HTP Munchkin 926 0-10v control

Teemok

Has anyone used this kit 7250-374. I'm guessing it is just a $230 wiring change kit were the return sensor is dropped for a 0-10v input. I found this below 926 instructions for the Elite boiler that doesn't seem to need a kit due to a jumper on a sub-board. I know I need to change programing option 17 in the 926

I'm investigating replacing a failed vision3 board with the Tekmar 294. The dirty way is converting all the boilers to 0-10v and running individual wire pairs for each 0-10v modulation signal.

Or the clean way, using the factory A+B+ground RS485 BUS wiring and the tekmar modbus output. I'm not confident the Tekmar 294 (rs485 capable) will talk correctly to the 926 boards like the vision3 RS485.

Any thoughts or experiences?

mattmia2

I use a 10v crestron dimmer on the 10v input of my uft-100 to call it for some zones that are controlled by a crestron processor. the 10v is unlikely to break with a firmware change on something and much easier to troubleshoot than serial.

Teemok

@mattmia2 I expect I'll be going the 0-10v route. That means I need conversion "kits" for the boilers. I'd like to know exactly what's in kit 7250P-374. I may just pull some molex plug pins from a parts bin and test out my theory with a lightly fused 9v battery. If the kits turn out to be $230 for $5 of pins and instructions valued at $225. I'll make my own "kits" The tekmar Rs485 either works or doesn't. I'm not going down the "why" rabbit hole. 0-10v also means I can start replacing Munchkins as they fail and the system will work with a mix of new and old boilers.

mattmia2

If you can find a picture of the kit that will tell you if it is some electronics or just a breakout. I'd use resistors instead of a fuse that way it will limit the current instead of shorting something then blowing the fuse because it shorted (although a 9v doesn't have much current available so it damaging something is unlikely)

Teemok

No pics I can find. Two descriptions: wiring harness, control box and…. interface adapter kit.

Both sound vague. Likely the harness is a couple wires with a pins/ connector for the control box and instruction to cut and cap x8-7 and how to change the settings.

VinceBlade

I have that board, just purchased it for my project doing the same thing. Board had four resistors, two caps, and one transistor of some sort. The instructions say the unit can also be used for something called Boiler boosting. Six wires come out of the box. Two wires get plugged into empty slots on the boiler controller Molex connector. Two wires can be used for 0-10V boiler control or two wires for boiler boosting. I plan to use this board to get my Tekmar 403 controller communicating to my Munchkin via 0-10V tomorrow. Will almost be as good as my old Vision2 system that died earlier this year when done, I hope!

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Teemok

@VinceBlade That's cool. Maybe a labeled shot of the wires and molex for the record. 😁 I don't know enough to make an informed guess but a wild one is easy. 0-10v to pwm?

VinceBlade

Munchkin 0-10V Adapter.pdf

VinceBlade

My project was replacing my Vison 2 controller system that died because of a power surge caused by the power company replacing a pole transformer this past summer. My main problem was that I have three zones using mixing valves, and I could not find any boiler controllers that could manage three independent zones with mixing valves. At least, not without redoing all my plumbing work, which I did NOT want to do. So, my solution was to use a Tekmar 403 controller, and drive all three zone valves in parallel. My main problem was how to feed the Tekmar zone temp sensing with only one input. I used a TECO PLC that I programed to feed the Tekmar the zone I wanted temp sensing when heat was called. So far, it is working as planned, and with the final addition of being able to have the Tekmar communicate with the Munchkin via 0-10V for modulation, I think the system should work well. This is a picture of my creation to replace my broken Vison 2 unit.

VinceBlade

This is my wall of plumbing that I did not want to redo.

VinceBlade

The transistor on the board is a C556B W71 unit if the helps.

VinceBlade

FYI. The Tekmar 403 has documentation to work with the Munchkin. I found the documents online for it, and so that is why I chose this solution. The only requirement was to use this adapter board for it to communicate correctly.