Central Heating Resistance

[barry wilkins]

I know this might be a strange subject for an electronics forum, but some of you might know about plumbing .After all one of the unions for electricians was the plumbers.
As we all know a metal conducter has an impedance to the flow of current through it,and current is proportional to the voltage which is one Georges laws ( E= I R).
The same must apply to a gas or liquid flowing through a pipe or tube ,it must have its flow impeded by the pipe.
Is there a measurement for this?
What is the result ?( cant be ohms surely).
You could say the pressure is E ,so the flow rate is I ,and the impedance is R.

what do you think ?

I want to know if you can measure the resistance to the flow of the water in my central heating.

I seem to rember when I worked in the paper mills you measured the flow of steam by the pressure difference across an orifice.

Barry Wilkins

[selldoor]

Seems quite a sane enquiry and you will probably get a sensible answer.

I have googled and come up with this
http://www.engineersedge.com/fluid_f...ssure_drop.htm

but have no idea what it means.

Usual way of doing thing with CH is by temperature - balancing things with
two or more thermometers and moving lockshield to get the desired results.

[kaboom]

Take an old hot water system, as used in older houses, with the cast iron pipes.

ASSume there were 2" or bigger lines for the mains and each radiator had a 3/4 supply and return tap. Maybe 1 or 1 1/4 risers to feed the second floor.

What happens when someone taps 1/2" copper, right at the boiler, to feed a distant loop, such as a new room on the side of the house? "Bad things." The central portion of the house satisfies sooner (bigger lines), while the add-on "grandma room" is ice cold. Too few GPM at a given head loss underfeeds the distant loop.

Ultimately, Grandma complains!


With the 'newer' copper fin-tube, there are tees with "diverters" that sort of split the flow. Other times, all the fin-tubes in a zone are piped in series.