Adequate radiator for living room?

[Possom]

What temperature would you want a radiator to allow a living room to be able to get up to when the rad and boiler is set to max?

That is, in order to allow for exceptionally cold evenings/nights.

For example, I set the boiler to max (stated 85.5 degrees on boiler for heating system) and turned a vertical radiator up full, was able to a room temperature of 27 degrees when there an outside temperature of 12 degrees.

The room temperature before heating was turned on was 15 degrees.

Do you think this radiator is providing enough heat for the room to allow for exceptionally cold temperatures (e.g. beast from the east)?

It didn't get up to this 27 degrees quickly though as it's a column rad, possibly took a couple of hours or more. It reasonably quickly got up to 22 degrees in the room though.

Thanks.

 

[denso13]

Do you think this radiator is providing enough heat for the room to allow for exceptionally cold temperatures

You need to calculate the required radiator size/output based on the heat loss of the room. No other way of doing it properly,

 

[Possom]

You need to calculate the required radiator size/output based on the heat loss of the room. No other way of doing it properly,

Do you mean using the online calculators where the dimensions of the room are input? If so, I have used them in the past and they provide varied outputs depending upon which website is used.

 

[denso13]

Do you mean using the online calculators where the dimensions of the room are input?

Yes, online or offline. They can give varying results but calculation is the only way to size a radiator. The other option is guessing but that is a lot more unreliable.

 

[JohnD]

when I've had radiators that were too small, they've been fitted by housebuilders using a calculation tool. The assumptions used are overoptimistic, so pretty sure to be undersized.

But it cuts the builders' costs and it ups their profits.

All mine get upgraded to bigger or doubles so they can run at "warm" rather than "scalding" and keep the rooms at a more even temperature with the boiler condensing economically.

Also heats the house up faster from cold.

If you have a radiator that is fully hot, all over, and incapable of warming the room sufficiently, then, obviously, it is too small.

 

[Possom]

All mine get upgraded to bigger or doubles so they can run at "warm" rather than "scalding" and keep the rooms at a more even temperature with the boiler condensing economically.

Here, are you referring to the temperature of the heating system as stated on the boiler? If so, what temperature would you be looking to see on the boiler with regards to the heating system?

 

[JohnD]

A modern condensing boiler is at its most efficient/economical with a flow temperature around 60C. If your radiators are small, you may need to increase the temperature to 80C in cold weather. 80C is really scalding but old boilers used to run at that temperature.

Modern boilers usually have more than enough power for an ordinary house. Old, underpowered boilers sometimes run "flat out" at full power in cold weather because they were not powerful enough to keep all the radiators fully hot. modern boilers will modulate down the flame size according to demand. For example my house has a calculated heat loss of 12.5kW with a 20C indoor at 0C outdoor temperature. When I had an old iron 15kW boiler it would run flat out on frosty nights, and if you ran a bath, the house would cool under the extra load of reheating the cylinder. The new modern boiler modulates between 8kW and 24kW and can easily accomodate any demand the house can put on it.

if you have TRVs they will reduce the flow, and hence the demand on the boiler, as each room reaches its target temperature. The TRVs reduce the radiator temperature so it can hover round about the level needed to keep the room at your preset temperature without huge swings from hot to cold. Some give better control than others.

 

[Harry Bloomfield]

Why would you ever need a living room at 27C? I currently have my stat set to 20C, all internal doors are open, it is actually recording 20.4C in the living room, where I am and I am perfectly comfortable in just a T shirt. Ambient outdoor is 10.2C, boiler return is showing 33C.

 

[Possom]

A modern condensing boiler is at its most efficient/economical with a flow temperature around 60C. If your radiators are small, you may need to increase the temperature to 80C in cold weather. 80C is really scalding but old boilers used to run at that temperature.

The living room in question is relatively small at just 2.90 m x 3.14 m.
I am using a WB 30i combi boiler:
https://www.screwfix.com/p/worcester-bosch-greenstar-30i-gas-combi-boiler/7091h

with one of these vertical rads in the room (2411 W), and a TRV fitted.
https://www.radiatoroutlet.co.uk/1800-x-470mm-white-vertical-traditional-3-column-radiator

Mid terraced house with cavity wall insulation in the exterior wall.

 

[JohnD]

for a 9 sq m living room, with a habitable room above, 2.4kW nominal should be ample. Check that it is fully hot all over.

Your modern boiler has much more power than a typical terraced house needs, though while you are running a bath, it will stop heating the radiators. This should take no more than ten minutes and not matter, unless you like long showers.


Unless there is, say, an uninsulated loft above, or a draughty boarded floor, an open fireplace, or a large window with no curtains, all of which are big heat-loss causes.

 

[Hugh Jaleak]

Why would you ever need a living room at 27C?

Have you never lived with a Woman? Unless it's positively sub tropical, most seem to complain they're cold....

 

[JohnD]

A dummy room stat, screwed firmly to the wall and connected to nothing, will keep them happy.

 

[Possom]

So I tried this again yesterday evening as it was only 4C outside, so it was a good opportunity to get an idea as to how high a temperature can be achieved in this 9 sq m room with the following 2.4 kW column radiator and 30i Worcester Bosch combi boiler

https://www.radiatoroutlet.co.uk/1800-x-470mm-white-vertical-traditional-3-column-radiator
https://www.screwfix.com/p/worcester-bosch-greenstar-30i-gas-combi-boiler/7091h?source=aw&awc

I set the boiler setting for the radiator heating to the "e" setting which is the recommended setting and this gave a heating temperature on the boiler of between 57C and 60C. Radiator was turned up full.

The unheated room was at 12C, the maximum temperature I could get the room to was 22C but it took literally 4.5 hours to get to this temperature. In my opinion, this is an excessive amount of time in order to get up to 22C. Perhaps I should consider a convection radiator?

There is no open fireplace, nor draughty floor, nor open window. I kept the room door closed throughout.

 

[Harry Bloomfield]

The unheated room was at 12C, the maximum temperature I could get the room to was 22C but it took literally 4.5 hours to get to this temperature. In my opinion, this is an excessive amount of time in order to get up to 22C. Perhaps I should consider a convection radiator?

If any of my rooms fell to such a low temperature with no heat input, I would be expecting to find a window open. I checked my temperature log for when the temperature fell to 2c over night here. My heating was off (set back to 16C) from 22:45 until 10:00 next morning, so the boiler never fired. The indoor temperature only fell to its lowest at around 08:00 18.6C.

My programmed day temperature from 10:00 is 18C and it felt a bit chilly, so I tweaked it up to 21C at around 10:15. It hit 21C 35 minutes later.

Your 12C and 4.5 hours to get to 22C, suggests that you have massive heat loss, or a massively under sized radiator.