June 18, 20206 yr This technology is similar to modern diesel engines in motorcars. They both have substantial advantages but somehow the market doesn't react accordingly. Anyway, forget about the cars. Let's get some clarity on heat pumps for geyser heating..
June 18, 20206 yr 2 hours ago, Richard Mackay said: Anyway, forget about the cars. Let's get some clarity on heat pumps for geyser heating. What do you want to know?
June 19, 20206 yr Author Quote Heat pumps use a third of the power that electrical elements consume. That is a substantial improvement. With that capability I would assume there would be more users of heat pumps. Sure there are the solar heating options for water but in the domestic environment they are not ideal since much hot water is used at night & early morning before the sun gets going. That leaves one having to store this energy by keeping the geyser from losing heat. My experience with this has been disappointing. (with geyser blankets etc.) Heat pumps have the advantage of producing the same heat (for a fraction of the electricity used) as an element any time of the day. So one doesn't have to jump through these hoops. I have had no experience with these appliances. Clearly they are not simple and expensive. But are they?? Edited June 19, 20206 yr by Richard Mackay
June 19, 20206 yr 1 hour ago, Richard Mackay said: With that capability I would assume there would be more users of heat pumps. You might not be aware of this, but Heat pumps are widely used through out SA. With a COP (coefficient of performance) of between 3 and 5 depending on the Brand and model they proof to be one of the most efficient methods of heating water, and with an average power demand of 1.25kwh it makes a great addition to your Solar system, ensuring that you can heat your water from your existing solar system without having to add 3kwp on the roof to try and rub your normal geyser. The price of the heat pump is cheaper than 3kwp and that is without buying an extra MPPT to allow you to add 3kwh panels. The hotter the area you stay in, the better the performance of the heat-pump. Comparing the performance of a Flatplate vs Evac tubes vs Heat-pump during overcast days, the heat-pump will come out on top, with night time usage being an added benefit over the others. Like with everything, there are cheaper, not so efficient units and quite a few claiming exceptional COP ratings, but only a few of them can deliver on their products. One trusted brand that I would strongly recommend is ITS solar's range especially their 5Kw Super unit that can off 10 degC higher outlet water temp than most of its competitors. Note: A COP rating of 3 for example means that the unit is 300% efficient and 4 is 400% and so on, and the only way that is possible is because the heat-pump is not producing the Heat, its is merely moving it from the environment into the water. It takes less energy to move the heat compared to producing the heat. (The process is a bit more complicated, but this is the simple explanation of things.) Edit: I forgot to mention, the only Drawback of heat pumps is, no power = no heat. but as i mentioned , the power demand is small enough to add it to your existing solar backup system. And another important point. Flat plates and Evac tubes, can normally produce between 4 and 4.7kwh of heat per sq meter per day and their size is between 1.4 and 2 sq meters. So at best you can expect in the region of 9kwh heating from them in a day. The heat pumps on the other hand can supply its kwh rating per hour. The main units i prefer to install is 3.6kwh, 4.7kwh and 5kwh. It will take the 4.7kwh unit less than 2 hours to preform the same heating a evac tube can do in a day.
June 19, 20206 yr Hi @Jaco de Jongh thank you for the useful information. I am thinking of adding a heatpump to my one electric geyser which is using on average double the amount of electricity compared to the other one. Am currently pushing excess solar to both geysers during the day for hours and in the end it's not enough to cover everything. For instance the batteries don't get fully charged during the day. I then also get complaints on some mornings of the geyser water being cold due to all the hot water being used up in the night. Is it possible to keep the existing electric geyser element on the grid side while adding the heatpump for that geyser on the solar side? My plan is to then be able to run the heatpump on the inverter at night (on batteries) since it's using much less power than the geyser and the system should be able to cope with the load provided I am not overdoing it. Edited June 19, 20206 yr by francois
June 19, 20206 yr 5 minutes ago, francois said: Is it possible to keep the existing electric geyser element on the grid side while adding the heatpump for that geyser on the solar side? Yes it is, but you will soon see that you dont need the element, once you get use to the Heat pump, you would pretty much stick to using it. 8 minutes ago, francois said: My plan is to then be able to run the heatpump on the inverter at night (on batteries) since it's using much less power than the geyser and the system should be able to cope with the load provided I am not overdoing it. Most 5kva inverters will cope with a heat pump without any problems providing you have enough batteries to back it up.
