Good afternoon Forum,

I'm looking for a solution to heating water.

I have 6 330W panels that are currently collectiong dust but I would like to use them to assist in the heating of water for 2 geysers (they are 150l and 200l kwivot geysers) at my home.

Currently both geysers run on a timer through a 5kw inverter, but they're killing the batteries (2 x 51.2V100Ah lithium batteries in parrallel) and I'm wondering if there is something I could do to assist with warming the geysers before the geysers have to run through the inverter that would help stop them running the batteries down.

Thoughts?

Geyserwise Eco installation, one for each geyser, and 3 panels per geyser. As a possibility, if you're not planning to upgrade the inverter setup with panels.

Tim, give us some stats to help us to give you good advice: current inverter and solar panels, time of hot water use, number of users, geysers' element wattage, etc. A graphic of your inverter/solar/battery usage (24 hour period), or at least a summary of times and power usage would also be helpful, as would details of the inverter - no of MPPTs available, and in use, etc.

One possible way (without having any further data...) would be to install a DC element in each geyser and then run your spare panels to just feed their loads directly, although that would only work on sunny days; a second option would possible be to add more batteries, but that would be very expensive...

Hey Hennie,

Current Inverter: Mecer SOL-I-AX-5P

Panels: 8x545W connected in 4P2S

GEYSER 1

1 geyser is for showers and it’s used at night from about 18:00 by three users (this is the 150l geyser)

GEYSER 2

1 geyser is for the kitchen and is purely for washing and occasionally a guest in the guest bathroom (this is the 200l geyser)

Geyser 1 runs via the inverter from 11:30 to 13:00. Geyser 2 runs via the inverter from 13:30 to 14:30.

Hope this helps. Unfortunately I don’t have much further info with the older style inverter.

Batteries are 2 x EasyPower Elithium 51.2V100Ah (5120W) connected in parallel so 200Ah in battery.

Utility kicks in at 51V and turns off at 54V on the battery.

I guess what could add as well is average usage is between 400-500W.

But additional items that run daily:

• toaster (2slice)

• Washing machine (1-2 loads)

You could connect 3 panels to a geyser element and its thermostat... I think someone on the forum said they run DC on their elements.

If you need Eskom backup, you can put diodes onto the DC circuit. I wouldn't use battery energy to supply geysers with a grid connected inverter.

35 minutes ago, TimG said:

Geyser 1 runs via the inverter from 11:30 to 13:00. Geyser 2 runs via the inverter from 13:30 to 14:30.

Thanks Tim, this helps, but is confusing at the same time 🤔 In your first post, you stated: "Currently both geysers run on a timer through a 5kw inverter, but they're killing the batteries" If the geysers are only run during the day, presumably after the batteries have been recharged, why are they draining the batteries? If your solar panels are working correctly (i.e. facing north at a reasonable incline angle, and not being shaded) they should be able to supply the geyser load... or do they only drain the batteries when it's cloudy?

Could you confirm the wattage of the two elements? If 3 or 4 kW, you could change them for 2kW units that will take longer to heat up, but draw less power. My 200l geyser has a 2kW element, and uses between about 6 and 9kWh to bring the water up to about 65 degrees after most of the previously hot water has been used - that is between 3 and 5 hours of heating (including an early morning boost to the geyser by running it for 1 hour from the batteries before sunrise in the mornings). My system has larger batteries, and I like hot water early in the morning, but you should be able to heat your geysers during the day without using the batteries...

Hey Hennie,

I’m not 100% sure, but by viewing the draw on the inverter.

Geyser one is 3kw and geyser 2 would be 4kw.

Panels face north at 21degrees. Max power I’m currently getting from the panels is about 3-3.2kw.

I have a feeling the batteries are just never catching up, so they charge but don’t ever seem to hit the 100% mark. So when the geysers kick on, the 3kw draw and 3.5-4kw draw from the geysers take battery power.

I’m hoping for a relatively inexpensive way to assist the geysers heating so the dar isn’t as long when they run through the inverter.

Looking further at your data, I also guess that your geysers are not being heated fully during the daylight time that they are powered by your inverter.

The 150l unit is heated for only 1.5 hours, and the 200l unit is only heated for 1 hour during the day. Are they further heated during the night (or any other time) by grid? When (time wise) do they run off your batteries?

On average, geyser one draws about 5kw a day and geyser 2 about 4kw.

1 minute ago, HennieL said:

Looking further at your data, I also guess that your geysers are not being heated fully during the daylight time that they are powered by your inverter.

The 150l unit is heated for only 1.5 hours, and the 200l unit is only heated for 1 hour during the day. Are they further heated during the night (or any other time) by grid? When (time wise) do they run off your batteries?

Nope, this is the only time they run. I don’t have them set to run over night.

Looks like we were typing responses at the same time, hence my previous post does not make much sense coming in after your response 😁

Going by the above, I think your cheapest bet would be to downgrade the elements to 2kW units, and then use your old panels hooked directly to them, still using your existing thermostats. I would still prefer to use DC elements and perhaps a Geyserwise controller/thermostat, or at least DC switchgear, as DC could be more dangerous to use, being known for arcing through AC switches...

