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> Low Power Consumption 24v Ac Relay, Looking for a low power consumption rela
ggaudreau
Posted: March 08, 2017 03:52 pm
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Hi all

I am looking to buy/build a low power consumption relay that operates on 24V AC as its signaling supply to drive another relay, this one, consuming a lot of power.

Any suggestions?

Thank you

Guy
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kellys_eye
Posted: March 08, 2017 08:03 pm
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What do you use as reference to describe 'low power consumption'?


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Sch3mat1c
Posted: March 08, 2017 08:53 pm
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Well, go search for one... the most popular electronics distributors have selection sorting for that. smile.gif

For the least power consumption, use a latching relay. Warning: it doesn't turn off on its own (obviously), so the big relay will be stuck on (or off) if your circuit is powered down.

Tim


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ggaudreau
Posted: March 08, 2017 10:10 pm
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I don't want to use relays as the powerdraw is probbly high,
Let me explain a little more my issue,
I built a house a while back and forgot to lay one set of wires for thermostat feed thinking that the thermostat I had its own battery power . After I closed all my walls and finished the house I looked at the thermostats that I had purchased and low and behold they required power.

I had close by each thermostat 2 wires that were not doing anything but they are of small caliber (2 strands of a cat5 cable). So the 2 strands are suffiicient to feed in one instance 2 thermostats but not much more.
So each of the thermostats requires the following
2 wires for 24V AC for power
2 wires for output.

I my basement,where the wires all go, I have plenty of low voltage to supply any kind of device that would detect or not detect voltage outputed by the thermostat. I know thati will need to "drain" builtup power by puling the output of the thermostat to the ground via a resistance butI do not wan tto draw any more power fron the wire that is required.

Hoping that this is a little clearer

Thank you
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ggaudreau
Posted: March 08, 2017 10:18 pm
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THESE ARE THE SPECS FOR 1 THERMOSTAT

Maximum load: 0.5 A / 24 VAC
Heating cycle length: 15 seconds
Operating temperature: 32F to 122F (0C to 50C)
Storage: -4F to 122F (-20C to 50C)
Size (H W D): 124 x 70 x 23 mm (4.89 x 2.76 x 0.91 in)
Wire gauge: 14 to 22 AWG

And I don't want to burn the wire either.
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kellys_eye
Posted: March 09, 2017 12:58 am
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What do the thermostats connect to?

They have 'zero volt' contacts that open/close at the set limit and these contacts connect to .... what?

On many systems they connect to the system heater (boiler?) and activate a pump to circulate hot water through radiators (other systems are available YMMV).

The crucial issue is WHAT the contacts connect to - you may not need any other cable, the CAT cable should be quite sufficient.


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ggaudreau
Posted: March 09, 2017 03:51 pm
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I understand but the contacts will control a relay which in turn will control a pomp amongst other things. What I am worried about is th epower draw from the small relay X 2. I many be over reacting however. Like I said, I can't have the the 2 wires burn.

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kellys_eye
Posted: March 09, 2017 04:19 pm
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The thermostat contacts can only carry 0.5A (maximum) at 24VAC and CAT cable can carry that easily (up to (say) 20m length - probably a lot longer).

Use the wire you have - it won't be a problem.


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MacFromOK
Posted: March 09, 2017 11:24 pm
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I don't understand why you're considering a relay.

If the cat5 is heavy enough, there's no problem. If it's not, you need to run different wiring to the thermostat(s) anyway. Otherwise, some future electrician may not realize what you've done and create a fire hazard (assuming you don't).

Also (and more importantly)... unauthorized modifications will affect your AC/heat unit warranty, as well as your home insurance coverage if the place catches fire (whether your mod is the cause or not).

FWIW, you should be able to run wire into the wall from the basement or attic thru a drilled hole, then cut a hole in the wall (that the thermostat will cover) to fish for the wire.

Just my 2 ... beer.gif


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kellys_eye
Posted: March 09, 2017 11:47 pm
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It's actually quite common to see CAT wiring to such thermostats - I used to wire up valve actuator motors (controlled by thermostats) using the stuff on small boats. These 'actuators' opened/closed pipes in circulatory systems with pipe diameters of 3 to 4 inches.....

If the thermostats are part of a complete system then check the system specs and wiring data as it will probably state therein that this is perfectly acceptable.


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BlueVanACD2005
Posted: March 10, 2017 08:09 pm
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Just use a transistor to turn on a relay if you are worried about current draw. i.e. a 2222A.

https://i.stack.imgur.com/GH8dz.png
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