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By Colonel Panic
#1892767
Thanks @defcribed ; the room has two outside walls; we will look at style options next week, but will probably aim for ~10,000BTU total and turn them down if required. @Flyin'Dutch' knows how much MrsMe likes the kitchen warmth, so will err on over sizing the rads.

We have no other cooking facilities other than the Aga, so are not able to turn it off during the summer. It was installed by our predecessors, and is a pre- 1974 model. We did consider bottled gas for the new cooker, but felt that installing a new fossil fuel device was suboptimal, especially as we do have PV panels and storage battery already.
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By defcribed
#1892778
Colonel Panic wrote:We have no other cooking facilities other than the Aga, so are not able to turn it off during the summer. It was installed by our predecessors, and is a pre- 1974 model. We did consider bottled gas for the new cooker, but felt that installing a new fossil fuel device was suboptimal, especially as we do have PV panels and storage battery already.


We had nothing but the Aga when we moved in.

The previous owners put in an expensive fitted kitchen (solid wooden cupboards, granite worktops, built-in dishwasher and fridge/freezer) which seemed to have been designed around the Aga. We aren't going to rip it apart to put in the alternative cooking facilities that they should have included, and indeed with the layout they chose there isn't really anywhere you could do it.

As a solution for summer I purchased a four-ring induction hub - the sort designed to be sunk into the work surface (the portable ones are a bit rubbish) and made it into a semi-portable one by building it a wooden frame to sit in with feet on the bottom and fitting a plug. When the Aga is off we remove the hob covers and place this on top. Coupled with one of those fancy microwaves that is also a grill and an oven, we just about manage in summer
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By Big Dex
#1892917
(Qualified heating bloke):
As a rough rule of thumb, in a living room (as opposed to a bedroom), I would suggest 100w per square meter. Yes, there are vagaries with external walls, north facing, no cavity etc, but this approximation will do the job just fine. Oversizing has no real downside, the TRV will sort it out.

Assuming that you have a condensing boiler, this should be set so that the return temp is below around 57C in order to make the boiler condense and maximise it's efficiency. A flow temp of 65C is normally pretty good to achieve this. Radiator outputs are quoted at a Delta T of 50 or 60 normally; reality is that it's closer to 45, so allow for a degree of under-performance on your chosen rad unless you have an old non-condensing boiler, in which case the 60 figure will be close (but your boiler will not outlast the rad, and it's replacement will be condensing).

Your 10000BTU rad will do just fine; anything over 8500BTU/2500w is adequate imho. If you're using standard pressed steel panel rads, a 600h x 1200w double panel double convector will be splendid. If you're going for tall column radiators, treat their output with great suspicion: The temperature variation from the top to the bottom of a 6' tall radiator is huge, unless it has a massive water flow through it.
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By Grelly
FLYER Club Member  FLYER Club Member
#1892928
Another vote for underfloor heating. :thumleft:

Before upgrading the kitchen we had a tile floor laid on concrete. Cooking in cold weather, the floor sucked the heat out of your body through your feet! More than ten years of quite unpleasant discomfort.

Top of the list when replacing the kitchen was underfloor heating and we haven't regretted it.

I also agree that radiators work best when placed under windows. I have heard tales of people avoiding that because they think that the rising warm air goes straight out of the window. This is the wrong way round. The descending cool air mixes with the warm air around the radiator and pushes it out into the room. (Apologies if you already knew that)
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By Colonel Panic
#1892952
Thanks @Big Dex - that was very helpful. We do have a 16yo (oil) condensing boiler but TBH I have never even thought about what the return temperature is. Should I just strap a thermometer on the return pipe and see? IIRC the boiler itself has no gauge.

Your 100w/m2 fits in well with my target of 10,000BTU, which is reassuring. I'm aiming to get a couple of 1,100 x 500mm flat panel radiators (single but with fins, TBC) to replace the single 1,000 x 600 c/w fins we have now (plus the Aga).
By Big Dex
#1892954
No problem.

I use a clip-on thermocouple that is part of my Anton Flue Gas Analyser, but a thermometer against the pipe, wrapped in some for of insulation for the reading would work well. I'd go as far as to say (no liability accepted) that I have found that a 65C pipe can be touched for 3 seconds before it hurts.... If you can hold it longer than that, it'll be about right!
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By defcribed
#1892997
@Colonel Panic nearly all oil boilers don't modulate their output - they're either burning or not. This means that with any given system setup (pump, radiators - including how they are adjusted, pipework) the return temperature will be whatever it'll be.

