how to ID wire from junction or panel?

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Qwertyjjj

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I must not have explained myself properly :)
I am replacing the baseboard and buying a new 240 t-stat to replace completely. I need a digital thermostat on the wall, not the built in one on the heaters.
I'm still trying to ID which cable from the junction goes to which room - I think the disconnecting a cable in the junction might be the best solution.
 

DonL

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I must not have explained myself properly :)
I am replacing the baseboard and buying a new 240 t-stat to replace completely. I need a digital thermostat on the wall, not the built in one on the heaters.
I'm still trying to ID which cable from the junction goes to which room - I think the disconnecting a cable in the junction might be the best solution.


I think you are making it harder than it needs to be.

Why do you need to even mess with the power feed ?

Other than knowing for sure Power is off, I do not get the problem.

"I think the disconnecting a cable in the junction might be the best solution."
I agree.

I just am Clueless at times.
 

LLigetfa

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I am replacing the baseboard and buying a new 240 t-stat to replace completely. I need a digital thermostat on the wall, not the built in one on the heaters...
If the new T-stat is a line voltage version, it will need the wire upgraded.

I'm still trying to ID which cable from the junction goes to which room - I think the disconnecting a cable in the junction might be the best solution.
If you don't have a clamp-on, then yes.
 

Qwertyjjj

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If the new T-stat is a line voltage version, it will need the wire upgraded.


If you don't have a clamp-on, then yes.
The existing wire to baseboard is 12/2.
I was going to add some extra 12/2 (red cable) and connect that to the new 240 thermostat and wire it up as per instructions: 2 or 4 cables depending on the t-stat.
 

Qwertyjjj

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If you play with electricity, the proper tools are nice.

www.mcmelectronics.com/product/72-7218
I've not used a clamp on before, I only have an electrical meter with probes.
With the clamp on do you have to connect to the copper wire or can you clamp it around any part of the cable?
With a 24 t-stat and open circuit, won;t the baseboard always be live, so the clamp on will measure current anyway?
 

DonL

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I've not sued a clamp on before, I only have an electrical meter with probes.
With the clamp on do you have to connect to the copper wire or can you clamp it around any part of the cable?
With a 24 t-stat and open circuit, won;t the baseboard always be live, so the clamp on will measure current anyway?

It will be low current, just what the transformer draws, If the T-stat is satisfied.

You just clamp it around the hot wire. No connection needs to be disconnected. But power does need to be on.
 

Qwertyjjj

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It will be low current, just what the transformer draws, If the T-stat is satisfied.

You just clamp it around the hot wire. No connection needs to be disconnected. But power does need to be on.
But it needs to be connected to copper or is it sensing current flow through the PVC? The way they write it you can clamp it anywhere on a wire and it will sense it.
 

DonL

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But it needs to be connected to copper or is it sensing current flow through the PVC? The way they write it you can clamp it anywhere on a wire and it will sense it.


You should not be playing with electricity.

Sorry, I have no better answer than that.

How in the hell do you expect to get a reading if you clamp around all conductors in PVC ? It clamps around 1 Hot conductor. Maybe I misunderstood, again.

If you have current flowing thru your PVC, you have big problems.

Please forgive me, if you can.
 
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LLigetfa

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But it needs to be connected to copper or is it sensing current flow through the PVC?
Ignore DonL, he is just being an ass.
The meter does not make electrical contact with the wire. It clamps around a single conductor.
The current draw when the heater is on would be higher than what the transformer uses.
 

DonL

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Ignore DonL, he is just being an ass.


Yep, I am good at that.

I do not like to see people get hurt because they do not know what they are doing.

Look up "electronics 101" before playing with electricity.


Yes it may be just me. I must be a Nut too think of safety first.
 
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Qwertyjjj

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Yep, I am good at that.

I do not like to see people get hurt because they do not know what they are doing.

Look up "electronics 101" before playing with electricity.


Yes it is just me.
It's fine, I've made many connections before, I've just not heard of a clamp before and the way it was written in the advertising it was some kind of magic sensor...a bit like how a stud finder works.
 

DonL

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It's fine, I've made many connections before, I've just not heard of a clamp before and the way it was written in the advertising it was some kind of magic sensor...a bit like how a stud finder works.


I did not mean to come over harsh.

The link I posted is for a cheap meter that works.


All you need to do is learn how to use it.
 

Qwertyjjj

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Once I have found which wire is which, does this plan look ok (all using 12/2 wire 20A 2 pole breaker, 240 t-stats and 240 baseboards)? It is wired with 2 wire t-stats using the existing power supply to the heaters as the junction point.
If the newer t-stats have 4 then I'd have to have double the wire I think to go to the thermostat first and then back to the baseboard to break both legs of the power.
 
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Jadnashua

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It sounds like the 240vac is run into that control box which probably also has a 24vac transformer and a relay or contactor to control the power to the unit...the 24vac transformer would be on when ever power is applied to the unit.

Do you know where the junction box is? One cable coming in, and three going out? It shouldn't be all that hard to figure out which one goes where. Instead of disconnecting things at the breaker (to be safe, it would still probably be a good idea, at least make sure it is off!), do the same thing at that junction box with each cable - disconnect a pair, short the leads together, and find the other end that is now shorted together.
 

Qwertyjjj

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What's the aim behind shorting the leads together?
The most confusing one is the single bedroom where there's a 24vac thermostat but it's not connected to the heater. I can't see any other transformer/relay in the panel downstairs so no idea where it is.
 

Jadnashua

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If the wires are not connected to anything at each end, to determine continuity from one end to the other, you'd have to have your meter leads long enough to go from one end to the other. But, if you short two wires together at one end, then check the continuity between them at the other end...those that are still open will show an open circuit...only the pair that you connected together will show a short.

As stated...a clamp-on ammeter maybe would more accurately called a clamp-around meter. The single wire under test passing through the center of the clamp-on probe (which is effectively a coil of wire) will induce a voltage in the probe that can be measured. It needs to be a single wire, not the whole cable since the current will be opposite in each wire and cancel any reading out.
 
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