12VAC smal ice cube relay 1

[wrsharper]

We have some new equipment that is using 12VAC relays powered by 16.5VAC. This is over 30% designed coil voltage. The relays are all hot. The wiring matches the drawing. Is this in the range of voltage tolerance? I searched the internet but was unsuccessful to find the answer so here I am where I get factual and accurate advice.

 

[OperaHouse]

I thought this off label application deserved more than speculation. I too thought that overdirving this AC relay with half wave DC might be enough to hold it in. Took a 24V AC relay out of the box and drove it directly with a variac. Pull in was 18.6V AC as expexted. Put a diode in series and even at 40V it still chattered. So, maybe the diode really isn't in the circuit. A 24V relay is likely to work with the lower current draw through the resistor, but could be on the edge if other circuits draw off this transformer.

 

[waross]

Although the term is not generally applied to relay coils, the X/R ratio will determine whether an AC relay needs more, voltage, less voltage, or the same voltage to pull in on half wave rectified current.
One test will not fit all. It sounds as if your relay was highly resistive. Try your test with a relay with a higher ratio of reactance to resistance and you may get different results.
respectfully

 

[wrsharper]

My feeling is that the circuit is specifically designed for a relay coil with a set impedance. I recently relearned about impedance from another forum at this site. It is a series RL circuit and for it to work as designed it needed a particular relay. The new system was designed around the same principle and they found some off the shelf circuit boards that seemed to fit their bill without any testing. I am sure they will find out in a year or two when the relay bases start cracking and falling apart. I have yet to decide whether or not to send a feed back because this was a pricy installation. Thank you all for the valuable inputs.