entertaining video of what's inside an SPD
- Thread starter Urge38
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FilterGuy
Solar Engineering Consultant - EG4 and Consumers
I agree that the thermal break does not seem very robust.
However, In a real event, a few factors could come into play:
1) By the time the solder bridge pops, everything is pretty hot. The solder could remain liquid longer and the solder flow away. (In the soldering iron test, the heat is immediately removed)
2) If a solder bridge is formed the current will continue to flow, generating heat and causing the solder to flow away
- OR -
3) It could be that the rapid heating of the soldering iron is not representative of what happens. Could it be that the solder bridge breaks before the solder is soft but not fully liquified?
To properly test the device would require actually over-voltaging it.
However, In a real event, a few factors could come into play:
1) By the time the solder bridge pops, everything is pretty hot. The solder could remain liquid longer and the solder flow away. (In the soldering iron test, the heat is immediately removed)
2) If a solder bridge is formed the current will continue to flow, generating heat and causing the solder to flow away
- OR -
3) It could be that the rapid heating of the soldering iron is not representative of what happens. Could it be that the solder bridge breaks before the solder is soft but not fully liquified?
To properly test the device would require actually over-voltaging it.
Midnite at least did test theirs in a more realistic scenario and posted the results:
. I definetly wouldn't trust that DIN rail one that is that cheap to protect my system. There is other DIN rail SPDs available from more reputable companies and they are over $100.
bolhuijo
TechnoGeezer
Big Clive is a worthwhile watch for all kinds of teardowns.
meetyg
Solar Addict
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- Jun 4, 2021
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One important thing you should note when using these DIN rail SPDs (whether DC or AC):
They always need to come AFTER an MCB!
As they will (by design) short to ground (via the MOV, when high voltage is applied), they will in fact heat up. I recall a post here on the forum where an entire combiner box or distribution box melted/caught fire when using one of these.
Having them after an MCB means that even if the internal disconnect fails to break/disconnect, your MCB should open (or fuse should pop, if you have a fuse).
They always need to come AFTER an MCB!
As they will (by design) short to ground (via the MOV, when high voltage is applied), they will in fact heat up. I recall a post here on the forum where an entire combiner box or distribution box melted/caught fire when using one of these.
Having them after an MCB means that even if the internal disconnect fails to break/disconnect, your MCB should open (or fuse should pop, if you have a fuse).
I would also not trust the cheap ones, BUT the other types are big money for a simple device.
it can get expensive if you need 3 or 4
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