I'm trying to stave off some PG&E butthurt this
summer by getting the economizer to work on the
air conditioner.

Briefly, the air conditioner is like most in that
it has a fan, heat, and cold control wires along
with a 28vac line to energize the appropriate
functions. It also has a control line that will
move vanes and allow the fan to draw air from the
outside into the building. This is the economizer.

I discovered it's existence while changing the
filters. I verified that it works, but it has
never been hooked up to a controller.

The plan is to run fan+economizer at 5am to 7am
to cool the building down to 65 degrees. This will
hold off having to start the air conditioner in
the morning.

My plan was to install a second thermostat to
control the fan+economizer control wires and program
it to come on between 5 and 7. The problem is that
all the inexpensive thermostats I can find hard
connect the fan and aircon wires together all the
time when in cool mode. If I tried to use two of
these thermostats, I'd get fan+aircon+economizer
on whenever either would come on.

Now I know I could build a box to fix the problem.
The problem is that the thermostat is in a very
public location and there's not a way to reroute
the wires. I'd like something that is inexpensive
and looks nice.

On 5/15/2011 4:04 PM, Jim Stewart wrote:
I'm trying to stave off some PG&E butthurt this
summer by getting the economizer to work on the
air conditioner.

Briefly, the air conditioner is like most in that
it has a fan, heat, and cold control wires along
with a 28vac line to energize the appropriate
functions. It also has a control line that will
move vanes and allow the fan to draw air from the
outside into the building. This is the economizer.

I discovered it's existence while changing the
filters. I verified that it works, but it has
never been hooked up to a controller.

The plan is to run fan+economizer at 5am to 7am
to cool the building down to 65 degrees. This will
hold off having to start the air conditioner in
the morning.

My plan was to install a second thermostat to
control the fan+economizer control wires and program
it to come on between 5 and 7. The problem is that
all the inexpensive thermostats I can find hard
connect the fan and aircon wires together all the
time when in cool mode. If I tried to use two of
these thermostats, I'd get fan+aircon+economizer
on whenever either would come on.

Now I know I could build a box to fix the problem.
The problem is that the thermostat is in a very
public location and there's not a way to reroute
the wires. I'd like something that is inexpensive
and looks nice.

Why not just hook it up as it should be?

The you would have no visible extra wiring, enthalpy control (will be
overridden when it is cool outside but the humidity is high) & it would
come on anytime needed (not just in the morning)

MikeB

On 5/15/2011 4:04 PM, Jim Stewart wrote:
I'm trying to stave off some PG&E butthurt this
summer by getting the economizer to work on the
air conditioner.

Briefly, the air conditioner is like most in that
it has a fan, heat, and cold control wires along
with a 28vac line to energize the appropriate
functions. It also has a control line that will
move vanes and allow the fan to draw air from the
outside into the building. This is the economizer.

I discovered it's existence while changing the
filters. I verified that it works, but it has
never been hooked up to a controller.

The plan is to run fan+economizer at 5am to 7am
to cool the building down to 65 degrees. This will
hold off having to start the air conditioner in
the morning.

My plan was to install a second thermostat to
control the fan+economizer control wires and program
it to come on between 5 and 7. The problem is that
all the inexpensive thermostats I can find hard
connect the fan and aircon wires together all the
time when in cool mode. If I tried to use two of
these thermostats, I'd get fan+aircon+economizer
on whenever either would come on.

Now I know I could build a box to fix the problem.
The problem is that the thermostat is in a very
public location and there's not a way to reroute
the wires. I'd like something that is inexpensive
and looks nice.

Don't change it at the thermostat, put your modifications adjacent to
the other end of the wires down at the furnace.

you don't need a thermostat, you need a timer, and a relay to kick the
A/C off and the economiser on when the timer says to. Sounds like a
DPDT relay fired by a 24 hour timer will get you there.

Stuart

BQ340 wrote:
On 5/15/2011 4:04 PM, Jim Stewart wrote:
I'm trying to stave off some PG&E butthurt this
summer by getting the economizer to work on the
air conditioner.

Briefly, the air conditioner is like most in that
it has a fan, heat, and cold control wires along
with a 28vac line to energize the appropriate
functions. It also has a control line that will
move vanes and allow the fan to draw air from the
outside into the building. This is the economizer.

I discovered it's existence while changing the
filters. I verified that it works, but it has
never been hooked up to a controller.

The plan is to run fan+economizer at 5am to 7am
to cool the building down to 65 degrees. This will
hold off having to start the air conditioner in
the morning.

