Nest + Honeywell ra832A + Hydrostat 3200
Good Morning All-
I was hoping for a little help here. I'm having some difficulty installing the Nest 3rd Gen Learning T-stats on this system. I originally had regular 18/2 to both locations but pulled a new 18/7 to the locations to provide for AC in the future. I under stand that the Z terminal in the 3200 does not act as a C terminal so I installed a small 120>24v step down transformer and wired the a terminal to Red (Rh) and the New "C" to the blue as shown. The Nests even after a full charge will not recognize the voltage and "see" the C wire or register 24v on the Rh. Even if I try to utilize the just the 2 wire ability of the nest they will not see the voltage and just die after a while.
Any ideas? Wiring Diagram included.
Thank you
Comments
-
The Nest may need the Rh and Rc terminals jumpered.
But
I see another problem. You have the W from the thermostat going to one of the T terminals on the 832A — but nothing going from the thermostat to the other T terminal. You need a wire from Rh to that other T terminal — without that, the 832A has no way of energizing its relay to make anything else happen.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
Try This
Wire the RC from the thermostat to Aux Transformer.
Wire RH from the thermostat to Relay T terminal.
Not sure if this will work, But it is worth a try.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
1 -
Replace the RA832A relays with R8845s. The 8845 has a Common terminal that will complete the circuit the Nest needs.
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
2 -
Agree that will work …but you already have the 24 VAC transformer (you don't need to purchase anything else) so try the rewire first. You may need to change some parameters in the set up section of the Nest. And you never need to jumper the EC and RH on a Nest as Jamie Hall has suggested. That happens automatically in the set up menu …and you don't want that on this wiring option.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
0 -
Well some headway, Now the error code has moved from E74 to E79. I was able to boot it up and restart it initially, but as soon as the setup completed it threw out the E79 at me. It says the C wire has no power on it and that should be the way it is supposed to be, due to it being the defacto neutral conductor in the circuit. Am I incorrect? or correct on that assumption?
0 -
It appears that you're getting Rh and C from two different transformers. I'm sure the Nest will not like that.
I don't think you'll be able to use the 832 without some unauthorized surgery to get to the point AFTER the relay where it returns to the transformer. If you do that, you don't need the new transformer.
See figure 2
You can see how the 8845 has a terminal for C right before the transformer. This is the surgery you'd need to perform on the 832 to get to the common for the Nest
0 -
I am assuming that you tried this wiring diagram:
If you did this diaram, and there is 24 VAC from this transformer connected to Rc and C on the Nest thermostat, then there is a missing wire or wire connection somewhere.
If you just placed a jumper from RC to RH like this diagram, then you will not get the result you are seeking. This will not work.
Use the top diagram.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
0 -
Yes, the step down transformer is a constant hot , it is not switched. But with this wiring in the above Diagram as soon as I connect rh the coil closes for the pump without the nest in it's base
0 -
Try swapping the Rc and the C on the Nest base and see if that makes a difference
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
0 -
That would be a lot better than sending power from one transformer to another.
0 -
If you tried it the way in your first post, you could've damaged the sub base.
0 -
Reversing those just gives me an E72 error now
0 -
OK then you need ot go the isolation relay route
You can either purchase 2 Taco SR501 circulator relays (or the R8845 as @Steamhead suggested)
Or you can purchase 2 RIB relays: part number RIB U1C. I will give you that diagram since the Rib Relays are less expensive and you won't need to replace and rewire the R832A circulator relays.
Sorry the rewire didn't work. The isolation relays will.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
0 -
ONE MORE IDEA
Put your wires back the way you originally had them and try this
Connect a wire from R on the thermostat (already near the boiler) to the unused T on the R832A like the orange wire in my new diagram above.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
0 -
Your first diagram with the twin RIB relays is excellent and will work.
Your second diagram will absolutely not work because you have sent 24V from the external transformer to the 832 which already has 24 V at the T terminal.
DO NOT WIRE IT THIS WAY.
0 -
Are you working with a new 24 volt AC transformer and not a 24 volt DC transformer?
0 -
24v AC secondary
1 -
Not exactly @LRCCBJ. It does not have the return path to make that problem you indicated. It is just like a 3 wire zone valve where the #2 terminal shares both transformers. I think it is worth a try.
A on transformer to R on thermostat thur microprocessor load to C on thermostat with return path to the B on transformer is a separate circuit (shown highlighted in Blue)
Transformer in R832A to T. From R832A T to R on thermostat to W on thermostat on call for heat back to other T on R832A to the relay coil in the R832A to the return path back to transformer in the R832A is a separate circuit. (shown highlighted in Green)
They just share R on the thermostat and don’t interfere with each otherHere are both circuits on the same diagram.
Blue is the external transformer circuit.
Green is the R832A internal circuit.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
0 -
I agree. The problem might occur when someone has to replace a transformer later and gets R and C reversed. This is way too easy to do, and will blow out both transformers. Keep your 24V circuits totally separate and this will not happen.
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting1 -
Not exactly @LRCCBJ. It does not have the return path to make that problem you indicated. It is just like a 3 wire zone valve where the #2 terminal shares both transformers. I think it is worth a try.
It seems counterintuitive to me that you can connect both transformers positive side together without issues. But, if it can be done on the Taco zone valves, you might as well give it a try. The Nest is quite sensitive to such deviations from the norm.
I like your Rib solution much better. Far less risk today and in the future as Steamhead noted. The additional cost is minimal.
0 -
RIBs installed... just cap off the blue and white black?
0 -
the blue and white black?
Say what……………?????
0 -
Relay came with 6 leads.
0 -
You were originally correct.
The blue and the white/black get capped.
0
Categories
- All Categories
- 86.3K THE MAIN WALL
- 3K A-C, Heat Pumps & Refrigeration
- 50 Biomass
- 419 Carbon Monoxide Awareness
- 75 Chimneys & Flues
- 2K Domestic Hot Water
- 5.4K Gas Heating
- 93 Geothermal
- 156 Indoor-Air Quality
- 3.4K Oil Heating
- 64 Pipe Deterioration
- 922 Plumbing
- 6.1K Radiant Heating
- 373 Solar
- 15K Strictly Steam
- 3.3K Thermostats and Controls
- 50 Water Quality
- 39 Industry Classes
- 47 Job Opportunities
- 17 Recall Announcements