If it's higher than you want then you either need to add more radiator (opening lockshields counts) or pump the system harder - in essence you're trying to increase its ability to dissipate the heat the boiler generates to the rooms. If it's lower than you want then you've got too much radiator or you're pushing the water round the system too quickly.

If you can spare the space, double-panel radiators produce much more heat. As @Big Dex says, anything tall will have a big temperature delta from top to bottom and isn't an efficient means of transmitting heat into the room. Even 600mm high rads have a noticeable difference unless the flow is quite high, so your choice of 500mm high is good. But then I don't know your system and whether or not (as is often the case) the boiler is over-specced.

Spent a month last summer sorting out our terrible system, with an over-specced boiler and very restrictive microbore pipework. After replacing all radiators to increase capacity and pushing the pump as hard as seems reasonable, we have decent heating without the boiler short-cycling. Eventually I will rip the microbore out.
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By Colonel Panic
#1894037
Any views on aluminium radiators? Popped in to a "designer" radiator shop earlier and they had one that gives out a huge amount of BTUs - so much so that I could easily get away with just one rather than two. It would be almost cost neutral as it is double the cost of a normal one.

Looking on 'tweb, some say I need to change ALL of my existing rads to aluminium, others just say to ensure I have enough (suitable) inhibitor in the system. AIUI warm up and cool down periods are notably shorter, so that might make getting a constant temperature difficult.

One of these 600(h) x 1207(w) x 95(d) gives out a whopping 9,871 BTU ...
https://www.theradiatorcentre.com/desig ... r-radiator

Why would I not go for aluminium?
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By Rob L
#1894043
Grelly wrote:Another vote for underfloor heating. :thumleft:

Before upgrading the kitchen we had a tile floor laid on concrete. Cooking in cold weather, the floor sucked the heat out of your body through your feet! More than ten years of quite unpleasant discomfort.

Top of the list when replacing the kitchen was underfloor heating and we haven't regretted it.(snip)


I have proper terracotta tiles on my kitchen floor (no underfloor heating, although I do have one central heating radiator fitted against one wall) and the floor is reasonably warm against bare feet even in winter.
I assume terracotta is a better insulator than the glazed surface of tile.
By riverrock
FLYER Club Member  FLYER Club Member
#1894048
My understanding is that it can be harder to balance a system which has both Aluminium and Steel radiators.
As you say - aluminium heat up faster, but also cool much faster. To maintain a temperature, the boiler needs to keep hot water circulating through them. So you need a boiler that can throttle down low enough to maintain that flow (otherwise it will keep cycling, wasting energy and you'll get quicker room temperature fluctuations).
With steel, they have a much higher thermal mass, so will keep outputting heat long after the boiler has stopped circulating hot water, so the cycle time can be much longer, with the heat changes much more gentle. Having a mix means the system ends up a little compromised (but then setup is always a bunch of compromises!).
I suspect it would be made to work fine - TRVs on the steel radiators will keep each room more stable as the cycle time is reduced to keep your kitchen to the temperature you want.

2 radiators should indeed make a more consistent atmosphere - but as I say - any system is a compromise!
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By Rob L
#1894051
Warning: slight aviation content

I wouldn't mix ali radiators with steel radiators (and possibly copper or iron or stainless steel pipes)... the possibility of dissimilar metal corrosion [even with Fernox] raises my metalurgical heckles!
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By riverrock
FLYER Club Member  FLYER Club Member
#1894053
The heat exchanger in lots of boilers is made of aluminium, most houses have copper pipes and most likely mild steel radiators. That is why you add a corrosion inhibitor and install a magnetic filter to the system.
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By rikur_
FLYER Club Member  FLYER Club Member
#1894054
defcribed wrote:Eventually I will rip the microbore out.

Interestingly I've warmed to microbore, (excuse the pun). House#2 is all microbore off a manifold beneath the boiler, and seems:
(a) far easier to properly balance, than the random T here, T there in 22mm
(b) warms up far quicker as there's less water in the system

Mixed microbore and 15mm is a nightmare though.