JLD-612 to control gas valve

[bedek]

Have scoured the documentation and this forum for information on setting up a gas valve to heat liquid and hold temperature.

All the information I read is on controlling an electric heater. Those can be pulsed when getting close to temperature so there is no overshoot. But you can't have momentary pulses for gas as it will never light.

I'm using a SSR and OutY set to 2.

Do I adjust the "ot" Control Period to a much higher value??

Or am I way off and should be using a different OutY altogether??

[richiem]

My opinion (given without knowing anything about the particulars of your application and so may be untrustworthy) is that you want to use the HY (hysteresis) mode so that the JLD612 and the SSR function like an ordinary thermostat with a few temperature degrees of separation between on and off. See Outy mode 3 on the bottom of page 3 of the manual and fig. 3 on the top of page 4.

This will not give you proportional control, but with gas heat, the time to warm up is probably much shorter than with electric heat, and so the temp stability should be pretty good.

Using the Hy temp spread will keep the gas on long enough to light and heat, and depending on heat loss, will keep it off long enough to avoid "mixed messages" to the valve. The amount of Hy spread will depend on your particular application.

[bedek]

Thank you for the reply richiem

I'd done some more poking around and found a PID from Auber. Their SYL-2362 is almost the exact same thing as the 612 ( maybe the same but different label ) . Their manual has a lot more detail so I was able to get to the same the same suggestion you have made.


In fact I can probably go one further than your idea and by pass the SSR as I'm only controlling a 24 volt gas valve that draws very few amps. This by using OutY 4 J2 as the hot direct to the transformers 220V side.

The 612 manual calls OutY 3 and 4 differential. Auberin's calls the same mode On/off control output.

[richiem]

Careful about amperage ratings -- I wouldn't use the 612's internal relays for more than 1 amp or so, even though they are rated for 3A. The 24V gas valve is probably usually run off of a 24V transformer's secondary winding, so use that as your power source, not the primary winding.

Good luck.