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Discussion Starter · #1 ·
I'm in the planning phase of my garage project and I'm thinking about installing door sensors on each garage door to turn off the heater when they are open.

I will have an electric heater which will be controlled by a low voltage digital thermostat via a 24V relay/transformer.

I'm not sure how to tie in the door sensors wire to the thermostat. See my wiring diagram below.



Thanks in advance
 

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Discussion Starter · #3 ·
Wire the sensors in series with the W circuit
Thanks for the quick response. So both wires from the last sensor should be wired to the W terminal on the thermostat.

Best technique would be to put both sensor wires into a marrette connector along with another wire that would go into the W terminal of the thermostat ? Am I right ?
 

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You would install the switches in series with each other. This would allow either one or both opened doors to turn off the heater.

Disconnect the w wire from the thermostat and connect it to one of the wires on sensor 1. Take the other wire from that sensor 1 and connect it to a wire on sensor 2. Take the second wire from sensor 2 and connect it to the w contact on the thermostat.

I'm assuming these sensors are the normally open type? (They make contact when the magnet is near to it). This being the case then line the switch up with the magnet when the door is in the closed position.
 

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switches need to be in series.... mount a utility box between the doors ceiling high. run a 2 wire bell stat wire to that utility box from the stat...run both switches to the box..connect 2 switch wires together wire nut(they are in series now)connect the remaining door switch wire to the bell stat wires "one each" wire nut....now at the stat remove the W wire ...nut it onto a bell wire and the other bell wire to the W terminal...your done
 

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Taken from your diagram there was only 1 door/sensor... so add another in the same manner and it will work as you like.
 

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Discussion Starter · #12 ·
Thanks to everyone for your help.

My plan is to mount the thermostat on a single gang (utility) box so I would use the utility box to do all the wire connections inside.

Would it be possible to confirm if the diagram below is ok (please note that I didn't wire the C and R terminal in my diagram) ?
 

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Are these switches the same as they use for house alarm systems? Are they an actual switch (snap action switch) and will not reduce ANY voltage? If they are proximity sensors meant for alarms and drop any voltage to the W of the furnace then it can get damaged. I would want a switch that operates a relay (Honeywell R8222 D or K relay) that has a normally open contact and put your W wiring thru that contact.

Basically you get a extra 20 VA 24 volt transformer and run power to those sensors and operate the R8222D relay with them. run your W wire thru the normally open contacts on the relay and it is safe.
 

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Discussion Starter · #14 ·
Yuri
I was thinking about going with a garage door sensor like this one:
http://www.seco-larm.com/pdfs/PI-SM-226LR-3.pdf
It's considered a switch; only on and off are possible.


Are these switches the same as they use for house alarm systems? Are they an actual switch (snap action switch) and will not reduce ANY voltage? If they are proximity sensors meant for alarms and drop any voltage to the W of the furnace then it can get damaged. I would want a switch that operates a relay (Honeywell R8222 D or K relay) that has a normally open contact and put your W wiring thru that contact.

Basically you get a extra 20 VA 24 volt transformer and run power to those sensors and operate the R8222D relay with them. run your W wire thru the normally open contacts on the relay and it is safe.
 

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I did this in my shop years ago.

I used a simple and cheap micro switch that has a short spring lever. The switch is mounted on a bracket fastened to the track and I fabricated a simple arm on the door to trip the switch. When the door is completely shut the normally open/common terminals close allowing the heater to run. I used the wire from these two terminals to interrupt the signal from the thermostat. It's mounted up high just below the curve track so it wouldn't get bumped. Decided to install this after I got home one morning from working the night shift to find my door standing open at -15. Installed almost 20 years ago and it still works perfectly.
 

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I am concerned that you have a proper strong quality switch/contacts. That one is rated for 3 W watts but I don't know the wattage of your circuit. Like iamr's method he used a actual switch which can carry some current w/o arcing etc. When you are using switches and components from alarm systems or garage door openers that are low voltage/low current that is not the same as what a furnace uses, there are safety issues. My system of using a R8222D relay (google it) uses a strong general purpose relay and I used it hundreds of times in the old days for millivolt systems to trigger them with modern 24 volt thermostats. You should be able to go to graingers and get that relay and a basic 120/24 volt 20 VA transformer and mount it in a box and screw the relay onto a beam beside it and run some wires. Use 18 gauge wire (LVT or bell wire and nothing smaller) HDepot has it.
 

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Discussion Starter · #17 ·
Thanks for the feedback.

I'm not an expert so getting your input is helping me a lot.
I have a relay with a built-in transformer between the thermostat and the heater. This one: http://www.aubetech.com/products/produitsDetails.php?noLangue=2&noProduit=42



I am concerned that you have a proper strong quality switch/contacts. That one is rated for 3 W watts but I don't know the wattage of your circuit. Like iamr's method he used a actual switch which can carry some current w/o arcing etc. When you are using switches and components from alarm systems or garage door openers that are low voltage/low current that is not the same as what a furnace uses, there are safety issues. My system of using a R8222D relay (google it) uses a strong general purpose relay and I used it hundreds of times in the old days for millivolt systems to trigger them with modern 24 volt thermostats. You should be able to go to graingers and get that relay and a basic 120/24 volt 20 VA transformer and mount it in a box and screw the relay onto a beam beside it and run some wires. Use 18 gauge wire (LVT or bell wire and nothing smaller) HDepot has it.
 

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That relay is a high current relay to handle the 220 volt high current heater element. You need a different/additional relay to do the 24 volt control side.
 

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Discussion Starter · #19 ·
If I want a reliable solution and would like to avoid a relay on the low voltage side (for thermostat and door sensors) what are my options ?

Thanks again. Much appreciated.


That relay is a high current relay to handle the 220 volt high current heater element. You need a different/additional relay to do the 24 volt control side.
 

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None that I know.

Trained monkey:laughing:
 
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