Heat pump, Good Idea?

Lupus said:
I've never had a boob, not even with the old system :-P batteries are charged by 12, even with the geyser once it was warmed the next time it went off was 4pm in the afternoon when generation was under it's demand.
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I switch on the geyser in the morning to drag the battery down before solar is on full song

And run all the load i can to have battery in play mid day

ie i don't dump power into geyser etc after battery is full, keep the charging as slow as possible in the morning

But yea easier on small systems
With a high base load
 
wingnut771 said:
Now imagine if you had 2 geysers so you didn't have to use power in the early morning to heat the water up but instead, letting the solar production run later into the day. You would be saving 900kWh per month instead of 700.
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Then connect a contacter with a normally closed config on main geyser with

2nd geyser live throug contacter
That way 2nd geyser can only power on once main geyser is off

So for smaller inverter you can only have 1 running at a time
 
leon.davibe said:
Then connect a contacter with a normally closed config on main geyser with

2nd geyser live throug contacter
That way 2nd geyser can only power on once main geyser is off

So for smaller inverter you can only have 1 running at a time
Click to expand...
I like this a lot, actually. I would have the geyser that feeds directly to the showers/taps heat up first. The inlet of which comes from the second geyser to feed it. When it is hot, then as you say, the thermostat will switch that one off and heat the second one. Even if it never gets to temp, it will feed the main geyser with warm water, allowing more people to bathe rather than feeding it cold water, which quickly cools the hot water like in typical geysers.

Only extra wiring is between the 2 geysers. This would be ideal for my situation since my geyser controller is doing nothing for 3/4 hours a day when the water is hot. It could instead preheat water in the other geyser to feed the main geyser with warm water.

No worry about bacteria if the second geyser never hits temp, also because for as long as the water isn't still water, it will be fine. Batteria only grows when the water is not being used.
 
leon.davibe said:
Then connect a contacter with a normally closed config on main geyser with

2nd geyser live throug contacter
That way 2nd geyser can only power on once main geyser is off

So for smaller inverter you can only have 1 running at a time
Click to expand...
This is actually brilliant. The best idea I have read about when it comes to series geysers. I will actually save this post to remind myself to implement sometime next year. I can have some 350 litres of hot water by just adding a 200-litre geyser. I did not like the other series' geyser implementations at all.
 
denmendez65 said:
This is actually brilliant. The best idea I have read about when it comes to series geysers. I will actually save this post to remind myself to implement sometime next year. I can have some 350 litres of hot water by just adding a 200-litre geyser. I did not like the other series' geyser implementations at all.
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I'm not sure I understand. Would it be an AC contactor? Is the idea to use PV DC for the main geyser and excess inverter output for the pre-heater geyser?

What other implementations did you look at?
 
Tomtomtom said:
I'm not sure I understand. Would it be an AC contactor? Is the idea to use PV DC for the main geyser and excess inverter output for the pre-heater geyser?

What other implementations did you look at?
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Yes, when thermostat 1 turns off, it closes contactor for thermostat 2.
 
Tomtomtom said:
I'm not sure I understand. Would it be an AC contactor? Is the idea to use PV DC for the main geyser and excess inverter output for the pre-heater geyser?

What other implementations did you look at?
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Some people had the element in the first geyser and it fed a second one that feeds the house. Others had it the other way round with a little circulation pump. I hated both ideas.
 
Tomtomtom said:
Do normal contactors work for 200 V chopped up DC from an MPPT?
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I don't know how your Geyserwise one works exactly. But with my controller, it is a pulsed DC wave. So yes, it can work with AC contactors and will get a COC for it.
 
wingnut771 said:
How does a DC pulsed wave operate an AC contactor?
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You get AC and DC universal coil contactors. So one with an operating range of 110 to 250 should do the trick. What matters is the RMS. I could be wrong though but I dont think it matters. A 230VAC one might not operate. But a 110 to 250 VAC one should.

If not, then a universal coil one should work since it accepts AC and DC.
 
denmendez65 said:
You get AC and DC universal coil contactors. So one with an operating range of 110 to 250 should do the trick. What matters is the RMS. I could be wrong though but I dont think it matters. A 230VAC one might not operate. But a 110 to 250 VAC one should.

