Stiebel Eltron solar hot water - losing pressure

[CharlieFromMass]

I have a Stiebel Eltron solar hot water system approx 15 years old for which I've been doing most maintenance the past 7 or so years. The system slowly loses pressure - used to be over a period of a year or longer but now more like 3 months. When it does it eventually blows off steam on the pressure valve at the top of the collectors.

I'm not certain whether there is some pressure blow off earlier in the pressure cycle nor whether the system is always sensing temps and pumping to avoid a high temperature blowoff when the pump should be operating. The sensors occasionally read out very high temps when I look at them . Also the programming for max tank temperature and releasing excess heat from tank might be off; I sometimes find the sensor temps at collector as very high well after dark. So I can't say for sure whether the problem might be in the pipes & pressure valve, or in the sensors & electronics.

Any suggestions what to do and where the likely failure mode is? Do the pressure valves need to be replaced or reset? The pipes for this installation used quick sealing joints with a tool to install them , not solder; might the seals after 15 years have reached end of life? Any gotchas around the Stiebel electronic controller ? Thanks for any pointers on tracking this down.

 

[WorthFlorida]

I know nothing about these solar heaters. Is there a water pressure regulator to keep water in the system or is it a closed system running an antifreeze solution? As far as the high temps, after 15 years could there be mineral build up on the temperature sensors or inside pressure relief valves? Is there a maintenance procedure to flush the system? Any leaks could be due to age of the seals since they are subject to extremes in temperature and pressures, but without any visual clues it is hard to be sure.

 

[Sponsor]

 

[CharlieFromMass]

Thanks for your reply - this is an antifreeze closed loop with a pressure tank and relief valve. There could certainly be some mineral deposits in the relief valves or some related issue with them if the require any kind of maintenance. The temp sensors sometimes get flaky and I have replaced one or two in the past.

Charlie

I know nothing about these solar heaters. Is there a water pressure regulator to keep water in the system or is it a closed system running an antifreeze solution? As far as the high temps, after 15 years could there be mineral build up on the temperature sensors or inside pressure relief valves? Is there a maintenance procedure to flush the system? Any leaks could be due to age of the seals since they are subject to extremes in temperature and pressures, but without any visual clues it is hard to be sure.