Solar/Wood Hot Water-ping ihfarm

[Larry Caldwell]

I'm thinking of setting up a hybrid solar/wood hot water system. I'm planning an active system with low wattage circulation pumps. One loop will go to the roof solar collector, and the other loop will go to the wood stove. The storage tank will have an electric backup. I think it will give me free hot water just about year round.

I want the system to automatically shut off loops if there is no heat there. I noticed ihfarm mention that his hobby is home automation. I'm looking for suggestions for temperature sensors and control systems that will control a circ pump and valves.

I'm also looking for suggestions on how to make the plumbing bulletproof. I'll be 64 on my next birthday. I don't want this thing to fall apart after 20 years and require a bunch of expensive repairs. I own 93 acres free and clear, and plan to live here until they carry me out feet first, or I have to go into nursing care. I figure with free hot water, I can get my electric bill under $100 a month, which is my only utility bill.

 

[lhfarm]

I said "hobby" and that is my level of expertise. Not really qualified to give advice, but there a couple of sites where you can ask for advice and find solutions. One is CocoonTech.com - Home automation news, reviews, forums, tutorials, wiki, chat and more! . This site is focused on automation and not a single product. The second is Home Automation Systems - HomeSeer . This is the software I've used for over 10 years to drive all my automation projects. Check out the forum sections of both.

I'm sure there are others with favorite sites too. I know there are automation folks on this board. One suggestion is to look at some vendor offerings, to see what solutions (automated) might be available. At the bottom of the Cocoon Tech page is a list of vendors.

Finally, I'd work with the folks here who have experience with hot water system. Once the system is designed, it may be easier to see what needs to be automated.

Good luck!

 

[inveresk]

I had solar panel hot water heating in my last place. The solar panels also preheated the return leg of the low pressure hot water underfloor heating loops although the main source of heat for the underfloor heating was gas boiler. It worked well. I used antifreeze in the solar system at that time but would now opt for a drain back system instead. Less to go wrong. In addition, instead of timers and stats, I'd install a small p.v. panel to power the solar panel pump. That way the solar system automatically starts up with the sun and stops when it drops. The system would also work if the mains power goes down.

 

[mmurphy]

Larry, try some research at BuildItSolar: Solar energy projects for Do It Yourselfers to save money and reduce pollution
This has a lot of info.

 

[Redneck in training]

I'm thinking of setting up a hybrid solar/wood hot water system. I'm planning an active system with low wattage circulation pumps. One loop will go to the roof solar collector, and the other loop will go to the wood stove. The storage tank will have an electric backup. I think it will give me free hot water just about year round.

I want the system to automatically shut off loops if there is no heat there. I noticed ihfarm mention that his hobby is home automation. I'm looking for suggestions for temperature sensors and control systems that will control a circ pump and valves.

I'm also looking for suggestions on how to make the plumbing bulletproof. I'll be 64 on my next birthday. I don't want this thing to fall apart after 20 years and require a bunch of expensive repairs. I own 93 acres free and clear, and plan to live here until they carry me out feet first, or I have to go into nursing care. I figure with free hot water, I can get my electric bill under $100 a month, which is my only utility bill.

You can buy PLC with 24 discrete inputs and 16 relay outputs for less than$100. I paid $80 for my LG K120S including the programing software. Since the analog card that would accept thermocouples or RTD temperature sensors was about $350 I bought two dual programmable temperature controllers with relay output $40 each. The system runs my geothermal heat pump and hot water. One of the controllers controls heating and cooling, and the other hot water heater. The PLC controls temperature in every room and also decides when to switch from cooling to heating and vice versa.
The switches can be programmed as either two independent units or as differential switch using two sensors (that would be your application I suppose). Unfortunately I am out of home and don't remember the brand to give you better information.

 

[Larry Caldwell]

Thanks for the tips on PLC setup. I'll have to do a bunch more research. My temperature sensor setup will have to allow differential control, since it won't do me any good to run a heat exchanger loop when there is 140 degree water at the collector and 170 degree water in the tank. I can probably handle the programming without too much difficulty.

 

[Redneck in training]

I am using controllers from Love Controls, Div. of Dwyer Instruments, Inc. They use cooper 1000 ohm two wire sensors that are cheap. I just checked the price for the controllers about doubled in past few years. I am using TSS2 dual stage temperature switch. You can download the manual from the site. I think it can be programmed for differential function.
I would avoid using valve(s) for selection of the heat source. You will be better off using a pumps with a check valve for each loop. They are very reliable, and will allow you to use both heat sources in the same time.
I bought my PLC on ebay. There are other brands but as far as I know only LG gives the programming software free.
In fact I am in process of building new shop and face similar issue. How to heat it, if AC it etc.
The shop has metal roof and it gets very hot there when sun shines. so I am thinking about instaling a heat exchanger air/liquid under the roof and blow air trough it by a fan. When the shop is built I will research what the summer/winter temperatures are and if they are high enough to be usefull.

 

[hr3]

All very good ideas but before you start what are going to be the cost savings ?? How many people in the house and how much hot water is used ??

 

[Redneck in training]

Here is what you might need for your solar HW system.

ThermokSolar Differential Temperature Controller - Starter Package - Off Grid Options
or this one

 

[DavidVT]

I have had good luck at work with small projects using the TECO PLC/R from Factorymation. Their software is free.

Programmable Logic Controllers and Logic Relays

I am getting ready to use one at home on my outdoor wood furnace and water flow control.