Impedance of 0-10v control on HTP UFT-100

mattmia2

Does anyone know what the impedance of the 0-10v control input on an HTP UFT-100 is? I am trying to control it with a 0-10v output from a Crestron processor (the device is actually intended to be used with 0-10v dimmers). When I set the output of the processor at 100% I get 5 volts and some change with it connected to the boiler (so it heats to about 50% of the max water temp setting) but if I disconnect it I measure 10v. The measured polarity is correct. I am trying to determine if the new old stock control is bad or if the impedance of the boiler is too low. I have impedance specs for the control, I couldn't find impedance specs for the boiler. I could measure with a milliammeter as well. Is there something weird about the circuitry of the Crestron output that makes it not work right with how the boiler is referenced to ground?

mattmia2

I got an answer, at least a theoretical one, from a crestron programmer. A dimmer works by the dimmer providing voltage and the control loading that source to the desired voltage, so i need something like a pull up resistor or a voltage divider off of the 24v dc crestron supply to make it provide 0-10v to the boiler. i will probably test the theory this weekend.

ratio

Never mind, I reread the first post.

mattmia2

Now i want to know what your question was...

ratio

I was going to say that a pullup to 24 volts doesn't sound quite right, but when I reread everything (after I posted, of course!), I saw where you implied that the output on your controller was a sink, not a source.

IIWM, I'd look around for a schematic of something known working & work backwards from that. Or talk to someone who knows what they're doing.

mattmia2

This seems to work like a charm: