Hi there

 

I'm fairly new to the whole solar thing. Had a previous question and you guys gave awesome advice. I'm back with a new question. My current system is 2 x 5kw Deye inverters, 4 x 5.2kw batteries and 20 x 545w bifacial panels...I sorted all the stuff out from my previous issues regarding the low voltage etc. For the summer I have a lot of fans for cooling the house down. This winter will be my first winter with solar. I spoke to a few people and I get mixed answers...Currently I have a few heaters that I used last winter. We usually only use them fore an hour or 2 in the morning to heat up the room when getting dressed. What is the do's and don'ts regarding heaters and the inverters/solar/battery?

Get your ceilings insulated. That does make a difference. There may be old insulation in there that has collapsed. If it's one of the glass fibre products then getting it removed may be tricky, but maybe the new product can be laid over the old.

Do some sums. You know what those heaters draw and you know how long they will run for. If they are plug in heaters then get a Kill-A-Watt and verify the consumption figures.

Then look at what you typically have left in your batteries at that time of the morning. Does that give you enough to run the heaters for 2 hours? And add up the total draw for the heaters and add in anything else that's likely to be running: How close are you to the 5kW limit on those inverters?

The ceilings are insulated. The reason for my question is that I got various answers for my question...some saying that your'e not allowed to run heaters/elements on a solar system....some say only a specific infra red type of heaters or specially designed heaters for inverters. At that stage in the morning my battery is at least 40% and my total house usage is less then 1kw at that stage. The load gets split between the 2 inverters, so not even 500w per inverter...This is at 5-7 in the morning...Have a gas stove for boiling water etc....so minimal stuff is on...I think the 1 heater draws about 800w and the other maybe 1.5kw....not big heaters...is used just to warm up so you don't "freeze" while getting dressed...:)

First I hear of this limitation, but maybe some cleverer people know better. You've got an inverter and battery that can output up to 10kW of power, which is probably enough for your heaters. The concern would be, if you only have 40% battery capacity left at that time during summer, then you'll probably have less battery capacity left in Winter, due to shorter days, less intense sun, and longer nights. If you're down to say 30% battery at the same time in Winter, then you'd probably not be able to run the heaters for long enough before reaching shut-down capacity of maybe around 20%.

5 minutes ago, termdj said:

The ceilings are insulated. The reason for my question is that I got various answers for my question...some saying that your'e not allowed to run heaters/elements on a solar system....some say only a specific infra red type of heaters or specially designed heaters for inverters. At that stage in the morning my battery is at least 40% and my total house usage is less then 1kw at that stage. The load gets split between the 2 inverters, so not even 500w per inverter...This is at 5-7 in the morning...Have a gas stove for boiling water etc....so minimal stuff is on...I think the 1 heater draws about 800w and the other maybe 1.5kw....not big heaters...is used just to warm up so you don't "freeze" while getting dressed...:)

OK... so do the calculations. Ask yourself what will happen if, for EG, somebody turns the microwave on. Does that push you over the 5kW limit?  Could that happen? The kettle? Both? 

There is not an absolute right or wrong for this, there is whether or not your system can handle the peak load and deliver the kW required.

Suggestion: Put the heaters on a timer switch. I used to do this years ago. The heater would run for an hour. When I got out of bed the room was nice and warm, and my electricity billy was tolerable.

My biggest concern was that I can't run the heaters on a solar system...If I can run the batteries on solar without "damaging" them, I know I will be able to manage the battery/usage to not deplete the batteries completely...

2 minutes ago, Bobster. said:

OK... so do the calculations. Ask yourself what will happen if, for EG, somebody turns the microwave on. Does that push you over the 5kW limit?  Could that happen? The kettle? Both? 

There is not an absolute right or wrong for this, there is whether or not your system can handle the peak load and deliver the kW required.

Suggestion: Put the heaters on a timer switch. I used to do this years ago. The heater would run for an hour. When I got out of bed the room was nice and warm, and my electricity billy was tolerable.

That time of morning we get dressed for the day etc...food was prepped the previous evening...there is almost no load in my house untill 07h30 when my sprinkler system comes on..that time of morning a microwave won't throw me over the limit. My biggest concern is that the heating "element" may cause damage as per some people's advice that I spoke to.

 

I can manage the time the heater is on when getting up and leaving the house manually, so if there isn't enough battery, then I will adjust the time I run the heater

3 minutes ago, termdj said:

My biggest concern was that I can't run the heaters on a solar system...If I can run the batteries on solar without "damaging" them, I know I will be able to manage the battery/usage to not deplete the batteries completely...

It is possible with a Deye inverter to put a limit in the battery discharge level, and on the discharge power rate, within the settings, to manage it in line with what your battery's specifications demand. And as I said earlier, in your setup with 2x5kW inverters, and 4x5kWh batteries, check the maximum discharge rate per battery and per inverter, but you appear to have enough capacity on-hand to handle your loads.

The installer set the discharge limit...it's currently at 115ah. So, basically the heaters won't damage the inverter/batteries...it's more to do with the soc of the batteries and managing the load on the inverters when using the heaters so I don't go over the max load of the inverter/s

Edited January 20, 20251 yr by termdj

I run two 3kw oil heaters on our system often in mid winter - albeit at the 1kW setting.  This is off a 5kW Deye.  They cycle on/off during the day when working from home to keep the two rooms occupied liveable.  They do chow power - but they are probably the simplest form of load for an inverter - a constant resistive load.  There is nothing that makes them "incompatible" with a solar system.

