Help c wire

ratio

Huh. The description is pretty precise, it says that whatever's hooked up to the Y1 terminal is drawing too much current. Are you sure you got them exactly the same? IIRC the red & white going out to the condenser were backwards form what I'd usually use. Not sure of that plays a part though.

So, where we're at now is you have a hot, common, & heat call coming from the zone controller, and a hot, common, cooling call & fan call coming from the air handler, right? & we've had a number of different errors, depending on which common is connected? & about 8ish volts between the two commons IIRC. What's the voltage between the two red wires?

Jamie Hall

Well, in your diagram, blue is, indeed, the common or ground wire for that piece of equipment, and red (terminal 5 of the plug) is constant on, fused, 24 volts AC.

One distinct possibility -- which I don't recall seeing mentioned -- is that your heating equipment and your air conditioning equipment are on different 120 volt circuits -- and that the two 24 volt transformers which you are playing with are out of phase. You have an exactly 50% probability of that happening, if they haven't been checked. If that does happen, then the 24 volt line from the AC will be out of phase with the 24 volt like from the heating equipment -- and there will be 48 volts between them.

To which, I think, the Nest would object, and quite properly so. Exactly which combination of errors would occur I don't know -- the Nest's internal circuitry does not seem to be easily available, if at all -- but I doubt that it would be good.

Anytime there are two 24 volt AC transformers involved in control circuitry, it is absolutely essential that they be checked for being in phase, and if not, rewired to be correct.

diego168

Hi ratio look this picture shows red and white coming out of the actual condenser. That red wire connects to the blue which is common ( terminal 6) . And the white wire coming of condenser connects to the yellow which goes to the Y on the thermostat.
Ratio I have 2 nest E that only control heating in those I used the common that we did from the boiler side ( which works fine). My other thermostat Is the nest learn that controls both ac and heating I’m trying to use the common from the ac system.
Do you mean that the red and white might be reversed and that could affects things?


Jamie, yes my boiler is using one transformer and the AC is using another one.
Yes terminal 5 ends up being my Rc wire.
Jamie how can I check if the 2 transformers are in phase. I will go read up on this subject.

Jamie Hall

Check the voltage between the two "R" wires. Should be zero.

ratio

I mean that the wires may have gotten crossed somewhere accidentally the second time you connected it, since you got a different error from the thermostat.

diego168

I checked the voltage between rc and rh without unplugging them from the nest back plate as there was a little tiny copper stick out. The voltage difference was 19.8 volts.

ratio

@Jamie Hall, 8.8 volts common to common and 19.8 volts hot to hot. That sounds like they might be on opposing phases, but not really? AFAIK the Nest should be able to handle that, as it can't be so uncommon that it wasn't a design consideration, esp. with something aimed to be as 'user friendly' as the Nest.

@diego168, is your incoming power 120/240 volt single phase, or two legs of a 120/208 three phase system? (Measure between the two high voltage wires at the condenser, on the highest AC volts range.)

Jamie Hall

They do appear to be out of phase, but not 180 -- and looking again at that circuit diagram, I see that the 24 VAC trasformer is dropping from the 220 or 208 lines directly, not connected to neutral. You may be right, @ratio .

Either way, there doesn't appear to be any convenient way to get them to play nicely together. Interesting.

Should the Nest be able to handle it? Probably, or at least some design thought should have been given to the possibility. Is it? Did the wizards of Silicon Valley think of it? As to the second question -- in my experience with other hardware (and software) from that part of the world, probably not.

At this point, @diego168 , you best bet may be to hope that the power stealing of the Nest does work, and leave the C wire out completely. If it doesn't, however, I'd go to the wall wart option of a completely independent 24 VAC supply for the Nest.

diego168

> @ratio do you mean to measure outside at condenser or at the air handler.
Back when we started getting the common from the heating transformer we had switch the 24v leads. It’s used to be white to r and red to c. Now it’s red to r and white to c.
would this have to do anything with the volt differences.

Jamie Yeah I’m starting to give up I just get obsess graying to solve things

EdTheHeaterMan

I have experienced this, sometimes Rc and Rh wiring with 2 transformers the Nest has no problem, other times error codes.

