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G8MNY > TECH 29.02.24 12:17l 85 Lines 3899 Bytes #999 (0) @ WW
BID : 2376_GB7CIP
Read: GUEST
Subj: Essential Mains Changeover
Path: IW8PGT<I3XTY<I0OJJ<N6RME<CX2SA<VK7AX<GB7CIP
Sent: 240229/1001Z @:GB7CIP.#32.GBR.EURO #:2376 [Caterham Surrey GBR] $:2376_GB
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (Updated Sep 13)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
I designed this simple unit to bypass 230V mains problems at a local community
radio station, that needs essential mains for 24/7 computers. The building's
Mains Consumer Unit had been updated with two Residule Current Devices (Earth
Leakage Circuit Breakers), feeding 2 Main Contact Breakers banks, but also with
a separate "Alternate Non RCD feed" provided just to the UPS system.
SCHEMATIC
NORMAL Bypass UPS Bypass
RELAY RELAY
Normal ÚÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄ¿
RCD feed >ÄÄÅÄo on ³ ÚÄÄÄÄÄÄÅÄo off³
³ \____³___³ ³ ____³_____\ Essential
Alternate>ÄÄÅÄo off³ ³ ÚÄÄÄÄÅÄo/ on ³ / Power
Non RCD ÀÄÄÄÂÄÄÄÙ in³ ³out ÀÄÄÄÂÄÄÄÙ Feed
Bypass ÚÁÄÁ¿ Bypass
³UPS³
ÀÄÂÄÙ
External
Battery
CIRCUIT
For maximum flexibility, the source load plugs & sockets, are all Standard UK
13A fused type on the mains source box. But studio distribution is only to
separately fused IEC bank units.
Alternate Normal
Non RCD RCD
EÄÄÄÄÄÄÄÄÄÄEÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄE
Mains Mains ³ Essential
Plug Plug ³ UPS 250V~ Sockets
N L N L NORMAL ³ ÚÄÄÄ¿ 470n N L
³ ³ ³ ³ ÚÄÄÄ¿ ³ ÚÄ´30KÃÄ´ÃÄÄ¿ ³ ³
³ ³ ÃÄÄÄÄ)ÄÄ´30KÃÄ¿ ³ ³ ÀÄÄÄÙ 15K ³ ³
³ ³ ³ ³ ÀÄÄÄÙ ³ ³ ³ Use ³ ³ ³
Ãneon´ Ãneon´ Use 15K ³ ÀÄÄÂneonÂÄ\ÄÙ Ãneon´
³ ³ ³ ÃÄÄÄ\ÄÄÄÄÙ ³ ³ ³ ³ ³
³ ³ ³ o ³ ³ ÃÄÄÄo ³ ³
³ ÀÄÄÄÄÄ)ÄÄÄÄo\ÄÄÄÄÄÄÄÄÂÄÄÄÄÄ)ÄÄÄÄÄ)ÄÄÄÄ)ÄÄÄo\ÄÄÄÄÄ)ÄÄÄÄÙ
³ ³ NORMAL ³ ³ ³ ³ UPS ³
³ ÀÄÄÄÄo ³ ³ ÃÄÄÄÄ)ÄÄÄo ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄo\ÄÄÄÂÄÄÄÄ)ÄÄÄÄÄ)ÄÄÄÄÄ)ÄÄÄÄ)ÄÄÄo\ÄÄÄÄÄÙ
³ ³ ÚÄÄÁÄÄ¿ ³ ³
N³ in ³L ³E E³ N³out ³L IEC
ÚÁÄÄÄÄÁÄÄÁÄÄÄÄÄÁÄÄÁÄÄÄÄÁ¿Connectors
³ 1kW 36V 100% UPS ³
ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ
The four neons indicate power status, the two switches enable safe manual
override of the relays for Normal Mains circuit & UPS servicing etc.
I found good quality 3x 15A changeover AC relays with 30kê coils, but they held
operated down to 140V! So I added series 15kê 1W resistor to obtain a better
operate to fail voltages of 205V to 190V.
PROBLEM
However on flattening the UPS battery, I discovered the UPS can put out 300V DC
blowing kit fuses (SMPSUs PCs OK, Transformer kit NOT!) So I add a series 250V
AC Cap to the UPS bypass relay to ensure the UPS gets bypassed if it does a
mains wobbly again!
WARNING
Bypassing RCDs is not to be taken lightly! The station need for 24/7 essential
power is considered very important. Normal building mains is all RCD protected,
only the specialised kit on IEC distribution panels have the bypass capability.
And this can be easily be configured back to RCD only, for safer live mains
while wiring work is going on etc. you just unplugging the non RCD supply, put
in an a temporary RCD adapter (N.B. Most Adapters DO NOT STAY ON on a mains
fail!) to be fully safe again.
See my Tech buls on:- "APC Smart 900 UPS", "DURITC 1kW 230V Inverter/UPS",
"META HF Millennium 810H UPS", "Constant Voltage Transformers", "Variacs",
"70-260V Mains Auto Transformer", "Maplin Mains Meter 2000MU-UK",
"Mains Power Protection", "Mains Peak/RMS/Mean Meter", "Voltage Dependent
Resistors", & "Portable Appliance Testing"
Why don't U send an interesting bul?
73 De John, G8MNY @ GB7CIP
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