I’m pretty much set on installing heat pumps, now just waiting for the minister of finance to come through with the bank balance. :smily
Some questions,
As I understand the standard geyser element is left in place as a backup and I read some people say you should install a change over switch to switch between the element and heat pump. Why is a change over switch necessary, what will happen if both are on at the same time, will something go boom?
There was a post on here recently of someone who had a issue with their heat pump and the insurance wasn’t interested in the claim, I assume one should specify to the insurance that you have a traditional geyser as well as a heat pump?
When I have a heat pump on a geyser, depending on the change over switch answer, is there any advantage to having a Geyserwise timer to control the element over a normal smart breaker like a Astute?
BTW I specifically ask about the element as a backup because for one or two weeks per year we get very cold weather, this last winter we measured -5 and I have a guest house, so not having enough hot water isn’t really a option.
I think that’s just a backup measure, in case the heat pump fails. Then you can still have hot water. I didn’t do that on my system. I have a gas geyser as backup, and in the rare case I need it, that is sufficient for me. If the problem persists for any length of time, I’ll wire the geyser element at that point.
There is however another better way to do this. Some heat pumps have a built-in “boost” feature, which requires wiring the existing element through a switch in the heat pump. This allows the heat pump to turn on the resistive element, in case 1) you enable the “boost” option on the panel, or 2) ambient temperatures are low, reducing the COP, and for the purposes of speed of efficiency it wants to switch to the resistive element.
If both are on at the same time, it is probably not a big deal. The heat pump needs around 1kW (give or take), the resistive element about 3kW. As long as the wiring is rated for 4kW you will be fine.
Don’t put an external time switch or a Geyserwise on your heat pump (I am not sure if there are Geyserwise units that are built to work with heat pumps). A heat pump has some built-in smarts, when you switch it off it does a graceful shutdown (the unit runs for a bit after you hit the button). An external switch will lose all of that.
Some heat pumps can be programmed to run at certain times, so you may not need a time switch.
The time on mine drifts terribly, so I just let it run whenever it wants to, according to the happy wife happy life motto, and not messing with things concerning hot water.
I’ll be looking at ITS heat pumps, as convinced by @JacoDeJongh
I don’t want to install any additional switches on the heat pumps for control, I know they have their own timers and stuff, I will however put a Shelly or something in line purely for power monitoring.
I mentioned Geyserwise because I already have them on my geysers, so leave in place or take out?
Not needed. The heatpump comes with a changeover to select between element and heatpump. Automation should be easy because the Heatpump app is running on the Tuya platform via Smart home app.
But how does a heat pump actually heat the water in you geyser?
I assume that there should be continuous circulation of the water between the geyser and the pump until it is hot enough.
So how does the plumbing work?
Does the geyser need an additional pipe to the pump leaving the normal cold water inlet to the geyser untouched?
Or is new plumbing required to first send the cold water through the pump where it is heated and only passed on the geyser when hot enough through the normal cold water inlet of the geyser?
Outside, on the wall, there is something that looks like an air conditioner’s outdoor unit. There is a water pipe running from your tank to this box, and another one coming back with the hot water.
There is a small pump in the outdoor unit, that ensures the water is circling.
There might also be a “loading valve” that recirculates the until it is properly heated, before it goes back to the tank. Sending the water through the heat pump once only heats it slightly. To avoid dumping cold water in the top of the tank, a loading valve circles it back into the heat pump until it is hot enough. A bit like a reverse-tempering valve.
It works using the usual heat pump methods, where you have a refrigerant being cycled between a condensor and an evaporator. When the refrigerant goes through the the evaporator, liquid turns into gas (because of a change in pressure), which requires heat. It absorbs this heat from the environment. When the refrigerant goes through the condensor, gas turns back into liquid, which means it now has to get rid of the heat. By placing the condensor in a heat exchanger (where that heat is transferred to the water), you heat the water. Basically it means you have two sets of pipes running next to each other in a mesh, one with water, one with refrigerant.
Also contemplating the heat pump thing. Luckily in my case, I would be able to have the outdoor unit with the pump installed right next to the geyser ensuring minimal losses from this circulation with a very short pipe.
Thing is, I need to decide whether I rather want a heat pump to warm up my living room in the winter, or to heat my geyser. Cant have both, the distance will be to great I think. But it would be awesome if the heat pump could do both, at different times obviously.
Geyser performance I am actually happy with in terms of its battery usage.
