NEED SOME SOLAR HELP

EBEBRATT-Ed

I have never worked on solar but I am trying to help an existing customer.
1. What static pressure do I need at the top of the solar aray? Is 4-5 psi ok like a std. hydronic system?
2. Do I need more pressure to prevent the fluid from boiling?
3. Do the pumps that pump through the solar aray need to be run 24/7 to keep the fluid from overheating.
The system is Bosh/Buderus if that helps

wogpa67

1- Depends on the height of the array from pump station and relief valve installed.
2 - The controller should have a function to cool the array.
3- same as above.
Nothing on Buderus website. I install Roth. here's their install manual. They are all about the same.

http://www.roth-usa.com/PDF_Download_Files/Solar_Install_Manual_HelioStar.pdf

hot_rod

Does it have an air vent up on the array? You want at least 5 psi at the highest point. You are correct that higher operating pressures increase the boiling point.

If the expansion tank is sized large enough there is no harm in running higher pressures. The Euro closed loop glycol systems I visited run 4- 5 bar, around 60 psi for extra fluid over heat protection. Most of the pre-plumbed Solar Pump Stations have a 6 bar ( 87 psi) relief valve installed.

Typical solar glycols are rated to 300- 325F or so. At 60 psi boiling is around 300F. Ideally you don't want the system to get to those temperatures regularly.

I think Bosch/ Buderus uses Steca solar controls. It should have several over-heat protection functions that can be enabled. Do you have the manual for the control?

On the Caleffi i-solar and most Resol brand controls you have 3 or 4 over-heat functions. Steca should be similar.
Collector cooling
System cooling
Tank cooling
Holiday cooling

Usually 1 or more of these functions allows adequate over-heat protection for residential systems. On large systems, or in-frequently used systems, vacation homes for example, an over heat or dump zone may be required.

Or turn it into a drainback system

EBEBRATT-Ed

Thanks for the help. That will get me started in the right direction.

wogpa67

I couldn't find anything on Buderus website. I install the Roth systems. Take a look at this they're all pretty much the same.

http://www.roth-usa.com/PDF_Download_Files/Solar_Install_Manual_HelioStar.pdf

hot_rod

I don't see any info regarding the control in that Roth manual?

Here is what the most common solar controllers look like. Resol and Steca, they both have installation manuals on their websites.

It may have another brand name on the front. Remove the lower cover and you can usually see the actual control manufacturer and serial or model numbers.

wogpa67

Roth uses the Resol controllers. This is the one I most commonly use.

http://www.resol.de/Produktdokumente/48005931_DeltaSol_BS_Plus_V2.monen.pdf

Ironman

The Buderus system uses Steca controls, usually the TR0301, but a more complex system may use the TR0601.

Hot Rod has given some good general info which should help you with about anything. One caveat though: you can't convert the newer SKS4 panels to drain back due to their meandering tube pattern.

The system should have about 50 gallons of buffer per panel to prevent stagnation or a dump zone to compensate. There are also parameters in the TR0603 that can be used to prevent it such as irradiating back through the panels at night.

Buderus just changed their website last week to redirect to Bosch's. You could download the Buderus solar applications manual from the old site, but I don't know about the new. I've got it on my IPad and I can email it to you if you p/m me with your address.

Sadly, the bean counters at Bosch have decided to stop offering solar on this side of the pond. Buderus would not have done this, but like they say "things change". Too bad, it's a good product. Parts and service will still be there.


Posting some pics would help.

Ironman

To answer another of your questions: the Steca control will bring the solar pump on when the collector temp is 16* above the tank temp and turn it off when the differential drops to 8*. In other words, the controller operates the pump to charge the tank when the collectors are hot enough.

EBEBRATT-Ed

Yes , I had herd from our supplier that parts were going to be tough to get. I have to dig into the system a little more. Thanks.

hot_rod

If you get stuck, let me know. Really any solar differential controller will drive that. As long as the pump is 1 A or less