Direct to water heating.

[Capt Bill]

PWM MPPT Boiler Heater Charging Controller for Solar PV Panels Controller Controller ACTii AC7391

PWM regulator for heaters with an algorithm for finding the maximum MPPT power point from photovoltaic panels. The regulator enables powering standard heaters of electric hot water boilers (operating at 230V or 110V AC) from PV solar panels. The photovoltaic panel works at maximum power only at...

actii.pl

Interesting; I was not sure which country you live in by the currency that web link shows / got converstion of cost to USADollars of: $178.13 ... Hope it works good. and that we get a report when you dial it in.

 

[christian1980]

It will take time because i have to build this first: Link Link2 I am collecting the things and start the projekt next year.

 

[100kwh-hunter]

My two cents worth of thought:

Did not read all the posts, but next month i start mine hot water project, yes during winter time.
I will connect 2 solar panels 32v @ 12a direct to a temperature controls to a 48v heating element.
With a well insulated barrel with pir sheets, rd value of 8.
The experiment will contain a 205liter drum.
110V 220V 12V 24V Digital Temperature Humidity Controller Thermometer Hygrometer Incubator Dehumidifier Thermostat Humidistat DC|Temperature Instruments| - AliExpress
This one i bought for a tobacco curing room, but they have also for 48v system that will cut off at my desired temprature: 70 Celsius.
If this will work to my liking, i will convert the old water well under the house to a massive insulated hot bath ~2000 liters.
Fingers crossed.

With best regards Igor

 

[Capt Bill]

My two cents worth of thought:

Did not read all the posts, but next month i start mine hot water project, yes during winter time.
I will connect 2 solar panels 32v @ 12a direct to a temperature controls to a 48v heating element.
With a well insulated barrel with pir sheets, rd value of 8.
The experiment will contain a 205liter drum.
110V 220V 12V 24V Digital Temperature Humidity Controller Thermometer Hygrometer Incubator Dehumidifier Thermostat Humidistat DC|Temperature Instruments| - AliExpress
This one i bought for a tobacco curing room, but they have also for 48v system that will cut off at my desired temprature: 70 Celsius.
If this will work to my liking, i will convert the old water well under the house to a massive insulated hot bath ~2000 liters.
Fingers crossed.

With best regards Igor

Noticed: Very Nice selection of Temperature Controls; .... and even if link shows a source that does not ship to USA; That is good info to find same on Alibabaexpress or eBay :+)

 

[100kwh-hunter]

Sorry the link is to my country, you will have to change that yourself, sorry.
Make an account or a one time order with no account and fill in your home adress, postal would be the same $0

Best

 

[z80]

A hot water system doesn't know or care whether it's AC or DC being supplied.
In Australia we can get second hand 250w panels for about 20 bucks a piece.

The way you connect is directly to the heating element.

You need to use ohms law to match the resistance of the heating element to the internal resistance of the panels.

It goes something like this....

If it is a 3600w/ 240v element then the resistance is P=Volts x Amps.

3600=240x15 amps....

and

Volts = amps x ohms
240 =15 amps x ohms

240/15 = 16 ohms....this 16 ohms is the important parameter.


Now look on the compliance plate of the solar panel....

For example a 250watt panel might have this on the sticker

Vmp=35v
Imp=7A

The internal resistance of the panel is about 35volts=7amps x ohms

35 divided by 7 is 5 ohms

This means 3 of those 250w panels in series adds to 15 ohm which is close enough for a match to connect directly.

This however supplies 750w continuously (as long as the internal bi-metallic thermostat in all hot water systems allows current to flow a the set temperature)

If you want more panels, hence a faster heating...simply add more panels in series and parallel combinations to mathematically match the resistance of the heating element.

The matching of the panel resistance to the element is maximum power transfer.

But you can do it roughly matched but power output will vary by the same magnitude as the mismatch.

Hope that helps, it works for me and has zero electronics to maintain....and costs nothing in addition to panels.


attached is a spreadsheet that a youtuber put together, he is roughly on the ball..although he tries to sell shit on amazon...

rename the file solar.txt to solar.xlsx

 

[Solarfun4jim]

Only just seen this thread, so haven't read through the 10 previous pages...

