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]

Why have you not balanced all the rads in your home?

If you mean before now, it's because it's not something I'd ever given any thought to. I had heard the term before, but didn't really know what it was exactly until I looked it up on Youtube.

So, the other rads on that floor are:
a) the other vertical rad has 1192 watts (4071 BTU) at delta 50C
b) panel radiator - this is a 1980/90s single panel radiator size: 25" x 28" (output unknown) (64 cm x 71 cm)
c) panel radiator - this is a 1980/90s single panel radiator size: 47" x 28" (output unknown) (119 cm x 71 cm)

The boiler is running continuously usually at 62 C, sometimes up to 66 C. This is with it set to the recommended "e" setting on the boiler.

I re-ran warming the room up with the main vertical radiator in question, with an already hot boiler, beginning at a room temperature of 13 C it took 3 hrs 10 minutes to get to 20 C and a total of 3hrs 30 minutes to get to 21 C.

I assume you throttled in the vertical rad lockshield to give that 7C delta?, wonder what it is with no throttling which would tell if reversing the valves does give a higher flow.

The lockshield is open as little as possible, just enough that I feel heat starting to arise in the TRV. I'll have to repeat my room warming experiment from a cool room again to discover that.

 

[John.g]

I would think that your particular model definitely modulates below 8kw in order to run continuously, more like 3 to 4kw which is good, can you post a link to it if available, also interested in this e setting as it seems distinct from ECO which only works in HW mode and stops the pre heating of the cold water.

The only way IMO to increase your vertical rad to max output is to open the lock shield valve fully and increase the boiler set point to 70/75C, you tried this previously but I think the boiler was cycling, you may then have to re balance the other rads. You could maybe live with slow heat up with the lock shield valve full open but boiler at 60C.

I came across a old Quinn radiator brochure and their column rated outputs are very similar to yours so there is no logical reason why your rad when emitting 2 kw shouldn't heat the room as fast as the 2 kw electric heater?.

 

[Mossop]

The only way IMO to increase your vertical rad to max output is to open the lock shield valve fully and increase the boiler set point to 70/75C, you tried this previously but I think the boiler was cycling, you may then have to re balance the other rads. You could maybe live with slow heat up with the lock shield valve full open but boiler at 60C.

Can I just check, so open lockshield fully on the rad in question only, turn boiler up to 70/75 C, then re-balance other rads if required so that their lockshields still only open as little as possible whilst still allowing flow? Once this is done, then turn set boiler temp down to 60 C?

The "e" setting is a temperature setting on the boiler. When set to "e" it means the boiler temp is ~ 60C/62C for the CH.

 

[John.g]

Yes, that's it basically, you may not even have to re balance the other rads, just take their deltaTs when running at 70/75, also check the vertical rad deltaT with lock shield full open at your present setting and again at 70/75C.

Its the link to your boiler that I'd like.

 

[Mossop]

Greenstar i System (27kW and 30kW) | Worcester Bosch

Our higher output Greenstar i System boiler is part of that latest generation of smaller and lighter boilers. Find out more information here.

www.worcester-bosch.co.uk

In the image at the link above you'll notice there is a dial under the screen. The dial here is set to "e", which stands for "Eco".

 

[gpbeck]

If you increase the flow in that radiator, I can’t see how your return temperature will be low enough to condense. You will just be going round again, boiler will short cycle. You could try incrementally increasing boiler temperature though if return temps stay below 53 or so. Worcester seem very shy of stating the minimum CH output of that boiler.

I wondered if you had more radiators because you have twice said “on that floor”.

 

[gpbeck]

The problems with vertical radiators is that they are size restricted, by height of room and width. They are heavy and need to be mounted safely. They are expensive. 2kw is close to max available. Then, when you think about it, the top half is heating rising air that has been already heated by the lower half, so heat transfer is lower in the upper half. Less efficiency, hotter water return temps. The exiting air flow is near to the ceiling and tends to sit there. Feel the ceiling directly above.

So either a second radiator below the window or a new window.

 

[Mossop]

I wondered if you had more radiators because you have twice said “on that floor”.

From what I had interpreted from Youtube clips was that the circuit would be on one floor. A different floor would be a different circuit. I could well be wrong, but that's what I had taken from it.

So when I balanced the rads, I balanced the rads on the floor of the rad in question.

The exiting air flow is near to the ceiling and tends to sit there. Feel the ceiling directly above.

Yes, I've noticed that the air nearer the ceiling is warmer.

 

[gpbeck]

From what I had interpreted from Youtube clips was that the circuit would be on one floor. A different floor would be a different circuit. I could well be wrong, but that's what I had taken from it.

So when I balanced the rads, I balanced the rads on the floor of the rad in question.

Yes, I've noticed that the air nearer the ceiling is warmer.

Newer systems can have separate circuits upstairs do you have 2 thermostats?Either way, they should all have been balanced, starting with the furthest away all thermostats high so all running. Furthest away radiator may well be upstairs.

