Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Help with Cross Manifold wiring installation

I am confused about how to wire the CM devices. I think I know; but I am just not positive.

I was told that I must not apply power to the control inputs because it will damage the controller. This single point is driving this post. It is a more complicated discussion than it probably needs. But I am real concerned I may screw up.

Normally, CM inputs are direct connected thermostats. In my system, the inputs to the CM controllers will be from multiple Tekmar 369 controllers. The only connection to thermostat demand is through the Tekmar controllers. The Tekmars normally operate relays to feed operating valves on the manifold. In my case it will need to feed the CM controllers. The relays in the Tekmar have terminal blocks for the connection to the "valves". The relay terminals have an output to the controlled device. They are organized as six terminals with each pair sharing a common connection for the pair. That common connection can be either power or a system ground. Thus I need to define what that common wire should provide to the CM controllers. I can provide (normal) 24 VAC power or a common (ground goes to all Tekmar devices) to the base CM controller. The common appears to be the ground plane for the controller.

Then we get to the problem.

There are three CM input wire connections for every valve. Just ignore the valve part. It is also unusual, but not involved in the issue. These contacts are for operating the controller. They receive the demand generated by the Tekmar controllers.

There are three wire connections available for each controlled device on the CM controller. They are labeled R, W, and C. I have attached an image of the control documentation.

My understanding:

COM - connection may or may not be involved with my connections. Not used for 2 wire connections. Might be involved.
RED - seems to be power. Which contradicts what I have been told about power input. It also appears to sit on a bus that spans all of the RED connections and is isolated from the board ground plane. Presumably, RED provides bus power to all of the inputs. Probably 24 VAC.
WHT - seems to be the active switching wire. It can be extended to adjacent input sets, without an additional RED connection.

My conclusion:

COM may or may not be connected to the grounding system of the Tekmar controllers. Somewhere there needs to be a common system ground between CM and multiple Tekmar devices. CM provides an isolated wall wart to provide 24 VAC to the board. That needs to have a ground common to the Tekmar system. The COM on the power connection and the COM on the input connections seem to be the same. All Tekmar controls have a system ground.

WHT appears to service the trigger signal from individual external switches. Voltage (or lack of voltage) not specified. Needs to have a system common relationship.

RED seems to be the power supply for the control inputs. Voltage 24 VAC? This appears to have to be an external source. There is already an external 24 VAC supply connected to the overall power input for the board. Why are these not the same power system? RED is isolated from the board ground.

Question - what do I connect to what. I have several CM devices. Even if I damage just one; it i expensive.


    EBEBRATT-Ed Member Posts: 15,517
    I see your issue. Others that may have work wit these controls may know something I don't know but I am a licensed electrician so I am going to take a shot.

    Your have R, Common and W on the Cross control. You have common zone 1 and zone 2 on the tekmar. (other additional zones will be wired the same way)

    R on the Cross control will be your 24 volt power.

    I would wire R from the cross control to the common terminal on the tekmar for zone 1 & 2. Then zone 1 on the tekmar will go to the "w" for zone 1 on the cross control and zone 2 on the tekmar will go to the "w" for zone 2 on the cross control.

    R for zone 2 on the cross control and common on the cross control are not used.

    For every 2 zones you wire you only use 1 of the red terminals on the cross control

    Repete for your other zones.
  • Harold
    Harold Member Posts: 249

    Just to provide feedback on what I have found

    I finally got (I believe) correct information and understanding. I have been quite wrong. I over-thought things on top of everything else. I have received enough information to feel secure in using a multimeter on various parts of the CM.

    Had I done it the most (in my mind) apparent way, I would have caused damage. The direction of power flow and voltage is not what I thought. What EBEBRATT-Ed said is correct.

    CM RED to power bus for each pair of relays used on the Tekmar, CM WHT to individual associated Tekmar relays. The sort of tricky thing is that the RED is getting power from the CM, and it appears to be 12 VDC. I had it in my head that the Tekmar was going to power the inputs on the CM. I was dead wrong in that perspective. EBEBRATT-Ed was not.

    Bottom line: RED from CM to only unpowered individually used pairs of relay power supply points on the Tekmar. Each of these attachment points power 2 relay outputs using the WHT CM wires. The 24 VAC Tekmar power must not be connected to any power point being used by the CM.

    There is still the COM terminal on the CM. It appears to be 24 VAC for "3 wire" thermostats. Not my problem.

    EBEBRATT-Ed Member Posts: 15,517
    edited March 2019
    Yes the common terminal would be used if you had thermostats that needed 24v power to operate. Glad you got it figured out.

    24 volt wiring isn't easy I think more difficult that power wiring. Using multiple conductor cables with colors that don't always match makes it difficult to keep in your head.

    Best way for me, I can get easily fouled up is to sit down with the parts and pieces and the spec sheets and make a rough diagram before I start
  • Harold
    Harold Member Posts: 249
    I tried that. A number of times in different ways. See Attachment.