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Old 09-04-14, 07:59 AM   #21
Mikesolar
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Quote:
Originally Posted by Ormston View Post
Pipe is 17x2 PEX, that is 17 OD and 2mm wall.
As this is a renovation project things were incomplete when we moved in last November, I manually balanced the flow through each zone and run the system with no thermostats. It was controlled using weather compensation (certain outside temp = certain flow temp).
We generally had 21-22C air temp on the ground floor and 17-18C upstairs, not quite warm enough when getting out the shower.
Attic was poorly insulated as loft conversion was planned.
I think the main issue is that PEX in screed with carpet covering emmits far more heat than PEX with aluminium spreaders through wooden floor boards and carpet covering.

Will post more details and some photos when I get home.

Steve
17mm is an odd size, I thought. I guess it depends on the manufacturer but fittings are usually standard.

For those who don't know, screed is similar to gypcrete and is a easily spreadable cement based topping (non structural)

I have had this on going argument with a lot of people about heat spreaders vs cement. To me cement is vastly superior so I expect you are right. Even IF you could get the same spacing with spreaders, there is a lot of emission area which is missed as a percentage of the total floor area. Not so with cement.

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Old 09-04-14, 10:22 AM   #22
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Default Request: Heating Degree Days

Ormston,

A missing piece in our discussion is your local climate conditions.

Heating Degree Days will express this.

THIS _SITE can calculate the heating degree days (HDD) for your particular local. It would be most useful if this were expressed in Metric and also Imperial.

If you would like me to run the calcs for you, I'd be quite happy... I just need to know your location.

Best,

-AC
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Old 09-04-14, 01:39 PM   #23
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Quote:
Originally Posted by AC_Hacker View Post
Ormston,

A missing piece in our discussion is your local climate conditions.

Heating Degree Days will express this.

THIS _SITE can calculate the heating degree days (HDD) for your particular local. It would be most useful if this were expressed in Metric and also Imperial.

If you would like me to run the calcs for you, I'd be quite happy... I just need to know your location.

Best,

-AC
AC Location is Hereford, UK
Last winter was remarkably warm, only a few days below freezing. We do struggle for heat when temperatures drop below freezing as the output of the ASHP drops to 2KW by that temp.

Celsius-based heating degree days for a base temperature of 15.5C
Month starting HDD % Estimated
2013-09-01 75 5
2013-10-01 106 4
2013-11-01 269 3
2013-12-01 277 2
2014-01-01 307 0.2
2014-02-01 257 0.1
2014-03-01 257 0.2
2014-04-01 172 0.03
2014-05-01 111 0.06
2014-06-01 48 0.03
2014-07-01 23 0.1
2014-08-01 56 0



Fahrenheit-based heating degree days for a base temperature of 65F
Month starting HDD % Estimated
2013-09-01 259 5
2013-10-01 337 4
2013-11-01 638 3
2013-12-01 656 2
2014-01-01 710 0.2
2014-02-01 606 0.1
2014-03-01 618 0.2
2014-04-01 462 0.03
2014-05-01 341 0.06
2014-06-01 183 0.03
2014-07-01 107 0.1
2014-08-01 219 0
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Old 09-04-14, 06:07 PM   #24
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Have started a new thread to discuss my project here:
http://ecorenovator.org/forum/renova...n-project.html
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Old 09-05-14, 06:57 PM   #25
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Here is another illustration that was mentioned in the Heatsprings presentation, but a better illustration was found at home power:


This is a very low water temperature radiator from JAGA.

It uses small fans that look ever so much like computer fans, and if you look at the power supply, it looks ever so much like a 12v wall wart power supply.

Some more info RIGHT_HERE.

This idea has abundant DIY potential.

-AC
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Old 09-05-14, 07:02 PM   #26
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They are quite cool. I haven't put them in but I have seen them in a couple low energy houses. Nice and quiet.
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Old 10-01-14, 09:08 PM   #27
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Default Air stratification and ceiling radiant heat

Hi AC, This is a bit late, I just noticed this thread. My 2 cents worth:

The temperature of the air in contact with a flat ceiling radiator will have virtually no effect on the heat output of the radiator. Air is basically transparent to infrared and thus does not affect the amount of heat transferred to the solid objects in the room below. Hot air stratified at the ceiling or suspended radiator-face will totally prevent any convection of course but you wouldn't want any up there anyway.

The output of the radiator per unit area is proportional to (Tr4 – Ts4), where Tr4 is the fourth power of the radiator face temperature and Ts4 is the weighted average of the fourth powers of the surrounding solid surface temperatures in the room. (Note that these are absolute temperatures, i.e. in degrees above absolute zero, so, for example, 20degC is 20 + 273.15=293.15 degrees Kelvin). I have seen published claimed figures of about 1kW per square metre radiant heat output for electric ceiling panels operating at 110 to 115degC, which by my calculation would imply less than a 10th of that for low temperature hydronic systems.

Note that wall “radiators” actually deliver most of their heat by convection. This makes them more efficient per unit area at getting heat into the room. Against that, a lot of the heat goes straight to the ceiling! Also, radiant heat delivery seems to be generally accepted to be more efficient than convected heat for delivering comfort. Radiant floors presumably deliver quite a bit of convection too. For a given area and temperature this would result in a greater output than a ceiling radiator. I imagine calculating the proportion would be difficult but I imagine that the figures in the various programs you use will already have taken all that into account? Do any of those programs handle ceiling radiant heating AC?

The following is speculation by me, based on my understanding of the physics only. I’d be interested in what others think. Compared to other forms of radiators, ceiling radiant has the following:

• Somewhat lower output per unit area for a given radiator temperature. This may be at least partially compensated for by the fact that the ceiling is unencumbered by furniture etc., as floors usually are;

• The floors will be warm. If you use low temperature floor heating, the floors will usually be below blood temperature, so if high conductivity flooring is used, as recommended for efficiency, they will actually feel cold to bare feet. For ceiling radiation, carpets on floors actually improve effectiveness, the reverse of the situation with radiant flooring.

• Some people dislike heating directed more at the head than the toes. On the other hand, that is the most efficient way to reduce body heat loss and others prefer it.

• For timber frame houses, it is impractical to add thermal mass to the ceiling. However, there seems to me to be no great disadvantage to having a high thermal mass floor or wall that is indirectly heated by a radiator, compared to heating the floor directly? You can of course have the thermal mass in a storage tank instead, possibly at greater cost?

Last edited by Snail; 10-02-14 at 02:15 AM..
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Old 10-02-14, 05:41 PM   #28
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http://www.tealinternational.com/Thi...%20Balance.pdf

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