Help… radiator changed in ensuite, now got a walk in fridge…

Heated towel rails are never going to be as good as a radiator at heating a room – the surface area is smaller so they can’t transfer the heat to the room as efficiently. If it’s always hot that tells you it’s not working very well – it should transferring the heat from itself to the room. A mate of mine had a vertical tubular style radiator in his lounge and it was always hot but was useless at heating the room – looked nice though. Replace it with a normal radiator – a device designed to heat space – and your problems should be solved.

But teef – they only had a towel radiator before…

But teef – they only had a towel radiator before…

Maybe it had a larger surface area than the new one…

Hello everyone 🙂

Right, I can now confirm the radiator really does get hot, all the way bottom to top. Doing that lockshield valve thing hasn’t magically cured the problem though, still quite fridgey in there this morning…

Is the floor in the room different?

There were these tiny tiny square tiles on the floor before (ugh), now we have proper big floor tiles. Could be that they feel a bit colder?

Where’s the window?

It’s above the toilet (a big dormer one)

hammyuk,
It doesn’t have a TRV – does your idea still work with a “normal” valve?

Not sure about the surface area, I never measured the old one; however, going by how the towels fit on it, it can’t be that much different (the old one was wider, the new one is higher).

The new one is this one.

FWIW, our towel rail (about 6ft by 2ft6) keeps our en-suite boiling, and has to be turned down almost all the way off.

… but is it chrome 😆 ?

The whole system might need re-balancing – the lock-shield valves on the radiators which have had TRVs fitted may well have been shut off and opened again without noting the setting, and the new rads that have been fitted should be balanced into the system. (Does the room with the new rads get nice and warm?)

The other room with new rads gets very warm… Maybe we really should get the boiler man to come back and balance the system!

Who knows? You’ll get used to it.

Sure, but only once I know I’ve asked on here and that’s the conclusion 😉 😉

Right, I can now confirm the radiator really does get hot,

How hot though? On full chat our hottest rads are too hot to hold a hand to for long.

but is it chrome

Of course!

Balancing could be the answer. The ones that are too hot, turn them down. It might also help to figure out which order the rads are moving away from the pump. Our house is three storey, and the bottom’s quite hard to keep warm. The hot water goes from the boiler straight up to the top floor then down through the rads to the ground. So the top floor rads were the hottest, which is the opposite of what you want because the heat rises in the first place.

I turned the top two practically off, and installed a much bigger rad in the hall so that most of the heat starts off down there.

Guessing – it’s getting hot but not “using” the heat.

If the rad gets to 80 deg (or whatever it gets to) then there is a fixed* amount of heat going from the rad to the room.

Water speed affects return temp into boiler which IIRC affects how fast/slow the boiler cycles + how efficient it runs.

* yes, not quite fixes, varies a bit depending on temperature of room, etc.

Maybe it had a larger surface area than the new one…

Well yes maybe, and that has also been covered 😉

What shape and what position (ie height from floor) is the radiator compared to the old one? If it is higher on the wall and more narrow (so the top of it is higher up the wall) then more heat will be heating the top of your room.

How hot though?

Well, so hot that I can’t even touch it properly, like a pot handle when it’s been in the oven for 10 minutes…

What shape and what position (ie height from floor) is the radiator compared to the old one? If it is higher on the wall and more narrow (so the top of it is higher up the wall) then more heat will be heating the top of your room.

The old one was wider, so the towels ended up side by side on two levels, the new one is narrower with towels on four levels. I’d say that the new one is not significantly higher from the floor, maybe 10cm? But yes, the top of it is very high compared to the old one, so maybe all that lovely heat stays hovering on the ceiling 🙁

Yes – it’ll work without a TRV on there – you want the water to be going through each rad at the same speed – hence listening for the “shhhhh” noise – turn the lockshield off and then on and you’ll know what I mean.

The comment above about TRVs does not apply to most modern systems as the radiator without the TRV should be in the room with the room stat. An old system with a convection loop might have 2 rads without TRVs as one provides active cooling for the boiler (in our case the bathroom) and then another is the return loop for the system (in our case the landing and stupidly we have a TRV in the kitchen with the room stat so I took it off as the place is rented and not mine to mess with any further).