The reason installers say you cannot run them is because they assume people are going to flatten their batteries too quickly and run them into the groud (underspecced system) and then complain - especially during load shedding when there is no grid available.  If you understand how much power your heaters consume, and manage your battery levels accordingly, there should be no issue running them within reason - as already said by others.

I just wanted to add that, assuming you're not off-grid, and there is no loadshedding, you can draw +-15kW from two Deye's in Parallel - as long as the grid is available.  It will "pass through" the excess that is over the 10kW inverter capacity from grid instead and won't trip.  So your chances of tripping anything is very minor!  (In addition, if items such as your geyser is connected as non-essential equipment, their usage won't 'count' towards the inverter's trip limit either - they will just draw any excess that the inverter cannot provide from the grid directly.)

 

Thanks for the feedback,  much appreciated. Will try as advised...won't have need for the whole day...

1 hour ago, termdj said:

That time of morning we get dressed for the day etc...food was prepped the previous evening...there is almost no load in my house untill 07h30 when my sprinkler system comes on..that time of morning a microwave won't throw me over the limit. My biggest concern is that the heating "element" may cause damage as per some people's advice that I spoke to.

I've not heard that before. Though there will be cases where people plug in a heater, something goes pop, and so the heater gets the blame.

A resistive load? Well then you couldn't iron or use a kettle. Or use an incandescent light. 

Maybe those peeps you have spoken to are being a bit too cautious?

A heater is simply another appliance pulling current, like those of us who run electric geysers for hours per day of the system or pool pumps etc, seems like there is no difference so to speak.

Manage your loads so you dont trip your system, which can be hard or not hard to do...also your time of use settings will determine your battery level you want to consume.

I'm running 2 x households of the system so that just means double of everything basically, have had no issues and no trips to date (touch wood).

Remember these devices - Inverters and Batteries are purpose built for this to supply/charge/discharge as and when the load requires it to.

A friend of mine also has 2 x 5kVa Deye's...they have a constant load of like +5000w at any point in time almost 2yrs now...albeit he only uses his 2 x batteries if the grid fails.

7 hours ago, termdj said:

some saying that your'e not allowed to run heaters/elements on a solar system....some say only a specific infra red type of heaters or specially designed heaters for inverters. At that stage in the morning my battery is at least 40% and my total house usage is less then 1kw at that stage. The load gets split between the 2 inverters, so not even 500w per inverter...

You can. I am running 4kW of heating elements on my solar system every day, from spring to fall, without any issues (Europe).

Also, charging EVs from my off-grid solar quite often. It's 7kW of load.

With your system a couple of heaters will be no problem.

Thanks people...I will give it a go this winter...I feel a lot better and more relaxed regarding the can and can't with the inverter etc.

12 hours ago, Youda said:

You can. I am running 4kW of heating elements on my solar system every day, from spring to fall, without any issues (Europe).

Hey dude, between Spring and Fall is Summer, why would you run a heater in Summer 🙂

In my case, it's for the hot water baths and showers. You know - having girls in the house means that you need a LOT of it 😂

 

BTW: For a shame, here in the Europe PV works really great from the start of February till the end of October, but during November-December-January, the sky is dark, cloudy and the snow is falling too. So the winter solar yields are totally unusable for anything serious 

PVGIS Calc 10kWp:

 

2 hours ago, Youda said:

totally unusable for anything serious

well. here have heard of clouds 😉 winter is mostly clear skies, but PV is down to around 20-24kWh/day, whereas spring to autumn will yield a lot closer to 30+ a bit kWh/day (that's from 4.7kWp), totally reliant on a hot water cylinder that has 12 evacuated glass tubes to make warm/hot water, even in winter, when temperature range is -2degC on a miserable cold winter morning to 25degC on a nice winter afternoon...

here, the green Kalahari, is pretty much desert area, similar to the western parts of north & south America and Western Australia, rainfall since beginning of spring (1st of September) is 53.2mm, so, 4 months, and 21 days has given us nearly 1/3mm daily on average, winter, June, July & August, gave us 0mm in all... the northern parts of South Africa are summer rainfall regions, where thunder & lightning makes its way down from the equatorial regions to give us some moisture, a lot more on the eastern half of the country, towards the warm Indian Ocean (currents down from the equator), whereas we're closer to the cold Atlantic (currents up from the Antarctic)... the south-western parts, Cape Town and surrounding areas, different to the northern parts, have more winter rain and even snow on the mountain tops in winter...

Edited January 21, 20251 yr by Kalahari Meerkat
speeling....

2 hours ago, Youda said:

PVGIS Calc 10kWp:

here its 9 x 280W panels looking north at probably 50dgrees off the vertical and 8 x 280W panels looking at 45degrees off the vertical to the east, between app. 11 and 14:00 lying, flat looking straight up and after 14:00 looking at 45degrees off the vertical to the west...

PV Calc: 4.76kWp

Edited January 21, 20251 yr by Kalahari Meerkat
kWp calculation missing