Rate of heating in a living room?

[Mossop]

If a radiator has been correctly sized for a room and the boiler is adequate and fully functioning, at what rate of C/Hour would you want a living room to be able to heat up at?

Thanks.

 

[John.g]

Was the boiler just in service to this one rad only with everything else turned off and was it cycling on and off.? those readings should be up around 60/65C?.

 

[Mossop]

Was the boiler just in service to this one rad only with everything else turned off and was it cycling on and off.? those readings should be up around 60/65C?.

No, there were other rads on. Should the others be turned off?

Yes, the boiler was cycling on and off.

 

[John.g]

How many rads are on that circuit now?, if the boiler is running and even if cycling (which it shouldn't) if more than say 4 rads on then the flow temp should be at the boiler SP whatever that is now, 60C? and the return should be around 10/15C lower.

 

[Mossop]

How many rads are on that circuit now?, if the boiler is running and even if cycling (which it shouldn't) if more than say 4 rads on then the flow temp should be at the boiler SP whatever that is now, 60C? and the return should be around 10/15C lower.

There were 3 other rads on (so 4 in total) though they're not on full and they're small rads. Perhaps it would give a better indication if I were to turn off the other rads?

 

[John.g]

No, not at the moment, if the other rads are hot just now then they must be heated from your boiler so the boiler flow and return should be hot?, is the room stat turned up? and programmer calling for CH? otherwise you are measuring the wrong pipes, also the boiler should not be cycling with 4 rads on.

 

[Mossop]

No, not at the moment, if the other rads are hot just now then they must be heated from your boiler so the boiler flow and return should be hot?, is the room stat turned up? and programmer calling for CH? otherwise you are measuring the wrong pipes, also the boiler should not be cycling with 4 rads on.

Yes, the flow/return pipes on the boiler were hot. The temperatures above are the sets of temperatures which I go on these two 22 mm pipes. It appeared that there wasn't one pipe which was consistently warmer than the other (which is strange).

I'm not sure what you mean by the room stat? Do you mean the TRV?

By "Programmer calling for CH", I expect this is "central heating", I just flicked the relevant switches on the controller to set the boiler running, and the central heating temperature increases to 60 C or so, so I presume the controller has called for the central heating.

 

[gpbeck]

Yes, the flow/return pipes on the boiler were hot. The temperatures above are the sets of temperatures which I go on these two 22 mm pipes. It appeared that there wasn't one pipe which was consistently warmer than the other (which is strange).

I'm not sure what you mean by the room stat? Do you mean the TRV?

By "Programmer calling for CH", I expect this is "central heating", I just flicked the relevant switches on the controller to set the boiler running, and the central heating temperature increases to 60 C or so, so I presume the controller has called for the central heating.

I think you’ve missed the pipes and measured the wall behind.

 

[Mossop]

I think you’ve missed the pipes and measured the wall behind.

The red dot was directly on the pipes. I'll try again and see what happens.

 

[Mossop]

When I attempted this the second time, I had the boiler on for 90 minutes in advance. I found that if I trigger the contactless thermometer about 5/6 times at the one spot, it settles more at one temperature. By doing this I was able to determine that the right hand pipe under the boiler is the flow as it was consistently hotter.

The boiler temperature for the central heating ranged between 58C - 64C.

However, there wasn't any substantial uptick in temperature readings when I took them at various intervals. For the two pipes, I got (in C):

18.3 - 19.6
17.3 - 19.0
19.5 - 22.0
17.9 - 20.9
18.9 - 22.9
16.2 - 21.4
17.6 - 20.0
18.1 - 22.2
18.0 - 21.5
16.3 - 21.6

These are two 22 mm pipes, one to the left and one to the right. There is one other central 22 mm pipe and two other 15 mm pipes to either side of this central pipe - all three of these are cold to touch.

 

[gpbeck]

When I attempted this the second time, I had the boiler on for 90 minutes in advance. I found that if I trigger the contactless thermometer about 5/6 times at the one spot, it settles more at one temperature. By doing this I was able to determine that the right hand pipe under the boiler is the flow as it was consistently hotter.

The boiler temperature for the central heating ranged between 58C - 64C.

However, there wasn't any substantial uptick in temperature readings when I took them at various intervals. For the two pipes, I got (in C):

18.3 - 19.6
17.3 - 19.0
19.5 - 22.0
17.9 - 20.9
18.9 - 22.9
16.2 - 21.4
17.6 - 20.0
18.1 - 22.2
18.0 - 21.5
16.3 - 21.6

These are two 22 mm pipes, one to the left and one to the right. There is one other central 22 mm pipe and two other 15 mm pipes to either side of this central pipe - all three of these are cold to touch.

Was the flow pipe too hot to touch? Should be if over 55 deg. If so your readings are wrong. If not too hot to touch then your boiler is not running.

 

[Mossop]

Was the flow pipe too hot to touch? Should be if over 55 deg. If so your readings are wrong. If not too hot to touch then your boiler is not running.

It wasn't too hot to touch. So, there must be some boiler issue then?

It's strange though that I'm getting this temperature on the boiler flow, as when I'd measured the flow on the rad in question, I was getting 50 C or so.

Presumably the rad can't be hotter than the flow from the boiler?

 

[John.g]

Can't remember what the colour of your rad is but you could just put a bit of tape on the copper pipes, try black/white or something near the rad colour. Presume you can't read the return from the boiler display (menu).

 

[Mossop]

you could just put a bit of tape on the copper pipes, try black/white or something near the rad colour.

The pipes to the radiator are plastic and covered in a shroud above the floor. Maybe you're referring to the flow/return copper pipes at the boiler?

What would the tape on the copper pipes do?

Presume you can't read the return from the boiler display (menu).

The display gives an overall temperature for the heating system which when set to the recommended "e" setting where I usually have it, is usually about 60 C which it states on-screen.

I don't know if it can provide a specific temperature for the return at the boiler, it's a WB 30i, I'd have to check that.

 

[John.g]

It might allow you to read the correct temperatures. (Yes, flow/return boiler copper pipes).

 

[Mossop]

It might allow you to read the correct temperatures. (Yes, flow/return boiler copper pipes).

Sorry, I don't understand - how does this work? Do you mean to apply tape to the copper pipes at the boiler and take the temperature through the tape?

 

[John.g]

I havn't the faintest idea, I think I read it somewhere.

 

[John.g]

This may help......

https://www.jensentools.com/pdfs/noncontactmeasure.pdf

 

[John.g]

Even if you can't take the temps you might consider watching the boiler cycling on/off with those 4 rads on and note the on and off times for say two complete cycles, then do the same with that one rad only, if you feel like it, you would have to close one valve on each side of the other 3 rads to achieve this.

 

[Mossop]

you would have to close one valve on each side of the other 3 rads to achieve this.

So close off both the TRV and the lockshield on the other three. Okay.

 

[gpbeck]

I suspect that your boiler cannot deliver its minimum output (9kw?) with all that hot water returning from the living room radiator and so is constantly shutting down. Flow pipe should be too hot to touch.

Wind the living room radiator back down so outflow from it is 50 deg or so and you may be surprised.

Oh, and sort that window. Radiator will be fine.
I’m done now.

 

[John.g]

So close off both the TRV and the lockshield on the other three. Okay.

No just one on each is grand, you only want to stop the flow through each rad.

 

[John.g]

Its the heat demand and the boiler minimum output that determine cycling or not.
The return temp to the boiler shouldn't make any difference to the boiler output or cycling time for the same heating demand, if you had 4 rads of total output of say 6 kw with a return temp of 50C (from 70C) then (assuming the boiler can modulate to 6kw or lower) the flowrate through the boiler is 4.3 LPM and the boiler deltaT is 20C giving a boiler flow temp of 70C.
if a ABV opened to give a flowrate of say 4.3 LPM (at 70C) you will now have 4.3 LPM at 70C mixing with 4.3 LPM at 50C resulting in a return temp of 60C but the flowrate through the boiler is now 8.6 LPM resulting in a boiler deltaT of only 10C but the boiler flow temperature will still be 70C..

That is also a reason for installing ABVs, to give a reasonable boiler Hx deltaT.

 

[gpbeck]

Its the heat demand and the boiler minimum output that determine cycling or not.
The return temp to the boiler shouldn't make any difference to the boiler output or cycling time for the same heating demand, if you had 4 rads of total output of say 6 kw with a return temp of 50C (from 70C) then (assuming the boiler can modulate to 6kw or lower) the flowrate through the boiler is 4.3 LPM and the boiler deltaT is 20C giving a boiler flow temp of 70C.
if a ABV opened to give a flowrate of say 4.3 LPM (at 70C) you will now have 4.3 LPM at 70C mixing with 4.3 LPM at 50C resulting in a return temp of 60C but the flowrate through the boiler is now 8.6 LPM resulting in a boiler deltaT of only 10C but the boiler flow temperature will still be 70C..

That is also a reason for installing ABVs, to give a reasonable boiler Hx deltaT.

Don't think Greenstar 30i goes below 8kW?

 

[Mossop]

you could just put a bit of tape on the copper pipes, try black/white or something near the rad colour.

Even if you can't take the temps you might consider watching the boiler cycling on/off with those 4 rads on and note the on and off times for say two complete cycles, then do the same with that one rad only, if you feel like it, you would have to close one valve on each side of the other 3 rads to achieve this.

So, I've placed black electrical tape onto the two 22 mm pipes under the boiler and that has made a substantial difference when taking the temperatures. I let the boiler run for 40 minutes before taking any temperatures.

Firstly, with just the one radiator in question switched on. On/Off below refers to the "flame" symbol coming on or off on the boiler screen. Boiler temperature on-screen ranged from 48 C - 67 C. So, on average it's turning on and off every 2 Minutes & 25 seconds.

The flow/return at the rad was 45.8 C and 40.6 C (I also used black electrical tape here).

Time:
0:00 On
0:02 Off
0:05 On
0:07 Off
0:10 On
0:12 Off
0:15 On
0:17 Off

Below are temperatures I was getting on the flow/return under the boiler at various intervals:

50.9 - 39.4
47.0 - 40.9
45.2 - 37.9
61.6 - 39.0
49.7 - 38.1
60.3 - 38.5


Separately below is with the radiator still on, but with another couple of rads on the same floor turned on. I left it about 40 minutes or so to allow the other rads to warm up. Boiler temperature on-screen ranged from 57 C - 67 C. So, on average it's turning on and off every 3 minutes 43 seconds..

The flow/return at the rad was 47.5 C and 42.7 C

Time:
0:00 Off
0:03 On
0:08 Off
0:11 On
0:15 Off
0:19 On
0:23 Off
0:26 On

 

[gpbeck]

Told you I was done!