I would check that the system is definitely bled, close off all but one rad at a time and force the water through and check that the towel radiator is definitely getting the proper flow and EVERY bar is getting hot as it could also be an internal fault with the towel rail that you’ve not noticed.

Didn’t know there were different ways of pluming them in, I assumed they all had 2 pipes running in a loop round the house, a bit like the ring main for electrical sockets, then the last one was left open to give the hot water somewhere to go if all the heaters are ‘off’. So the boiler churns out hot water until either the thermostat clicks off, and it modulates the heat input to maintain a constant water temp, so when only the towel rail is open it’s not running full wack?

Am I going to bugger something up having TRV’s everywhere apart from the towel rail?

Some of the rads (specifically the TRV’s) make one hell of of a racket when almost closed, I just put that down to them not being quite as bi-directional as the blurb claimed (so the flow is forcing them closed, spring open, flow restarts, etc at about 50hz).

All the lockshields are fully open, the TRV’s modulate the flow. Without the TRV you’d use the adjustable valve on the other end to modulate the flow surely, not the lockshield?

Well, so hot that I can’t even touch it properly, like a pot handle when it’s been in the oven for 10 minutes…

That’s a sign it’s inefficient and not heating the room – it should be dissipating the heat. Get rid of it and get a proper radiator in.

But yes, the top of it is very high compared to the old one, so maybe all that lovely heat stays hovering on the ceiling

I think that might be your problem then – we replaced two very old ‘standard’ radiators (not even finned ones) with much higher output vertical ones but we had to do quite a bit of faffing with the balancing before we got them heating the room enough.

That’s a sign it’s inefficient and not heating the room – it should be dissipating the heat.

Does not make sense – are you saying that a cooler radiator will heat a room more efficiently? Surely if the radiator is hotter more heat gets radiated into the room?

There should be a loop.
So even if every radiator is on the boiler can still circulate.
Off that flow/return loop there is a take off for each rad.
Often the TRV gets put on the “wrong” side.
This still allows water into the rad and it gets hot – can also cause the back pressure issues on the TRV’s as noted.
The TRV allows the water IN to the rad.
The lockshield closes the output.
Again – I was taught to turn the heating to max.
Then at each rad – open the TRV fully (or remove the head).
Then close the lockshield.
At this point you open the lockshield again slowly listening for the point it goes silent (or as quiet as it gets).
Once is goes quiet – close the lockshield slowly until you hear a good solid “shhhhhhhhh”.
This is now holding the water in the rad and allowing it long enough to convect heat. But not stopping it returning into the circuit.
Repeat this for each rad.
Most people (and loads of plumbers) just wind the valves fully open and then “back a quarter” so the valves doesn’t corrode open.
This doesn’t match each rad though as the pressure will be different around the circuit as molgrips has found.
In theory you should use a manometer on each one but not as easy as you think for diy.

Teef – if the rad isn’t getting hot then it isn’t working – so your comment is so bad it’s almost not worth commenting on. Basic junior school physics – it needs to take the heat from the water (about 70 degrees centigrade) and radiate that into the air – if the rad isn’t hot then it isn’t working – if it is hot – the same temp as the water flowing through it then it IS working efficiently.
The issue here is that the overall temp coefficient of the room has changed.
Large ceramic tiles will take a lot longer to warm to room temp than small ones so for a start it will feel colder underfoot.

Does not make sense – are you saying that a cooler radiator will heat a room more efficiently? Surely if the radiator is hotter more heat gets radiated into the room?

The idea is that the heat is transferred from the radiator to the room – not just kept within itself. A proper radiator is able to perform it’s task more efficiently because it has a larger surface area. Think fins on brake pads – they dissipate the heat away from the brakes more effectively due to increased surface area.

But you only need one valve to regulate the flow, TRV’s aren’t on/off they close gradually so when TRV set point is reached it’s still slightly open, but that’s academic as they’re not calibrated, and that style of valve is very much on/off (you’ll get 90%+ of the flow when it’s nominally 10% open, so even if the actuator is going from 0-100% it’s not doing much util the valve is almost closed).