 

[John.g]

If you increase the flow in that radiator, I can’t see how your return temperature will be low enough to condense. You will just be going round again, boiler will short cycle. You could try incrementally increasing boiler temperature though if return temps stay below 53 or so. Worcester seem very shy of stating the minimum CH output of that boiler.

I wondered if you had more radiators because you have twice said “on that floor”.

That's interesting but I don't quite follow it, if you increase the flow to the rad, the return will also increase but the rad output will also increase and the boiler output will decrease by the lost % condensing gain so the boiler will have to fire more both due to the greater rad output and to compensate for the lost condensing effect to maintain the same boiler temperature, so can't see why this should lead to cycling.

 

[gpbeck]

That's interesting but I don't quite follow it, if you increase the flow to the rad, the return will also increase but the rad output will also increase and the boiler output will decrease by the lost % condensing gain so the boiler will have to fire more both due to the greater rad output and to compensate for the lost condensing effect to maintain the same boiler temperature, so can't see why this should lead to cycling.

This is a LONG thread but if you recollect the boiler was short cycling UNTIL he wound the radiator down. Formerly it was wide open, a massive open bypass returning a high flow at near flow temp. So boiler couldn’t add enough heat to the water even at the high flows so flamed out.

 

[John.g]

Before addressing the by pass issue there is another strange issue, we know that the boiler was running continuously (with rad throtting). Even if the 4 rads were running at their rated output which I estimate at 3.15kw then the boiler would need to have a almost 10:1 turndown, even worse, my dreary calcs would indicate that with a 60C flow and the return temps as provided that the total rad demand was only 2.1 kw, I've looked up a number of links to this boiler and the "best" case I can make for it is a minimum output of 7kw, the only way that I can see this boiler running continuously is that the upstairs zone was running as well, Mossop can verify that the upstairs stat (if installed) was turned down or one way or the other that these rads were not "on".

Re: By pass.
The vertical rad running with both valves full open had a flow/return of 60/56C which will result in that rad output of 1.7kw with a flow rate of 6.1 LPM, which one might expect for any type of rad with both valves full open so a "1.7kw" boiler will run with the same deltaT of 4C but will not cycle.
the throttled number for that rad was flow/return of 60/53C to give a 1.6kw demand with a flow rate of 3.3 LPM, the "1.7kw" boiler will run with the same flow rate of 3.3 LPM but with a deltaT of 7.4C and will cycle eventually, this is also how a TRV affects boiler cycling.
I would classify a massive by pass as perhaps a wrongly set manual or automatic by pass valve installed very close to the boiler.
Obviously, the proof of the pudding is in the eating as the cycling did cease with the the throttling but in view of my first paragraph, I wonder did it coincide with the upstairs rads in service as well?

I run all my 10 rads (8 on TRV) and 2 on a roomstat with both valves fully open on all and even though I have often run on the 2 roomstat ones only it certainly doesn't cause excessive cycling IMO.

 

[Mossop]

the only way that I can see this boiler running continuously is that the upstairs zone was running as well, Mossop can verify that the upstairs stat (if installed) was turned down or one way or the other that these rads were not "on".

When the boiler was switching on/off every 3 minutes, there were only the 4 rads on in total. After getting the connections to the main rad switched around, I also switched on some other rads on the other level.

There is no "stat" that I am aware of. I'm not entirely sure what this is. There is the boiler, the boiler handset, then all (but one) radiator have thermostatic radiator valves. You seem to be possibly referring to something else.

I've taken the readings with the boiler set to 75 C (sometimes it moved up to 77 C)

a) the main radiator in question has a 72.2 C flow with a return of 66.1 C. This is with the lockshield fully open.
b) the "other" vertical rad had a flow of 70.6 C with a return of 60.3 C.
c) the two 1980/90s single panel rads had essentially the same of 74 C flow with 59 C return.

I then re-took the temperatures of the flow/return of the main radiator in question with the lockshield open as little as possible whilst still retaining flow and the boiler still set to 75 C. I got flow of 63.8 C and return of 56.0 C

I think are the reading you were looking for John.g

Perhaps I should only have the 4 rads on when taking the readings, as I still have some rads on on the other level?

 

[John.g]

Thanks, I think one mystery has been cleared up.
Are the other few rads still open? and is/was the boiler still running continuously with both valves fully open on the vertical rad at 75C.?

 

[Mossop]

Thanks, I think one mystery has been cleared up.
Are the other few rads still open? and is/was the boiler still running continuously with both valves fully open on the vertical rad at 75C.?

The other few rads are still open when I took the last measurements. I could easily take these again with these other few rads closed off again.