If not, then a universal coil one should work since it accepts AC and DC.
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The AC rating is a bit low on this one though but they exist
Screenshot 2025-10-30 163026.png
 
denmendez65 said:
I don't know how your Geyserwise one works exactly. But with my controller, it is a pulsed DC wave. So yes, it can work with AC contactors and will get a COC for it.
Click to expand...

I'm pretty sure the Geyserwise Eco MPPT is basically just a modified battery charger at ~72 V output.

I'm curious what the high voltage ones like yours do, because to work with the existing thermostat they must presumably be chopping DC at very low frequency. And/or have some sort of arc detection to sense when the thermostat has opened?

Either way, they're not truly AC or DC, so I'm not sure they're necessarily going to play nicely with electromagnetics designed for either. Perhaps the universal type will work.
 
Tomtomtom said:
I'm pretty sure the Geyserwise Eco MPPT is basically just a modified battery charger at ~72 V output.

I'm curious what the high voltage ones like yours do, because to work with the existing thermostat they must presumably be chopping DC at very low frequency. And/or have some sort of arc detection to sense when the thermostat has opened?

Either way, they're not truly AC or DC, so I'm not sure they're necessarily going to play nicely with electromagnetics designed for either. Perhaps the universal type will work.
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Mine just takes the panel voltage, chops it up and sends it through at a high frequency. So if the panel voltage is 200V, you get some 170V RMS.

I think it will work out fine because a coil acts as an inductor. If you use an oscilloscope to measure across the coil, I am almost 100% sure you will see a smooth DC wave with a little ripple. The coil doesn't need to be that big to achieve that. But I don't think you can feed a coil that is 230VAC a 230VDC voltage; you might burn it out. Something like our controllers with lower voltage should do fine. Mine outputs about 130 to 140VDC depending on how strong the sun is.

I would still rather go with the coils that take both AC and DC.
 
denmendez65 said:
Mine just takes the panel voltage, chops it up and sends it through at a high frequency. So if the panel voltage is 200V, you get some 170V RMS.

I think it will work out fine because a coil acts as an inductor. If you use an oscilloscope to measure across the coil, I am almost 100% sure you will see a smooth DC wave with a little ripple. The coil doesn't need to be that big to achieve that. But I don't think you can feed a coil that is 230VAC a 230VDC voltage; you might burn it out. Something like our controllers with lower voltage should do fine. Mine outputs about 130 to 140VDC depending on how strong the sun is.

I would still rather go with the coils that take both AC and DC.
Click to expand...
And no arc detection, because the pulsed DC goes to zero it doesnt need one.
 
denmendez65 said:
Mine just takes the panel voltage, chops it up and sends it through at a high frequency. So if the panel voltage is 200V, you get some 170V RMS.
Click to expand...

Any idea what that frequency is exactly? Haven't found a proper datasheet for any of these things...
 
Tomtomtom said:
Any idea what that frequency is exactly? Haven't found a proper datasheet for any of these things...
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Nope. I have been wanting to get an oscilloscope for fun but can’t justify the cost. Maybe those Temu ones can do the job.
 
Tomtomtom said:
I'm not sure I understand. Would it be an AC contactor? Is the idea to use PV DC for the main geyser and excess inverter output for the pre-heater geyser?

What other implementations did you look at?
Click to expand...
This is all AC just a method to limit 2 geysers that only one can come on at a time not to overload inverter

A contacter is just an electric switch that can handle high load

The live that comes from thermostat to the element is used to power the contacter

The contacter is a normaly closed. So once powered it switches of the 2nd live going to thermostat of 2nd geyser and once it switvhes off when 1st geyser is up to temp normally closed allows power to go to 2nd geyser thermostat sonthe 2md geyser can not switch on while 1st geyser is pulling power
 
Tomtomtom said:
Any idea what that frequency is exactly? Haven't found a proper datasheet for any of these things...
Click to expand...
The solar geyser kits with panels

Uses a DC element and an MPPT to supply a constant volltage to the element in DC the reason a mppt is involved is to supply a constant voltage llikey 48v (salt thumb sucking)

Mppt is a DC to DC converter
So no AC freq in play here

I may be wrong , have no clue if there is AC solar conversion kits
 
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