power flap detector

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David Lesher 18 years ago

So I'm trying to protect a 5 ton heat pump from power flaps, the kind that occur when heavy winds blow trees across the primary feed to a rural home.

The HVAC industry seems to have some prepackaged solutions, such as the ICM491 but I'm wondering..

It seems to say it samples the power for 5 seconds before acting. That strikes me as way too slow. I want to drop the compressor offline in a second or two, so it does not attempt to resume after falling to say half speed or so.

But it appears to be popular in the HVAC industry...

What say the learned ones here?

A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that\'s close........[v].(301) 56-LINUX Unless the host (that isn\'t close).........................pob 1433 is busy, hung or dead....................................20915-1433

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Phil Allison 18 years ago

"David Lesher"

** Is a " power flap " the same as a " power flop" or different ?

Perhaps the latter is a prime cause of the former ?

....... Phil

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Martin Brown 18 years ago

I guess what we would call a power brown out in the UK where incandescent lamps dim etc. Ours used to dim when it was wet and stormy as strips of the antique perished insulation would bridge two phases. They replaced the old cables with aluminium 3 phase with a steel hawser core a few years back - that proved strong enough to support a fallen tree! Although it did bend all the power line poles along the road as a result.

The spec seems to say 50mS response to a total power disconnect and a

5s of 12% under or over voltage set point. And then a preset lockout time before it retries if the power resumes normality. That seems fairly reasonable to me. Although I would hope that it might act a bit quicker if it found the line voltage suddenly at 1kV.

Regards, Martin Brown

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David Lesher 18 years ago

A brown out [to me...] is gentle. A power flap is anything but that; as the limbs short/unshort in the wind, the line voltage dives and restores suddenly. The compressor, winding down to a stop, lurches back toward full speed, only to have the line drop again.

The question is: is "total" zero volts, and do you really get zero in a flap? Not 25% or so, but zero?

A host is a host from coast to coast.................wb8foz@nrk.com & no one will talk to a host that\'s close........[v].(301) 56-LINUX Unless the host (that isn\'t close).........................pob 1433 is busy, hung or dead....................................20915-1433

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power flap detector

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