When all else fails I use an isolation relay. Disconnect the RH and W from the Nest to the zone valve, Place a wire from the Air Handler wiring on Nest W terminal to operate a relay, with a set of normally open contacts, in the air handler. Complete the circuit of the relay coil with a wire to Common. you need to supply the relay like RIB https://www.energycontrol.com/Functional-Devices-RIBU1C?gclid=Cj0KCQjwoaz3BRDnARIsAF1RfLc816svpTvP7TFflFg_DpbfqyCPr6_FTvKVS48AWuOJ8Y5ExLtU4FwaAvKyEALw_wcB

Now the Nest is using only one transformer and is getting power from R and has a C to charge the internal battery The W is operating a "HEAT" relay

From the NO contacts of the relay, you can power the zone valve as if the relay contacts are thermostat contacts.

ratio

@EdTheHeaterMan has the best solution, I think, or at least a real solution that can be implemented in just a few minutes, vs tracking down a problem that could be located anywhere from the incoming power to inside the Nest.

diego168

Thank you Ed and ratio!
@EdTheHeaterMan i understand what you mean And the diagram. The relay on the link you posted will it work with my set up I mean does it have adequate rating.
In this diagram Of the relay I’m not sure which terminals I would use to connect the white and red coming of the zone valve. Or where the c would attach and the white one that would end up at the thermostat.
I actually have 2 more extra wires behind my thermostat so I think I can attach the red and white coming of the zone valve to this 2 wires and up to the air handler to the relay. Oh but then I’ll be missing one wire to send down to the w on the thermostat. I guess I would have to fish one more .
Does it matter where I locate the relay up at the air handler or at boiler.

EdTheHeaterMan

i have pasted the relay diagram on the and labeled the pasted diagram. I also labeled the original relay illustration with the color code of the RIB relay

The parts I covered up with the RIB diagram do not change

diego168

Started mapping this out and if I place the relay in the basement where the zone valve is I don’t need to fish new wires. Example: I can take what used to be the Rh wire connect it to one of the unused wires behind thermostat that go up to air handler and connect it to the transformer 24v. Those 2 wires would be connected with a wire nut then tuck behind wall, only issue is that there is no junction box behind thermostat so that wirenut would be free floating. Do you guys find that an issue. Probably not up to code.
Or I could solder it or crimp it

ratio

This is low voltage, so no jbox is required; and wirenuts (suitably sized, check the wirenut packaging to see what size & count of wires are permitted) are fine.

diego168

@EdTheHeaterMan Now that I’ll be using the transformer in the air handler is this transformer going to be able to handle properly or will it get hot?

EdTheHeaterMan

No problem with this overloading the transformer. Remember you won't be using all three relays at the same time. The call for heat will only energize one relay. A call for cooling energizes two relays. Fan and Compressor relays/contactors.
I have consulted Capt. Obvious on this question

I do like the fact that you were able to think "outside the box"... The AHU Box and put the relay near the zone valves
There may be hope for you yet!

EdTheHeaterMan

So, I have been thinking about your statement: "Started mapping this out and if I place the relay in the basement where the zone valve is I don’t need to fish new wires. Example: I can take what used to be the Rh wire connect it to one of the unused wires behind thermostat that go up to air handler and connect it to the transformer 24v." and wanted to tell you That wire is already there There is no need to connect it again. More than one wire can go to a wire nut. You might even try to put it in the same hole in the Nest. (Only if it is 20 gauge or less). Two 18 gauge wires might be a tight fit. but you can wire nut a short 4" or 5" piece under a wire nut and use that for the thermostat connection.


You already got all the wires you need w/o adding more

diego168

@EdTheHeaterMan
Thanks Ed.
On the first diagram you posted white/blue ended at the W at the thermostat. But on the Second diagram white and blue ends at the common on thermostat.
First diagram white/yellow was supposed to go to 24v from Ac transformer. I’m confused as to which way it should be.

But I understand what your doing in connecting both 2 wires at c which would attach the relay to 24v on the ac transformer side.
I don’t understand why on the latest diagram the ZV still attached to the old transformer ( maybe I’m reading wrong)
I thought I was supposed to disconnect the Zv from heating side transformer. And the 2 yellow wires connect one to the orange and yellow wires that come off the zv connect to the relay. I’ll attach a diagram.

Or on the second diagram you utilize both transformers but put them in phase. ?

I thought we were eliminating the heating transformer and connecting both 2 yellows to the relay. In my second diagram is how the zv is wired now. So if I wire how I’m thinking there is no rc. Doesn’t seem right to me.

EdTheHeaterMan

this is the corrected diagram

But both diagrams would work

Both transformers are on separate circuits. The dotted line in the basement indicates the invisible wall between the different transformer circuits.

Your picture of the zone valve circuit connected to the relay won't work. It is the equivalent of plugging an extension cord into itself. no power source???

picture in your mind's eye connecting a switch to a light bulb. it will never light You show the zone valve connected to a set of contacts. No power source. That is how a relay works. One side is the switch, that's all. The other side is the load. The relay coil is using power from a source

You must connect the power to the switch then the switch to the light bulb, then the light bulb return path of the power source common.

You need to take a course on basic electricity

EdTheHeaterMan

This is elementary stuff for technicians. Understanding how a relay works is key to our discussion. This RIB relay is like a firewall between the AHU transformer and the ZV transformer.

So you have to get your head around the concept of:
Source (battery, house current, load side of a transformer)
Load ( light bulb, line side of a transformer, relay coil, solenoid Coil)
and Control (Toggle switch. Contacts in relay, Contacts in thermostat)
Until you demonstrate that you understand that, all you can do is follow the diagram.

Zman

@Erin Holohan Haskell Have you considered a collection of articles and posts about the dreaded "C" wire? Or maybe a small book in the bookstore similar to "Pumping Away"
I am pretty sure you could create an entire website dedicated to the subject given the number of people "Nest" is confusing.

Erin Holohan Haskell

Zman said:

@Erin Holohan Haskell Have you considered a collection of articles and posts about the dreaded "C" wire? Or maybe a small book in the bookstore similar to "Pumping Away"
I am pretty sure you could create an entire website dedicated to the subject given the number of people "Nest" is confusing.

Great idea, @Zman. We're on it!

diego168

@EdTheHeaterMan thank you for explaining. Yes I agree I should have read about relay first. And yes I’m looking to understand how things work so that I’m not just following the diagram. Thanks again.
Will report once I get the relay

EdTheHeaterMan

That would be awesome to have a @DanHolohan book to go to for electricity. I'm sure he would have the eloquence of Benjamin Franklin and the combined knowledge of Alessandro Volta, Georg Ohm, André-Marie_Ampère, and Heinrich Hertz.

The way Dan, might tell the story of the Electron who walked into a Bar... well all I can say is " it would be Magnetic"

bar magnet pun intended

DanHolohan

Thanks for the good laugh, @EdTheHeaterMan. I was attracted to the bar joke!

diego168

@EdTheHeaterMan so i installed the relay today. Heating worked well. Ac fan on the I got the same error e103. Over current yellow wire. Any ideas could there be something with how the ac is wired.

ratio

It seems like it's something that just happened, it's completely different that the errors we were getting before.

Check all the wiring between the thermostat & the condenser outside, looking particularly for a short, like the wire pinched under a cover or chafing against a sharp edge.

diego168

@ratio e103 is the error the nest gave last time before I switch to the relay set up.
So it seems that With a common wire from the air handler makes the nest complain about the y wire.
Ill check the wires at the condenser see what I can find.
Thank you

ratio

Originally, the error was some kind of 'no power', then after we fooled around with it we got an 'over current' error. Those're kind of opposites.

The over current fault means that something on the Y terminal is using more current than the Nest thinks is appropriate. A short would most likely blow the fuse (although it's possible the Nest can limit the current, I just don't know), but a pinched wire somewhere could be allowing more-than-usual current to flow without blowing the fuse.

diego168

@ratio I’ll check the wires I know the compressor looks old and connections dont look great. Going back to the error on y. When I revert the common wire connections I don’t get an error on the y. Shouldn’t I get that same error always? Regardless of having the a common?
Would the problem be at the wires leading to the nest ? I could try a different wire out of the bundle for a C.
Or would it be the 24v wires that come off the condenser.
This is just how I’m trying to trouble shoot

ratio

Ok, it goes away when you switch the C connection back to the common from the heat?