I need to double check that the boiler was running continuously at 75 C with both valves open in order to be 100% sure , but certainly on the various occasions I looked in at the boiler it was running continuously,

 

[ShaunCorbs]

Shouldn’t be running the heating temp at 75dc

max you should do for a condensing boiler is 65 ideally lower the better

 

[John.g]

The other few rads are still open when I took the last measurements. I could easily take these again with these other few rads closed off again.

I need to double check that the boiler was running continuously at 75 C with both valves open in order to be 100% sure , but certainly on the various occasions I looked in at the boiler it was running continuously,

OK, the reading taken with the vertical rad throttled in might indicate that the boiler may not be running continuously as you are only getting a flow temp of 63.8C but that makes sense to me as that rad is emitting 1.7kw vs 2.4kw unthrottled.
I would suggest reducing the boiler temp to 60c again (original e setting) and reopening the vertical rad valves fully which will still give 1.7kw but only as long as the boiler is running continuously which we now know is dependent on those few other rads being on.
Or you may decide to shut them (extra rads) off and put up with a further reduced vertical rad output (due to cycling) and/or install another rad in that room. Also installing another rad may mean that you can shut off the other rads and get the heat where you really need it.

 

[John.g]

Shouldn’t be running the heating temp at 75dc

max you should do for a condensing boiler is 65 ideally lower the better

Yes, I have a SE (non condensing) boiler and because I have a a lot of TRVs installed that even with a boiler temp of 75C I regularly get down to a return of 40/45C, no real advantage with a SE boiler, mine runs with a fairly constant flue temp of 230C and hasn't changed much in 15 years.
There is a lot of emphasis put on getting the (HE) boiler to condense, condensing only begins at a flue gas temp of 55C so even a boiler return temp of 50C will have very little condensing benefit, you have to get down to return temps of 35/40C to get real condensing benefit, the real, easily got benefit of the condensing boiler is that it takes no effort to get down to say 75C flue temperature with a ~ 7/8% increase in boiler efficiency based on my 230C temperature, above,

 

[Mossop]

I would suggest reducing the boiler temp to 60c again (original e setting) and reopening the vertical rad valves fully which will still give 1.7kw but only as long as the boiler is running continuously which we now know is dependent on those few other rads being on.

I'll maybe set the boiler to 60 C, switch off the other rads on the other level. Leave on, as originally, only the rads on the same level as the main rad and determine with certainty if cycling is occurring.

 

[John.g]

What size approx. are the other two? rads you had on to stop the cycling?, just trying to see can we determine what the minimum boiler output is.

 

[Mossop]

WBosch have informed me that the minimum central heating rated output for my boiler is 7.2 kW.

The other rads which I had on on the other level, are:

Double panel radiator: 42" x 23" (107 cm x 58 cm)
Single panel radiator: 47" x 28" (119 cm x 71 cm)
Acova column rad: (60 cm x 62 cm) 3540BTU 1037W according to manufacturer

I have now switched off all 3 rads above which are on the other level, and looked at the boiler where the cycling has returned.

Below the rads on the same level as the main rad in question are open again just slightly at their lockshields. So it's just the main rad in question which is on, the "other " vertical rad, and the other two 1980/90s panel rads. So back to the original setup. The boiler is set to 60 C for all below.

With the lockshield on the main rad in question open only slightly the boiler cycle times (in minutes) were as below:

0:00 On
0:02 Off
0:05 On
0:09 Off
0:09 On again
0:12 Off
0:15 On


With the lockshield on the main rad in question open fully the boiler cycle times (in minutes) were as below:

0:00 Off
0:02 On
0:04 Off
0:07 On
0:14 Off
0:17 On
0:18 Off
0:22 On

With the lockshield of the main rad in question open full, the flow has a temp of 59 C with a drop of 3.3 C. The "other" vertical rad has a flow of 61.4 C and a drop of 6.5 C. The other two 1980/90s panel rads have flows of 63 C and drops of 14 C. (The boiler sometimes ranged up to 65 C itself which explains some 60+ C temperatures here).

With the lockshield of the main rad in question open only slightly, the flow has a temp of 48.7C with a drop of 5 C. The "other" vertical rad has a flow of 61.9 C and a drop of 10.1 C. The other two 1980/90s panel rads have flows of 60 C and drops of 12 C.

 

[John.g]

Your total heating load is ~ just above the minimum output of the boiler so you will get continuous cycling when running on the 4 rads downstairs, you really can't do anything about this.
I would increase the boiler temp to 70C and note the cycling on/off times, this is with main vert rad valves full open, the other vert rad as is and remaining rads as is, if the boiler on time averages 3 mins then you will be doing well IMO.
Also see can you can range rate the boiler from the user menu, this means that you can reduce the boiler maximum (but not the minimum) output from its present 30 kw to say 10 kw or the next lowest setting, this won't affect the hot water output but should cause reduced cycling and more consistent radiator temperatures, if this option is not available then it should be possible to get it carried out at the next service. You can ask WB if this range rating is available on this model.