Could this work (see link below) as it has battery less support...ie connect solar panels to one side and load to other. Gives you a lot of flexibility on both the solar array set ups and also various heating elements on the load side??? (needs a minimum of 150v on the PV side)
Only one 'box'. When your tank is fully warmed...use another load.
USB Bluetooth 5KW Inverter 500Vdc PV Input 230Vac 48V 80A Batteryless Support | eBay

 

[TRW]

A hot water system doesn't know or care whether it's AC or DC being supplied.
In Australia we can get second hand 250w panels for about 20 bucks a piece.

The way you connect is directly to the heating element.

You need to use ohms law to match the resistance of the heating element to the internal resistance of the panels.

It goes something like this....

If it is a 3600w/ 240v element then the resistance is P=Volts x Amps.

3600=240x15 amps....

and

Volts = amps x ohms
240 =15 amps x ohms

240/15 = 16 ohms....this 16 ohms is the important parameter.


Now look on the compliance plate of the solar panel....

For example a 250watt panel might have this on the sticker

Vmp=35v
Imp=7A

The internal resistance of the panel is about 35volts=7amps x ohms

35 divided by 7 is 5 ohms

This means 3 of those 250w panels in series adds to 15 ohm which is close enough for a match to connect directly.

This however supplies 750w continuously (as long as the internal bi-metallic thermostat in all hot water systems allows current to flow a the set temperature)

If you want more panels, hence a faster heating...simply add more panels in series and parallel combinations to mathematically match the resistance of the heating element.

The matching of the panel resistance to the element is maximum power transfer.

But you can do it roughly matched but power output will vary by the same magnitude as the mismatch.

Hope that helps, it works for me and has zero electronics to maintain....and costs nothing in addition to panels.


attached is a spreadsheet that a youtuber put together, he is roughly on the ball..although he tries to sell shit on amazon...

rename the file solar.txt to solar.xlsx

Wow, lots of interesting info here, I have a busy day but will try to sort this out and understand it this evening. Thanks for the info, I will have a few questions later.

 

[Hedges]

A hot water system doesn't know or care whether it's AC or DC being supplied.

Actually, it does care.

The heating element doesn't care. But the thermostat and the over-temperature switch are only designed to interrupt AC. If fed with DC there is a very good chance they fail to open the circuit. This could burn up the switch, could leave heating element powered so water tank goes into an over temperature, over pressure condition.

Sure hope the pressure relief valve is installed and functions as intended!

For something that could level a house (or if not that, present a life-threatening hazard), I want at least two fail-safes that work properly.

 

[BiduleOhm]

 

[GLC]

Test was not by code, where was the pressure relief valve?

 

[100kwh-hunter]

Good old mythbusters, what would happen if you have no safety valves, build a locomotive in gauge one without safety.....

 

[BiduleOhm]

Test was not by code, where was the pressure relief valve?

They can fail... or worse, be replaced by a plug because "it was leaking"...

Also, it's a redundant safety; if you deliberately use the thermostat on DC then the relief valve becomes the only safety...

You really don't want xxx L of pressurized boiling water in something without redundant safeties... 1 L of liquid water will make about 1700 L of steam, and it all happens in a few ms. I'll let you do the math on what damage it can do to a typical house, but I think the photos and videos are enough

 

[100kwh-hunter]

They can fail... or worse, be replaced by a plug because "it was leaking"...

Also, it's a redundant safety; if you deliberately use the thermostat on DC then the relief valve becomes the only safety...

You really don't want xxx L of pressurized boiling water in something without redundant safeties... 1 L of liquid water will make about 1700 L of steam, and it all happens in a few ms. I'll let you do the math on what damage it can do to a typical house, but I think the photos and videos are enough

2500 to 3500L in high pressure steam...it climbs faster than you think....WAY faster

 

[sunshine]

I will connect 2 solar panels 32v @ 12a direct to a temperature controls to a 48v heating element.

pv ohms is 2.7ohms
From the table provided by z80 the closest element with this resistance is the 1000w/48v with 2.3ohms -
This element will put out 380w with the 2 panels in parallel - 300w into heating water 80w wire loss.
You wont need a thermostat!!

