Diy solar water heating pump

[pornodoll]

Hi.

After being inspired by some links I found on here, I am going to have a bash at building my own solar water heating panel. Now...because I am initially just experimenting and playing around, for ease I was thinking of sighting it on my detached garage roof (just while I see the results).

The problem I have is that the water would need pumping up to my cylinder which is upstairs. So....'a' What pump could I use? Maybe a central heating pump? (I want to keep things as simple as possible initially), and 'b' would I need to run the pump constantly or intermittently?

Thanks for any replies, and please keep it simple!

Pornodoll.

 

[JohnD]

gravity flow could do it.

But have you got an unused coil in your cylinder? If not I don't see how you can design it.

 

[Agile]

You can use a CH pump and a simple way to operate it is with a pipestat controling the pump. It will then keep pumping until its cooler.

A proper system would have several temperature controls to ensure any useful heat is circulated but not if there is no heat to be gained. That requires analogue sensors and is quite easy to build for anyone with a little electronics experience.

If you wanted to use lots of motor valves then you can use a single coil cylinder but remember you will need to dose the heating system with antifreeze to stop the panels freezing.

Tony Glazier

 

[pornodoll]

Ok. Thanks for that.

Strangely, a new shop has just opened a few miles up the road and I had a look today. They are doing Worcester/bosch water heating systems (which cost around £4000 by the way) and I managed to glean some information.

They seem to have two temp sensors, one on the hot water cylinder, and one on the panel. When there is a temp diff of >5 deg, the pump cuts in.

So onto the next question. Whislt I am happy to make the panel and plumb it in, I havent the slightest clue when it comes to control. So where would I get thermocouples from, what sort would I need, and what would be the cheapest way to cut the pump in and out using these thermocouples?

Again, lots of thanks in advance, and please...as simple as possible.

 

[croydoncorgi]

One unfortunate feature of solar panels is the high temperature they can reach when the pump is NOT running (for example, when the DHW is already hot enough). Since the temperature can easily go to 140C on a hot sunny day, with a reasonably efficient panel, you have to design it so that it does NOT boil. To stop it boiling needs an overpressure of 2.5 Bar or so. Also, because of the high temperatures that can be reached, plastic plumbing and soft-solder joints are both big No-Nos.

 

[Nige F]

One unfortunate feature of solar panels is the high temperature they can reach when the pump is NOT running (for example, when the DHW is already hot enough). Since the temperature can easily go to 140C on a hot sunny day, with a reasonably efficient panel, you have to design it so that it does NOT boil. To stop it boiling needs an overpressure of 2.5 Bar or so. Also, because of the high temperatures that can be reached, plastic plumbing and soft-solder joints are both big No-Nos.

Does that mean I can use my dinosaur gas bottles and bronze welding @ last ....It`s Solar for me then.....What`s that hot working insurance FFS

 

[ChrisR]

Somebody must produce a cheap module which closes an output contact for a given temperature difference on the inputs but I don't know of one.

Even if you have no electronics knowledge, you can adapt something, with a little learning.

I was asked for one many years ago and used a Maplin thermostat kit, altered somewhat.

The Maplin module used one thermistor(temperature dependent resistor) whose resistance was compared with an on-board pot (variable resistor with a knob on it) so you get a relay closing at a certain temperature. It was quite simple to alter it so it compared two thermistors, with the pot used as the "difference" control.
Had a quick look - similar looking Velleman kit is about a fiver.
If you can understand Ohm's law, you could go the same way.

There are many circuit diagrams you could find, but using an existing module does at least give you a board which works, to work from.