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terminal strips and glass fuses

Discussion in 'General Electronics Discussion' started by SolderBuster, Feb 14, 2012.

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  1. SolderBuster

    SolderBuster

    3
    0
    Feb 14, 2012
    hi. I am sorting through the process of a possible build but I am stuck on some correct parts. I ran across this forum trying to google an answer so here goes. I am using 240VAC 50 Amp as my power source. Hot side A (6AWG) will be routed to the input of two SSR's. The output of each SSR currently has two 6AWG wires with each going to a 30 Amp 240VAC DPDT relay with a 120VAC coil activation. Only one of these two relays can be operated at any time due to the influence of a 3 position selector switch dictating which relay to energize by allowing the 120VAC coil to supply the respective relay. The switch will be labeled: Relay 1 - OFF - Relay 2
    I would like to transition my wire gauge from #6 (250VAC 50AMP) to a #10 (250VAC 30 AMP) between the SSR and its' respective two 30Amp relays as the max load will only be 19Amps.
    My question is what is a good choice for a terminal strip and fuse strip which would take up the least amount of real estate in the control panel.
    My second question is to confirm that the fuse would need to be 125VAC 30 amp instead of 240VAC 30 amp since we are only dealing with Hot Side A at this point of the circuit.
    I am hoping there is a product out there that will let me utilize a standard sized 8 circuit terminal strips (2 for Hot A and 2 for Hot B for each SSR for a total of 8) which allows termination of the #6 wire so that the transition to #10 can occur. But then this is only possible if there is a fuse solution out there that allows small inline fuses between the two different gauges. Is there such a thing out there? If so, please point me to its' source. Otherwise what would be a good solution for protecting the smaller wire while still keeping the valuable real estate down to a minimum? Thank you and sorry for the long post.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    I don't understand.

    How is the 120V relay coil not going to suffer from death at the hands of 240V?

    Or is this the funny 2 phase 240V that has a common neutral giving 120V between each phase and neutral?

    A circuit diagram would help no end.
     
  3. SolderBuster

    SolderBuster

    3
    0
    Feb 14, 2012
    sorry, I should have included this originally. This block diagram is the current control panel. By updating from 30Amps to 50Amps, I realize I will need to go with #6AWG wire from the electric panel to the control panel. I will replace the current 240VAC 30Amp GFCI breaker with a 240VAC 50Amp GFCI breaker. Once inside the control panel, I want to use as little #6 wiring as possible. I was hoping I could insert a terminal strip with fuses in the "dashed blue line" areas and transition back to the original #10AWG wiring while also adding the other two relays with #10AWG wiring. The size of the existing panel is 20x20x8 and I have more than enough real estate remaining to add the other two relays. The larger SSR's will be fitted with their corresponding heat sinks. I also have enough room on the front panel to add the new switch. My concern is I am unfamiliar with what to use to transition the #6AWG back to the #10AWG within the dashed blue lines. The smaller the footprint that the terminals and fuses use, the more feasible this update can occur. thank you again...
     

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  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,477
    2,820
    Jan 21, 2010
    It looks to me that fuse A is in a 120VAC circuit. It also looks to me that 30A is way too much. Isn't that circuit just for control of the relays? 1A would be ample.

    The cost difference between a 120V and a 240V fuse should be negligible. We're talking glass fuses, right? (or are they circuit breakers?)
     
  5. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    8 awg copper will suffice for 50A. What I use inside breaker boxes for RV's all the time. But your diagram suggest you may be pulling close to 80A at one time?

    A two pole breaker will set you back under [email protected] unless it is a FP.

    I am also a little confused on your labeling, if those colors are supposed to match up to a standard US color code, then the black and red are 120VAC with reference to Neutral. 240VAC between the pair, but neither are 240VAC by themselves. Unless this is a 440V service at an industrial building???
     
    Last edited: Feb 15, 2012
  6. SolderBuster

    SolderBuster

    3
    0
    Feb 14, 2012
    thanks for your responses guys... please disregard the color of the wires in this drawing.. The actual control panel follows NEC color coded wiring codes.. These colors are the only ones my cheap drawing program allows and I just wanted to make it easier to follow the lines instead of all of them being black.

    The control panel will only be pulling 40 amps from the 50amp breaker back at the panel at any one time, which puts me right at the 80% rule of the rated breaker. Unfortunately, the SSR's (solid state relays) go from a max 40 amp out size to a max 80 amp out size, so I wanted to bump up to the 80's to keep the heat sinks cooler. If I would have stayed at the original 40's, I doubt my triple sized heat sinks could have even kept up.
    The Hot A side splits and goes to the input of four 30AMP DPDT relays.
    The Hot B side controls the SSR's and their output is controlled by RTD temperature sensors feeding into a PID with its' output opening and closing the Hot B output side of the SSR 10 times per second. This output is connected to the other pole of the DPDT relay. The relay is energized by either S1 or S2 via the 120VAC it allows to pass on through to the relay's coil which operates the relay from a normally open to a closed state. This coil is ONLY used to operate the relay which then closes the DPDT contacts for the output side of the relay. If that relay has been selected by the selector switch, then the ouput of the SSR and the Hot A side, is connected to the 19AMP load. If the selector switch is not positioned to operate the coil of a relay, then the output of the SSR is not carried through and the circuit to the load remains open.
    I appreciate your concerns, but none of this has anything to do with my quandary of finding a term strip and fuses that will allow me to transition from the new #6 wire being placed on the 50Amp sides, to the original and new 30AMP relays and loads... We are only increasing the supply to accommodate only one more load. I really don't want to go to 4 contactors as it is much cheaper to just add 2 more 30Amp DPDT relays and switch S2.
    Maybe I should have placed this in an equipment section... All I am hoping for is that someone knows of the correctly Amperage sized terminal strips and fuses to place into the "blue dashed areas" so I can transition and protect the wire gauges shown ( #6 to #10 )...If you do know those correct sizes mathematically, then do they actually make them? by whom? If you can point me to the manufacturer and the source then you have made my day.... help please...
    thank you...
     
    Last edited: Feb 15, 2012
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