General > General Technical Chat
What is the real story around heat pumps?
Zero999:
It appears as though a few people, including myself, have forgotten the forum rules, so I thought I'd post a quote to serve as a reminder.
--- Quote ---This is an electronics forum, so try to stay on-topic. We understand that threads drift off-topic, but try not to start deliberately and grossly off-topic stuff.
There are a couple of pet topics that always get out of control on forums, namely, religion, politics, guns, war, conspiracy theories, and the latest Current Thing that's happening or being championed by the public. They are not welcome here. This includes inside signatures and profile bios. This isn't Twitter where you virtue signal to everyone with your flags, emoticons, and hashtags.
--- End quote ---
https://www.eevblog.com/forum/chat/forum-rules-please-read/
In light of this. I have gone back and edited some of my posts, removing references to politics, net zero being one of them. If anyone spots a post I've missed, please either report it to the moderator, or just drop me a private message. I have also reported several posts to the moderator. I strongly recommend others do the same.
Siwastaja:
--- Quote from: zilp on February 24, 2024, 02:19:05 pm ---
--- Quote from: Siwastaja on February 24, 2024, 02:07:18 pm ---A tip, assuming you have either a boiler, or a separate storage tank with, with heat excharger for domestic how water. Plumbing: connect the monoblock to feed heated water into the boiler or storage tank, with the heatpump's own curve as optimized for house heating needs. You then get lukewarm "preheated" DHW out of the existing heat exchanger, so all you need it to install a small electric boiler "in series".
--- End quote ---
Beware of legionella, though, if you have a storage tank that is filled with DHW (as opposed to a storage tank with a low-volume heat exchanger for DHW).
--- End quote ---
That's why you set the electric boiler to maintain at least 60degC. Which is actually more idiot proof, given a simple mechanical thermostat, than a complex system with turnover valve and two tanks heated by a heatpump and controlled by the heatpump's (possibly buggy or hard to configure) control system.
Another plus side for my proposal is that you will have an independent back-up system for DHW, just smaller capacity, which Just Works without modifications even if the heatpump fails.
zilp:
--- Quote from: Siwastaja on February 24, 2024, 02:26:51 pm ---
--- Quote from: zilp on February 24, 2024, 02:19:05 pm ---Beware of legionella, though, if you have a storage tank that is filled with DHW (as opposed to a storage tank with a low-volume heat exchanger for DHW).
--- End quote ---
That's why you set the electric boiler to maintain at least 60degC. Which is actually more idiot proof, given a simple mechanical thermostat, than a complex system with turnover valve and two tanks heated by a heatpump and controlled by the heatpump's (possibly buggy or hard to configure) control system.
--- End quote ---
I'm not sure that that would be sufficient with a DHW storage tank!? AIUI, the problems is that the large volume (a) means that the concentration of bacteria never gets reduced much if they ever are established because use of hot water only dilutes things a bit while the growth is exponential and (b) sediments will settle in the tank, which adds additional protection for the bacteria from being cleaned out from the tank. At the same time, killing a high-ish concentration of bacteria down to a low-risk level would require heating to 60°C for many minutes, maybe up to 30, which a simple electric boiler at the output can't do. To kill them in seconds would require 70°C or more. Or you would have to occasionally heat up the tank to 60°C using the boiler somehow.
Siwastaja:
--- Quote from: zilp on February 24, 2024, 03:27:53 pm ---I'm not sure that that would be sufficient with a DHW storage tank!? AIUI, the problems is that the large volume (a) means that the concentration of bacteria never gets reduced much if they ever are established because use of hot water only dilutes things a bit while the growth is exponential and (b) sediments will settle in the tank, which adds additional protection for the bacteria from being cleaned out from the tank. At the same time, killing a high-ish concentration of bacteria down to a low-risk level would require heating to 60°C for many minutes, maybe up to 30, which a simple electric boiler at the output can't do. To kill them in seconds would require 70°C or more. Or you would have to occasionally heat up the tank to 60°C using the boiler somehow.
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No need to overthink. Just set to 60degC. Water is always held at 60degC (plus minus hysteresis of thermostat, and small excursions during heavy water use, but that's only for a short time). This is OK at least per legislation here. Maybe some other country requires 55 or 65degC. Set it to +70 with a further small decrease in total COP, if worried.
And this is definitely safer than than the "official" way of doing it offered by heatpumps, namely heatpump maintaining 50-55degC in DHW tank, which is a tad too low, with a 60-65degC "legionella" program running once a week. The risk is this program being too short or failing somehow. Even then, I'm not aware of any actual problems.
You probably did not understand what I suggested from my description in the first place, and being lazy I'm not going to try to draw a picture of it right now so just reread carefully my (possibly poor) explanation. Single storage for house heating -> pre-heated lukewarm DHW through existing heat exchanger -> small electric boiler in series to final temperature. This small boiler sits at high temperature all the time.
zilp:
--- Quote from: nctnico on February 24, 2024, 10:37:02 am ---
--- Quote from: zilp on February 24, 2024, 01:24:13 am ---
--- Quote from: nctnico on February 24, 2024, 12:59:57 am ---There is no such thing as a delicate balance.
--- End quote ---
You are aware that you are in disagreement with about everyone who does research in that area professionally, right?
--- End quote ---
Citation needed... Maybe you should actually do some research into the subject like I did for over 25 years already.
--- End quote ---
https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf , search for 'tipping'.
--- Quote from: nctnico on February 24, 2024, 10:37:02 am ---If you start looking carefully you'll notice that a lot of data is being filled in by assumptions and thus the 'conclusion' is only an assumption. Trying to model something erratic as weather / climate is next to impossible so anyone claiming to have an absolute truth in that area is leaving out a lot of details which may even prove that person wrong. There are some long term effets (like recurring CO2 peaks, sun cycles, cold / hot periods centuries ago, etc, etc) which are not explained by models used for global warming. In the end global warming predictions are a line fitted onto the temperatures from the last 100 years with the assumption that CO2 levels are the major factor driving the temperature up.
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You do realize that you have no idea how climate models actually work, right? The idea that somehow it is all based on weather data of the last 100 years is just ... wild.
Also ... why would you possibly expect a climate model of earth to explain sun cycles?! Sun cycles are obviously an input to climate models, not something that they try to explain!?
And also, who has ever claimed absolute truth? Are you saying that we should ignore risks unless we are absolutely certain that they will be realized?
Oh, and also ... now, what is it, is the climate chaotic, or is there not a delicate balance? You can't have it both ways. Either there are forking points where minor perturbations in inputs are amplified into huge effects or there aren't.
Oh, and ... why are you still mentioning the weather? How is chaotic behaviour at the micro scale relevant for the macro scale of climate?
Other than that, your objections really are just too vague to be useful.
--- Quote from: nctnico on February 24, 2024, 10:37:02 am ---IOW there is a good reason that people are getting fed up with fear mongering and start to vote for right wing politicians which want to continue burning fossil fuels.
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Which is all based on the baseless assumption that it is fear mongering. So, you are just assuming your conclusion. If it is a real danger, then politicians acting to mitigate the risk are not fear mongering, and just claiming that it is doesn't create a good reason to be fed up with what they are doing.
--- Quote from: nctnico on February 24, 2024, 10:37:02 am ---In turn this circles back that renewable energy sources and reduction of energy usage needs to be made cheap enough for the masses.
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Which still is a useless statement if you can't explain how that could be done.
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