Indicator Lights wiring

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  #1  
Old 08-04-15, 06:35 AM
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Indicator Lights wiring

Hi:

Im trying to connect status lights to a series circuit of thermostats, to know when each one is working.

Is there a way to connect a status light to each thermostat?

-[T]-[T]-[T]-

The only way i know to do it is using this circuit with the thermostat and lights in parallel with each other but the thermostats need to be in series only so its not possible.

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Thanks for the help
 
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  #2  
Old 08-04-15, 07:58 AM
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You need to have a return (neutral) line available at each thermostat location to make it possible. Are the thermostats configured such that any one of them causes the HVAC to come on or that all of them must be on for the HVAC to come on?
 
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Old 08-04-15, 08:08 AM
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All of them must be on for the system to turn on
 
  #4  
Old 08-04-15, 11:47 AM
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You need to run a second low voltage circuit to each thermostat. The original circuit going from one thermostat to the next remains more or less as-is connecting the three locations in series. This is reconnected to the controlled contacts of a relay installed at each thermostat location instead of to the thermostat itself. The second circuit going to each thermostat is controlled by the thermostat to activate the indicator light and the relay coil.
 
  #5  
Old 08-04-15, 02:55 PM
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The circuit is 120V AC, can you make a diagram, because these thermostats behave like a switch (relay), two temrminals (spst) while the temperature is below a limit, they are closed, once the temperature passes the limit, it opens and the complete circuit is turned off.
I know what you mean, but i cant visualize it, thanks
 
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Old 08-04-15, 06:10 PM
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Last edited by AllanJ; 08-04-15 at 06:41 PM.
  #7  
Old 08-04-15, 10:48 PM
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If you only have a SPST at each thermostat then what you want to do is almost impossible.
Not impossible but close.

What kind of distances are we talking here ?
You have five thermostats in a series loop and all five must be closed for the circuit to work.

If that was a job that was handed to me I'd run a three conductor cable to each thermostat location. It would be low voltage control. I'd remove the 120v wires from the thermostat and put them on a relay. I'd use 12vdc on two of the controls wires to activate the relay by using the stat as the switch. The third wire would be used to send a 12v signal back for an indicator light.

This would require.......
A 12v power supply
5) 12v indicators
5) SPST relays with the coil voltage the same as the control voltage.
You could use 24vac as the control voltage too...... allows longer runs with less voltage drop.

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A quickee sketch
 

Last edited by PJmax; 08-04-15 at 11:49 PM.
  #8  
Old 08-05-15, 04:56 AM
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Thanks for the help, i will try it like that.
 
  #9  
Old 08-05-15, 06:06 AM
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Here is a diagram for adding indicator lights to the thermostats. The lights show which thermostats are calling for heat but no heat is forthcoming unless all thermostats call for it.

A separate circuit feed (positive and negative, or hot and return, shown as black and white) must be brought to each thermostat location to control a relay and also light up an indicator lamp.

Any voltage can be used for the separate circuits but the voltage has to be suitable for operating the relay coils and also the indicator lamps.

The separate circuits can all have a common power source.

Optionally (as suggested by the previous diagram) wires may lead away from each thermostat location to go to indicator lights all in yet another location.

This solution is mainly for illustrative purposes. There is considerable expense involved in adding more wires and adding relays.
 
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Last edited by AllanJ; 08-05-15 at 07:36 AM.
  #10  
Old 08-05-15, 06:33 AM
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Thanks for the diagram, those relays are spst or dpdt?
Also the way i see it, the thermostats are the control circuit, they determine if the circuit its open or closed, a relay on place of the thermostat will always be closed. Thanks for the help
 
  #11  
Old 08-05-15, 06:50 AM
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The relay contacts would probably be SPST and normally open since I guess you are using just one set of contacts on each thermostat which for two wires would be equal to SPST.

This project converts a single stage control to a two stage control. (Or maybe it is already a 2 stage control which is being converted to a 3 stage control.)

The new setup has the thermostat turning the light and the relay on and off. The relay in turn does what the thermostat used to do, make or break a portion of the original 120 volt series circuit.

At each thermostat location it is a simple 2 stage control; both stages are switched on and off together. You can think of all thermostats together as a complex 2 stage control after the project is completed. The second stage (the original series circuit) does not actually go on until a certain combination of first stage switch positions (namely all of the thermostats) are on.

By 3 stage I mean that, for all I know, the existing 120 volt series circuit being converted to stage 2 controls another relay (whose contacts would become stage 3) as opposed to power the heater itself.
 

Last edited by AllanJ; 08-05-15 at 07:37 AM.
  #12  
Old 08-05-15, 07:00 AM
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The thermostats are currently connected in series so i would had to rewire everything, but i think it will work.
Basically the thermostats are now in parallel, cause thats the best way to control each one individually and turn on or off the individual lights.

I will need to connect everything to the same 120V AC power source.
The thermostats and relays can use the same power source as the heating system, 120V AC?

Thanks for all your help
 
  #13  
Old 08-05-15, 07:17 AM
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If you want to rewire the thermostats in parallel, changing the control system so any one of them will turn the heating system on, then you would not need relays.

You may still need to rewire the thermostat boxes to have at least one 3 wire cable or two 2 wire cables so you have a neutral and also source power and power out to the heater at each box.
 
  #14  
Old 08-05-15, 07:34 AM
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Exactly, there are more than 10 thermostats limiting temperature at diferent parts of the furnace, thats why it needed to be in series and if only one thermostat opens, it turns the furnace off, but using relays it can be rewired as you wrote.

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Thanks for your help AllanJ, PJmax and ibpooks
 
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