|This section covers installing the controls for the combined solar
water and space heating system.
Installing the Collector Loop controls...
Installing the Radiant Floor Loop controls...
|An off the shelf differential controller is
used to turn the collector loop pump on when the collector is hotter
that the water in the tank, and to turn the pump off when the collector
cools to the point where it is no longer heating the water.
Most commercial differential controllers come with a whole array of other features such as: displaying collector and tank temperatures, setting maximum storage tank temperatures, pump short cycle protection, vacation settings, ... and more. You can download the manuals from the suppliers of these controllers, and review the features and see what you think you need or want.
I'll pass on that I have our controller mounted in the bathroom, and
I do look at the temperature displays for the collector and tank and
find these helpful. I also have the maximum tank temperature set
to around 165F to increase the life of the EPDM lining. I think
its is also helpful to be able to set the difference in temperature
between the collector and the tank that causes the controller to turn
the pump on. That said, I have used very simple differential
controllers that only cost about $50 that did just fine -- so, this is a
place you can save some money if the budget is tight.
Installing the Differential Controller
You will want to follow the instructions for the particular differential controller that you buy, but normally the install will consist of four steps:
John Canivan and Richard Heiliger at the
offer a kit or assembled differential controller at a lower price.
This Shem 32 is another imported possibility. I've been using one of these on my Solar Shed system for this winter, and it has been fine. Features similar to the Steca and Caleffi. Price is attractive.
And this interesting myDTC one that looks kind of formidable, but does some logging -- would like to hear from anyone who has experience with it.
If you are using a PV driven pump, Guy Marsden offers a differential controller for PV systems ... As does IMC (listed above).
This shows how the connections are wired for the Steca controller I had earlier. The two orange wires go to the collector and tank temperature sensors. The black wire is the controller line cord that plugs into a wall outlet. The pump lugs into an outlet on the controller just to the left of the black cord.
|The radiant floor control system basically
consists of two thermostats in series. The first thermostat senses
the solar storage tank temperature, and turn "on" when the tank water is
warm enough to provide heat. The 2nd thermostat senses the room
temperature, and turns "on" when the room is cold enough to need heat.
So, when both thermostats are "on", the radiant floor circulation pump
is activated, and hot water from the solar storage tank is pumped
through the floor loops.
I have been operating the system manually, and have not actually hooked up the controls as shown in the diagram yet, but it is will be quite similar to the setup I use on our Solar Shed heater, so, I think it will work fine.
Installing the Radiant Floor Loop Control System
Gary February 12, 2011