Tall upright radiator efficiency

[BotusBuild]

My daughter was consider two of those tall upright radiators either side of a wall between living room and a dining room.

A plumber she had in for something else was asked whether this could be done (yes, it can) but opined that the efficiency of such radiator is not as good as "normal" ones, by which I think he means bog standard stelrads.

So, is there any evidence that this is the case, before she decides one way or the other?

[JohnMo]

We had a similar reaction a decade or so ago in our last house. Plumber wanted to install loads of radiators., way more than needed.

 

Start from the basics, work out room heat loss, then size radiators appropriately. Go with manufacturers data, not a finger in the air from a plumber. Ensure you size to radiator to temperature differential between mean radiator temperature and room temperature.  All the data is the manufacturer datasheets.

[Gus Potter]

41 minutes ago, BotusBuild said:

So, is there any evidence that this is the case, before she decides one way or the other?

I think it's debatable. Both a low or tall radiator will still set up similar convection currents in the room. My own view is that the position of the radiator is more important and in a principle room appearance and position of the furniture will often lead to a compromise. 

 

12 minutes ago, JohnMo said:

Start from the basics, work out room heat loss, then size radiators appropriately.

Ok for a bit of fun to size a heating radiator system in the old days (35 years ago) when I was a building contractor .. still can apply when at the ball park quote stage.

 

To get the customer interested I used to take them round the house and say... Imagine you had a one bar electric fire in this room ( 1.0 kW) or a two or three bar fire (3.0 kW) working on and off. Think of your Grans house. In this day and age we can use the equivalent of a fan heater. Most folk can relate to this. You run round the big rooms and as you go you say.. hey big window here and a draughty door say in a big hallway. You want to be able to make this room nice and hot if feeling like a duvet day? 

 

Now you add that up and with a bit of experience you can feel for the size of heating system you need. As an SE I use rules of thumb to size floor joists and steels and this is no different. 

 

OK so you now have a well insulated modern house. Take the above preliminary size and half it as condensing boilers work better at lower return temperatures. 

[marshian]

15 hours ago, BotusBuild said:

My daughter was consider two of those tall upright radiators either side of a wall between living room and a dining room.

A plumber she had in for something else was asked whether this could be done (yes, it can) but opined that the efficiency of such radiator is not as good as "normal" ones, by which I think he means bog standard stelrads.

So, is there any evidence that this is the case, before she decides one way or the other?

The plumber (IME) is right vertical rads do not deliver the same level of energy as convector rads surface area is far less than an equivalent convector rad and it’s the combination of flow temp and surface area that transfers the energy to the room.

 

My main point is this is difference is exaggerated at lower flow temps (30 to 45 Deg C) so use manufactures outputs with caution when matching vertical rads to room heat loss when running lower flow temps

 

If running higher flow temps (50 - 60 deg) the difference is much less and you can size based on manufacturers rating with a lot more confidence

[BotusBuild]

Older house, so they'll be running at higher temperatures.

 

Thanks all, I'll work with them to help them select.

[SteamyTea]

23 hours ago, BotusBuild said:

is there any evidence that this is the case, before she decides one way or the other

Yes, physics.

The hottest part of the radiator, which is really a water to air heat exchanger, will be at the top, which is also the hottest part of the room, so less delta T.

How much if a difference it really makes is probably pretty minor in the scheme of things.