I'm trying to get the nest thermostat to functione with the Honeywell Aquastat L8148e. There is a stand alone air handler in the attic. My wires are Rh and w1 from the Aquastat and Rc and G and Y1 from the air handler. I get 24 volts at the aquastat between the Rh wire and W . Zero volte between the white wire T at the Aquastat and at the thermostat. 24 volts between Rh and C at the thermostat. When I connect the C wire to the nest, it tells me it recognizes that a wire is there but there is no power. Without the c wire I get an E30 code saying there is no power to the y1 terminal. the air conditioner will not work. Is there something wrong with the Nest or do I need to make some other adjustments?

 

Welcome to the forums.

What C wire ? You don't have one in your description.

The C wire must come from the air handler.
Rh and W1 is strictly for the heat.
You need a fourth wire to the air handler.

If you wanted to go with a poor mans C wire...... you change wiring at both ends.
At the nest...... Rc is Rc - Y1 is Y1 - G wire becomes C.
At the air handler.... Rc is Rc - Y1 is Y1 & G and G wire becomes C.

In other words.... you lose the FAN ON position on your thermostat. The G wire becomes your C wire.

 

I'm sorry I didn't completely explain. I ran an extra wire from the thermostat to the Aquastat on the boiler and attached it to the W terminal on the Aquastat. Are you saying that I must get the C wire from the air handler and not the Boiler?

 

The air handler is in the attic and the wire connections are difficult to see. I did notice there was a block where the wires connected that was numbered 1-5 or 6. Is there any way to tell which connection would be for the C wire. Extra wires are already there if I just knew where to connect one.

 

Hi, can you post a pic of the control board at the AH so we can see what you have.
Geo

 

Here are three pictures of the terminal. I don't know what the red and white wires on # and #7 are. I have Blue,Green and Red at the thermostat with the white and Yellow Free. The second picture is the condensate pump

 

I'm not happy with the way the pictures showed, but I don't know how to fix them. Hopefully you can see the situation and advise me. I have a free yellow and white wire, if I just knew where to connect the wire at the air handler I think I would be in business.

 

Hi, it appears that #s 6&7 go to the condenser unit outside , there also appears to be a transformer there with a Black and Blue wire coming off of it, where does the Black wire connect? Do you have a volt meter? If measure between the Black &Blue, you should get 24 VAC, if that is the case you can connect one of the spare conductors to the Black and the other end to C on the Tstat
Geo

 

It's a little tricky posting pictures.

That looks like an old system. That will more than likely have the C line grounded. Connect your white wire to any screw on the metal frame. Give that a try..... it can't hurt anything.

 

If I get the C wire properly installed, where should I check for 24 volts? At the red wire or the blue wire? The blue wire is Y1 in the thermostat and the red wire is Rc.

 

Between the Red and C C will be which ever color wire you connected to the common at at the AH.
Geo

 

Thanks for the replies. I really appreciate your help. This system belongs to my daughter. I’ll have to go to her house and give it a try. I’ll be sure to let you know how everything worked out. Thanks again

 

Had 24 volts between the blue and black wires. I connected a wire to the black wire and connected it to the C terminal on the nest. All is working well right now. Thanks for all the help. You guys are awesome

 

Good job. Thanks for letting us know how you made out.

 

Ya, put yourself in for a raise.
Geo