Direct to water heating.

[Daddy Tanuki]

Thank you for your feedback. I am grateful to have your perspective.

I wonder if short cycling is less of an issue with newer inverter based AC units.. Due to gradually ramping up and down? Anyways, cheers!

Wanted to make DIY thermostat after a “smart” thermostat forgot how to use wifi.. then remembered that it’s necessary to have hard delays for the machine to settle and whatnot… moved onto a safer project ?

newer types with soft start do not suffer from this issue. when I say AC i really should have said compressor based refrigeration systems. I just short handed it to AC as it is easyier than explaining what I actually do

I repair a multitude of machines that use compressors to cool down products. think drink bars, slushy machines, ice cream machines etc. etc. non of these use soft start tech (at least not yet) so you often see a compressor where it stops and if power is sagging it does not have the oomph to turn over...so it sits there and burns up the compressor motor.

I would hope at what heat pumps cost that they would already have a soft start circuit and a pressure relief of some sort to let the compressor come up to speed easier. though I am cognizant of them honestly I have not looked at them in detail as I don't have one and they are not something that comes across my bench.

 

[TRW]

150L PV Water Heating System – Geyserwise

Here is a product that I am going to experiment with. Firstly I just want to buy the AC / DC element and feed the DC side directly from the PV panels. Also note that the element is not a standard resistance type but uses ceramic chips. Full details on the website.

I looked at the website and find it interesting. I do have a few questions. What does this cost excluding the panels? Here is a generic question that I should know. If you have 1000 watts, the three 335 watt panels, how many BTUs are you putting into the water on in a sunny hour.

 

[Frick]

150L PV Water Heating System – Geyserwise

Here is a product that I am going to experiment with. Firstly I just want to buy the AC / DC element and feed the DC side directly from the PV panels. Also note that the element is not a standard resistance type but uses ceramic chips. Full details on the website.

Interesting, looks just like a mppt with temp controller but sorted out so no tinkering involved.
Here’s what I used if you just want the element.

Amazon.com

 

[Pierre]

I looked at the website and find it interesting. I do have a few questions. What does this cost excluding the panels? Here is a generic question that I should know. If you have 1000 watts, the three 335 watt panels, how many BTUs are you putting into the water on in a sunny hour.

The price for the complete system in ZA is approx US$ 530 . You can read all the information on their website about the special PTC heating element with ceramic chips. The only problem with this system is that you need to replace the geyser flange plate that houses the element and thermostat. As it is a ZA developed system it works with locally made geysers.
Tomorrow I am going to view another system with a much simpler installation method. This one uses all the standard components already installed in your geyser and uses the signal from the thermostat , AC and DC inputs into their interface unit. I will link this product as well once I have more information.

 

[TRW]

The price for the complete system in ZA is approx US$ 530 . You can read all the information on their website about the special PTC heating element with ceramic chips. The only problem with this system is that you need to replace the geyser flange plate that houses the element and thermostat. As it is a ZA developed system it works with locally made geysers.
Tomorrow I am going to view another system with a much simpler installation method. This one uses all the standard components already installed in your geyser and uses the signal from the thermostat , AC and DC inputs into their interface unit. I will link this product as well once I have more information.

OK, thanks for the update and I will wait for the link when you get it.

 

[GLC]

I looked at the website and find it interesting. I do have a few questions. What does this cost excluding the panels? Here is a generic question that I should know. If you have 1000 watts, the three 335 watt panels, how many BTUs are you putting into the water on in a sunny hour.

In my application, I purchased 3 used 305 watt panels, hooked them up parallel ran wires to a DC element in the bottom of my AC water heater and that was it. Free hot water for cheap.

 

[TRW]

Wow, very interesting. Now time will tell how long this works for you, you clearly will not stress anything other than the switching thermostat contacts, and maybe not too much, as the voltage is not high. Any idea on how much water you heat in an hour? Have you ever looked for hot wires going to the element?

Please keep us posted!

 

[GLC]

I have been running this for about a year. No issues as of yet. We no longer have kids at home so it is just me and my wife so we don't waste waste hot water. When we have full sun days we have more hot water than we know what to do with. We have a regular 40 gallon 220 volt water heater. The top element is still installed with a water heater timer that comes on in the morning for an hour and an hour in the evening. Mainly it is just in case we have a rainy or very cloudy day where our solar gain is minimal. Normally, it never comes on and trust me the water can get very hot with just one dual element in the bottom of the tank. I do however have six panels tied to the dual element. Three panels on the east side of our roof and three panels on the west side of our roof. That way we always have solar gain pumping. I have little cost in the setup. Wire and $85 dollars apiece for used panels and then the cost of the heater element. Zero maintenance. As far as volume of hot water, a coupe of nights ago my wife filled the tub with 104 degree water to do a detox bath. Tub is huge. I still had enough hot water to take a shower after she finished. The water was still too hot for me to have the valve all the way on hot.

