Re: Pilot relay on HVAC control board

On Mar 3, 6:41 pm, Spehro Pefhany <speffS...@xxxxxxxxxxxxxxxxxxxxxxx>
wrote:
On 3 Mar 2007 12:40:59 -0800, the renowned jimlave...@xxxxxxxxx wrote:





I have a Viconics HP727 controller board in a swimming pool heatpump.
The circuit I'm concerned with is the one that controls the 'pilot
relay' for the compressor contactor.
The pilot relay uses a 12vdc coil. It's contacts are 15amp / 24vac.

This board monitors thermostat, pool temp, water flow sensor and
compressor high/low sensors. IF the water is flowing AND the
thermostat is calling for heat AND the freon sensors are reporting OK,
THEN the board will energize the 'pilot relay' coil. When the coil
energizes, it closes the load-side contacts which are 24 VAC and those
in turn energize the contactor coil and the compressor starts.

This board has gone through two pilot relays in a month. I replaced
the original with the exact same part. I've seen other threads on
this board talking about driver circuits of these miniature relays.
It looks like there's more to the driver circuit design than you'd
think. I'm not sure if a capacitor is used to assist the circuit to
provide enough power to energize the relay's coil or not. But
something on that board has caused the coils of two relays to run hot
enough to open up. Both relay coils were open when tested with a
multimeter.

I don't have the schematic of this board. Should I just chock it up to
'something failed' and buy a new board?

Sorry if this is off-topic. I'm a novice (can you tell?).

What does the coil voltage measure when it is energized (just a quick
measurement on a cheap digital meter is close enough)?

Is the environment where the relays are located particularly hot?

What is the relay part number and manufacturer?

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
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Spehro,
My relay is a Hasco Relay part number = KLT1C12DC12

The voltage going to the relay was 13.20 volts.
I soldered an LED across the coil connections to verify when I had
power. I also soldered a switch across the load-side contacts. When
the LED illuminated, I turned the switch on. The compressor started
and I noticed the voltage to the coil at that time was 12.72.

One more thing. The only resistor that I could see that was wired in
series to the coil was one with Brown/Black/Brown - Gold stripes
(100ohm). I check it. It measured 100ohms.


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