Increasing radiator output and improving CH performance

MJN · 14 Oct 2010

I would appreciate some advice regarding my thinking-out-loud assessment of our heating system, and the best way to improve it somewhat if at all possible. I'm afraid it's rather lengthy...

I've recently bought a relatively new (2007) 3-bed 2.5 storey semi which is obviously very well insulated and given the variety of sizes of radiator appears to have had the heating system designed through calculation, even if just following rules of thumb. The radiators, with output figures obtained from similar-looking Flomasta spec sheets, are:

(Room HxW Type Output)
Kitchen 500x700 Double 1048W
Hall 500x600 Double 898W
Downstairs Loo 300x400 Single ~250W? (a real tiny one - I think it looks great!)
Lounge 600x1000 Single 948W
Conservatory 600x600 Double 1041W
Front Bedroom 500x1000 Single 812W
Rear Bedroom 500x1000 Single 812W
Guest Bathroom 600x500 Double 868W
Top Bedroom 400x700 Double ~1000W?
En Suite 600x500 Single 488W
Dressing Room 600x600 Single 570W

Total: 8735W

The boiler is a condensing Ideal Icos HE15 (I know - it's probably not the best place to start but it's what we've inherited and it seems to work well enough so I'm not looking to replace it just yet) which can modulate between 8.8kW and 14.6kW. It's an S-plan layout run in 10mm (the branches at least - I note the presence of 22mm at the boiler end and within the airing cupboard), with a digital CH stat in the lounge and a sealed indirect cylinder for the HW. The neighbours are only present at the weekend so for all intents and purposes I think their house is unheated most of the time.

I have a few issues that I'd like to address:

1. Whilst I have yet to perform a full and proper observation the boiler appears to cycle a fair bit even before the house is up to temperature. I am wondering if this is because the total radiator output (even before any necessary derating) is at/below that which the boiler can modulate down to? That is, the system cannot get rid of the heat quick enough so the boiler has no option but to cut out? As described below I am planning on increasing the size of some of the radiators - would this help?

2. The full-width conservatory was built after the house, and I am pretty sure that the 600x600 Double 1041W radiator in there was originally in the lounge under the window of the then outside wall i.e. they simply moved it from the inside to the 'outside'. It appears that this radiator is inadequate for heating the conservatory in colder weathers and whilst it has not been too much of a problem yet I think it may well be in the winter. For better or for worse we want to use the conservatory all year round so should I replace this radiator with something bigger? Or should I just supplement it with electric heating, perhaps a portable convector heater, as required? The latter might be beneficial for those times when we need a little heating in there when the CH is off (e.g. cooler summer nights).

3. Given the suspected re-siting of one of the lounge radiators into the conservatory this has left just the 600x1000 Single 948W in the lounge and it seems to struggle by itself to bring the temperature up in any reasonable time i.e. the rest of the house seems to reach target temperature (as set by their TRVs) well before the lounge yet I can confirm the lounge radiator is very hot to the touch so it does seems to be trying. I was thinking of replacing it with a 600x1400 Double 2428W (maybe bigger?) thus bringing the heat output in there back up to 2kW+ as originally designed. Does this sound sensible? Would it help with the cycling? The stat is in the lounge hence no TRV. The lounge opens into the conservatory, and for various reasons we may well want to keep the doors to it continuously open (or at least partly), and so it is obvious it will also be partially attempting to heat the conservatory too. I could add an additional radiator back in there (perhaps where the original second one was) but that'd be a bit more work - replacing the single radiator would be much easier.

Any thoughts? Sorry for the waffle, but hopefully it describes the situation for you to be able offer some advice.

Mathew

D_Hailsham · 14 Oct 2010

MJN said:
1. Whilst I have yet to perform a full and proper observation the boiler appears to cycle a fair bit even before the house is up to temperature. I am wondering if this is because the total radiator output (even before any necessary derating) is at/below that which the boiler can modulate down to? That is, the system cannot get rid of the heat quick enough so the boiler has no option but to cut out?

What has the weather been like where you live? Don't forget that the radiators are sized for worst conditions, i.e. an outside temperature of -1C. If, like us, you are experiencing a long "Indian Summer", the temperature is rarely dropping below 10C overnight, so the house only needs half the heat allowed to bring it back up to 21C. The boiler can't modulate that low, so all it can do is turn on and off to maintain the required water temperature.

Conservatory
It appears that this radiator is inadequate for heating the conservatory in colder weathers and whilst it has not been too much of a problem yet I think it may well be in the winter. For better or for worse we want to use the conservatory all year round so should I replace this radiator with something bigger?

A larger radiator would be cheaper to run than an electric heater. The conservatory is supposed to have separate time and temperature controls to meet Building Regulations. I doubt if this has been done if all the previous owners did was move a lounge rad!

Lounge
This has left just the 600x1000 Single 948W in the lounge and it seems to struggle by itself to bring the temperature up in any reasonable time. ... I was thinking of replacing it with a 600x1400 Double 2428W (maybe bigger?) thus bringing the heat output in there back up to 2kW+ as originally designed.

You could move the conservatory rad back to its original position (Tee into the pipes to the conservatory) and put a new, larger rad in the conservatory. If the lounge is fairly large, it's better to have more than one source of heat.

Would it help with the cycling?

Not necessarily - depends on the weather! Having a comfortable house is more important.

MJN · 14 Oct 2010

D_Hailsham said:
What has the weather been like where you live? Don't forget that the radiators are sized for worst conditions, i.e. an outside temperature of -1C.

That's a good point. It has been pretty chilly recently around here, dropping to around 7C during the evening/night. Point taken though as to the effect it has on the heat demand.

A larger radiator would be cheaper to run than an electric heater. The conservatory is supposed to have separate time and temperature controls to meet Building Regulations. I doubt if this has been done if all the previous owners did was move a lounge rad!

Are they that specific? I thought it was just required have its own 'seperate control' in which case a TRV is arguably compliant given it can be used to turn the radiator off (automatically if not manually)?

You could move the conservatory rad back to its original position (Tee into the pipes to the conservatory) and put a new, larger rad in the conservatory. If the lounge is fairly large, it's better to have more than one source of heat.

Yeah I thought about that but was leaning towards upgrading the remaining lounge rad for simplicity. I'd rather not cut corners though, particularly if there's additional comfort (in addition to raw heat) to be had. The lounge is 4.6m x 4.2m for what it's worth.

[...Would it help with cycling?...] Not necessarily - depends on the weather! Having a comfortable house is more important.

Indeed. I just wanted to ensure we were achieving that in the most efficient manner.

Mathew

Pedro26 · 14 Oct 2010

I know many people who use or want to use their conservatories all year round, (some opened them up to rest of the house, i.e. no DG patio style doors in between, a bit naughty as then then are not exempt from BC remit) but the insulation factors and in a lot of cases particularly those of the roof, mean you will always struggle especially on the colder winter days to maintain the same temperature as the rest of the house. That is unless you throw lots and lots of watts at it, which will be expensive.

I can't remember exactly the rule of thumb for specifying rads in this situation but I think it is at least double that which it would be for a room on that side of the house. You will find figures like 200W per m^2 of floor area, augmented in cold snaps by 2-3 kW convection heaters. Cheaper to close off and retreat if possible.

ajrobb · 14 Oct 2010

If you put too large a radiator in the lounge with the thermostat, you run the risk of turning off the thermostat too soon for the rest of the house. I suppose you could turn it down (balance it) at the lockshield. My preference is still to go with the oversize radiators in the lounge but have one on a TRV and move the thermostat to the hall (no TRV). That way the lounge heats up quicker than the rest of the house (great for couch potatoes

).

MJN · 14 Oct 2010

My preference for the stat in the lounge is that that, due to the layout, the hall is heavily affected by heat from the kitchen. Likewise the first landing seems to get warm when cooking due to the rising heat through the open stairwell. Our electric fan oven automatically cools itself after cooking by dumping its heat into the kitchen as quickly as possible so the additional heat gain can be significant!

Our lounge doesn't have any supplementary heating and limited solar gain and so, to me, seems like the ideal place to act as the index for the rest of the house particularly as that's where we tend to congregate. Being connected to the conservatory also makes it the coldest room too given our current strategy of leaving the conservatory doors open! That may well change as it gets colder, and I take on board Pedro's points about adequate heat input should we attempt to keep it habitable.

I think I'll try balancing the system as a whole - I'd bet money on it not being done (properly) by the installers and will see how if that helps matters, particular with regards to the cycling during initial heat up. As you say, I can then tweak back the lounge radiator to keep the stat open beyond the rest of the house being satisfied.

Thanks everyone for the advice - will come back with any results (or further questions if required!).

Mathew

MJN · 14 Oct 2010

MJN said:
My preference for the stat in the lounge is that that, due to the layout, the hall is heavily affected by heat from the kitchen. Likewise the first landing seems to get warm when cooking due to the rising heat through the open stairwell. Our electric fan oven automatically cools itself after cooking by dumping its heat into the kitchen as quickly as possible so the additional heat gain can be significant!

Our lounge doesn't have any supplementary heating and limited solar gain and so, to me, seems like the ideal place to act as the index for the rest of the house particularly as that's where we tend to congregate. Being connected to the conservatory also makes it the coldest room too given our current strategy of leaving the conservatory doors open! That may well change as it gets colder, and I take on board Pedro's points about adequate heat sizing should we attempt to keep it habitable.

I think I'll try balancing the system as a whole - I'd bet money on it not being done (properly) by the installers and will see how if that helps matters, particular with regards to the cycling during initial heat up. As you say, I can then tweak back the lounge radiator to keep the stat open beyond the rest of the house being satisfied.

