seadoggie01
Posts: 7
Joined: Wed Jul 24, 2019 9:52 pm
Location: Florida, USA

Pi 3 - Thermostat Wiring Issue

Thu Aug 08, 2019 10:04 pm

I've recently decided to upgrade my Thermostat from an un-program-able one to one powered by my new Pi 3. I purchased a relay hat from Amazon and decided to set it up today. I wired it up using instructions I found on the internet (https://camo.githubusercontent.com/ffbe ... 4c2e706e67) which was the same as other 4 wire thermostat setups I had seen elsewhere. I wired it using the jumper cables supplied with the RaspPi... which I fear may have caused the issue later. When I connected the wires, everything was good. So I wrote a simple python script to turn the AC on. I heard it start up and rejoiced. I realized I forgot to have the fans come on, so I stopped the script, added a delay before turning the fans on, and ran it. The AC started back up. After the 60 second delay (I heard you charge up the AC before turning on the fans, and let the fans run for a minute after the AC goes off, but I'm not sure where), the fans came on, bringing with them a burning smell. I yanked all the cords out and put the original thermostat back in.

TLDR: Setup Pi relays with jumper cables and got a burning smell after the fans came on.

Any idea what could make that burning smell? Was this because I used jumper cables to connect the relays?

trejan
Posts: 571
Joined: Tue Jul 02, 2019 2:28 pm

Re: Pi 3 - Thermostat Wiring Issue

Thu Aug 08, 2019 10:17 pm

seadoggie01 wrote:
Thu Aug 08, 2019 10:04 pm
Any idea what could make that burning smell? Was this because I used jumper cables to connect the relays?
Something was wired wrong somewhere and got very hot. Check everything for a melted or burnt section. Be careful with the HVAC wires as some systems use line voltage.

pcmanbob
Posts: 6934
Joined: Fri May 31, 2013 9:28 pm
Location: Mansfield UK

Re: Pi 3 - Thermostat Wiring Issue

Thu Aug 08, 2019 10:24 pm

From your post it's obvious you have no electrical qualifications , I suggest you refrain from making any more changes to you mains electrical system before you end up burning your house down or killing some one.

Oh and the reason you had a burning smell is because you used incorrect cable to make you connections or you connected it wrong.

Jumper wires are not ment to carry mains voltage or mains currents.
Last edited by pcmanbob on Thu Aug 08, 2019 10:27 pm, edited 2 times in total.
We want information… information… information........................no information no help
The use of crystal balls & mind reading are not supported

seadoggie01
Posts: 7
Joined: Wed Jul 24, 2019 9:52 pm
Location: Florida, USA

Re: Pi 3 - Thermostat Wiring Issue

Thu Aug 08, 2019 10:25 pm

trejan wrote:
Thu Aug 08, 2019 10:17 pm
Something was wired wrong somewhere and got very hot. Check everything for a melted or burnt section. Be careful with the HVAC wires as some systems use line voltage.
The weird thing was that the smell only came after the fan turned on, and my wiring setup didn't smell... I thought at least.

RonR
Posts: 515
Joined: Tue Apr 12, 2016 10:29 pm
Location: US

Re: Pi 3 - Thermostat Wiring Issue

Thu Aug 08, 2019 10:34 pm

R1 (G) = Fan Control

R2 (Y) = Heat Pump (compressor) Control

R3 (O) = Swich-Over Valve (cool vs heat) Control

If you didn't activate R3 when you activated R2, your HVAC would be in heating mode instead of cooling mode. If heating mode hasn't been used for a while, the air coming from your vents when you activate R1 often has a slight burnt smell.

User avatar
solar3000
Posts: 1051
Joined: Sat May 18, 2013 12:14 am

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 12:12 am

I hope you are not running 250 volts 10 amps through those relays.
Antikythera

RonR
Posts: 515
Joined: Tue Apr 12, 2016 10:29 pm
Location: US

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 12:50 am

solar3000 wrote:
Fri Aug 09, 2019 12:12 am
I hope you are not running 250 volts 10 amps through those relays.
HVAC control lines to a thermostat are 24v A/C and low current.

wh7qq
Posts: 1326
Joined: Thu Oct 09, 2014 2:50 am

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 2:13 am

The OP provides us with no detail as to how he is connected to any of the components... RPi, relay, or HVAC system so there is no basis for a comment other than that of @pcmanbob and no basis to assume that smell relates to anything the OP cobbled up. If the OP wishes help, complete details of his setup are needed including any wiring direct to the RPi, the relay, and the thermostat wiring. A hand sketch of the hookup would be most helpful. Otherwise we are completely in the dark.

