Does a radiator like this make sense?

pieroabcd

Hi in a corner of the lounge I have this radiator, high and short. 
This is definitely the coldest spot in the house. I keep the flow a bit lower than it could be to keep the system balanced and get the top floor warmer in less time. Also nobody ever stays in the lounge. 

Would it be better to replace this radiator with a full length, half height one?
If heat tends to rise it won't do me the favour to go down to keep me warm. 

Thanks

EssexHebridean

We have a pair of them in our kitchen-diner and find they work really well for us - it’s a 12’ x 21’ space with 2 windows, patio doors, and 3 velux roof lights, high ceilinged too, but the rads are surprisingly effective. I too was concerned before we bought the house that they wouldn’t actually warm the place up and were more for show, but we’ve had no issues. Ours are black - no idea if that would make a difference - and ai have noticed that they never get really hot, but certainly still heat the room well. 

ETA - ours are taller than yours - roughly 7’ tall. 

FreeBear

pieroabcd said: Would it be better to replace this radiator with a full length, half height one?
If heat tends to rise it won't do me the favour to go down to keep me warm.

The first step is to measure the size of the room and window/door area. Then punch the numbers in to an online heat loss calculator. I use this one -> https://www.stelrad.com/basic-heat-loss-calculator - A Delta-T of 50°C is OK for a gas/oil boiler with a 70°C flow temperature.

Once you know what size radiator you actually need, you can make an informed choice. If you can't get the room up to a reasonable temperature, you need a bigger radiator (or cut the heat loss).

pieroabcd

Well, it's not freezing. Just a bit less comfortable than the other rooms when it's particularly cold outside. 
Thanks for the calculator links.

Belenus

Does that radiator get hot all the way to the top?

If not, try bleeding it.

Might it have sludge in the bottom restricting water flow?

pieroabcd

The top is a bit colder. Sludge may be there, yes 

ThisIsWeird

pieroabcd said:

Hi in a corner of the lounge I have this radiator, high and short.
This is definitely the coldest spot in the house. I keep the flow a bit lower than it could be to keep the system balanced and get the top floor warmer in less time. Also nobody ever stays in the lounge.
Would it be better to replace this radiator with a full length, half height one?
If heat tends to rise it won't do me the favour to go down to keep me warm. Thanks

Hi Piero.

I'm guessing you mean 'make sense' in terms of heat output, and not aesthetics? But, for the latter point, it does appear to be a bit of a misfit in taking up that whole wall, whilst not occupying it properly.

If you want more heat, then the simple option would be to fit a much taller column rad and make it a feature. Or, fit a lower and wider rad to achieve the same power, but put shelves or a pic or whatevs above.

There seems to be a bigger issue, tho', as you've explained that you tweak that rad down in order to get the upstairs rads to heat up more quickly? Something amiss there, especially when coupled with you saying that this wee rad doesn't even get that hot. 

And, that rad also doesn't have a TRV, so cannot regulate itself.

There's nothing wrong with that style of rad in itself - I have two slimmer-but-taller ones of these successfully heating a 6x6m sitting room.

First, is that rad actually 'working' ok in itself? For this, you need to ensure it's getting adequate flow, so you need to open it up more to check. If you give both these valves a full-turn more open, does the rad now become properly hot? As hot as the hottest other rad? Does the coldish top now disappear?

A cold top usually means one of two things - trapped air in the rad which needs to be bled (have you done this?), or an inadequate flow (which you may have given it as you turned it down).

So, these tests, please; 

(1) Bled the rad of air. Let us know if any came out. And how much. And then capture a couple of teaspoons of system water in a glass and see what it looks like. Re-top your system pressure to 1-1.2 bar if needed.

(2) Open each valve anti-clock one whole turn, and see if it heats up properly. If it does, but still leaves that room cold, it ain't big enough. What you do about that is up to you.

It would also appear that either your whole rad system isn't balanced correctly, or your boiler is not powerful enough (unlikely).

pieroabcd

Yes, i mean in terms of heat output. 
Given two radiators with the same thermal capacity,  in terms of heat distribution is it better one that is longer rather than taller?

The balancing in this system was a bit of a nightmare. I had to do 4 or 5 tests to get a good result (as I wrote in another thread) because when I moved in I couldn't get any heat at all at the second floor.
Now it's working, but I had to sacrifice a bit this corner of the lounge ( not too much). 

The boiler seems to have 14Kw of power, so it should be more than enough.

