Operation of sauna timer not as expected

Other Hardware Motors, Mechanics, Power and CNC
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I have a project going that wanted to "read" the output of a sauna timer. The timer is the Phoenix El-Mec Time switch MS65, but details aren't available to the general public, AFAIK.

I made an HCPL3700VM circuit to detect voltage on the "output" of the timer, and it works fine to detect 120VAC, but I've since realized that the timer doesn't operate the way I thought it would.

The timer runs on 240VAC (in the USA, so L1 and L2 of opposite polarity). You feed it L1 and L2, and a third terminal rises to 120VAC (L1) when the timer is activated.

The part that surprised me is that the "output" is tied to the second input via a resistance of ~8.58kΩ (as measured by a simple multimeter), which sort of "pulls up" (?) the output to around 70VAC (referenced to neutral) and makes my voltage detection circuit believe that the timer is on all the time, since that detection circuit doesn't load the 70VAC output in any meaningful way. When the timer is activated, there is also suddenly a similar resistance between the two inputs. Here is a diagram that illustrates how it operates:

sauna_timer_operation
sauna_timer_operation477×636 14 KB

In the original sauna, the timer "output" is fed directly to a contactor which is also receiving L2 on its other control input, so the contactor control sees 240VAC when the timer is activated, and 0VAC when it is not (since the 70VAC is coming from L2 as well).

I don't really need this part of the project to work, so I'm not going to bother changing the detection circuit to ignore the 70VAC, and I'm just going to leave the timer out of it altogether. I'm just curious about this timer -- I assume this is normal and expected in the world of such timers, but can anyone explain what is going on? I'm not surprised to see the 8.58k somewhere, as there is a motor in the timer and presumably that is why I see that, but I don't understand why a second 8.58k shows up while it is "on" across two other terminals. I guess it could be the coil holding the timer "on", but why would it be the identical resistance as input2-output?

One other detail that may be important: the timer has a range where it is "on", and a range where it is "off" but still counting down -- this allows the operator to have the sauna wait e.g. 4 hours and then turn on for an hour and then turn off. I.e. there are 4 hours where the timer is counting down but still in "off" mode.

Thanks for any insight!

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Mystery things.

Try and post schematics for Your build. Words is not the language to do it.

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Thanks -- but I'm not really wondering about the interaction with the HCPL3700 circuit -- that part works and it makes sense that it reads the voltage as it does -- I'm just asking about the timer itself and why it works the way it does, etc.

But for the record, that schematic is just like here (120VAC version only).

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