Wiring Nest with U1 wire
#1
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Wiring Nest with U1 wire
I just bought two Nest learning thermostats for my new house, and am having problems installing the downstairs one. The thermostat replacement upstairs was fairly easy as I only had to match the wires. The downstairs unit has wires in the U1 terminal, and don't see a place for them in the nest thermostat. I went up in the attic, and traced the wire to where it goes. Pictures attached below
Thermostat Wiring
HVAC Control Board
U1 wire leading to this device
Thermostat Wiring
HVAC Control Board
U1 wire leading to this device
#4
In order to come up with a work around..... you'd need to know how your old stat is controlling it.
In other words.... when does it open and for how long.
In other words.... when does it open and for how long.
#6
Ok. In heat or A/C or both ? I don't know what climate you're in and how much fresh air you require.
It could be wired to open with the blower running or open when the heat is on.
It could be wired to open with the blower running or open when the heat is on.
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I live in Houston, so I we get a lot of humidity here. I went in the attic, and turned on Heat, and A/C individually which triggered the vent to open both times. It even turned on with just the fan on. What do the numbers on the actual fresh air damper mean?
#8
That's a Honeywell M847D-VENT "tru-zone" normally closed fresh air actuator.
The numbers refer to how far the damper opens. 3 = half way open.
M874D manual (pdf)
The numbers refer to how far the damper opens. 3 = half way open.
M874D manual (pdf)
#14
The board number is HK42FZ053 (CEPL131071-20)
If you connect the brown (vent) wire to the G terminal..... the vent will open when the blower is in FAN ON mode or A/C. If you put the brown wire on the W terminal..... the vent will open when the heat was on.
To have it open with heating and cooling...... you'd need a 120vAC relay or a 120vAC - 24vAC transformer. There is a terminal on the board called EAC. (electronic air cleaner). This terminal gets 120v whenever the blower runs.
Probably easiest to use a 24vAC transformer. Many places sell them.
24vac transformer.
The black connects to EAC 1 terminal. The white lead to neutral.
The two wires from the vent connect to the screw terminals.
If you connect the brown (vent) wire to the G terminal..... the vent will open when the blower is in FAN ON mode or A/C. If you put the brown wire on the W terminal..... the vent will open when the heat was on.
To have it open with heating and cooling...... you'd need a 120vAC relay or a 120vAC - 24vAC transformer. There is a terminal on the board called EAC. (electronic air cleaner). This terminal gets 120v whenever the blower runs.
Probably easiest to use a 24vAC transformer. Many places sell them.
24vac transformer.
The black connects to EAC 1 terminal. The white lead to neutral.
The two wires from the vent connect to the screw terminals.
#20
Sure. You can use an Intermatic ST01 timer. It's electronic and runs for several years on its own internal battery. It could switch the vent directly. You can get 24vAC from the furnace or air handler.
Available in many home improvement stores and the like.
Intermatic ST01
Looking around on Ebay...... there are tons of timers. Here's one...
Timer
Available in many home improvement stores and the like.
Intermatic ST01
Looking around on Ebay...... there are tons of timers. Here's one...
Timer
#22
That timer needs and switches 120v. So if you were to use that..... you'd need a small 24vAC transformer that the timer would turn on.
#24
Sure.... that will work. Install the transformer on the side of a deep 4" square (1900) box and put the timer in a 1900 decora plate.
#25
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https://www.intermatic.com/en/timer-...ll-timers/st01 is this the same one you posted? Only you reason I ask because the model has a K after it.
#27
The K after stands for the three way timer. You only need single pole.
I posted the box and the plate. The transformer attaches to the box and the vent connects to the 24vAC terminals. The only additional thing needed is power to the box. You could use a power cord in the side of the box thru a connector.
I posted the box and the plate. The transformer attaches to the box and the vent connects to the 24vAC terminals. The only additional thing needed is power to the box. You could use a power cord in the side of the box thru a connector.
#30
Bring hot and neutral into the box.
Connect the neutral/white to the transformer white.
Connect the hot wire to one lead of the timer.
Connect the other lead of the timer to the black of the transformer.
Connect the damper to the 24vAC terminals on the face of the transformer.
Connect the neutral/white to the transformer white.
Connect the hot wire to one lead of the timer.
Connect the other lead of the timer to the black of the transformer.
Connect the damper to the 24vAC terminals on the face of the transformer.
#32
I don't know where power is around your furnace. If it's easier...... mount the transformer to the furnace or furnace safety switch and switch the 24vac leads instead of the 120v.
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Hot = EAC 1
Neutral = ?
Neutral ---- > Transformer White
Hot ----> Timer Lead
Transformer Black ----> Second Timer Lead
Damper Leads ----> Transformer 24vAC
Does that look correct?
Neutral = ?
Neutral ---- > Transformer White
Hot ----> Timer Lead
Transformer Black ----> Second Timer Lead
Damper Leads ----> Transformer 24vAC
Does that look correct?
#34
Oh....ok. You're going to have the furnace and the timer control the damper.
Looks correct. There are extra neutral connections on the main board. You can use any of them.
Looks correct. There are extra neutral connections on the main board. You can use any of them.