 

[TRW]

I think I see the day coming when this is common, so good for you! Did you say you are using a replacement element? Do the panels do any other work of any kind, or just heat water?

 

[GLC]

I think I see the day coming when this is common, so good for you! Did you say you are using a replacement element? Do the panels do any other work of any kind, or just heat water?

Replacement element. 36 volt , 1200 watt. Those panels are dedicated to hot water heating. But i am also running dual 40 amp controllers with other panels to power most of the 110 circuits in my home including latest install of a 110 ductless ac unit in our bedroom.

 

[TRW]

OK that is a great contribution to my knowledge, thanks a bunch.

 

[Hedges]

Replacement element. 36 volt , 1200 watt. Those panels are dedicated to hot water heating. But i am also running dual 40 amp controllers with other panels to power most of the 110 circuits in my home including latest install of a 110 ductless ac unit in our bedroom.

You must not be in earthquake territory like me. I would put straps over the batteries to keep them on the bench.

 

[GLC]

You must not be in earthquake territory like me. I would put straps over the batteries to keep them on the bench.

No sir, thank God i live in Texas for many other reasons too.

 

[curiouscarbon]

You must not be in earthquake territory like me. I would put straps over the batteries to keep them on the bench.

I literally had problems reviewing the entire image because of subconsciously preparing to stop the batteries from shaking off the table ? written from earthquake country.

Nice build.

 

[curiouscarbon]

This paper reminded me of this thread: Performance of a Solar-Assisted Air Source Heat Pump in Heating Condition [zhou2010] it's about heating indoor air but applies to water heating just as much.

Reviewing options:

1. Joule Heating: resistive element in water tank
2. Air Source Heat Pump: pump heat from outdoor air into water
3. Solar Thermal Source Heat Pump: pump heat from solar concentrator into water
4. combination of all the above

Solar Thermal Source Heat Pump can use either dedicated solar concentrator or be integrated into the back of photovoltaic panel.

My ideal solution would be a photovoltaic panel with heat exchanger on back. During winter pump supplemental heat out of them to harvest otherwise wasted solar thermal energy. Bonus: photovoltaic production will increase due to temperature coefficient of most panels...

This would allow the air heat harvesting device ("condenser") to be smaller

 

[TLJester]

Trying to understand exactly how this works.
When you dump power to a water heater, is the excess power coming directly from the solar/MPPT system, or are you really using battery power and letting the solar/MPPT keep topping up the batteries ?

FYI i have a MPP solar system, and from what i can tell all i can do is open a relay that taps into the inverter to power my water heater. Im pretty sure the MPP unit does a mixture of both direct powering from the solar array to the high load on, but also taps into the batteries to make up any delta between what the solar is producing and what the load is pulling. not sure if i am correct with this or not :D

 

[Ampster]

I would guess it depends on whether the water heater is connected to the AC side of the inverter or the DC side and whether you have grid power.
My system uses a heat pump water heater on the AC side and I am grid tied. Are you grid tied? Is your water heater AC or DC?

 

[FilterGuy]

Trying to understand exactly how this works.

If you are talking about the 'Direct-to-water-heating' as per the thread title, there is no inverter involved.


As long as the resistance of the DC element is well matched to the Vmp and Imp of the array, the power harvest should be pretty good. The only active component in the whole system is the thermostat at the DC element.

The AC heating element is a separate system that is independent of the direct-to-water heating system.

With the price of panels getting so low, this is probably cheaper than traditional water heat collectors and plumbing.... and it is certainly a lot simpler.

 

[TLJester]

Im not tied to the grid (boat system).
water heater is AC

 

[TLJester]

If you are talking about the 'Direct-to-water-heating' as per the thread title, there is no inverter involved.

View attachment 68489
As long as the resistance of the DC element is well matched to the Vmp and Imp of the array, the power harvest should be pretty good. The only active component in the whole system is the thermostat at the DC element.

The AC heating element is a separate system that is independent of the direct-to-water heating system.

With the price of panels getting so low, this is probably cheaper than traditional water heat collectors and plumbing.... and it is certainly a lot simpler.

ahh never quite understood that. Have not found DC elements for the hot water tank/heater i have. so would assume in that case its a relay off the AC inverter ?