June 19, 20206 yr 6 minutes ago, Jaco de Jongh said: Yes it is, but you will soon see that you dont need the element, once you get use to the Heat pump, you would pretty much stick to using it. Most 5kva inverters will cope with a heat pump without any problems providing you have enough batteries to back it up. Thanks Jaco, I am cycling the batteries at night but limiting the discharge on the batteries to 20a, so the rest of the power for the load comes from the grid side. The battery bank is 2 x US3000 and 2 x US2000. Inverter is only 3kw though, Infini. Am I being too ambitious with this plan based on the inverter size? Edited June 19, 20206 yr by francois
June 19, 20206 yr 2 hours ago, francois said: Am I being too ambitious with this plan based on the inverter size? No I dont think so. Brand? and what is the inrush current its rated for?
June 19, 20206 yr 5 minutes ago, Jaco de Jongh said: No I dont think so. Brand? and what is the inrush current its rated for? It's a 3kw Infini Plus. Sorry for the blurry spec sheet. Hope it's readable. Edited June 19, 20206 yr by francois
June 19, 20206 yr 18 minutes ago, francois said: It's a 3kw Infini Plus. From what I read here, you should be fine. Just ensure your maximum load does not exceed 2.4kwh..
June 19, 20206 yr 16 minutes ago, Jaco de Jongh said: From what I read here, you should be fine. Just ensure your maximum load does not exceed 2.4kwh.. Perfect thank you Jaco.
June 19, 20206 yr 3 hours ago, Jaco de Jongh said: 4 hours ago, francois said: Is it possible to keep the existing electric geyser element on the grid side while adding the heatpump for that geyser on the solar side? Yes it is, but you will soon see that you dont need the element, once you get use to the Heat pump, you would pretty much stick to using it. My heat pump is set up like this. The Heatpump cycles the water in your water tank(ie. the old geyser), while the water tank can keep the old heating element as a backup. Like Jaco mentioned, you won't ever use the backup unless you need to send the heatpump for repairs or something. An interesting fact: heat pumps are even more common than most think. A heat pump moves the heat from one place to another. The place where the heat is extracted gets cooler and the place the heat is taken to gets warmer. This is the same principle your fridge (and most air conditioners) work with, they just remove the heat to make it cooler. (That is why the back of your fridge get so got) If you want to read up some more on this check out https://en.wikipedia.org/wiki/Heat_pump
June 19, 20206 yr Just now, Louisvdw said: My heat pump is set up like this. The Heatpump cycles the water in your water tank(ie. the old geyser), while the water tank can keep the old heating element as a backup. Like Jaco mentioned, you won't ever use the backup unless you need to send the heatpump for repairs or something. An interesting fact: heat pumps are even more common than most think. A heat pump moves the heat from one place to another. The place where the heat is extracted gets cooler and the place the heat is taken to gets warmer. This is the same principle your fridge (and most air conditioners) work with, they just remove the heat to make it cooler. (That is why the back of your fridge get so got) If you want to read up some more on this check out https://en.wikipedia.org/wiki/Heat_pump Thank you Louis. I am seriously considering converting the one existing geyser now.
June 19, 20206 yr 20 hours ago, Richard Mackay said: This technology is similar to modern diesel engines in motorcars. They both have substantial advantages but somehow the market doesn't react accordingly. Apparently these are especially efficient...😉 With that out of the way, the efficiency of heat pumps are very appealing from an energy cost perspective. I do think the upfront cost can scare people away a bit. I am only now starting to realise that "saving money" is not the same as making an investment. BUT with the electricity supply issue in South Africa the decision becomes a bit more complex. For the average 4..6 person family. If you have say R20 000 - R40 000 to use and so far have nothing (no PV, no solar heating etc.) where do you put your money and what do you focus on? Saving on energy/electricity costs or making provision for grid failures? Is there an option that will allow for both? My gut still leans towards the PV based (solar panel/inverter) route.
June 19, 20206 yr Author Heat pumps are refrigeration equipment with all the specialist support that this equipment needs. I have heard that they need to be regularly serviced by approved companies in order to keep the warranty valid. Also I believe the equipment can corrode in coastal conditions..
June 19, 20206 yr 38 minutes ago, Richard Mackay said: I have heard that they need to be regularly serviced by approved companies in order to keep the warranty valid. Not true with all brands, it needs to be serviced once a year. Only need to clean the "Evaporator" and check the Strainer for blockages. Both of these can be done by the client. They require very little maintenance. Normal maintenance takes less than 30 min. Not servicing them, wont break them, it will just effect the efficiency. I have personally seen some units that was installed in 2008 and never cleaned, in 2018 they were removed as the client though they were damaged. The manufacturer cleaned them and started them up and they were still working.
June 19, 20206 yr 3 hours ago, francois said: This is the same principle your fridge (and most air conditioners) work with My eye caught a air-con spec label this week and at 4.5A input you basically get 3KW output power. That looks like the way to go when installing air-cons, It also made me thinking, imagine having one unit that could cool/heat a room or be switched and used as a heat pump for hot water.