Or add another 4 panels, more likely 6, to get 1000w

 

[Hedges]

PWM MPPT Boiler Heater Charging Controller for Solar PV Panels Controller Controller ACTii AC7391

PWM regulator for heaters with an algorithm for finding the maximum MPPT power point from photovoltaic panels. The regulator enables powering standard heaters of electric hot water boilers (operating at 230V or 110V AC) from PV solar panels. The photovoltaic panel works at maximum power only at...

actii.pl

"The solar panel operates at maximum power only at the optimal voltage. Connecting the heater directly to the photovoltaic panel causes too heavy load and as a result voltage drop. At reduced operating voltage, the panel produces even several times less current than at optimal voltage. The use of a charge regulator eliminates this problem. Even on cloudy days it will be possible to heat the water in the boiler.

A buffer module containing capacitors, a choke, diodes is added to the regulator, which allows greater efficiency (up to 30%) and reduction of interference caused by PWM regulation."

At reduced operating voltage, the panel doesn't produce several times less current, it produces more.
What it does produce is several times less power than at Vmp.

This PWM charge controller isn't going to do anything about that. MPPT would. Switching in more or fewer heating elements would.
All PWM does is regulate average power delivered.

Whether with this unit or PV direct, I suggest incorporating the water heater's over temperature sensor and thermostat for pilot duty to turn off heating. That could be a low voltage low current DC to operate a relay, or AC to operate a relay. Multiple shut-off mechanisms is a good thing.

 

[z80]

A lot of fear mongering and negativity here.

 

[Hedges]

A lot of fear mongering and negativity here.

Not really.
Just offering a sincere technical review.
If anyone thinks it is OK to simply connect a DC voltage to a system designed and tested for AC, it is important to understand the failure mechanisms, and what could go wrong.

That system requires 3 independent failures before a catastrophic accident occurs.
The Mythbusters video mentioned a couple cases where what they deliberately did (in a controlled situation) had occurred in a house.

An electrical water heater has a thermostat (UL listed for AC), an over-temperature cutout (UL listed for AC) and a pressure relief valve (UL listed).
If someone connects 120V DC or 240V DC, both the thermostat and the over-temperature cutout are expected to fail. The pressure relief valve is expected to function.

Two down, one to go ...

... and people have been known to replace leaky pressure relief valves with a pipe plug.

Once you understand why the water heater system was designed the way it was, and how bad failure could be, you can set about designing something which accomplishes what you want but still is acceptably safe.

 

[sunshine]

A lot of fear mongering and negativity here.

An option is to leave the hws intact and place the dc element at the inlet, sloping up to use thermo siphoning for heat transfer.

https://diysolarforum.com/attachments/polyhousing-jpg.22764/

This is #1
#2 the poly has been replaced with galvanised fittings, another T added for another 12v/600w element, the tap removed to increase the opening,
and covered with insulation- why no photo

#3 will be when I find an old hws system to replace #2

The mains has been off for a few months except for a once a week legionella kill.
Any thing will work during an Australian summer!

temp readings at 10am (now)
33c air
28c cold water in
54c under the insulation at inlet
39c hot water out

 

[z80]

Not really.
Just offering a sincere technical review.
If anyone thinks it is OK to simply connect a DC voltage to a system designed and tested for AC, it is important to understand the failure mechanisms, and what could go.I would appreciate you proving that these components will fail as you say.

Please prove that the components will fail ?

The heating element is a passive resistor.

It doesn't care what type of voltage is applied to it, AC is simply instantaneous DC.

Directly connecting solar panels, with care to match panel resistance to heating element resistance, is by far the cheapest and reliable way to accomplish that.

In the past the cost of the panels has precluded that approach, but panels are cheap now.

Connecting microprocessor controls to do all that is soooo wrong.

For control,the mechanical thermal setting switch on a standard hot water system is robust and durable and the best way to do it.

After all that's it's default mode of operation in any other domestic situation.

Can't see how sensationalist photos of burst water jackets has anything to do with the price of fish.