OK, here is the equipment:

10 yr old Carrier A/C unit with Carrier non-programmable tstat with available connections:

• DO NOT USE
• R
• Y/Y2
• G
• C
• W/W1

25 year old Pensotti oil fired boiler for baseboard heat with a simple Round Honeywell tstat

I purchased a LUX TX1500 to control both units (I hope)

The AC tstat had 2 wire bundles feeding it, RC, Y, and G fed the tstat from one bundle, and the white wire from the second bundle was connected to the C terminal, no other wires were used from the second bundle. (2) terminals were not in use on the AC tstat (DNU, and W/W1).

The boiler was simply hooked up to the tstat with the RH (red), and W (White) wires.

I fished the boiler control wires up through the same hole as the AC control wires.

First attempt failed to provide any cooling (but the fan did run) here was the wiring configuration:

RH to RH (red from boiler wire bundle)
RC to RC (red from AC 3 wire bundle)
(left the factory installed RC to RH jumper in place, this was a mistake)
G to G (green from AC 3 wire bundle)
Y to Y (white from AC 3 wire bundle)
W to W (White from boiler wire bundle
C from the AC 1 wire bundle was taped off

In this configuration, the heat worked, and the fan of the AC unit worked, but the cooling unit did not kick in. After a few minutes the fan kicked off (the Tsats fan setting was on).

Sat down and read the wiring diagram again and noted that I should have removed the RC to RH jumper. After removing the jumper the system still functions exactly as above (no cooling).

Did I "cook" something by having the jumper installed? Where should I look first?

Thanks for the help.

Scott

Does your system have 2 transformers? 1 for the heat/boiler and 1 for the a/c? If not you need the jumper from rc to rh,,

Uhmm, not sure, how can I tell?

As I said, they are currently 2 separate systems, heating , and cooling. I guess there would be 2? One for each?

Thanks for the help.

Scott

It is possible you smoked the transformer on the one system.

See if the thermostat has 24 volts going to it on the RC leg and the RH leg. If not back track and find the problem. You were correct in removing the jumper with a two transformer system.

I do have 24 vac on both the heating and cooling legs (RC, and RH), So I will assume that both transformers are OK. Anything else I should know, or should look for? Should it be working as I've described the wiring? If so, maybe the Tstat is no good.

Scott

Do you have 24 volts coming out of the Y1 at the stat when in the cooling mode? If so the problem is not in the thermostat if not then the problem is with the thermostat.

RC to Y =24vac
RH to Y =11vac
RH to W= 24vac
rc to w = 11 vac

I can only check this with the tstat face plate removed, there are no test points to try and check it while it should be operating.

Scott

You may have to check it at the wiring on the inside unit.