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.

 

[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!

 

[Mossop]

Thanks gpbeck.

 

[John.g]

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

One Rad:The boiler would appearing to be firing for ~ 40% of the time with a average flow temp of 52.5C & return of 39C, based on a min output of 8 kw (post above) then theoretically a average boiler output of 3.2 kw, even if the boiler efficiency is very low while cycling its difficult to see that rad producing its rated output, very difficult to determine anything from a relatively small heat load with a boiler with such a high minimum output.
The second test would indicate firing for 62.5% of the time so theoretically a more believable output of 5 kw with 4 rads on.

I don't think you can really do any more to figure out what the true output of that rad is.

 

[Mossop]

One Rad:The boiler would appearing to be firing for ~ 40% of the time with a average flow temp of 52.5C & return of 39C, based on a min output of 8 kw (post above) then theoretically a average boiler output of 3.2 kw, even if the boiler efficiency is very low while cycling its difficult to see that rad producing its rated output, very difficult to determine anything from a relatively small heat load with a boiler with such a high minimum output.
The second test would indicate firing for 62.5% of the time so theoretically a more believable output of 5 kw with 4 rads on.

I don't think you can really do any more to figure out what the true output of that rad is.

So you're not seeing anything from the figures to indicate that it's a problem specific to the boiler. It's more likely an issue with the radiator and the window?

 

[gpbeck]

One Rad:The boiler would appearing to be firing for ~ 40% of the time with a average flow temp of 52.5C & return of 39C, based on a min output of 8 kw (post above) then theoretically a average boiler output of 3.2 kw, even if the boiler efficiency is very low while cycling its difficult to see that rad producing its rated output, very difficult to determine anything from a relatively small heat load with a boiler with such a high minimum output.
The second test would indicate firing for 62.5% of the time so theoretically a more believable output of 5 kw with 4 rads on.

I don't think you can really do any more to figure out what the true output of that rad is.

I think OP means that is the total run time. Not sure how long it rests before starting up but it’s in the boiler program. He has a big short cycling problem because boiler is oversized and system is not balanced. Rapidly rising return temp cuts it out. He has 2 jobs, balancing all the radiators and glazing.

 

[gpbeck]

So you're not seeing anything from the figures to indicate that it's a problem specific to the boiler. It's more likely an issue with the radiator and the window?

Once more, the radiator is PERFECTLY FINE! Boiler should not be stopstarting like this at all. It is getting too much hot water in the return and cutting out. Balance all your radiators. Set boiler temp to 55 deg and see how long it runs. Slowly increase running temperature until it runs for at least 15 minutes before cutting out.

Draw curtains.