Describe the connections you have, both when you get the e103 & when you revert the common connection. Tell the wire colors, but also where they connect to. I know you've posted it before, but take a few minutes & look at it again, maybe in the morning after you've not thought about it for a while. It sounds like there's still an interconnect somewhere that's causing us heartache. With the RIB installed like @EdTheHeaterMan suggested, the two system should be electrically isolated, but if we're getting an error, well, maybe we missed something.

At his point, what I'd do if I were on a job, is pull all the wires off, ring them out for continuity & shorts, & rewire it according to our standard wiring scheme. I hesitate to suggest that, however, because it kinda works now, but if you unwire everything it certainly won't work again until it gets wired back up again, correctly.

diego168

I mean no error when I revert to no common wire at all. Just y, w, g, rh and rc. Yeah I’ll work on it tomorrow clean wires at the condenser and depending on that will do another detail diagram. Thank ratio

diego168

@ratio so I check the wires at the compressor and the white and red wires where stripped off their sleeves and then tapped right over by the previous owner. I think rats got to it and ate wires and previous owner out tape over even duct tape in some areas. Im refreshing all the wires at the compressor.

2- The 24v wire that comes up from the compressor to the air handler is made up of 3 wires (w,g,r) green not being used. Interestingly there is continuity between green and white but not between red and white. I think this wire is old maybe when they stapled it to wood it got damaged. I will check end to end continuity to make sure I’m dealing with the correct wires but I’m 99% that it’s the correct wires.

At the air handler The bundle wire that goes to the thermostat is made up of 6 wires. 3 which were not being used (brown, R, W) before I started this adventure 🙄. Brown was the one I used as my common. I unplugged both yellow and brown and check continuity between them and there is continuity which there should not be. the remaining white and red don’t have continuity so I’m going to re arrange based on previous diagram. And will see.

I think it would be good to replace both of this wires entirely but since they are stapled I don’t know how I could run it. Either way I’m glad I checked compressor and fixed the wires it was bad. I don’t know how it was working before.

diego168

@ratio so at last it works with a common wire and no error. The wiring scheme I have is the same one you and Ed said just without the relay. Yesterday when it didn’t work I had removed the relay to keep things as they were prior. today after fixing all the wires I just wanted to try see if that would work. So I didn’t get around to putting back the relay.
I think The problem was the low voltage wiring at the condenser that was eaten by mice.

The bundle wire that connects air handler to thermostat has 6 wires. 3 that were not being used (brown, red white) initially I used the brown as the common and after that we got the error of over current on Y wire. Today I u plugged the yellow and the brown both ends then check for continuity and there is continuity between them. Do you guys think that because the short of the wires from the condenser the brown and yellow might have over heated and burn exposing the copper which is why now there is continuity between them? Or maybe they were just damage somewhere along instalación. As a result of this I ended up no using either yellow or brown. And used the other 2 wires that were not being used.
I think it would be ideal to replace the bundle wires coming from the AC to air handler and the air handler to thermostat. The one that goes to thermostat would be easier but the one coming from the outside would be a pain to fish. Any tips ?

ratio

My guess is that we disturbed the wiring enough to cause a fault at some point where it was right on the edge.

As for pulling the wire, tie the new wire on to the old one & use it to pull the new one in. If it's just taped to the lineset, there's a decent chance it'll work.

diego168

> @ratio said:
> My guess is that we disturbed the wiring enough to cause a fault at some point where it was right on the edge.
>
> As for pulling the wire, tie the new wire on to the old one & use it to pull the new one in. If it's just taped to the lineset, there's a decent chance it'll work.

Do you think I should change them? There is no tape they are stapled to beams so pulling I don thing it’s an option.

Jamie Hall

Staples? Ugh. Amazing how many times staples cut a low voltage wire. Or two. Or three...

Anyway, the best thing to do would be to replace the wires. You really don't know what other faults may be in the bundle, or where. This could be the only one, but...

diego168

@Jamie Hall so that’s common? From whats visible of the wire I can’t see obvious damage. But some of these staples are pinching the wire very tight against the wood.

HVACNUT

If you're going to run new wires, you should invest in something like the Taco ZVC-403 as mentioned earlier in the thread (I forget who) to really clean things up.
Run an 8 conductor wire. You never know.