I get the need to balance the valves when there are no TRV’s, but it makes no sense to do it with them fitted to all rads, unless you really want the house to warm up very evenly, rather than the TRV’s closing one at a time and the flow finding the next easiest route*.

*it doesn’t flow balances so the pressure drops through each route are equal, but the net effect is most will go the easiest way.

The idea is that the heat is transferred from the radiator to the room – not just kept within itself. A proper radiator is able to perform it’s task more efficiently because it has a larger surface area. Think fins on brake pads – they dissipate the heat away from the brakes more effectively due to increased surface area.

I get the argument about fins as you get more surface area from which heat can dissipate. But I cannot fathom your argument about a hot radiator not radiating heat. If it is hot it is hot and it will radiate that heat as efficiently as the design allows. Being hotter can’t possibly mean it isn’t as efficient as if it is running cooler.

I’m afraid that’s the case though, Towel rads, especially chrome ones are very good at getting hot locally to heat towels, they’re not very good at heating a room however. We have a massive vertical radiator in the living room, and although it looks very nice and gets too hot to touch, the room is always bloody freezing. The other room, exactly the same size which has a std, finned radiator is toasty warm all the time.

I suspect there’s not an awful lot you can do about it now shy of swapping the radiator for another type but I guess as you’re all tiled up it’s a bit late in the day for this.

If it is hot it is hot and it will radiate that heat as efficiently as the design allows. Being hotter can’t possibly mean it isn’t as efficient as if it is running cooler.

What I meant was that if it’s always hot then the heat isn’t being dissipated very well. Radiators should be hot when they’re raising the temperature in a room and cool down when the required temperature has been reached. A radiator with a larger surface area will perform this more efficiently than one with a smaller surface area.

I get the need to balance the valves when there are no TRV’s, but it makes no sense to do it with them fitted to all rads, unless you really want the house to warm up very evenly, rather than the TRV’s closing one at a time and the flow finding the next easiest route*.

You need to balance them as if the TRV isn’t there so that:

a) You get heat evenly around the house;
b) There’s enough load on the boiler to keep it firing until the whole house is up to temperature.

If the flow all whizzes through the first couple of rads and goes back to the boiler, then the boiler will reduce its output / cut off because it “sees” hot water coming back. This will mean that the house takes a lot longer to heat up than it should. [Which I think is what’s happening to alp_girl’s CH]

There’s only so much flow available from the boiler pump, so the rads need to be balanced using lock-shield valves to share it out (‘lock-shield’ so nobody inadvertently buggers about with the adjustment subsequently). The proper way to do this is to measure the temperature drop between flow and return on each rad and adjust the L-S valve until you get the design figure (12 degrees C?). A heating engineer will know this.

After that, adjust the TRVs to achieve comfort 🙂

I get the argument about fins as you get more surface area from which heat can dissipate. But I cannot fathom your argument about a hot radiator not radiating heat. If it is hot it is hot and it will radiate that heat as efficiently as the design allows. Being hotter can’t possibly mean it isn’t as efficient as if it is running cooler.

Think of it another way.

If you wrap a radiator in insulation it will get very hot and the room will stay cold.

As soon as you remove the insulation the heat will be transferred away from the radiator quicker and it’s temp will drop. It is then the job of the boiler to keep topping up the heat.

dT is the difference in temp between the source and the sink (not your bathroom sink). The radiator is the source and the room is the sink. In a lossy system like a draughty old house you generally opt for a high dT system like radiators and in a nicely insulated and well sealed house you can go for a low dT system such as underfloor heating. The higher the dT the higher the heat transfer rate will be, which is why you want a high dT in the draughty case but it will mean your boiler will work harder. But that assumes your radiator is efficient at transferring the heat.

Just like the insulation, the design of the radiator affects the heat transfer coefficient into the air. Smooth surfaces, shiny coatings, low actual surface area are all bad in terms of heat transfer. A radiator is designed so that air has to navigate up through fins as it rises due to convention, getting warmer and warmer and a shiny teapot will stay warmer for longer than a black one, if all else is the identical, as the radiative heat transfer is lower also.

towel rails are not designed to heat air effectively so they have a lower BTU output than the equivalent sized radiator. But if if you match the BTU output to that of a smaller radiator that was there then it should be fine.