RonR
Posts: 515
Joined: Tue Apr 12, 2016 10:29 pm
Location: US

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 2:37 am

wh7qq wrote:
Fri Aug 09, 2019 2:13 am
The OP provides us with no detail as to how he is connected to any of the components... RPi, relay, or HVAC system so there is no basis for a comment other than that of @pcmanbob and no basis to assume that smell relates to anything the OP cobbled up. If the OP wishes help, complete details of his setup are needed including any wiring direct to the RPi, the relay, and the thermostat wiring. A hand sketch of the hookup would be most helpful. Otherwise we are completely in the dark.
You obviously didn't read the original post:
seadoggie01 wrote:
Thu Aug 08, 2019 10:04 pm
I've recently decided to upgrade my Thermostat from an un-program-able one to one powered by my new Pi 3. I purchased a relay hat from Amazon and decided to set it up today. I wired it up using instructions I found on the internet (https://camo.githubusercontent.com/ffbe ... 4c2e706e67) which was the same as other 4 wire thermostat setups I had seen elsewhere.
The color-coding and lead lettering shown is precisely that used on all HVAC systems, and the wiring is connected to the Normally Open contacts on the relays as it should be. All the OP needs is a temperature sensor and he's well on his way to building his own HVAC thermostat.

You don't appear to have any knowledge in this area, which is the cause of your being completely in the dark.

seadoggie01
Posts: 7
Joined: Wed Jul 24, 2019 9:52 pm
Location: Florida, USA

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 2:45 am

Edit: Looks like I was ninja-d :)
solar3000 wrote:
Fri Aug 09, 2019 12:12 am
I hope you are not running 250 volts 10 amps through those relays.
Per the Amazon specs, I could. (If I understand correctly). Though as I understand now, probably not with jumper cables.
wh7qq wrote: A hand sketch of the hookup would be most helpful. Otherwise we are completely in the dark.
I wish I could, but I yanked everything out, as I mentioned. I posted the diagram that I copied. Other than that, there were only jumper cables making the connection between the relays and the wall. (I left the thermostat wire mounted and connected the jumper cables there).

User avatar
solar3000
Posts: 1051
Joined: Sat May 18, 2013 12:14 am

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 2:54 am

Ah, very good. I'm glad you are aware. maybe you can snap a photo for us to gawk at.
Antikythera

seadoggie01
Posts: 7
Joined: Wed Jul 24, 2019 9:52 pm
Location: Florida, USA

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 2:58 am

solar3000 wrote:
Fri Aug 09, 2019 2:54 am
Ah, very good. I'm glad you are aware. maybe you can snap a photo for us to gawk at.
A photo of what???
I yanked everything out
As I've mentioned twice now. I wanted to reduce any damage I could possibly have caused, so I pulled the plug.

User avatar
davidcoton
Posts: 4141
Joined: Mon Sep 01, 2014 2:37 pm
Location: Cambridge, UK

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 8:47 am

RonR wrote:
Fri Aug 09, 2019 2:37 am
The color-coding and lead lettering shown is precisely that used on all HVAC systems, and the wiring is connected to the Normally Open contacts on the relays as it should be. All the OP needs is a temperature sensor and he's well on his way to building his own HVAC thermostat.
  1. Never assume that.
  2. It is certainly NOT true outside the USA. European systems commonly use 220/240V control signals, with no (enforced) standardised wiring colours. This does mean that non-USA contributors may take a very cautious approach, which those only familiar with USA systems may take as an over-reaction.
Signature retired

wh7qq
Posts: 1326
Joined: Thu Oct 09, 2014 2:50 am

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 8:20 pm

RonR wrote:
Fri Aug 09, 2019 2:37 am
You obviously didn't read the original post:
The color-coding and lead lettering shown is precisely that used on all HVAC systems, and the wiring is connected to the Normally Open contacts on the relays as it should be. All the OP needs is a temperature sensor and he's well on his way to building his own HVAC thermostat.
You don't appear to have any knowledge in this area, which is the cause of your being completely in the dark.
Not only is RonR wrong in the above, he is insulting and rude. There is NO reason to expect "all" HVAC systems to be wired the same and so we are supposed to read the mind of whoever wired it up to know...sorry those skills aren't part of mere mortal's tool kit. Thermostats tend to be wired remote from the relay/HVAC unit and depend on the available wire/knowledge and care of the installer Further, color coding should never be solely relied upon for connection information because adherence to it can be highly variable. I did read the post and it assumes knowledge of all sorts of things about color coding and the methods used to connect the RPi to the thermostat or the relay...it makes a big difference that can cause your RPi to die instantly or not work at all. If you don't like the advice requested here, you are free to ignore it and go your own way as you obviously will, without snarky and insulting posts for time given in good will.

RonR
Posts: 515
Joined: Tue Apr 12, 2016 10:29 pm
Location: US

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 10:26 pm

wh7qq wrote:
Fri Aug 09, 2019 8:20 pm
There is NO reason to expect "all" HVAC systems to be wired the same and so we are supposed to read the mind of whoever wired it up to know...sorry those skills aren't part of mere mortal's tool kit. Thermostats tend to be wired remote from the relay/HVAC unit and depend on the available wire/knowledge and care of the installer Further, color coding should never be solely relied upon for connection information because adherence to it can be highly variable.
Actually, there IS a reason to expect all HVAC systems to be wired the same since it's an industry standard. And the skills required to wire up a thermostat IS considered to be part of a mere mortal's tool kit. There's a multitude of replacement thermostats available at places likes Lowes and Home Depot that are simple to install by mere mortals because the wiring IS industry standard. The danger to the installer is minimal because it's low voltage (24v A/C) and very little current is involved. All of the control lines expect to be fed 24v A/C via simple contact closures in the thermostat. Consequently, if you wire it incorrectly, the unit may not start up or run correctly, but any kind of damage is highly unlikely. Thermostats are consumer replaceable items.

