C Wire Install - Honeywell Aquastat L8148E

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Old 09-14-19, 09:31 AM
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C Wire Install - Honeywell Aquastat L8148E

Hi All! I have a few quick questions on a C wire install for a smart thermostat on the following setup…

Dunkirk gas fired furnace with hydronic heating
Honeywell Aquastat L8148E - also an external transformer for second zone valve
Honeywell V8043F1135 zone valves.
Two wires - Rh and W

I currently have three zone valves wired but only use two heated zones, each to their own thermostat (one was for an old hot water heater). I’m currently only looking to replace one of the two thermostats with a smart thermostat; installing an Ecobee 3 on Zone 1 only.

2 wires are connected to the transformer in the Aquastat running to Zone 1 as follows:
> The Tv is connected to the W of the thermostat (white wire)
> The T is connected to the RH of the thermostat (red wire)

2 wire are running from external transformer running to zone 2 (and tied into zone 3 that is not currently used) as follows:
> Red wire to C
> White wire to R (Load)

I understand that I need to do the following inside of the Aquastat:
Thermostat/Wire/Aquastat
RH ---/---RED---/---TV
W----/--WHITE-/---T
C----/--OTHER-/---W or Z

Questions:
Once I rewire to this configuration, do I need to rewire the zone valves?

Once i rewire inside of the Auqastat, does that impact the external transformer that is running to zone 2 and do i need to change that wiring as well?

Do I have to rewire anything? Can I just leave wiring as is and grab a C wire connection from a zone valve or the external transformer? If so, where do I connect the C wire to?

Any help, tips, feedback, etc., is greatly appreciated!! Thanks in advance!!

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Last edited by PJmax; 09-14-19 at 10:17 AM. Reason: resized pictures
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Old 09-14-19, 10:20 AM
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Welcome to the forums.

Are you sure your thermostat for zone 1 connects to the aquastat ? It shouldn't.
It should connect to the zone 1 zone valve. The two zone valves should be wired so that they both are connected to the aquastat to start the pump.

There will be a C wire in the zone valve wiring.
You need three wires to the thermostat. Do you have that ?
 
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Old 09-16-19, 07:00 AM
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Hello and thank you! This is a great forum!! Yes, you're correct, the thermostat i'm replacing is wired to the zone 1 valve. The two zone valves are connected to the aquastat.

I currently only have two wires to the thermostat, RH - Red and W - White. I'm going to run a third wire for the C, just unsure where to connect it?

I did some testing with a multimeter from the external transformer on Aquastat (pic #3) to the zone valve, results are as follows:

Transformer load side (white wire) to white wire on zone valve = 0v
Transformer load side (white wire) to red wire on zone valve = ~26v
Transformer red wire to red wire on zone valve = 0v
Transformer red wire to white wire on zone valve = ~26v

And thank you for resizing the pictures above, I resized them before I loaded however I guess they needed to be smaller.
 
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Old 09-16-19, 09:14 AM
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This diagram is typical wiring for a Honeywell zone valve. My transformer is labeled R and C strictly as a reference. Your transformer is labeled R and C but they might not be accurate.

TR (transformer) is the common terminal.
TH (thermostat) is the W line from the stat.
TH/TR is a blind terminal (nothing connected inside) and is used to connect the R from the transformer and the R from the thermostat together. Many times this is done with a wirenut and that terminal is not used.

When your stat only used two wires..... connection color was unimportant.
Now with the addition of the C wire.... your stat connections must match the diagram.

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Old 09-16-19, 03:59 PM
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Thanks for the guidance and information, it's greatly appreciated!!! Installed all new 18/3 wire, rewired everything to the zone valve as per the diagram (it was previously not wired to the standard color coding). New Ecobee5 smart thermostat is installed and operational!!
 
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