Hello all....

[The Solar Technician]

Nice to be part of this community.

I have been in the plumbing industry for over 25 years and spent the last 5 in solar thermal.

I have been doing a little reading and, i hope you don't take me the wrong way, i may have to educate some of you a little.

Starting with the use of expansion vessels.
i read somewhere, somebody was saying they use diaphram type vessels which are commonly use for heating systems.

i would totaly get away from this, and use the correct solar rated expansion vessel.

i have known in my time expansion vessels if not calculated correctly and being of diaphram type construction, to split in half on the crimp that hold them togther.
BTW,

an orange expansion vessel is for heating systems and only has a maximum working temperature of 95'c.

A solar rated expansion vessel, for one a reflex s, has a working temperature of 120'c.

I see no where on this board the calculation for these vessels and the pre-charge pressure or working pressure.
This should not be taken for granted and should be calculated for each and every system.

I then see nothing about boiling points and the alteration of system pressures to accomodate the greater amount of liquid in larger systems.

Then there is stagnation and how to avoid, or slow down with the referance to the hydraulic behaviour upon stagnation.

Not to be too in your face on my first post, but given the time for me to write and you to read, i will explain all.


Good evening to you all.

The Solar Technician.

[Ivan]

Welcome to the forum - hope you enjoy it here!

Your comments obviously invite answers so:

1. Specific 'solar' expansion vessels are indeed available, but they are still diaphragm units. Some manufacturers supply nitrile rubber solar vessels, which has a slightly higher temperature resistance. If you read other threads about the expansion vessels or our instructions, you will see that we avoid exposing the expansion vessel to over-temperature water quite easily - site low in the system(well away from the panel in case of pump failure/power failure which causes stagnation conditions), also the EM temperature limit can be set in the controller, to prevent overheated water being circulated.

As an aside, the 'Reflex S' that you mention has a membrane, and it is only suitable for temperatures up to 70C (see the specifications at http://www.reflex.de/reflex/pdf_engl/PR0106Ce_reflex_engl.pdf (look out for the asterick!)

2. If you have had an expansion vessel split in half, it suggests that there was no PRV in the system.

3. I think there is a thread somewhere concerning precharge pressure - there is also an instuction set that comes with each expansion vessel. Sizing the expansion vessel is not really an issue with Navitron-supplied systems, as we use a rather over-sized unit for solar installations. (If you calculate the size for standard systems on the basis of non-boiling expansion, you woud come up with an expansion vessel size of 2litres or less - we recommend a 12litre for standard installations, which gives far more margin for error than any central heating system). Part of the reason for chosing a vessel of this size is to allow for boiling, should stagnant conditions arise. We cover this in detail on our training course, but there are also threads on the forum detailing this. (just search for 'stagnation' or 'boil' or similar to locate these threads)

Have a good look around the forum, you will find lots of useful help and advice, and you-name-it the subject has probably been discussed in detail! There is a good search facility which can help you locate the subjects you are interested in. You should find plenty of lively discussion, and no shortage of humour.


Ivan

[O MidKnight]

Well said Ivan. You sure have a good way with words.

[O MidKnight]

The Solar Technician.

Reference your last post - Not to be too in your face on my first post, but given the time for me to write and you to read, i will explain all.

Can you find time to write some  more as your input is valued.

[lightfoot]

For anyone interested in the nitty gritty of EV's for solar applications, here's some useful bedtime reading: 

http://www.zilmet.com/cataloghi/14solarplus_ingl.pdf

Enjoy.

Lightfoot.