Thanks everyone for the advice - will come back with any results (or further questions if required!).

Mathew

Rhondo · 14 Oct 2010

mjn had you considered connecting your rads TBOE?

That means Top Bottom Opposite End.
Its results in a 15% increased output which is guranteed tried and tested. I did one once where I just welded a 65mm pipe into the end of the doubles and 20mm pipe into the singles and connected the primaries up to these.
Tools needed are an angle grinder , mig welder and a small buffing and polishing grinder and some white enamel.

MJN · 15 Oct 2010

Rhondo said:
mjn had you considered connecting your rads TBOE?

I hadn't, although to be honest I'd not heard of it before!

Tools needed are an angle grinder , mig welder and a small buffing and polishing grinder and some white enamel.

Ah... I could cope with the angle grinder aspect but welding is beyond me (and/or my available toolset). I don't mind just upgrading the struggling rad in the lounge (and conservatory if deemed appropriate) with a bigger size.

Mathew

D_Hailsham · 15 Oct 2010

Rhondo said:
had you considered connecting your rads TBOE? That means Top Bottom Opposite End. Its results in a 15% increased output which is guaranteed tried and tested.

Where do you get the 15% from???

The figure I have seen is a 1% or 2% increase. BS EN442 tests rads using TBSE.

MJN · 15 Oct 2010

Regarding heating my conservatory I have been looking at fan convectors however they all seem to specify 15mm inputs. Would they still function satisfactorily with my 10mm circuit? Running 15mm is not really a viable option for me.

Mathew

johnnojob · 15 Oct 2010

ideal he boiler = think about house move.

ok to be honest if i was in your position i would have electric under floor heating installed in conservatory so when boiler breaks down you have a warm room to survive till boiler repaired.
seems bigger rads and extending rad circuits like existing decent size pipes.
rads with top flow and bottom return connectors give off higher and i think quicker temperature rise.also easy to operate for us in the later flush of life.
have these in my amsterdam appartment.
uk rads are always plumed into ths bottom connectors probaly looks neater.

MJN · 15 Oct 2010

johnnojob said:
ideal he boiler = think about house move.

We've only just moved in!

ok to be honest if i was in your position i would have electric under floor heating installed in conservatory so when boiler breaks down you have a warm room to survive till boiler repaired.

I'm not sure whether you're being sarcastic or not. What's likely to be my achiles heel with regards to the boiler breaking down? It's got a V9 PCB for what it's worth. To me this boiler seems such a simple device with a low component count I'm not sure what I should be expecting to inevitably go wrong with it? If (or should that be 'when' by your experience?) it does fail then surely their simplicity means any monkey will be able to fix it?

I want any solution to my issues to be tailored for standard use i.e. that which is predominant over the hopefully-rare occasion that this boiler goes belly up. I don't consider electric heating really to fit that bill (but am open to persuasion by those in the know).

seems bigger rads and extending rad circuits like decent size pipes.

Before we get carried away, the house as a whole is toasty. My only concerns are cycling and the conservatory heating, and perhaps a quicker response in the lounge (but that could be due to the conservatory). I am hoping that the former will solved through proper balancing as I strongly suspect it wasn't done upon install.

Mathew

johnnojob · 15 Oct 2010

please remove the line of your last post regarding monkeys.

so its got the latest pcb fitted thats normal.

do you have plastic pipes on radiator circuits ?.

flowmasta rads are screwfix supplied rads nothing wrong with them you really need to do your calculations on older rads like stelrad,myson,quinn or wolsey plumb center.
heard but probaly wrong that flowmasta rads have a lesser thickness of metal than stelrad etc,in my opinion thats better as transfer of heat is quicker.
personally if i wanted to heat a conservatory i would use electric under floor so not to disturb existing system.

MJN · 15 Oct 2010

johnnojob said:
so its got the latest pcb fitted thats normal.

From reading the archives I thought maybe the PCB (older versions at least) was one of the main critical aspects of this boiler.

do you have plastic pipes on radiator circuits ?.

Yes - 22mm main trunk with 10mm branches (all Speedfit).

flowmasta rads are screwfix supplied rads nothing wrong with them you really need to do your calculations on older rads like stelrad,myson,quinn or wolsey plumb center. heard but probaly wrong that flowmasta rads have a lesser thickness of metal than stelrad etc,in my opinion thats better as transfer of heat is quicker.

I only picked them because they looked very similar to mine, but in light of what you have said in terms of wall thickness I guess there's more to this than meets the eye.

Assuming therefore that my rads are even less an output than suspected it is perhaps no wonder the boiler is cycling as it simply cannot modulate low enough (I guess that's another sign of it being a crap boiler?).

personally if i wanted to heat a conservatory i would use electric under floor so not to disturb existing system.

Ah okay. Point taken - I may take a look at my options there.

Mathew

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Increasing radiator output and improving CH performance

Rhondo

johnnojob

johnnojob

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