My plan was to install a second thermostat to
control the fan+economizer control wires and program
it to come on between 5 and 7. The problem is that
all the inexpensive thermostats I can find hard
connect the fan and aircon wires together all the
time when in cool mode. If I tried to use two of
these thermostats, I'd get fan+aircon+economizer
on whenever either would come on.

Now I know I could build a box to fix the problem.
The problem is that the thermostat is in a very
public location and there's not a way to reroute
the wires. I'd like something that is inexpensive
and looks nice.

Why not just hook it up as it should be?

And how would I do that? All I have to
work with is what I described.

The you would have no visible extra wiring, enthalpy control (will be
overridden when it is cool outside but the humidity is high) & it would
come on anytime needed (not just in the morning)

MikeB

Stuart Wheaton wrote:
On 5/15/2011 4:04 PM, Jim Stewart wrote:
I'm trying to stave off some PG&E butthurt this
summer by getting the economizer to work on the
air conditioner.

Briefly, the air conditioner is like most in that
it has a fan, heat, and cold control wires along
with a 28vac line to energize the appropriate
functions. It also has a control line that will
move vanes and allow the fan to draw air from the
outside into the building. This is the economizer.

I discovered it's existence while changing the
filters. I verified that it works, but it has
never been hooked up to a controller.

The plan is to run fan+economizer at 5am to 7am
to cool the building down to 65 degrees. This will
hold off having to start the air conditioner in
the morning.

My plan was to install a second thermostat to
control the fan+economizer control wires and program
it to come on between 5 and 7. The problem is that
all the inexpensive thermostats I can find hard
connect the fan and aircon wires together all the
time when in cool mode. If I tried to use two of
these thermostats, I'd get fan+aircon+economizer
on whenever either would come on.

Now I know I could build a box to fix the problem.
The problem is that the thermostat is in a very
public location and there's not a way to reroute
the wires. I'd like something that is inexpensive
and looks nice.

Don't change it at the thermostat, put your modifications adjacent to
the other end of the wires down at the furnace.

you don't need a thermostat, you need a timer, and a relay to kick the
A/C off and the economiser on when the timer says to. Sounds like a DPDT
relay fired by a 24 hour timer will get you there.

I realized that I could hack a second thermostat
to do just that. I opened it up, made some cuts
and jumps so that the three contacts of the double
throw relay come out to the terminals. I connected
the fan to the main thermostat fan, the compressor
to the normally closed contact of the economizer
thermostat, the economizer to the normally open
contact and ran the common back to the compressor
terminal of the main thermostat.

Everything works normally unless the economizer
thermostat is active. Then the economizer is
energized instead of the compressor.

On 5/15/2011 6:25 PM, Jim Stewart wrote:

And how would I do that? All I have to
work with is what I described.


The 'mizers I've worked on have the control as part of it. What is the
make & model of what you have? The manufacturer should have
documentation online or can fax it to you.

MikeB

BQ340 wrote:
On 5/15/2011 6:25 PM, Jim Stewart wrote:

And how would I do that? All I have to
work with is what I described.


The 'mizers I've worked on have the control as part of it. What is the
make & model of what you have? The manufacturer should have
documentation online or can fax it to you.

The aircon portion was replaced several
years ago and the old economizer remains.

I don't want to go there.

"Jim Stewart" wrote in message
...
I'm trying to stave off some PG&E butthurt this
summer by getting the economizer to work on the
air conditioner.

Briefly, the air conditioner is like most in that
it has a fan, heat, and cold control wires along
with a 28vac line to energize the appropriate
functions. It also has a control line that will
move vanes and allow the fan to draw air from the
outside into the building. This is the economizer.

I discovered it's existence while changing the
filters. I verified that it works, but it has
never been hooked up to a controller.

The plan is to run fan+economizer at 5am to 7am
to cool the building down to 65 degrees. This will
hold off having to start the air conditioner in
the morning.

My plan was to install a second thermostat to
control the fan+economizer control wires and program
it to come on between 5 and 7. The problem is that
all the inexpensive thermostats I can find hard
connect the fan and aircon wires together all the
time when in cool mode. If I tried to use two of
these thermostats, I'd get fan+aircon+economizer
on whenever either would come on.

Now I know I could build a box to fix the problem.
The problem is that the thermostat is in a very
public location and there's not a way to reroute
the wires. I'd like something that is inexpensive
and looks nice.

IIRC the Honeywell T7200xx T7300xx is a programmable commercial /industrial
thermostat that incorporates an economizer function with outdoor temp
sensing ....they're slightly obsolete and so usually available on Ebay.

http://masonsmill.com/Misc/T7300owners.pdf

Variations exist within the model lineup so be sure and do your
research--you probably just want a basic model instead of one with a bunch
of central control and data logging options.