When the flow valves are fully open and they receive water all rads get scalding hot, so it's definitely a matter of balancing. The tall ones get a bit less hot at the top, probably unavoidable? It doesn't happen to the regular rads, though. 

I bleed the radiators very frequently (twice a month in winter). Only the first two times I've seen some air. The water has always been spring clean. 

The pressure... This boiler simply refuses to work with less than 1.4 bar, complaining that there's too little water. 

Still to keep the pressure low, I keep the water temperature at 60 degrees, that serves me well in terms of comfort (or I begin to sweat). 
I'll open a bit more the flow valve here until it gets hot enough and I'll check what happens at the second floor. These are the only two variables for the moment. 

ThisIsWeird

pieroabcd said:

Yes, i mean in terms of heat output. 
Given two radiators with the same thermal capacity,  in terms of heat distribution is it better one that is longer rather than taller?
The balancing in this system was a bit of a nightmare. I had to do 4 or 5 tests to get a good result (as I wrote in another thread) because when I moved in I couldn't get any heat at all at the second floor.
Now it's working, but I had to sacrifice a bit this corner of the lounge ( not too much). 
The boiler seems to have 14Kw of power, so it should be more than enough.
When the flow valves are fully open and they receive water all rads get scalding hot, so it's definitely a matter of balancing. The tall ones get a bit less hot at the top, probably unavoidable? It doesn't happen to the regular rads, though. 
I bleed the radiators very frequently (twice a month in winter). Only the first two times I've seen some air. The water has always been spring clean. 
The pressure... This boiler simply refuses to work with less than 1.4 bar, complaining that there's too little water. 
Still to keep the pressure low, I keep the water temperature at 60 degrees, that serves me well in terms of comfort (or I begin to sweat). 
I'll open a bit more the flow valve here until it gets hot enough and I'll check what happens at the second floor. These are the only two variables for the moment. 

As you say, your boiler should be plenty powerful enough.
Most likely, I guess, is you still have some balancing issues.
When you tried to balance it all, did you use a couple of thermometers?
Anyhoo, to try and answer some of your Q's as best I can; although rads with convection fins are more likely to be better at heating a whole room than plain or column types, I doubt there will be much actual difference, if their respective outputs are the same.
And ditto with tall and standard - I cannot see it making more than a marginal difference either way.
Column rads should be hot all over - the I ternal water flow is designed to ensure that. But, like any rad, if they ain't getting enough flow, then it's the top that will suffer, and it makes 'sense' to me that tall rads would be especially vulnerable to a lack of flow.
Also, column rads must be connected the right way around - are you certain yours is?
I take it that subsequent bleeding does not produce any more air? Once settled, a sealed system should produce next to zero 'air'.
 How many storeys do you have? You may well need a higher system pressure if, say, 3, so that might explain the reluctance to operate below 1.4. 
In any system, 1.4 is ok anyway, not at all too high.
Do you have an analogue gauge? Either way, do you notice that the pressure drops the moment you turn on the CH? 
Does the pressure vary much, up or down, in use?
How many rads do you have?
Clean water is obviously a good sign? Do you also have a mag filter fitted? Inhibitor levels good?

FreeBear

pieroabcd said: The pressure... This boiler simply refuses to work with less than 1.4 bar, complaining that there's too little water. 

Still to keep the pressure low, I keep the water temperature at 60 degrees, that serves me well in terms of comfort (or I begin to sweat).

A sealed system should quite happily cope with 2 bar - The pressure relief valve is usually set to lift at 3 bar.

When it comes to balancing the radiators, you need to do a little bit of math to work out the ideal temperature differential between flow & return.

Flow temperature * 0.3 = Radiator ∆T

So with a flow temperature of 60°C, you should be looking at a difference of 18°C between flow & return. Most heating engineers (and web sites) say to aim for a ∆T 20°C - This works fine if your flow temperature is 70°C, but becomes more & more difficult at lower flow temperatures. And when it come to measuring the flow/return temperatures, you ideally want a sensor clamped firmly to the pipe. These IR non-contact thermometers are unreliable, especially when used on chrome plated pipes. The type I've started to use -

twopenny

I have the radiator beside the door and it's a case of keeping the door closed if you want to warm the room. And keeping it closed as you go in and out then the room warms up.

Are the ceilings very high? Yes, any radiator the heat will go up and then warm the room from the top down.

Only advantage with a low one is you can put a shelf over to send the heat into the room before it rises but the difference is slight.