AC circuit and relay

[KRe8ive]

Hi guys,

I am trying to trigger a 230vac circuit off of a 24vac circuit. I thought the easiest way to do this would be with a relay as it allowed for sufficient current on the 230vac side.

I got a relay with a 24vac coil, but with the coil resistance of 180 ohm it brought the signal voltage down to 12vac

I also have another relay with a 12vac coil but the coil resistance is only 46 ohm meaning the circuit only drops to 16vac. I added a 100ohm resistor which brought the voltage down within range for the relay to operate correctly but the resistor burnt out.

Am I going about this the best way and i just need to up the size of my resistor (was only a 1/4watt or is there a better idea?

 

[KRe8ive]

the problem I am having, is based on some really quick math i have slapped together i need a relay of >5watt

 

[CDRIVE]

It will help if you told us what the source is that will drive the relay coil.

Chris

 

[KRe8ive]

The purpose of this circuit is in a house with a Central Gas heating system, and installing a heat distribution system. But the way the gas heating works the distribution system I am putting in cannot operate while the gas heater is operating else it will gas the house out. (2 totally different systems for 2 different uses).

So i found the cable to the gas heating system which triggers from a controller. I metered it and when the gas system is 'off' there is a 24vac signal. it then goes to 0vac to turn it on.

I am using it to cut the power to the fans of the distribution system when the gas kicks in.

Hope this helps, am not actually sure where the 24vac comes from as the controller for the gas heating on the wall is powered by batteries

 

[KRe8ive]

thinking about it now that i just typed that, i would say the 24vac is coming from the gas unit itself and the controller is just opening and closing the circuit.

 

[CDRIVE]

The purpose of this circuit is in a house with a Central Gas heating system, and installing a heat distribution system. But the way the gas heating works the distribution system I am putting in cannot operate while the gas heater is operating else it will gas the house out. (2 totally different systems for 2 different uses).

So i found the cable to the gas heating system which triggers from a controller. I metered it and when the gas system is 'off' there is a 24vac signal. it then goes to 0vac to turn it on.

I am using it to cut the power to the fans of the distribution system when the gas kicks in.

Hope this helps, am not actually sure where the 24vac comes from as the controller for the gas heating on the wall is powered by batteries

Judging by your metering description I would say that the two nodes that you're measuring are across the wall controller (thermostat) contacts. Thermostat contacts might be a misnomer here because the battery powered thermostat may be totally solid state with no electromechanical contacts at all. The 24VAC will be sourced from a transformer located within the gas heater itself.

That's why the voltage swings to zero when the unit is on. The 24VAC that your reading is not directly from the 24VAC transformer but rather in series with a 24VAC relay coil that's also within the gas unit. You're attempting to put two 24VAC relay coils in series with each other. This is not what you want to do.

My advice to you would be to locate the 24VAC relay within the gas heater unit and wire your second relay coil in parallel with that relay coil. If your additional relay is a (SPDT) Single Pole Double Throw model you have the choice of using normally closed or normally open contacts.

Let me know if you need a schematic of what I've just described.

Chris

 

[CDRIVE]

Heck, I knew I'd draw this anyway but please read my disclaimer in my signature.

Chris

 

[Brianj_92505]

Working with electricity can be dangerous. Any information that I post, including schematics and or code are intended for educational purposes only. No warranty of circuit or code suitability is expressed or implied. Proceed at your own risk.
Chris

To say nothing about the danger of working with your gas heating system. This project sounds like an accident waiting to happen.

 

[CDRIVE]

To say nothing about the danger of working with your gas heating system. This project sounds like an accident waiting to happen.

Well yes, if someone doesn't know what they're doing it certainly is. On that note I'm not my brother's keeper. I don't want to be and I don't want my government to be either. That said it's a nanny state world. I'm a Redneck at heart and I find joy in watching Youtube videos of crackers using Hemi powered log splitters that would give OSHA inspectors coronaries!

Chris