Comment by craz8 | Hacker News Reader

Comment by craz8 | Hacker News Reader

I “upgraded” my HVAC to a super modern heat pump with fully variable compressor for efficiency. But the only thermostat that can drive it is a crappy Trane 1050

The remote thermostats can only be averaged and not switched (eg Measure Bedroom at night, Living Room & Office during day)

There’s only 4 time blocks per day

There’s no adjustment of start time based on outside temp. In fact, no way to say: Be at 72 at 8am when I get up

There’s a ”quiet mode” to reduce speed (and noise) at night, but clearly this is on an internal timer. It will come on at 67% for up to a minute before the timed Quiet Mode Function notices and scales it back to the pre-set maximum. Sadly, I’m already awake by then.

(Also, the default values at install are wrong - they have Day and Night switched)

Since this is the smartest thermostat they do for this, can they at least open up the API so I can have a chance to get back the features I liked about my Ecobee?

For so much money, there is so little “smart”

I think I can use what APIs I have to implement the OP solution without mechanical switches, but I can not control the compressor speed directly for Quiet Mode to work

My house has a Carrier Infinity system where the compressor and air handler is fully variable. It can retrieve weather data over the net and adjust heating/cooling. The compressor and air handler are "connected" which is HVAC lingo for a proprietary protocol. The brains are in a $700 thermostat with a buggy touch screen that has the resolution of a lite-brite and it cannot work with virtual assistants.

One benefit I did see in the manual, is that if the air handler was gas combined with a heat pump you can enter the price of electricity and the price of gas and it can compute which heating method is best: gas/heat pump/resistive (usually when heat pump cannot provide requested temperature). But I don't have gas.

ROMs are available for these systems distributed as hex files on Carriers website. So its been on my todo list to reverse engineer the software.

Someone with time combined with a Raspberry Pi + Raspberry Pi Display (around $80 USD) could build a much better thermostat than what Carrier has done.

At my house, Trane lost a sale because of that incompatible proprietary protocol. I really wanted to super modern heat pump with fully variable compressor. I refuse to be stuck with one vendor. I'm also not putting my system on the internet, though of course IP protocol within my own home could be nice.

Maybe the answer is to look at systems sold for business use.

I have a similar thermostat, and I ended up going the Home Assistant route with the Nexia integration[1]. It still relies on the Nexia cloud, which is unfortunate, but it lets Home Assistant directly control the temperature.

I don't think it'll let you use Quiet mode, but it will let you do all the other thing you're missing, and it'll be much simpler than building out everything yourself for sure.

[1] https://www.home-assistant.io/integrations/nexia/

I do have Home Assistant, and have thought about writing the code for this. But then it’s all On/Off, with no access to the variabe compressor speeds of the system I paid quite a bit for (as it’s more efficient)

Quiet Mode is clearly a checkbox festure they added for the city of Seattle noise ordinances (mentioned in the sales literature)

There are relatively inexpensive Z-Wave thermostats on Amazon, if you'd like to avoid the internet-connected requirement in the future. I have a couple of GoControl's.

Are you just supposed to run it more?

Or is it hard to keep things comfortable with the inputs you do have?

Since it’s a heat pump, the ability to heat the inside depends on the outside temperature. Warmer outside, faster to heat inside.

But there’s no way to tell the system - I want 72 at 8am, you work it out. So I need to see if tomorrow morning will be 30 or 50 outside and set the start time accordingly. That’s not smart.

Heat pumps aren’t great at large changes anyway, but even 68 to 70 or 72 would work for me

And I also want that inside temperature to be based on the rooms I expect to use at those times: Night time, bedroom. Daytime, living room. Ecobee has exactly this function, Trane/Nexia does not

How many degrees below your occupied temperature are you setting back?

I have a ground source heat pump and my understanding was to pretty set and forget unless you have multiple zones or are going to be away for a long period of time.

Reason being heat pumps have variable speed compressors and setting them back forces them into less efficient higher stages, and as you mention take a lot longer to recover compared to traditional heaters. If the system is sized right it should be running it should be running below max at a relatively stable power.

That's what I meant by using it more. If you just set everything to 72, then presumably the rooms will be that temp when you use them. Doesn't help if you want to sleep at cooler temps of course.

This would be a pretty reasonable approach in a building with high levels of insulation and efficient heating/cooling.

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