# Magneto Thermotank heat exchange geyser

This product popped up on my Youtube feed this morning.

It looks quite interesting, however for the price of R30k (quick Google), you can basically buy a traditional heat pump and traditional geyser, to end up with much the same.

Also it doesn’t state for how long it consumes 750W, how long it takes to heat the 200l of glycol / water to 60 degrees.

This looks very interesting.

It is discussed here: Magneto Thermotank heat exchange geyser

Dumb question.

Are not all watts equal?

It is claimed that 750W consumed gives 3Kw on output. So 3Kw output from this thing would equate to a 3Kw element in a normal geyser not so?

Or does heat pump tech work a little different?

Lets say a 3kw geyser element takes 2 hours to heat 200L water from cold to 60 degrees, would this heat pump not also be able to do it in the same time (under ideal circumstances off course)

I don’t quite know all the correct technical terms, however that’s basically how heat pumps operate, for a specific electrical call it input Wattage, it gives a higher heat output Wattage.

They’re saying that the 750W this device consumes does as much heating as 3kW with a regular element.

This is how heatpumps save - my 1.5 kW pump heats faster than a 3kW element.

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I would really like to get first hand experience on this product.
Unless it runs less than 6 hours per day at 750W to do its thing, then it won’t use less electricity than my 3 kW geyser.

My case is probably extreme since I live alone, I only run my geyser 1.5 hours a day which is more than enough in summer, I basically heat one tank of water per day.

We do the same, one tank per day.

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Heat pumps work by moving heat from one place to another, so they consume less energy than an element to perform the same amount of heating, as it is just moving heat from the outside into your geyser which is more efficient than an element which is just turning the electrical energy directly into heat. Heat pumps can move heat from a cold area (cooling it further) to a hot area (warming it up more) but I think they get a bit less efficient the higher the temperature difference. So basically in this case they claim that the heat pump consumes 750W to move the equivalent of 3kW of heat, giving it a COP (coefficient of performance) of 4, which sounds about right.

In other words (given my 200L water and 2 hour example), under ideal conditions I will need to run my 750W heat pump for the same time a 3Kw element would need to run. But I would just consume 1500 Watt over the same 2 hour period.

This is what I fail to understand why the running time for this device is possibly an issue.

No, it would consume 750W over the 2 hour period, resulting in 1.5kWh of energy consumed.

See this is where I fall out of the bus. 750W per hour = 1500W used over 2 hours (for the heat pump)

And the element would have been 3000W per hour = 6000W over 2 hours.

Running time stays the same for the 2 products.

Are we not saying the same thing?

No, W is a rate of energy consumption, like km/h. If you drive 100km/h for two hours, you have driven 200km.

There is no unit like W per hour, that would be the same as acceleration, which is the rate at which speed changes. So W per hour would be the rate at which your W changes.

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It is often helpful to remind people that a Watt is literally a joule per second. There is a “per second” hidden in the name, so it is literally a bit like “liters per hour”. If you run the tap half-open, and you fill the same bucket, it is the same amount of water and you pay the same for that consumption. It just takes twice as long.

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This is the part I don’t understand. Why should it take twice as long when the output is the same.

This I don’t get.

Watt Hour is comonly used though because it’s easy to quantify.

If I run a 1 kW motor for 1 hour then I’ve used 1 kWh, if I run the same 1 kW motor for only 30 minutes Ive use 0.5 kWh.

If the actual heat output is the same – which is of course the point of a heatpump, to have the same output at a lower electrical consumption – then it will take the same time to heat the water.

I think @_a_a_a is really just having the same eye-twitching OCD moment I get when people say “Watt” and they really mean “Watt-hour”

So if the 750W heat pump runs for two hours, it will consume 1.5kWh of energy. If we assume it has 3kW of heat output, then it puts 6kWh into the tank. If you used the normal resistive element, then it would of course consume 6kWh of energy. So this is a 75% saving. It assumes (of course) that the COP (coefficient of performance) of the heat pump is 4. Some of them are that good, although in my experience it is more like 3.5 usually.

I don’t disagree with anything you have said.

Watts per hour is the nonsense unit/term, not to be confused with Watt-hour.

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@_a_a_a and @plonkster you remind me of a maths teacher I had in school and a electronics lecturer I later had while studying.
I actually understand things perfectly well, but then the way you explain it makes my head spin and makes me doubt myself for a minute or 3. :smily

I’m glad I at least remind you of a MATH teacher. That could have turned out differently

For a large part of my life I spent a lot of time on understanding how people think. Which is also a personality thing, having an MBTI of ISTP, that means I’m in the back room taking an engine apart anyway. Then in the last year, my daughter was diagnosed with Aspbergers. Now the first thing many a parent will tell you, is they never thought this was even a possibility, because their kid wasn’t that different to how they themselves have always been.

Then slowly the pieces of the puzzle starts to drop into place. That family member who told you to your face you are hard to talk to because you ramble on and on about things they find uninteresting. Literally getting fight-or-flight response from people’s bad spelling or grammar. Having OCD about using the right units. Spending an hour after bedtime, because someone is wrong on the internet and this will not do. I think somewhere along the way, I started to realise… maybe this is not my fault.

It is liberating and maddening at the same time. Wish I knew sooner.

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