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|  DSH 719
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| Construction
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| 60335-2-21(ed.5)
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1 V8 _( s) g6 ]* wQuestion:. `2 P% }0 J( s' K7 n+ T% q
Sub-clause 22.106 of standard IEC 603325-2-21:2002 states that, a closed water heater shall incorporate a thermal cut-out providing all-pole disconnection which operates independently from the thermostat.
' T% p# C, N: z; p) ECan the thermal cut-out and thermostat control the same contactor, when a contactor is used or are two contactors needed, one controlled by the thermal cut-out and one controlled by the thermostat?
; W/ a3 A: S* \+ Y! SDecision:
7 p# B' ?4 Q \6 Z9 O! OTwo contactors or relays must be used because the contactor or relay may not operate if one set of independent contacts welds closed. See also 19.14 in IEC 60335-1 Ed 4.2..4 V. U4 ] j9 p( R, A/ T
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发表于 2012-9-8 12:11
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