Ian

[@SkillBuilder]

Let's hope you can get to the bottom of it.

[@lazylad9064]

Excellent diagram and explanation of what can or might be problems. Thanks Rodger a little bit of knowledge is better than none👍👍👍

[@factsoverfeelings9228]

Perfect explanation. Theres a reason for everything ... when someone like you can articulate that it makes the world a better place. Now time to find that out of place T, on the return from the cylinder. My heat is on in my home, and the thermostat is off. Im thinking to myself, WTF?! Def. subscribing

[@TheD7035]

Thanks Great video! our gravity fed Y system (with cyl) is a you have described, but has a small lock shield valve quarter to half turned on on the cyl pipe return to the boiler. The return pipe is in the correct place as you describe but I understand the addition of a lock shield valve also helps slow down the heating water in the cylinder coil so that the water in the coil is not going too fast as to "whizz" through the cyl and therefor heats the water as effectively as it can. I believe that the lock shield addition on the pipe return from the cyl also means the boiler should not receive back cyl coil water that is perhaps still too hot. NB. I'm Just in the process of tidying up the wiring centre (this is has been been a mess) with the larger Salus wiring centre ready for Hive to work on Home Kit. ( Grundfos UPS3 pump is set to Prop Pressure & working fine) Thanks again great video explanation.

[@buggalugs]

solid information yet again :)

[@peterdavies2847]

Now I understand. Thanks for posting.

[@davidknight4096]

Great content, keep it coming

[@zjzozn]

Nice one Dave 👍

[@patrickmulholland1840]

EXCELLENT EXPLAINATION THANKYOU

[@robertelliott6280]

Very helpful, thanks.

[@martynlaverick3405]

Brilliant! Thank you.

[@em8969]

Excellent video mate

[@steved5627]

Very useful information. Do you have a video covering a constant low level hum from a SSE 330 boiler - even when the CH and HW are off (at night)? Thanks

[@berryj.greene7090]

Bravo! Another nice video. Honest & true. Thanks. Yes now that you have reminded me I have heard about this reverse flow phenomenon. There's another similar possibility isn't there? To do with the header tank feed thermo-siphoning. So you feed it in BELOW the return from a sort of U bend so that the heated water cannot rise. Anyway my heating has worked fine for 17 years but this Summer the rads are getting slightly warm when there is a HW demand, I thought it must be the valve. But is it the ball or the motor? Should I bite the bullet and replace both bits of it? Can the ball be fixed in any way? Why would it get stuck or not seat?

[@george9710]

This is really good thank you!

[@573mughal]

I have just got the same problem, atleast I have got an idea 💡 what would be the problem. Now I know what is the solutions. Thank you for making knowledgeable video. Blessings

[@5ThingsI]

Have this same issue but only with my living room radiator. I’ll give this a go!

[@royster3345]

Great explanation, have this problem, rads get a little warm when just HW on, installed by a professional as well....!

[@SkillBuilder]

Some professionals don't know about reverse circulation. It is taught at college but not everyone goes to college.

[@stewartcross9939]

FANTASTIC nice and simple I also had a run in with British Gas 6 engineers came round still could fix my problem they couldn’t run a bath shame the is not enough good plumber like yourself. Great videos 👍👍👍👍

[@MAMDAVEM]

Excellent timing for me Roger, I'd planned to replace my 3-valve this week to solve this exact problem and now I'm wondering if the problem is as you described. thanks!

[@SkillBuilder]

If it has stopped then it is the valve. I think I unwitingly gave the reverse circulation too much weight. Thge important thing is that there is a simple way to find out which problem it is.

[@harveysmith100]

Very clear explanation Roger. I had this problem but with a different outcome so I will share it to help others. Rads getting hot when the heating was off but hot water on. Checked the motorised valve, all working correctly, even changed it, still no solution. Used my laser thermometer to see that the three port valve wasn't sealing. The rubber ball in the valve had just deteriorated and was allow some bypass. Changed the three port and the problem was solved.

[@SkillBuilder]

That is a good idea to use the infrared thermometer. I did mention the motorised valve but dimissed it a bit, I should have given it more emphasis. Thanks for providing a bit of balance.

[@harveysmith100]

@@SkillBuilder To be honest, I have never come across it before and never thought it could be the valve. It took three visits, a lot of head scratching, half a dozen cups of tea and a fair few hobnobs.

