Progressive EMS-HW50C unit

brulaz wrote:

ktmrfs wrote:

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that delay is for complete loss of input power, a voltage sag doesn't (at least on mine) trigger that delay. It causes the relay to drop out. When it does that it does NOT trigger an error message. the Low voltage error will only show up if it detects low voltage during initial connection or a much longer drop than I've experienced with the "generator chatter" problem. It would be better IMHO if the EMS unit (a) had the ability to stay connected down to say mid 90V for 3-5 seconds, and (b) a 3 or 4 second delay after trip out before the contacts go back in.

As it is, they have a very simple circuit on the input 120V relay to set the input voltage limit to near 104V with almost no hysteresis. Off at 104, On at 104, rather than say off at 104 not back on till 110 or something.
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Interesting.
I would prefer it to go off below 104V and stay off according to how the jumper is set. Wonder how long it takes below 104V before an error is thrown and the delay timer is started.

I can't imagine that chatter around 104V is good for the A/C.
Thought that was what the EMS was supposed to protect against.

I agree, the chatter isn't good for the AC or other things.

However, I suspect the EMS design was more aimed at line power, which usually is "stiffer" than a generator, and when it falls below 104V it stays below for a fairly long time, long enough for the electroncs to detect it. But most generators aren't anything close to the "ideal voltage source" like the power line, and don't have the line regulation power lines have so voltage can swing rapidly.

I to wish the EMS had better protection for generator sourced supply. Although with a generator you seldom have the problems a pedestal supply might present (swapped hot/neutral) open neutral, etc. However many generators do present the open ground fault that takes a cheater plug as a work around.

IMHO two improvements would be to allow voltage sag to about 90V for say 2 seconds and have a way to bypass the open ground fault. That would give a generator a few seconds to spin back up to accomidate a big load spike and keep from needing a cheater plug for the open ground "fault".

I keep thinking that one of these winter days I'm going to take out the EMS open it up and see what it would take to change the dropout voltage ciruit limit and/or add a time delay. Could be an easy task or a difficult one depending on how the circuit is implemented.

It may likely be that the input relay has a designed in 104V dropout, and if that's the case, the easy solution would be finding one with a lower voltage.