WEL 1-Wire Combo Module.
Contents
1. WEL 1 Wire Combo Module User Guide Rev 1 0 11 23 09 The WEL 1 Wire Combo Module combines two remote 1 Wire functions gt An 8 channel Thermostat Sensor module gt A 2 channel Pulse Counter module These modules operate independently and only share a common PCB and 1 Wire connector These functions are described separately in the following text P ilci j TRATES m SOUICO IR OWEN 8 channel Thermostat Sensor module On occasion WEL users would like to be able to know WHY their HVAC system is working when it does rather than just watching passively and trying to guess the cause In these cases the real need is to be able to monitor the various calls being made by thermostats and other system inputs These calls are commonly made by switching 24VAC control circuits so the WEL needed a way to sense when 24VAC is present on a pair of wires Since 24VAC is not compatible with the WEL or the 1 Wire bus a special input module was needed The WEL Combo Module can sense a wide range of input voltages by using optically isolated input circuits An On Off indication is provided for each input These independent inputs can sense the presence absence of AC or DC in the range of 9 to 24 volts Since the inputs are optically isolated they can be connected to totally different pieces of equipment without the concern of ground loops or stray electrical paths causing problems Each input comprises an LED and current limit resistor2. ing the WEL supply Raw DC to the Combo Module and using the Combo Module s on board regulator This keeps the WEL s local 5V supply clean and compensates for any voltage drop on the 1 Wire bus To do this connect the RED bus wire to the WEL s V Raw Output terminal on J3 and set the Combo Board s Power Source Select jumper to 12V This puts the regulator into the circuit The Combo Module provides a three terminal screw connector for hooking up the pulse inputs The center terminal is a shared Ground GND and the Pulse 1 P1 and Pulse 2 P2 inputs are on either side they are labeled on the PCB The P1 and P2 inputs have 1K pull up resistors tied to 5V so to signal a pulse the external hardware must short the input connector to GND Note that these inputs are NOT isolated so care must be taken not to connect these inputs to equipment that is connected to the mains electrical ground This will turn the 1 WIRE bus into a giant lightning rod Eg most PCs are grounded but most Watt meters are not Pulse Counter software setup Once the Combo Module is attached to the 1 Wire bus it will be found next time the WEL performs a bus scan This will happen automatically the next time the WEL reboots or it can be performed manually for several of the WEL s web pages Just click the Scan Bus button When the WEL discovers the Pulse Counter inputs it adds them to the device list as a pair of devices The first device will be t
3. roller and move the incoming thermostat wire from the HVAC terminal to one side of a channel on the Combo Board Then run a wire from the other side of the channel back to the original HVAC controller terminal Now the signal passes through the Combo Module Just do this with control signals not the common ground or power Thermostat Sensor software setup Once the Combo Module is attached to the 1 Wire bus it will be found next time the WEL performs a bus scan This will happen automatically the next time the WEL reboots or it can be performed manually for several of the WEL s web pages Just click the Scan Bus button When the WEL discovers the Thermostat inputs it adds them to the device list as a block of 8 devices The first device will be type 41 and the rest will be type 14 The 8 devices correspond to input channels 1 to 8 With the default scaling the resulting value for each input will be either 0 no voltage sensed or 1 voltage is sensed The following screen capture is an example of how the Thermostat inputs might appear on your device list In this example four inputs are active with names One final consideration is whether or not the On Off state of the thermostat signal needs to be reversed flipped Depending on how your HVAC controller is wired it s quite possible that there will be 24VAC present if the thermostat is NOT calling for an action and then this voltage will go to OV when the call is active This
4. simply means that you need to configure the WEL to reverse the on off indication This can be done by re calibrating this input If you go to the WEL s Calibrate page and locate the input channel in question simply set the Scale to 1 0 and the offset to 1 0 This will have the effect of converting a0 toa 1 anda 1 to a 0 In the example above ExHeat is set to invert the on off condition of the input The photo below shows the wiring hookup for this example Inputs 1 R 2 O amp 3 G share a common ground Y but input 5 is a dedicated pair of wires B 2 channel Pulse Counter If a user needs more pulse counter inputs than the WEL board provides or if the pulse signals are not located near the WEL it s desirable to be able to add additional channels on the 1 Wire sensor bus The Combo Module does this Pulse Counter Sensor hookup The Combo Module communicates to the WEL using the 1 Wire bus so the Black Ground and Yellow Bus wires need to be connected The Pulse Counter function ALSO requires external power to operate to facilitate high speed counting so it is necessary to use the third power wire of the 1 wire bus or to provide local power The Pulse counter hardware includes a 5V regulator and backup battery so either raw DC or Regulated 5V can be supplied to the board This will depend on what you have available at that location Unless there is a compelling reason otherwise I recommend hav
5. so there IS a small impact on the signal being measured so this must be considered when used with more advanced digital HVAC controllers Thermostat Sensor hookup The Combo Module communicates to the WEL using the 1 Wire bus so the Black Ground and Yellow Bus wires need to be connected However the Thermostat Sensor function does not require any external power to operate so it is NOT necessary to use the third power wire of the l wire bus See the Pulse Counter section for more about the Power connection Each Thermostat input requires a pair of wires to be connected 8 Pairs of input connectors are provided in a set along the long edge of the board Channels 1 and 8 are indicated at either end of the connector block Typically the inputs will be wired in parallel with across the thermostat wires eg bridging C and Y1 In a 24V system this will cause 6 6mA of current to flow though the Sensing LED Since this is not enough to active a relay it will usually not have any impact on the normal operation of the HAVC system However in some digital systems the current drawn by the sensing LED is enough to activate an HVAC function In this case the two Combo Inputs terminals should be wired in series with the thermostat control signal This will require breaking the control path at some point and wiring it in and out of the Combo Module input One easy way to test this is to mount the Combo Module next to the HVAC cont
6. ype 29 and the second one will be type 6 These correspond to P1 and P2 respectively With the default scaling Scale 1 0 Offset 0 0 these devices will read the number of pulses counted each minute NOTE the values for these devices only update ONCE A MINUTE so don t panic if you don t see an immediate change You can change the scale to convert the count into any other engineering unit like Gallons per hour Watts or even RPM You can also set the Accumulation letter for either device on the devices page to calculate total Gallons or WattHours See the WEL user manual for more details on Accumulations
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