10 hours ago, frivan said:

You could connect 3 panels to a geyser element and its thermostat... I think someone on the forum said they run DC on their elements.

DC current will fry the thermostat contacts, as DC does not have a 0v potential point 50 times every second so the contacts will arc violently when the circuit is broken.

what is the kW rating of the elements in you geyser?

and also the specs of the solar panels that you want to use?

Does your geysers have the new Solar port (renewable energy port) I think it is a M22 threaded hole, you do get DC pencil elements that fits into the port and it is a PTC element, you could wire DC directly to the element without a thermostat. they go for about R1000 a piece ad its 1100W DC.

you can power your AC element also directly from DC(heating elements does not care about ac or dc) from your panels, the problem comes in to regulate the temperature as you cannot use a AC thermostat with DC power. (you can do it but you should not do it)

Hi @TimG What 5kw inverter do you have?

If you have a DEYE or Sunsynk you could add up to a 2.5kw grid tie inverter onto the AUX port with your 330W panels for some extra power.

They control production from the grid tie and you will be able to use the power from your panels for things other than just heating water.

You won't have to change your geyser elements as they will still be on AC power.

Sorry, just went back through the posts and I see it is a Mecer :-( , no grid-tie option there unfortunately

Hey Scoobs,

Unfortunately no. :(

2 hours ago, stefan44 said:

what is the kW rating of the elements in you geyser?

and also the specs of the solar panels that you want to use?

Does your geysers have the new Solar port (renewable energy port) I think it is a M22 threaded hole, you do get DC pencil elements that fits into the port and it is a PTC element, you could wire DC directly to the element without a thermostat. they go for about R1000 a piece ad its 1100W DC.

you can power your AC element also directly from DC(heating elements does not care about ac or dc) from your panels, the problem comes in to regulate the temperature as you cannot use a AC thermostat with DC power. (you can do it but you should not do it)

Looks to me like a 3kw (Geyser 1) and 4kw (Geyser 2).

Attached are images of Geyser 1 (mounted outside) and Geyser 2 (which has the Kwikot 600 Dual sticker on it).

Geyser 1:

Geyser 2

Panels are:

2 x Canadian Solar 330W Panels

4 x Mecer 330W Panels

You could get a Geystertech unit? No modifications required to the geyser at all. It costs 3k for the unit. The unit can use grid or the panels. That is what I currently bought for my geyser as I did not want the geyser running off my inverter and batteries.. The 3k unit is for up to 150 litre geysers. They have a unit for 5k that is for 200 to 300 litre geysers. It outputs a modified sine wave so does not kill your thermostat.

I skipped Geyserwise as too many reported failures, too expensive and I dont want to use some fancy AC and DC element. I wanted to be able to keep my standard element and when it pops just replace with the standard elements that cost 300 rand, not some element that costs 1.5 to 2k.

10 hours ago, stefan44 said:

the contacts will arc violently when the circuit is broken.

Perhaps. I can't find the post about running DC through the thermostat. Here was an idea with AC on the thermostat:

https://powerforum.co.za/topic/20761-helping-those-with-less-knowledge-of-a-solar-sytem-especially-the-elderly/#findComment-212821

I would use an SSR-40DD instead.

10 hours ago, stefan44 said:

DC current will fry the thermostat contacts, as DC does not have a 0v potential point 50 times every second so the contacts will arc violently when the circuit is broken.

20 hours ago, HennieL said:

Going by the above, I think your cheapest bet would be to downgrade the elements to 2kW units, and then use your old panels hooked directly to them, still using your existing thermostats. I would still prefer to use DC elements and perhaps a Geyserwise controller/thermostat, or at least DC switchgear, as DC could be more dangerous to use, being known for arcing through AC switches...

Thanks for that correction, Stefan. Freudian slip of the typing finger there on my side - meant to type "...still using your existing elements", and not "thermostats" 🫠

Good day.

In my personal opinion one of the better options that I've seen, is to use one of the Geyser tech controllers

Geysertech Pi2R iX Geyser Solar Controller

Is a good option with an input voltage from 90v-325v DC, with 3 panels per controller you will have current flowing to your geyser.

The unit can run from pv only with an option of an AC input as well if you need to flick a switch and add power from your battery backup to increase the temperature rapidly.

These units I have seen to be efficient in getting the water hot if the sun is shining.

In my experience at my house my 150l geyser use 7.5kw to heat the water from cold to 73 degrees, then our whole household shower and we have hot water for dishes. My drawback is on cloudy days I don't let my geyser run the full allotted time in order to get my batteries full.

In my installation I've reset the thermostat on my geyser by first turning to 0 and then to maximum. I have relocated my geyser from the ceiling space to outside of the house and from horizontal to vertical and by insulation of the hot water outlet pipe for the portions that you can will also save on your heating bill, I currently still run my geyser off my inverter but would run one of the said controllers when I got my panels sorted.

With the said controller the output just go to the standard thermostat terminals and your geyser remain stock standard and when the element fails it is a standard affordable element and not the expensive elements that one find these days from various brands.

There is a smaller cheaper version of the controller as well, smaller version input is from 90v - 200v DC if I recall correctly.

Hope this helps