CH design and radiators...

On 31/01/2015 14:57, Tim Watts wrote:

IIRC, I used a few Kudox ones on my most recent rad juggling exercise. They seem equally well made as any of the better known brands, but were somewhat cheaper.
(note their figures specify the Tdelata as the difference between flow temperatur and ambient - rather than between flow and return)
http://www.kudox.com/Files/Website%20Technical/2014%2004%2009%20Kudox%20Steel%20Panel%20Radiators%20Technical%20Data.pdf
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On 01/02/15 23:15, John Rumm wrote:

Thanks John,

That's what I assumed - as deltaT-Flow/Return is only useful if you also know the flow rate, which noone does :)
I have been looking at my ZWave power measurements. Quite interesting...
To sustain at 20-21C with 2-3C outside, averager power over a day, no heating at night:
Our bedroom 1.5kW (contributes to hall, 2 outside walls, bay window) Daughter's bedroom - 400W (one short outside wall) Son's bedroom - 600W (2 outside walls, smaller windows) Kitchen 1.5kw (contributes to hall and rear lobby) - Also fire running in the kitchen, say 2kW more.
Total load about 6kW inc fire on an exceptionally cold day.
Conservatory - took a 2kW heater there plus power meter and temp sensor.
Started at 9C, 2kW flat out took it to 16C after 3 hours where it plateaued. Turned heater off - it fell like a stone, 13C in one hour.
So far I've managed to spec rads with a total output of 12.4kW at deltaT0C (ambient 20C) so I guess 55/45C ?
At deltaT@C the total output would be 17kW and according to your figures that is still running in condensing mode.
The conservatory would have UFH specced at about 2kW but in winter we'd use it just to keep the edge off the cold - say 12C and have a Myson fan convector for rapid boost - these seem rather good - their bigger wall model can shove out 3.8kW in Boost mode at deltaT@C
Now, these are using the biggest radiators I can comfortably fit in - Kitchen is awkward as I only have 2 500mm long spaces, but triple panel rads seem to be better than verticals.
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Tim Watts wrote:

If you're cutting it fine on heat output, are you allowing for the "book" figures for the radiators being quoted for TBSE plumbing, with slightly lower output (5 to 10%) when plumbed BBOE?
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Doesn't make any difference for a pumped system, and he's not going to be installing a convection circulating system.
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Andrew Gabriel
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On 02/02/15 10:04, Andrew Gabriel wrote:

Oh...
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On 02/02/15 09:19, Andy Burns wrote:

TBSE BBOE?
You mean because of heat drops in the pipes?
Overall I have more than enough - it is just the kitchen and rear lobby are hard to get a lot of power into as walls are very cluttered.
Myson blower in the lobby remains an option though. Will not be allowed one in the kitchen as SWMBO will veto it for being noisy.
She wanted to veto the conservatory one, but I said it was the only practical way to boost the heat there at short notice as it is of course very lossy. The UFH there is more for spring/autumn and to keep the chill off in winter.
Talking of which, I should probably look at antifreeze in the CH circuit as well as inhibitor.
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Tim Watts wrote:

flow at _T_op with return at _B_ottom of _S_ame _E_nd, flow at _B_ottom and return at _B_ottom of _O_pposite _E_nds, also flow at _T_op and return at _B_ottom of _O_pposite _E_nds.

The BSEN 442 spec states that is how rads are plumbed for testing, various sites give different de-rating factors for other plumbing types, but I hadn't picked-up that this was not* relevant to pumped systems.
[*] Can't see how it's /totally/ irrelevant, perhaps it's negligible though.
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If you search out infra-red pictures of radiators, you will see the hot inlet all rises to the top in the first channel because the convection effect inside the radiator is very strong. It therefore doesn't make any significant difference in the radiator if you pipe the inlet to the top or the bottom - the hot water goes straight to the top anyway, and then uniformly descends the whole rest of the radiator, making for a pretty much perfect contra-flow heat exchanger with the convecting air.
If you run a pipe to the top, you will get a tiny bit extra heat output from that pipe (but not as much as making the radiator wider to take up the space of the pipe).
The only important thing is that the outlet/return must be at the bottom.
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Andrew Gabriel wrote:

Searching for "radiator and FLIR" seems to find better results than "radiator and infrared", but these images seem pretty convincing
<http://signalsurveyors.co.uk/2014/08/04/117 > The only important thing is that the outlet/return must be at the

Yes, I can see BTSE being a really bad idea!
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Tim Watts wrote:

    Sounds like you'd be better off putting in heat pumps.
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On 02/02/15 10:30, Capitol wrote:

Why? That would make it worse with respect to CH flow temps.
Also - I did look at air source heat pumps. The economics are laughable.
They look good initially - with a 100% heat gain over the electrical power input. Until you notice that that is peak rate electricity and gas round our way is 1/3 the price of electricity kW for kW.
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I use one in my main room (which is also my office at one end) when I'm working at home, and don't need to heat the whole house.
Originally bought it for cooling in the summer, but it gets used only for a few days for cooling, but much more for heating.
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On 02/02/15 11:24, Andrew Gabriel wrote:

I agree if it has the purpose of cooling, then it is useful on a single room basis.
My criticism was levelled at whole house systems.
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Tim Watts wrote:

If my rooms were all at 20°C, I could live without central heating :-P
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On 31/01/15 16:36, Andy Burns wrote:

Valid point - when we are at 20C we will only be balancing the heat loss.
Starting temp back from a holiday might be <10C or 15C if out at work all day which is when we want it to heat up...
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On 31/01/2015 16:36, Andy Burns wrote:

Although if the heating is doing its job, that is the room temp (give or take a bit) they will be trying to maintain hopefully ;-)
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It's OCD to plan radiators. Just shove a radiator in each room where it's convenient to place it and see what happens. The boiler will come on more or less depending on what size you've selected and what the outside temperature is, you don't have to get it anywhere near correct.
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On 31/01/2015 16:43, Uncle Peter wrote:

You should be a plumber... or "heating engineer". You know, the kind of folks that explain why we DIY.
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On 01/02/15 23:22, John Rumm wrote:

Uncle Peter is being a wally.
CH installations is one of the biggest expenses so if you don't plan, you're a fool.

Although I'm subbing this out I don't trust any plumbers with the design so I'm specifying stuff :)
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You somehow think you can make it drastically cheaper by planning? Just buy a radiator for each room, a load of pipe, and a boiler. Fit it yourself, it's not rocket surgery.
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A fat girl served me in McDonald's at lunchtime. She said "sorry about the wait". I said, "Don't worry, you'll find a way to lose it eventually"

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