[@mickcarter670]

Brilliant Roger 👍🏼

[@paulthomas4701]

Its only been like that for 8 years! We thought we were going crazy or the controls kept losing connection. Our underfloor heating warms the tank and our immersion cooks the underfloor heating. The pipe work looks a little more complex, but I can see the returns are fighting in an equal T. Thanks

[@steve45678]

I'm going to start a campaign, to get you back on LBC radio " helps at hand phone in". Your brilliant and always liked listening to LBC when your radio show was on . Do you also remember the name of a motoring expert that was on LBC at roughly same time as your show? I think his first name was Gerrard?.

[@SkillBuilder]

Thanks but LBC will never revive that show. They are now purely political and it works for them. The motoring expert is Gerrard Sauer. I was in touch with him recently, a brilliant, brilliant man.

[@steve45678]

@@SkillBuilder Many thanks for your reply.

[@casinodelonge]

Really interesting, thank you.

[@doncodman913]

Many thanks . will look for that now, Bloody hate it when rads get hot when not needed. rgds Don

[@CrowdControl2K8]

I had this in a house in London. Radiators were hot when the boiler was switched off. Eventually I found the pipes going to the tenants house. The landlord had connected his radiators to his tenants house next door.

[@SkillBuilder]

That is a new one on me but I did see a flat in a conversion block that was using the neighbour's gas supply.

[@ryanogden5895]

Nice vid. Be even better if you did a loft opening enlargeing video lol. Keep em coming

[@ladypenelope99]

Rog knows his stuff! 👍🏻🙂

[@Georger392]

Thank you 🙏

[@greenj1m]

Hi Roger, great channel. Only thing I do different is run the heating to define flow and returns after I've witnessed the problem with just the hot water on. If the same pipe gets hotter it's the valve leaking, if the other one does it's reverse circulation.

[@SkillBuilder]

Jim Good way of explaining it but the same idea just the other way of coming at it.

[@simonstones1918]

Thanks roger, you’re such a generous man....👍

[@SkillBuilder]

That isn't what my wife says.

[@simonstones1918]

Skill Builder that’s cause you spend more time with us knowledge-hungry “builders”, roger! Get the white board out and show her in doors how you’re gonna spend more time with her, starting with a little trip to brighton 😎

[@brianobrain8985]

Thanks for that. I've been going crazy for the past week trying to understand what is going on with this three-way valve and Honeywell actuator on my heating system.

[@misshayirhayir2390]

The same thing has happened to me

[@zali1049]

Thank you for the really useful videos. I had reverse circulation on my downstairs radiators. This was resolved my fitting a non- return valve. However the issue now is that when i have both the Heating and Hot water on at the same time, the downstairs radiators are not warming up? Any ideas what it could be? Could it be there is too much resistance because of the non return valve?

[@livingladolcevita7318]

any chance you could do a film about under floor heating converting normal radiator heating system if indeed this is possible

[@adriatikqypi9356]

Brilliant video

[@SkillBuilder]

Thank you

[@jimcameron4672]

Excellent

[@1908FD]

I have this problem really great to understand why! My DIY solution - the radiator closest to the cylinder I switch off in summer seems to stop the reverse flow.

[@SkillBuilder]

That will work in most cases and with TRVs they will close in the summer anyway.

[@safeer4567]

Hi roger Great channel and video If i just have one radiator getting hot on the first floor when boiler on the ground floor how do i solve the issue ? Will i still need to lift boards to access pipework ?

[@colincowell8148]

Many thanks for explaning this problem,as I have a recurring problem with my central heating that I can not sort, Hopfully I will come across it in one of you blogs,

[@SkillBuilder]

Colin You can tell us the problem by going to the contact Skill Builder and I will do my best to help. If it is a good subject for a whiteboard I will do one.

[@colincowell8148]

Hi threre, The problem I have is I dont think that the Pump is powerful enough to pump water through the ground floor radiators ,As I have to switch the pump up to top speed to get them to warm up,I also suspect that the room stat is not talking to the Boiler and am about to replace it,the zone valve is working,but to get the heating to work I am using the Hot water Cylinder Belt thermostat to run the heating which heats the hot water in the taps and make it too hot. Any advise would be of great help.

