On May 26, 8:34*am, Pointer wrote:
On 5/26/2011 8:01 AM, jamesgangnc wrote:



On May 25, 8:50 pm, *wrote:
On 5/25/2011 5:24 PM, RBM wrote:

* *wrote in message
...
On 5/25/2011 8:22 AM, wrote:
On May 25, 8:05 am, * * wrote:
Have a Little Giant VCMA-15 condensate drain pump with a pan overflow
switch. *The pump has two low voltage connections coming from it which
have been wired together for the 13 years that the installation have
been in the house. *These connection I presume are for the high level
switch in the reservoir tank. *Why are they wired together. *It would
seem to me that both the pan overflow and the high level switches should
be in series with the thermostat circuit. *What is the correct wiring
for this pump? *What am I missing here?

Looking at the install manual online for a VCMA-15ULS there is only
one switch and it has both NC and NO contacts available. * What
you do with either of them is up to the installer depending on the
requirements of the installation. * You would use the NO connection
in the thermostat circuit to turn off the furnace and/or AC if the
water level exceeds the max. *Where you wire it in the thermostat
circuit can determine if it cuts off just heat or cooling or both.

The NC contacts could be used to wire into an alarm system
if you prefer that instead of the cuttoff approach.
Do you have any idea why they have been wired together all this time? By
the way I do not use the alarm but want only the high level shut down to
work. *Also it would seem to me that I would use the NC switch in series
for it would open on high water and shut the unit down. *The pan overflow
switch is separate from the pump and is definitely in series.

**I would guess that they assumed the one limit switch would be sufficient.
Just wire it in series the pan switch

Well this would be fine if there were two wires but how do you put two
wires that are together into a series circuit. *Really need someone with
first hand knowledge of this particular pump/wiring.- Hide quoted text -

- Show quoted text -

Is it possible a well meaning hvac person simply tied these two
together with a wirenut since they were not being used? *The absolute
accurate test would be to use a ohm meter on the switch while manually
moving the float.

I don't think so for the high level switch functioned. *The diagram
shows a com lead which would enable a series connection but there is not
a third wire. *Putting the NC and NO lines in series would shut down the
unit completely.

You can't have both NC and NO without a third common wire.
The manual shows it having 3 wires, but it's possible the manual
is for a newer version.


*The NO line which is an alarm circuit would appear to
have no effect if tied together with the NC line when there is no
alarmfitted as is the case here. *Still puzzled.- Hide quoted text -

- Show quoted text -

As James pointed out a simple test with a VOM meter
or even a battery and light bulb together with moving the float that
works the switch is all that is needed to determine how it works.
If there are only two wires, my guess would be 99% that it's NC
when the water is OK and opens when the water is too high.
That's how you'd want it to work to cut off a furnace, AC, etc.