Large drainback solar hot water project

[Mikesolar]

Good work Eric, how will you use the heat in the summer because that is the biggest issue. Given what I see there, I would use about 6' of copper to keep the heat away from the pex. You may be surprised (or not) by how much heat will flow into the pex. The copper can help a bit.

BTW, where in NS are you. My cottage is near Chester.

[Mikesolar]

There is a very neat tank called the ROTEX from Germany and they use 3-4 parallel loops of 1/2" pex as the DHW HX in the tank. Not much different from what you have done.

[ESharp]

I decided to use an Arduino for the controls. Since I wanted to integrate the solar with my heating system, I figured it would give me plenty of flexibility. I’m using one wire DS18B20 digital temp sensors for the inputs and a relay board (http://arduino-info.wikispaces.com/ArduinoPower) to control the pumps and furnace. There are four relays, one for the solar loop pump, one for the furnace loop pump, one to turn on the furnace fan, and the last is in parallel with my house thermostat. This allows three modes of operation for heating the house.

First mode/stage would be solar only. The water in the tank is hot enough to comfortably heat the return plenum air, so just the circulating pump and the furnace fan are switched on. Second stage is if the stored water is still warm, but not sufficient to provide all of the heat to maintain the house temperature. The oil burner will switch on, but I’ll also keep the circulating pump on. Third stage the water has cooled down to a point where it is pointless to circulate it. I’ll switch off the pump relay, and keep the oil burner on.

I also bought an Ethernet shield to hook everything up to the internet. I got most of the programming from Nateful’s Differduino site: Arduino Differential Controller | Arduino Solar Hot Water | Differduino | Nateful . I’m connected into Xively (previously Cosm, previously Pachube) to log data and can also control the thermostat set-point and pumps remotely. You can see the feeds here: https://xively.com/feeds/42603

Most of them aren’t hooked up yet, I’m kind of controlling things manually for now until I have everything set-up. Wiring is also still a bit messy.

[ESharp]

Originally Posted by Mikesolar

Good work Eric, how will you use the heat in the summer because that is the biggest issue. Given what I see there, I would use about 6' of copper to keep the heat away from the pex. You may be surprised (or not) by how much heat will flow into the pex. The copper can help a bit.

BTW, where in NS are you. My cottage is near Chester.

Thanks Mike,

Yeah I will definitely have an abundance of extra energy in the summer. A pool or hot tub is a possibility. It is a drainback system, so if the tank is maxed I just need to turn the pump off.

Perhaps I could make a few modifications and get some steam to power a turbine, haha.

I am a little concerned about the PEX connection at the beginning of the return. If I have a failure due to heat it will be there. One aspect helping me is that the loop will be un-pressurized in stagnated conditions. It is supposed to be good for 100psi @ 180F.

Chester is a beautiful place to have a cottage. I live close to Peggy's cove.

[Mikesolar]

I guess it was not as much fun to buy the panels from Thermo-Dynamics in Burnside, haha, but that is not what this forum is about, it seems.

Many years ago I had dreamed up and made a steam turbine for just that purpose using a tesla turbine but the amount of heat needed was pretty high to get much out of it, then you have to capture the condensate but it was a lot of fun to make.

You will have to just see how it goes with the pex. Although it is rated at 100/180F, this is just the agreed upon standard. It will take more temp at less pressure or vise versa. If it is a good tubing like REHAU, it may have higher capabilities.

Actually the cottage is near Blandford on the Aspotogan, lovely sunsets looking west (ish)

[ESharp]

Those are good panels, I've even taken a tour of their shop, but at $1k a pop, they were are a bit out of the budget.

The Aspotogan is just across the bay from me

[Mikesolar]

I may be forced (by curiosity) to drop in next time I am down, haha.

[ESharp]

Certainly, love to give you a tour.

[randen]

ESharp

This is some good stuff. I've been collecting solar for about 4-5 yrs. Still amazed at how much heat is available. In-floor heating just rocks. Using an arduino for controlling all aspects AWSOME!! Love that you have already installed the Water to air HX. Is there a 2 speed fan?? It will be interesting what your system will do. I'm on the edge of my seat.

Randen

[ESharp]

The furnace just has a single speed fan, and from what I can tell so far I'll need all the air flow I can get with the low temp water.

Here are a few pictures of some insulating I did yesterday. I’m using 1” thick EPDM closed cell foam made by Areoflex (http://www.aeroflexusa.net/products/aerocel_sspt/). It’s a bit pricey here at ~$3 a foot, but I’ve got a significant amount amount piping outdoors. It is also UV resistant and theoretically does not require any additional covering.





For the ‘trench’ to the house I’m using 2” rigid XPS board. I had to make a compromise/sacrifice here since it’s a drainback system the trench becomes a protrusion closer to the panels. I’m relying on the rigid box to help maintain a gradual slope back to the basement. I plan to do some grading to cover it, but the pipe and insulation is definitely not below the frost line. Time will tell whether this was a mistake.