HVAC Philosophy, Speculation, and General Brain Buzz

[AC_Hacker]

This thread is being created so that our HVAC-inclined community can share their opinions and pearls of wisdom in the comfort of a completely unstructured, un-moderated environment.

-AC

[MN Renovator]

Great idea. I'm sure we'll have plenty of discussions about all the different types of refrigeration, equipment, and heating methods related to heat pumps and air conditioners, although it seems this thread is open to anything.

Since this is one of the first posts, I'll post some of the most helpful resources for commercially built equipment, stuff things people can buy.

One of my favorite resources for mini-split heat pumps. This provides information for heat pump performance data at 5 degrees F, which to me, is far more useful information where I live than 17. The unfortunate part is this isn't necessarily derived from third party testing like AHRI data is but I think it fills in the gaps reasonably and also gives some data on pan heater operation. This data is information provided by the manufacturers so there is a chance that it isn't consistent and even a possibility that results could be inflated or changed. Particular pieces of note for me are the maximum capacity at 5 degrees and the input power and COP at that capacity. It's interesting to see some of these units pushing out reasonable amounts of heat with COPs above 2. That's something I didn't expect.

http://www.neep.org/initiatives/high...urce-heat-pump

For furnaces, air conditioners, heat pumps, boilers, etc. The AHRI ratings ARE third party tests performed in a consistent lab. The site allows you enter criteria, get results, and sort by column for the information that's important to the person searching.
https://www.ahridirectory.org

I've spent a bunch of time playing around in the AHRI directory site and have contemplated which systems I would buy for different scenarios(higher loads vs lower building loads, looking at what furnaces use the least electricity, looking for the best cooling EER in a system, that sort of thing.

Hopefully others find these resources helpful.

[AC_Hacker]

Originally Posted by MN Renovator

One of my favorite resources for mini-split heat pumps. This provides information for heat pump performance data at 5 degrees F, which to me, is far more useful information where I live than 17. The unfortunate part is this isn't necessarily derived from third party testing like AHRI data is but I think it fills in the gaps reasonably and also gives some data on pan heater operation.

Looks like great information that should be of interest for cold-climate folks who want to improve efficiency.

Good find.

-AC

[Mobile Master Tech]

As time permits, I will move the content of my posts in the Manifesto about the vapor compression components of a HP here, and just leave a reference to them in the Manifesto.

A caveat to component compatibility I just learned: Hermetic compressors can't use PAG oil, since it conducts electricity too well and hermetics have their motor inside the case.

Scroll compressors may be more resistant than reciprocating compressors to damage from extreme conditions, especially liquid/foam slugging: refrigerant is drawn through the motor, cooling it more effectively than just being surrounded by the refrigerant in a reciprocating compressor. If liquid tries to enter, the pressure drop caused by the liquid struggling to get through the motor plus the heat of the windings will evaporate it. If any liquid (or debris) makes it into the scroll, the scroll halves can separate slightly, allowing the liquid or debris to pass between to prevent hydrolocking or mechanical damage.

[Mobile Master Tech]

The European Union now allows flammable refrigerants per STANDARD EN378.

In short, A3 class refrigerants (such as R290) are limited to 1000g if any component is below ground, and 1500g if all components are above ground. This applies to comfort cooling and heatpumps too. Allowable amounts are further restricted by a "practical limit" based on the room size a component is in, the distance above floor, and the lower flammability limit of the refrigerant in question. A split system with a ceiling cassette in a 530 square foot room could use 650g of R290 without a flammable gas detector.

We haven't seen news reports of fires/explosions, even though there are millions of vending machines, cold cases, and other devices with flammable refrigerant in the EU.

Efforts are ongoing to standardize US regulations to these, which already allow charge amounts up to 150g.