But man I hate cold. Should I get one to heat the living room, it will have to be installed where it will be very unsightly and ugly, and probably noisy (right on my outside deck where we spend a lot of time). Also suspect there will be much more plumbing involved.
Regarding heat pumps for hot water would it be true to say that they would only be installed after a solar hot water system?
This is to be seen in the light of energy efficiency and the tackling of the lowest hanging fruit first.
On an annual basis, a solar water heater will save you more money. In summer you will get all your hot water for free, and a lot that you don’t need. In winter, the reverse will happen and your bill will shoot up.
A heat pump saves less money (it still uses some electricity), but it saves two thirds the entire year around. So less savings, but more levelised. Some people prefer that.
If you already have a solar PV system, a heat pump (that runs from solar energy, but in winter can run on grid power, but less of it) sometimes makes more sense.
Not one of my geysers is more than I’d say 2m from a outside wall where the heat pump can be mounted, so pipe runs won’t be long.
The position on my one outside wall even have power pulled to it already, because there’s a old aircon compressor which will be removed to make space for the heat pump.
I’m not yet sure of the mounting position on my parents house, if I put it directly next to the geyser on the outside wall, it will be right next to the braai area and lapa, which might be annoying in terms of noise.
The other option, well not really a option for me is inside, I read some people put them inside the roof, but thatch rooves so no ceilings, I’m sure it will make for one heck of a racket in the house.
We tend to become obsessed with one issue to the exclusion of other options. It’s the nature of the beasts that we are.
But if you are trying to get the best energy efficient solution try to be aware of the alternatives if you can.
I have seen a few hybrid systems before, in short, a geyser, heat pump and solar water heating systems all in parallel. Not after each other but the in parallel. They work well and contribute towards heating with the electrical element being the absolute last resort.
Also saw evacuative tubes connected to a geyser feeding a smart gas geyser. Should you have enough sun during the day the hot water just pass through the gas geyser without trying to heat it. Should it be cloudy with only partial heating of the storage tank, the gas geyser will only heat the delta required to reach its setpoint resulting in less gas consumption.
I have a geyser (2000w element), and solar water heating in an Xtreme Geyser setup and VERY happy. Hardly need to run the element in summer and in winter very little.
Typically we’re doing three things (I think). We’re trying to get the best bang for buck (that’s two of the three, best efficiency, least upfront cash), within the constraints of roof space and/or other physical constraints (the third thing).
If money and space was no object, we’d all put up a thermosiphon tank with a solar collector, and a heat pump to make up the difference. The solar water heater will pay back its investment very quickly. The heat pump, only making up on cold days, probably never.
Since many of us treat our energy management as a bit of a hobby, as we get used to the last thing we installed (and the itch starts again), and as prices also come down, I suspect many of us will probably end up with hybrid solutions.
I myself am considering a solar water heater in the future. I just decided to do the heat pump first. At the time it made more sense to me.
My point is that here in sunny SA solar water heating is a no brainer…
PS: Which one of these systems is up to you. We can kick the can around as to which one is the most efficient
I agree. And it is relatively cheap as well, because we benefit somewhat from scale. In other parts of the world, places that are often quite proud of being ahead, they actually went backwards.
Looking a while back, after the EV tubes had to be replaced, at heat pumps, Geyserwise solar panels, EV tubes, many other clever inventions posted everywhere, saw all where in a similar price range.
In speaking to repair shops, all may need replacement, like the EV tubes, in a decade or so. In other words, I have to spend over and over to keep Eskom costs low.
So I sat and thought a bit. Happens sometimes.
Result: (not for guest houses that has to have hot water 24/7/365)
All the solutions have challenges in Cpt winters.
All are a ongoing expenditure ito maintenance/replacement.
So what is the cheapest way to solve heating a geyser AND best bang for buck?
Conclusion:
A 3-4kw Solis grid-tied inverter.
Heat geyser/s on timer/s.
Rest of the time use the generation is shave off even more Eskom charges.
Direct solar water heating has too high maintenance requirements¹, that I would advocate installing extra solar panels instead and add a heat pump later.
In fact, panel and inverter prices are so low now that it might be best to just stick to resistive heating with a timer (unless you live in a place like CT, where you will still have to buy electricity for a good percentage of the time.)
[1] (or more accurately is too harsh on the geyser thermal/pressure valve, which fails when you are >1000km away and can cost way too much in water costs when it does.)