User avatar
davidcoton
Posts: 4141
Joined: Mon Sep 01, 2014 2:37 pm
Location: Cambridge, UK

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 10:30 pm

RonR wrote:
Fri Aug 09, 2019 10:26 pm
Actually, there IS a reason to expect all HVAC systems to be wired the same since it's an industry standard. And the skills required to wire up a thermostat IS considered to be part of a mere mortal's tool kit.
Again, that may be a reasonable assumption in the USA. It is certainly NOT reasonable in the rest of the world. Promoting such opinions without suitable warnings could lead other forum members into dangerous situations, including fatal accidents and burnt buildings.

Please think a bit more about the consequences of what you write.
Signature retired

RonR
Posts: 515
Joined: Tue Apr 12, 2016 10:29 pm
Location: US

Re: Pi 3 - Thermostat Wiring Issue

Fri Aug 09, 2019 10:37 pm

davidcoton wrote:
Fri Aug 09, 2019 10:30 pm
RonR wrote:
Fri Aug 09, 2019 10:26 pm
Actually, there IS a reason to expect all HVAC systems to be wired the same since it's an industry standard. And the skills required to wire up a thermostat IS considered to be part of a mere mortal's tool kit.
Again, that may be a reasonable assumption in the USA. It is certainly NOT reasonable in the rest of the world.
That's a fair statement, but it was not an assumption as the OP's message is vert clear:

Location: Florida, USA

User avatar
davidcoton
Posts: 4141
Joined: Mon Sep 01, 2014 2:37 pm
Location: Cambridge, UK

Re: Pi 3 - Thermostat Wiring Issue

Sat Aug 10, 2019 8:39 am

RonR wrote:
Fri Aug 09, 2019 10:37 pm
davidcoton wrote:
Fri Aug 09, 2019 10:30 pm
RonR wrote:
Fri Aug 09, 2019 10:26 pm
Actually, there IS a reason to expect all HVAC systems to be wired the same since it's an industry standard. And the skills required to wire up a thermostat IS considered to be part of a mere mortal's tool kit.
Again, that may be a reasonable assumption in the USA. It is certainly NOT reasonable in the rest of the world.
That's a fair statement, but it was not an assumption as the OP's message is vert clear:

Location: Florida, USA
Clearly, not everyone notices the location of the OP (it's not in the message itself, it's in the profile) when reading YOUR messages.
Signature retired

seadoggie01
Posts: 7
Joined: Wed Jul 24, 2019 9:52 pm
Location: Florida, USA

Re: Pi 3 - Thermostat Wiring Issue

Sat Aug 10, 2019 12:15 pm

davidcoton wrote:
Sat Aug 10, 2019 8:39 am
RonR wrote:
Fri Aug 09, 2019 10:37 pm
davidcoton wrote:
Fri Aug 09, 2019 10:30 pm


Again, that may be a reasonable assumption in the USA. It is certainly NOT reasonable in the rest of the world.
That's a fair statement, but it was not an assumption as the OP's message is vert clear:

Location: Florida, USA
Clearly, not everyone notices the location of the OP (it's not in the message itself, it's in the profile) when reading YOUR messages.
And clearly, I cannot choose the cup in front of me! :D

pfletch101
Posts: 510
Joined: Sat Feb 24, 2018 4:09 am
Location: Illinois, USA

Re: Pi 3 - Thermostat Wiring Issue

Sat Aug 10, 2019 9:31 pm

RonR wrote:
Fri Aug 09, 2019 10:37 pm
davidcoton wrote:
Fri Aug 09, 2019 10:30 pm
RonR wrote:
Fri Aug 09, 2019 10:26 pm
Actually, there IS a reason to expect all HVAC systems to be wired the same since it's an industry standard. And the skills required to wire up a thermostat IS considered to be part of a mere mortal's tool kit.
Again, that may be a reasonable assumption in the USA. It is certainly NOT reasonable in the rest of the world.
That's a fair statement, but it was not an assumption as the OP's message is vert clear:

Location: Florida, USA
I'm sorry! I am located in the US, but one of the first things I learned about electrical wiring is that you can never assume that the person who put in the wiring that you are looking at/modifying followed code and/or industry standards. You should always check before doing anything that depends on how it was done. This applies to low voltage (e.g. telephone, bell, or thermostat) wiring as well as to mains wiring.

Thankfully, most competent electricians/installers do follow standards, but the very fact that thermostat wiring is generally low-voltage (in the US) and tends to be regarded as 'fair game' for meddling by owners and tradesmen with limited skills and knowledge makes it more likely to be deviant. Every set of instructions for installing a replacement thermostat that I have read (and that is quite a few) recognize this. They typically warn the reader that wire color coding is not to be relied on and (usually) suggest that wires be detached from the terminals on the existing thermostat one by one and marked according to the terminal labelling on that thermostat.

Return to “General discussion”