Heating calorifier by inverter?

[Tim Good]

Do you know what make/model the inverter is ?

Heart Freedom 20.

 

[JumbleDuck]

There should be no reason that the inverter won't run the heating element, it's a purely resistive load and will only work at the power rating that the inverter can supply.

The heating element in the calorifier will be designed to produce 2kW at a high temperature. That means a higher resistance: a nichrome element at 400^oC will have a resistance about 15% higher than at 20^oC. Or, to put it another way, a nichrome element designed to run at 400^oC will draw about 15% more current on start up at 20^oC. If it's already marginal for the inverter, that 15% could be enough to break the camel's back.

You see the same effect with knobs on in incandescent light bulbs, which is why they normally blow as power is applied and not while they are working steadily. Tungsten has ten times the temperature effect of nichrome and bulbs run a hell of a lot hotter than calorifiers.

 

[PaulRainbow]

I might be missing something, but it seems to me you're trying to draw 166 amps out of the battery, assuming 12V. That's a lot of current, and you better be sure the wiring, connections and battery are up to it, or else you're doomed to failure.

You are missing something, about 34 amps. As i said earlier, a 2kw inverter under full load will draw about 200a. But you're right about one thing, it's a lot of current.

 

[elton]

You are missing something, about 34 amps. As i said earlier, a 2kw inverter under full load will draw about 200a. But you're right about one thing, it's a lot of current.

I worked it out as i=P/V which equals 166A. So where am I wrong?

 

[PaulRainbow]

I worked it out as i=P/V which equals 166A. So where am I wrong?

Doesn't translate literally where inverters are involved. Accepted rule of thumb is Watts/10 for 12v.

 

[elton]

Doesn't translate literally where inverters are involved. Accepted rule of thumb is Watts/10 for 12v.

Reference? I understand there are losses, but 90% is way beyond my experience.

 

[bristoljim]

Summary:
I want to heat my 2kw calorifier using my 2kw inverter but it won't work.

Details:
This season I've been using the inverter a lot more as we are able to generate way more power on solar than we can consume now that we're on the coast of Portugal. We always boil the kettle now on the inverter and I'm looking for more things to use.

For hot water, when the engine hasn't been run we fire up the webasto. However, I figure we could use the inverter. However the calorifier is rated at 2kw and so is out inverter. When I switch in the calorifier it simply doesn't activate when the inverter is on. I assume this is because the inverter just says "no it's too powerful".

I doubt the calorifier needs a pure some wave, which my inverter doesn't have.

So my question is can I buy some kind of in line resister that I install in the positive lead to the calorifier which will reduce its power to something like 1.5kw?

What you need is a voltage regulator available from RS components part no. 655-644, no major loss of energy & select what rating you want from the element , will handle up to 15amps,have used them for several year for this sort of application
Jim

 

[Graham_Wright]

You could try "soft starting" it. My wet vac will only switch on with the lid off (= reduced load), but that is inductive. Put a mains bulb (or two or three in parallel) in series with it and, if it then works, try shorting out the bulbs. If it stays on, wire it up properly.

 

[noelex]

What you need is a voltage regulator available from RS components part no. 655-644, no major loss of energy & select what rating you want from the element , will handle up to 15amps,have used them for several year for this sort of application
Jim

That look like an ideal solution.

The heating level could be set to make best use of excess solar power.

 

[VicS]

What you need is a voltage regulator available from RS components part no. 655-644, no major loss of energy & select what rating you want from the element , will handle up to 15amps,have used them for several year for this sort of application
Jim

That sounds like an excellent solution assuming that it will work OK on the modified sine wave output from the Freedom 20 inverter

 

[Barbican]

Yeah deffo. It works on shore power and when the generator is on. I wonder if something was originally installed in the system to prevent someone accidentally turning it on when inverting.

Our inverter is set up so that the really big loads including the water heater are not supplied by the inverter. Our element is 1.2kw and the inverter is 2.5, I think it was done to protect the battery bank and wiring from such a high current load, and avoid draining it.

 

[CLB]

What you need is a voltage regulator available from RS components part no. 655-644, no major loss of energy & select what rating you want from the element , will handle up to 15amps,have used them for several year for this sort of application
Jim

For the hard of understanding, can you explain in laymans terms what this item does and how it held the OP. Many thanks.

 

[JumbleDuck]

For the hard of understanding, can you explain in laymans terms what this item does and how it held the OP. Many thanks.

It's almost certainly a thyristor (or equivalent) dimmer, like those used for lights on a bigger scale. Basically they don't switch the power on until a particular stage of each cycle.

Works fine with a sinusoid, but as VicS says may get a bit upset by the stepped output of a lot of inverters.

 

[mattnj]

i added on of these inline near the immersion heater https://www.ebay.co.uk/itm/231679559039
for the same purpose, leave on full power for shore power....then can wind it up/down if on inverter (1500w) or generator (900w)

I added a few marks on the dial, so I know where to set it based on generator or inverter....it just works....

 

[savageseadog]

All the OP will be doing by using an inverter is introducing losses, at a guess the loss would be about 20%. The wiring to the inverter would have to be large to supply its rated output for other purposes in any case. The obvious solution would be a 12V immersion heater, no losses, simple, do they exist?

 

[PaulRainbow]

Heart Freedom 20.

OK, reason i asked is that some of the combi units have two AC outputs, both are powered when connected to shore power but only one is powered when the inverter is in use. Heavy current circuits, such as water heaters, would be connected such that they are not powered by the inverter. Yours does not have such a circuit.

My opinion is, running a water heater from the inverter is still a big load on your batteries, you'd need a hell of a lot of surplus solar to heat the water without having to resort to running the engine or genny. If you want free hot water, it would perhaps be better to look at solar water heating ?

 

[Mikedefieslife]

I managed to run a 1kw rated Atwood water heater from a cheap crappy 1.5kw inverter. It drew roughly 83amps according to my clamp meter and took 45 mins to get the water piping hot. No problems, with 50mm2 cable running 2m to a 675ah bank.

Unfortunately the output from my Websto heater going into the Atwood, is nowhere need as good, and I often end up showering in lukewarm water.

 

[bristoljim]

It's almost certainly a thyristor (or equivalent) dimmer, like those used for lights on a bigger scale. Basically they don't switch the power on until a particular stage of each cycle.

Works fine with a sinusoid, but as VicS says may get a bit upset by the stepped output of a lot of inverters.

 

[bristoljim]

They work fine on the sterling non sine wave inverters - fitted one to the heating element of a washing machine on an inland waterways wide boat so he could use it when off grid but supported by a Leece Neville 160amp alternator !
Jim

 

[mariadz]

We had exactly the same thoughts as some of the people on here.

I understand that the standard is not to run an immersion heater from an inverter but I specifically requested this when we had our new electrical panel, against the initial advice, so that I could run it from the solar if we were somewhere hot. I should point out that we have 880Ah of batteries so the excessive load is shared across these and whatever comes in from the solar. We have done this when we have had a surplus of power from the solar (we get 5KWh on a good day) and it works well, but remember to switch it off after 20-30 mins or the batteries will get hit hammered..