Is this practical?

Slow day is it ?

Let's take some numbers.

In the UK we'd be using 15mm dia copper pipe with 0.8mm wall thickness. The cross-sectional area of the coper in that is 35.7 mm^2.

Condcctivity of copper is 59.6.10^6 S/m.

That translates to 47mohm/m.

Let's tale a notional length of 5m to be heated.. That gives us 235mohm.

Suppose we use 500W to heat it. That gives us 46A and 10.8V.

Graham

Look, I guessed that the piped would have around 1/10000 ohms per ft because

1000ft AWG 0 is 1/10 ohm or AWG 0 is 1/10000 ohm/ft(actually I didn't guess as I'm sure its actually much lower depending on the size of the pipe).

Now, given that, by ohms law,

V = I*R P = V*I

Now suppose we have 100 feet of pipe that has the resistance of about

100*1/10000 = 1/100 ohms.

then dissipating 1W/ft means 100W total and 100W = V^2/(1/100) or 100*V^2 =

100W ==> V = 1V.

I screwed up the math before cause I divided both sides by 100 instead of multipled(and I was doing it with 1W/ft instead of working with the total pipe).

since V = I*R or I = V/R, I = 1V/(1/100) = 100A.

My numbers were off cause I multipled both sides by 100 instead of 1/100 but it has f****ng nothing to do with knowing ohms law or not but a simple miscalculation from not paying attention.

Instead the f****rs Fleetie and Eeyore have to feed there ego and try to make others feel stupid just so they look smarter. Instead of reading what I said and if they were smart as they think they could easily have saw the mistake. The logic is right and I'll be damned if they try to capitalize on a stupid math error(which I shouldn't have made but I'm not perfect).

If they actually had a clue they would have said "Go practice your basic math more" instead of "Go learn ohms law". I'm not saying I shouldn't have payed more attention to what I was doing but I do have somewhat of a life... much more than these f****rs.

Not even close to correct.

- you haven't calculated the temperature to which the pipe will be heated

- you haven't accounted for heat transfer to the water inside the pipe

- you haven't accounted for heat transfer to the environment outside the pipe

--
Regards,
        Doug Miller (alphageek at milmac dot com)

It\'s time to throw all their damned tea in the harbor again.

Since I've done the electrical bit maybe you'd like to do the above ?

Graham

There's not enough information available to do anything more than guess.

--
Regards,
        Doug Miller (alphageek at milmac dot com)

It\'s time to throw all their damned tea in the harbor again.

you want to ran AC through copper pipes to warm them.

that could work, but copper water pipe has a very low resistance so to get a little heating in the pipes will require a high current.

this means you'll need a special transformer, thick wire, and very good connections to the pipe at each end.

If the plumber has used compression fittings with nylon olives at any of the joins that may prove to be a point of high resistance that will steal all the heat, (copper olives or soldered joins will have low resistance and not be such a problem)

If this is an AC current it's going to radiate lots of hum, sensitive audio equipment (tape players, electric guitars,...) will be effected it could even turn steel panels into loudspeakers etc..

Bye. Jasen

You've got that backwards John, dividing by a small number (a number smaller than 1) makes the result bigger.

you really should learn to use the laws of thermodynamics as a check on calculatuions like this...

1w/ft on 100ft can't come out to anything other than 100w

That'd work, especially if the heater was in the circuit, although the circulating pump itself may produce sufficient heat.

Not true. two shorts of the wire to the pipe would take a section of it out of action as the current would be diverted through the pipe instead.

Bye. Jasen

well, it was a simple math mistake. I multiplied by 100 instead of 1/100... the logic is correct. I should have guessed that 1MW was a little high but I wasn't paying attention.

No, I mean coating the wire with some electrical insulated material that is thermally conductive.

either way plural shorts will stop it from working,

Bye. Jasen

Yes! We have a winner ...

Mark

"Now, with the walls covered and with benches permanently mounted he doesn't even want to consider trying to add more insulation."

Heat tape would be ideal, but would also require some wall digging.

I'd consider it before I'd try to implement some low voltage resistance heating scheme that uses the pipes themselves. Only takes one poorly sweated joint in a wall somewhere to destroy the whole wall.

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Yes.  Any time I deal with you I have to slow to a crawl in order to
allow you to keep up.

Does anybody make a heater that you can fish *inside* a pipe? That would make installation a lot easier in many cases.

John

Maybe this will help?

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida