We did new HVAC about 3 years ago. At that time, we found information that changing to a NEST thermostat would void our furnace warranty. Just FYI.

You haven’t provided much information to go on. What model ClimateMaster do you have exactly, a ‘Tranquility 27’? Although you seem to indicate no forced air.

I would speak with your installer before installing a Nest or any other T-stat to see if it’s fully compatible. Do ask what this Nest thermostat might not control properly or if any ‘Interface Module’ is required to use a Nest.

A ‘P’ wire might be a ‘Pump’ wire, as in a Circulator Pump control wire. Ask your installers how the Flow Center pumps are controlled that go out to the ground loops.

I’m not saying the Nest won’t work - but careful what you wish for…

IMPO

SR

A little history on Nest....

some guys from apple decided to make a thermostat with no prior HVAC knowledge / or the knowledge of all the various kinds of HVAC systems out there in the 'wild'.

after realizing their blunder, they pumped the company up via 'data collection' attributes and sold it to Google.

Jan 2014: Google buys Nest labs for 3.2 billion.

so who cares right?

Alphabet reluctantly tells investors how much money it's losing on Nest. Smart home gadget maker Nest sold $726 million worth of thermostats, security cameras and smoke alarms last year, but failed to turn a profit — losing $621 million, according to parent company Alphabet's latest quarterly report, published Monday.

What eventually happens when something keeps losing money? Sure Google has a lot of resources to throw at this for a long time... but I think you have to ask yourself some serious questions, going down this road with Google.

Note: Google is a search engine that comprises their income predominantly thru advertising. NOT HVAC controls.

The high end thermostat market is a small market. $250 for a 'self installed' --- with no help, and possibly HVAC equipment destruction attached to it because of installation blunders --- You may have found the thermostat for less than $250...

Ah, the ole we need to get rid of inventory so we can go over and shut the lights off to this experiment we know nothing about... No company is in business to lose money. No matter how big, they are in it to make money.

---- here's some more behind the scenes info------

Nest was founded in 2010 by former Apple executive Tony Fadell, widely credited as one of the creators of the iPod. He launched Nest with Matt Rogers, who helped design the software that powered the iPod and iPhone.

After the acquisition, Fadell’s brash management style clashed with his subordinates (Dropcam CEO Greg Duffy said selling his startup to Nest was a mistake) and his bosses at Alphabet, who pressured him to turn a profit at Nest. Fadell quit Nest in 2016. Rogers stepped down earlier this year.

Read the whole thing here...

If you can provide the model number of the thermostat, then it may be possible to locate the installation manual. That may give information about the "P" terminal.

It appears you have a water sourced heat pump. The Nest is probably not going to work in this application. You may be stuck having to use a Climate master thermostat.

I have the Honeywell instructions. They were tucked inside the box. It only shows various wiring diagrams. It is a T834b.

You can download the manual here. From what I can tell the "P" terminal is the "R" terminal. Perhaps the printing makes it look like a "P".

It looks like you don't have have a "C" wire. You will need this if you want to use the Nest or any WiFi thermostat.

Thanks @mike_home. Yes, there is no C wire that I can find. From what I have read, it sounds like if there isn't one, then Nest is a no-go. Maybe I should just replace the ClimateMaster with a digital thermostat at least so I have better control over the settings. Not as fancy but a decent upgrade. Thanks.

Re: Austin

We try to help and we're completely ignored.

BTW: I did take the time to look through a ClimateMaster Tranquility Installation Manual and look at the control board schematic, as well as the T-stat wiring diagram for useful information!

You can imagine what a lay person would understand of that.

I only had a few minutes to respond to this thread earlier today and I am at work now. I wasn't ignoring you. Thanks for the research but it seems like I won't be able to use the Nest.

I think there may be some confusion. Geoff is referring to the Honeywell thermostat as a "ClimateMaster." I have not found any documentation for the T834B thermostat with that name.

Fsq4cw is talking about a ClimateMaster Tranquility water source heat pump. Two different products made by different companies.

The thermostat that came with the condo is an old Honeywell ClimateMaster. That is the name on face plate. When I removed the thermostat from its box, someone tucked the manual inside the box for safekeeping. The manual says T834B as the model number on it. It may be that this thing is too old to find any manuals (circa 2002 or so). Either way, as you noted, I have no C wire, so I suspect this is a dead end attempt. I will return the Nest. Thanks everyone for your help.

It's interesting to me that the colors at the bottom of the unit (red, yellow, purple, blue) don't match the colors at the top (red, yellow, orange, black?, green?).

I found a manual for a T834N, but it is somewhat different. Could be that this one is for activating water valves.