June 19, 20206 yr 4 hours ago, Gerrie said: imagine having one unit that could cool/heat a room or be switched and used as a heat pump for hot water. I've had that thought too. The only issue is... when would you use it? In summer, you're water will be hot by noon... but your house is still hot (so you still need to run the AC), and in winter... well you want hot water... but you really don't want to cool any part of your house down! So I imagine it is a cool idea, but with limited use.
June 20, 20206 yr I have been told by our municipal electrical engineer that there is a possibility of deposits forming in the small diameter pipes of the heat pump evaporator over time. This will happen if there is dissolved calcium in the water for instance. Just see if deposits are on the element of your electric kettle. The heat pump may apparently require flushing with probably an acid solution every 3 years or so, which seems to be a job for experts. Heat pumps are energy efficient units and will save a lot of electricity used for water heating. That said I have a 200 litre Xtreme geyser which is very well insulated and a 12 evacuated tube solar heater. Electricity usage to compensate for lack of sunshine during winter on the West Coast was about 120 KWh last year. Has anyone perhaps have any experience or advice for using heat pumps for hydronic underfloor or in floor slab heating. Would one be able to use a pool pump heater for the purpose. Water temperatures of around 33C seems to be all that is required. I have pipes embedded in floor slabs but have not connected a heat source yet Edited June 20, 20206 yr by ebrsa
June 20, 20206 yr 5 minutes ago, ebrsa said: there is a possibility of deposits forming in the small diameter pipes I’m sure that is true that is where you need to open the strainer when you service it, it is a little filter that can easily be opened with a shifting spanner, rinse the strainer and put it back and it will be ok for many months depending on your quality of municipal water. Some municipalities with lots of burst pipe issues might be a problem as plumbers close up pipelines with mud and dirt trapped in the lines this ends up in customer water pipes. I lost a couple of taps mixer cartridges some years back because my incoming water line did not have a strainer, I found small stones and plant roots inside my mixers. I fitted a strainer on my main line and have not had that problem again. I don’t have a heat pump but a freind of mine was lucky he had one installed more than 10 years back when there were still a rebate he only paid about R6000 for his, and a month back I asked him about service he told me about the strainer and he washes the unit down with a hose pipe when he cleans out his gutters.
June 20, 20206 yr 3 hours ago, ebrsa said: Gas anyone perhaps have any experience or advice for using heat pumps for hydronic underfloor or in floor slab heating. Would one be able to use a pool pump heater for the purpose. Water temperatures of around 33C seems to be all that is required. I have pipes embedded in floor slabs but have not connected a heat source yet Do not have experience with it and do not want to derail the thread but have a look here (especially from the section "choosing your heat source").
June 20, 20206 yr 18 hours ago, Gerrie said: imagine having one unit that could cool/heat a room or be switched and used as a heat pump for hot water. In the link I posted about heat pumps and floor heating a MD involved in the heat pump sector at least implies that it should be possible: "As we have a high demand for cooling in summer, the heat pump should also be able to cool, so that the client can use one device for his domestic hot water heating, space cooling and pool heating" but so far could not track down info on one of these all-in-one options... I suspect it probably is on a somewhat grander scale than the average domestic system and probably involves a complex HVAC system 14 hours ago, plonkster said: well you want hot water... but you really don't want to cool any part of your house down! So I imagine it is a cool idea, but with limited use. Domestic application may be limited but commercial application may be an option.. ... cool room/refrigeration on one side + warm water on the other side = food production?... large hotel kitchens?
June 20, 20206 yr Author On 2020/06/19 at 3:19 PM, Louisvdw said: My heat pump is set up like this. The Heatpump cycles the water in your water tank(ie. the old geyser), while the water tank can keep the old heating element as a backup. Like Jaco mentioned, you won't ever use the backup unless you need to send the heatpump for repairs or something. An interesting fact: heat pumps are even more common than most think. A heat pump moves the heat from one place to another. The place where the heat is extracted gets cooler and the place the heat is taken to gets warmer. This is the same principle your fridge (and most air conditioners) work with, they just remove the heat to make it cooler. (That is why the back of your fridge get so got) If you want to read up some more on this check out https://en.wikipedia.org/wiki/Heat_pump Is your heat pump unit mounted outside and only the hot water cycles between the compressor and your old geyser?
June 20, 20206 yr 28 minutes ago, Richard Mackay said: Is your heat pump unit mounted outside and only the hot water cycles between the compressor and your old geyser? That is the way its normally installed.
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.