[@DjSkipAlexander]

Thanks

[@sawf6962]

Thanks for this video, I have been wondering why this has been happening in my house for the 7 years I've lived here. I assumed it was whoever did the plumbing being lazy/ignorant and now I know that is more than likely the case.

[@SkillBuilder]

Just carry out the tests before you start any work, that way you will be sure.

[@steviebye1]

Thanks for another great video, I have this problem but I have a combi boiler. Any ideas?

[@SkillBuilder]

It will be the divertor valve in the boiler that is letting by.

[@mfr58]

Great advice, as an amateur I would have thought just of the 3 way valve. However what I would say is that if this problem suddenly occurs some time after installation, I would think it unlikely the install problem that you describe as it would have been like it from the start....No?

[@TheD7035]

Just a thought to bear in mind perhaps there could have been a build up of magnetite some where inside the system near or at the three port valve / pump etc causing some obstruction / sticking if it's years after installation. May be Check with a magnet if you can on the copper pipe. Apparently Sentinel X100 or similar is supposed to help reduce magnetite build up esp with a Magnetic type "filter" regularly flushed or cleaned... as I say just a thought! 😀

[@easywatching]

Very good content

[@karlosh2422]

Brilliant. Makes sense to me :)

[@unionjakjakson]

I have had exactly this happening for years. i have had at least 4 new micro switches fitted during that time. Strangely(or maybe not when you explain), a new switch seems to solve it for a while. But sure enough it comes back again after maybe 2 yrs or so. Not sure how i now try and get my regular service guy to tackle this without him getting all manny about me trying to tell him what really needs doing(he was not the one who fitted the system 20 yrs ago}. He is close to retirement so i might take the cowards diplomatic route and speak to a young plumber i now know who is keen to get more work!!. I suspect there is more chance that the younger guy might be the way forward for me. Thanks, invaluable info/advice.

[@jamestranter2151]

Great video I have this exact issue but only 1 radiator getting hot in the hallway instead of all of them…..could it still be this issue that you have explained?

[@eddietheeditor]

Great no nonsense explanations - thanks Roger. My problem is the central heating pump comes on even when only hot water is selected. Motorized valve seems to be working and the programmer is only about a year old. Could it be the programmer is wired incorrectly? Anybody?

[@gazz4898]

Hi, great video; would this problem occur If an extra radiator has been installed and that one is the only rad getting partially warm when the hot water is regenerating? Kind regards

[@RandomRoshProduction]

well done

[@vanderpant2116]

Your're a master 👍

[@marcpatchett2690]

Of course that's what it is! Christ on a bike I've been addled about this problem for three years. Even thought about emailing you about it for your Q&A. Right, I'm all over that this weekend. I think the none return valve will be the solution.

[@SkillBuilder]

Just check the flow and returns on a radiator to see if they run the opposite way.

[@kennethslavin5469]

We have a gravity feed hydronic system that does not have electricity running to the boiler. The explanation I got was that the pilot produces millivolts of charge and if the charge is interrupted somehow the thermostat calls for the heat exchanger to ignite. Since there is no electricity the thermostat can't be turned off just down. The thermostat will call for heat even with no electricity.

[@110csw]

3 Plumbers in four years and I think you’ve solved my problem!

[@Bob3D2000]

Interesting, thank you. Very clear explanation. Can I assume that if I've only had this problem for the first time this year, after fifteen years in the house, then it isn't reverse flow (because the plumbing layout hasn't suddenly changed), and that therefore I can assume that it's the motorised valve that's faulty?

[@SkillBuilder]

Yes that it the most likely scenario.

[@Flamingninja4192]

Can you make a video on how to fix a conservatory that has dropped relative to the house please!

[@stevoc4023]

Hi Roger, i love the channel. Could you do a video with a diagram like this one for a dual system please? I had a guy do the job for me last year but I know its not right, he just connected stove back boiler into current system fueled by gas. I was advised he should have used a dual coil cylinder with seperate feed from attic tank and seperate overflow. Also, I realised that if I get a power cut my pump on the solid fuel doesnt work. He also has no non return between systems so when running gas I am heating the water in the back boiler aswel as the radiators in the same room. I would like a professional drawing so I can make sure the job is done right this time round. Cheers for the content, it s good to see professionals at work taking pride in what they do.

