General > General Technical Chat

What is the real story around heat pumps?

<< < (76/77) > >>

Zucca:
Did not have time to read all the pages...

Once you understand the physics behind the heat pump you can't go wrong.

This is what I did in my home in USA:
1) I replaced my 50gal gas water heater in my garage with an 65gal electric heat pump water heater [HPWH].
2) I installed 14KW solar panels using the unused gas chimney to bring the HV solar cables down in the garage. (YES there is a metal ground shield around them... everything is safe)
3) I installed my Victron inverters (16KW peak) and MPPTs few meters away from the HPWH.

In winter the Victron devices are heating up the air and the HPWH is happy.
In summer the HPWH is cooling the air and the Victorn devices are happy.

I am now in the process to install 4 Temp sensors from my Cerbo GX so I can log all the in-out temperatures and see how much the two systems are helping each other.

WIN-WIN!

pcprogrammer:

--- Quote from: coppice on February 26, 2024, 08:29:18 pm ---
--- Quote from: pcprogrammer on February 26, 2024, 08:09:51 pm ---
--- Quote ---The bigger ones, say over 5kW claimed output, are better (more reliable) with a 3 phase compressor.

--- End quote ---

Is there a difference in life expectancy and reliability between tri phase and single phase models?

For what I have seen of the De Dietrich models there is no difference in price between them. Don't know about other brands.

--- End quote ---
Unless you have a bargain basement heat pump, why would three or single phase power make any difference? They are all inverter driven these days. Is this single vs 3 phase issue related to old heat pumps? I can definitely see a three phase induction motor giving better results.

--- End quote ---

That was what I was thinking too. We have a single phase installation but could change over to 3 phase at extra expense if it would be beneficial. Looks like it won't be needed.

Siwastaja:

--- Quote from: pcprogrammer on February 26, 2024, 08:09:51 pm ---Is there a difference in life expectancy and reliability between tri phase and single phase models?

--- End quote ---

No. I think it is now impossible to buy line frequency on/off models. All are inverter machines, so there is no difference in the compressor motor, inverter power stage or drive logic. In both cases, incoming mains is just rectified. Assuming wye connection, three-phase inverter machine needs to work with internally higher DC voltage than the single phase equivalent, and single phase requires more DC bus capacitance to deal with more ripple, but such details are meaningless to normal end user.

Siwastaja:

--- Quote from: coppice on February 26, 2024, 08:27:01 pm ---Which Chinese unit do you have?

--- End quote ---

Amitime which I think is the second largest heatpump producer (after Gree). These large Chinese companies know how to get the basics quite right, they are not super sophisticated designs but then again a heatpump doesn't need to be. Whenever there are technological innovations that actually improve COP or performance (like inverter drive or EVI), first premium brands use them, then a few years later all the cheap ones adapt them too and make a big deal about it in their marketing, and then a few years later again it's just standard stuff and everybody forgets to even mention such technical details.

Funnily enough, as a designer myself, I can see a lot of potential for quite significant cost savings in my Amitime unit. A cabinet full of stuff like Windows CE computer, separate wifi-RS232 module, total of four RS485 buses, and massive control cards with 20 relays out of 2 are actually used is something I would not expect from the market's cheapest product. They clearly can afford it, but they could also easily shave off another $50-100 from their manufacturing costs.

You can clearly see air-to-water heatpumps are still quite niche compared to the ubiquitous air-to-air units which are better optimized for mass market.

JohanH:

--- Quote from: tom66 on February 26, 2024, 10:53:32 pm ---Pretty much every heat pump now, even with a single phase input, will be using a three phase compressor because they will use an brushless or induction motor and inverter to drive that motor.  That will probably be immune to losing a phase (will likely cause the unit to shut off though if it has any monitoring of the AC line.)

--- End quote ---

The ground source heatpump that I have, Nibe F1255-6, does have a three phase connection, but only one phase is used for the BLDC motor, which has its own motor driver (three phase 20 - 120 Hz). The second phase is used for control circuitry and pumps and the third only for electrical resistive heaters. You could run this model from a single phase. The resistive heaters are wired to all phases in this installation, but because they are almost never used, there is almost never any load on the third phase. Current load in this weather (outdoor 0°C): compressor is running on 600 W on one phase (right now motor speed 44 Hz), pumps on second phase 40 W and the third phase 0 W. The larger models of Nibe use induction motors with regular inverters and they might be differently wired. I've heard about some issues with some older heatpumps breaking when losing a phase. That could theoretically be protected with an external phase protection relay.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod