Marvin Posted January 23, 2022 Share Posted January 23, 2022 Can anyone explain in simple terms what effect adjusting the ASHP compressor and or fan settings will have on the output? Also is the ASHP pump that people have referred to mean the pump circulating the water? The ASHP involved is the Cool Energy inverTech Air Source Heat Pump CE-iVT9 4.3kW-9.5kW. Thanks for your help. M Link to comment Share on other sites More sharing options...
SteamyTea Posted January 23, 2022 Share Posted January 23, 2022 It is all here: maybe not that simple. https://mechanicalboost.com/carnot-engine/ Basically the equation PV/T=C means that you can change the pressure (P), the volume (V) or the temperature (T) and you will end up with the same constant number (C). So the air that passes through the unit will be at constant pressure (over the short term) but may vary in temperature, so changing the volume means you can extract the same, more or less energy, from that air. Within the actual heat pump, the volume is fixed, so you can only change the pressure before and after the compressor (within quite tight limits), this changes the temperature because the rate of expansion and condensation (latent heat of vapourisation) is varied. So you have two things that affect the output, the amount of air that passes through the unit, and the pressure within the unit. 1 Link to comment Share on other sites More sharing options...
Marvin Posted January 23, 2022 Author Share Posted January 23, 2022 Thank you @SteamyTea. I am sorry that I did not ask the right question but your answer has greatly helped me to understand the basics. (hopefully). So, I understand that when relating your information to my questions you are saying (as its easier than talking about Carnot engines) in a non pedantic sense, the heat (or cooling) produced by an ASHP depends on the existing air temperature, the air passing through the unit and the change of pressure in the compressed liquid. As such if you wish to keep the same output in heat if one of the 3 reduces the heat effect the others have to compensate: When air temperature goes down airflow and/or compressor pressure change would need to increase to produce the same output. When temperature rises airflow and/or compressor pressure change would need to decrease to produce the same output. If I have this right then it leads to what I meant to ask which was actually based on attempting to improve the COP. If we were to keep the same amount of heat production and the air temperature stayed static, which would improve the COP the most, increasing the fan speed and reducing the change of pressure by the compressor, or reducing the fan speed and increasing the change of pressure by the compressor. I assume that both processes use different amounts of energy. If there is no significant difference, what causes users to want to adjust the 2 parameters? Oh well I hope for a simple answer... Link to comment Share on other sites More sharing options...
SteamyTea Posted January 23, 2022 Share Posted January 23, 2022 (edited) 23 minutes ago, Marvin said: Oh well I hope for a simple answer... If you increase the airspeed though the unit, the temperature difference will be less, so less energy is taken out of the air. This is probably done because the heat exchanger (that thing that looks like a car radiator) is of fixed size, so if the air movement was too slow, it would freeze out the moisture from the air. It does increase noise though. I suspect with a decent inverter driven unit, there will be a factory default setting, that changes both the fan speed and the compressor speed. Slowing the compressor should reduce the power at any given temperature, or lower the maximum temperature for a given power. Without know the controller (and its internals, though I am going to meet some people that know about this shit), I suspect that there is not a great deal of interaction change between the fan and the compressor, probably more a case of setting minimum and maximum temperatures. By setting limits on the two scales, a power curve comes out naturally. May not always be best for the CoP, but if you can set it up without getting towards the extremes, the CoP should be close to where it is best. It is a real shame that not all controllers use a standard terminology, it would make setting up easier. Edited January 23, 2022 by SteamyTea 1 Link to comment Share on other sites More sharing options...
dpmiller Posted January 23, 2022 Share Posted January 23, 2022 Have you a copy of the full test cert for the unit, rather than just the COP quoted in the manual? It has a bit more info on when defrosts are likely, the required compressor speeds etc I've attached it just in case you don't... do you see the water pump throttling back much? I'd opine that flow through the heat exchanger (and therefore deltaT across the unit) is going to have more of an effect than fan speed. But again, look in Fan configuration to see the compressor speed and fan speed limits per ambient temp. CE-iVT9 EN14825 64.181.20.04362.01 Rev.00 TR Performance Pages.pdf 1 Link to comment Share on other sites More sharing options...
joe90 Posted January 23, 2022 Share Posted January 23, 2022 (edited) 35 minutes ago, SteamyTea said: It is a real shame that not all controllers use a standard terminology, it would make setting up easier. ? even our Jeremy had trouble understanding the controller for our (re badged ) carrier unit, I did not have a cat In hells chance but Jeremy did help me out (mainly because he not only understood that sh1t but he had time to play with his and work out what it meant.) apart from basic settings I don’t use mine and like Jeremy use a basic room stat. edit, as an aside I don’t have a flow meter on mine, how can I make sure my water pump is at the optimum speed? Edited January 23, 2022 by joe90 Link to comment Share on other sites More sharing options...
Temp Posted January 23, 2022 Share Posted January 23, 2022 42 minutes ago, SteamyTea said: If you increase the airspeed though the unit, the temperature difference will be less, so less energy is taken out of the air. Im not entirely convinced that's correct because the mass flow rate will be higher. Link to comment Share on other sites More sharing options...
SteamyTea Posted January 23, 2022 Share Posted January 23, 2022 1 minute ago, Temp said: Im not entirely convinced that's correct because the mass flow rate will be higher. Yes the mass flow will be higher, but the temperature differences is fixed. So to clarify, less energy will be taken out of the 'block' of air that is passing through. The overall energy should be the same over time. Except the other temperature differences, between the liquid refrigerant and the expanded refrigerant gas, will also be lower overall. It is a horrible balancing act that these heat curved try to sort out. 1 Link to comment Share on other sites More sharing options...
Marvin Posted January 23, 2022 Author Share Posted January 23, 2022 49 minutes ago, joe90 said: edit, as an aside I don’t have a flow meter on mine, how can I make sure my water pump is at the optimum speed? +1. 1 Link to comment Share on other sites More sharing options...
Marvin Posted January 23, 2022 Author Share Posted January 23, 2022 52 minutes ago, dpmiller said: I've attached it just in case you don't... Well I do but I don't necessarily know what I'm looking at.... Link to comment Share on other sites More sharing options...
ReedRichards Posted January 23, 2022 Share Posted January 23, 2022 I have never wanted to interfere with the the compressor or fan settings; AFAIK I don't have that option. Link to comment Share on other sites More sharing options...
Marvin Posted January 23, 2022 Author Share Posted January 23, 2022 19 minutes ago, ReedRichards said: I have never wanted to interfere with the the compressor or fan settings; AFAIK I don't have that option. As far as I'm concerned I don't have that capability. Link to comment Share on other sites More sharing options...
ReedRichards Posted January 23, 2022 Share Posted January 23, 2022 So it's "would" affect the output rather than "will" and a hypothetical question? 1 Link to comment Share on other sites More sharing options...
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