[@effervescence5664]

You don't have to have a dual coil cylinder if you have two separate heating appliances doing hot water cylinder+ heating. In the case of solar panels heating hot water yes you'd opt for a dual coil. In the case of two heating appliances for instance an older boiler that only heats a system up to 55c and a new one that's nominal operating temp would be 65c often the older boiler would be satisfied and not come on. Then to stop that boiler being heated you would just use a pipe stat linked to a 2-port valve to stop the flow through the appliance. The more important thing I'd be asking is - normally if the power cuts any modern boiler will stop functioning and the boiler is in control of the pump to stop it potentially overheating and going bang. If the back boiler on the stove is solid fuel you also run the risk of that issue. Also it may be capable of gravity circulation but all hot water cylinders now are legally required to be pumped on the primary side. Honestly though without a site visit to assess what you actually want/require it's impossible to give a drawing.

[@stevoc4023]

@@effervescence5664 Hi Mark, thanks for the reply, I am in Ireland so I don't know if reg's are the same. I already had a gas boiler closed system, and wanted a solid fuel stove. When I bought it, the builders merchant told me I would need a separate feed from tank and overflow, which would allow for expansion should the pump fail, no valve or restriction on expansion pipe and it should be 1 inch. Then have a non return valve connecting one coil to the other so the gas fuel circuit has all the radiators bar one, and wont heat the solid fuel side, and the solid fuel side has no restriction, one radiator for expansion and will heat the gas circuit aswel, as you said, modern gas boiler wont kick in with thermostat. I will say, I am not a plumber, the building merchant more than likely not a plumber so I really only have a very basic understanding, not knowledge or experience. When I got it done there were very few plumbers registered for solid fuel and none registered for both. He said it was fine to just tee into existing flow and return and change to vented system. I am doing the house up now and don't want to tear the gaff apart should a pipe go bang, or if I try to sell down the line I could have problems. System is working, and I will have a plumber inspecting it for me during works. My doubts only arise from the two differing opinions of the installer and supplier.

[@SkillBuilder]

Hi Steve I will do something on this even though it is niche. I had one in my house but it was such a headache that I took it out and returned to a conventional system. I did quite a lot of them on wood burners in country locations but they were also prone to condensation on the back boiler which caused them to rot like pears.

[@stevoc4023]

@@SkillBuilder Cheers, I appreciate that, I'll know if my plumber is a chancer or not. Look forward to it, I'll share it on and try and get you some more subs.

[@andypdq]

@@effervescence5664 You need a "neutraliser", a neutral point which supplies all the heating appliances thus equalising pressures in all circumstances. It's just a common tank where all the supplies for the heating appliances are fed from. See: dunsleyheat.co.uk/neutralizer.html

[@PedroPlckle]

I wonder if a good way to describe the correct positioning of that final return tee is that the cylinder return flow pressure at the tee is not greater than the total combined radiator return flow pressure, and that directs the cylinder return flow only one way - straight back to the boiler.

[@sutteren]

nice video, thx :)

[@grotekleum]

Even with the rads all tee'd before the primary return is there still not the chance of the water working back some, or would there be some sort of back pressure preventing it. Would it be reasonable to put a one-way valve in too, above the tee, but before the tank return?

[@mcphee1888]

What would it be if you have a combi boiler/no hot water tank and when the hot what runs, the radiators heat up. I believe my boiler also does not have a 2 port valve which most folk point to. Boiler is a worcester 28i, 8/10 years old

[@ButterFly-jm2fb]

October now. New boiler fitted in 3 floor house by Brit Gas last month. When heating goes off, top floor rads v hot. Same floor as emersion tank. Initially top floor rad long to heat. Now the opposite. Rads had power wash. Something stuck? What's the problem, do you think? Advice appreciated!

[@andysparks8245]

Lots of good info there, but... as an engineer and not a plumber why not fit a 2nd motorised valve on the CH return before the common return that shuts when only the hot water is required making a closed system for HW?

[@arkskotch1589]

I've just come across this problem. Ive had a plumber in as one of the radiators wasn't heating up. He said there was a blockage and used some type of sucking device and now the radiator is working again. But since he's done this, a few of my other radiators (ones closest to the boiler) are getting warm when the hot water is on. Never had this problem before.