Wiring Help

[Lennie]

I have looked through the many spa panel threads and am still not exactly clear on how to wire my setup. I have a 30amp breaker in the main panel, 10/3 with ground ruin to the garage where I brew, a 60amp breaker in a spa panel that will power a single 5500W element in an enclosure. I also have a Chinese SCR that has two power in lugs and two power out.

My electrician friend installed the breaker at the main and I ran the wire to the garage. He hooked the spa panel by attaching the two hots to the two lugs, the neutral to the neutral lug. He hooked the ground up to the neutral buss, which I'm not sure about.

I'm to the point now where I need to buy power cord, a couple plugs and hook this stuff up. I'm fairly sure I need a 10/3 power cable to hook to the two power connections and a ground on the enclosure. I'm not sure how to get the SCR in this loop, and I'm not entirely sure how to hook up the power cord to the spa panel.

Any help would be appreciated.

 

[Lennie]

I did just reread the entire sticky primer and have a better idea of what to do. I still don't understand why a 10/3 power cord doesn't have three wires and a fourth ground wire. Is this because the neutral isn't used in an element, so you have two hots and a ground? The "PJ" wiring diagram for a spa panel showed four wires in and four out, I don't get this. If I hook the output directly to the element without the SCR I could run full out and turn on/off with the breaker switch. I might do this initially unless there is a reason not to.

 

[trimixdiver1]

I did just reread the entire sticky primer and have a better idea of what to do. I still don't understand why a 10/3 power cord doesn't have three wires and a fourth ground wire. Is this because the neutral isn't used in an element, so you have two hots and a ground? The "PJ" wiring diagram for a spa panel showed four wires in and four out, I don't get this. If I hook the output directly to the element without the SCR I could run full out and turn on/off with the breaker switch. I might do this initially unless there is a reason not to.

Power cords are designated as what you see is what you get 10/3, structural wiring such as NM-B (Romex) is designated as 10/2 with ground.

If you have only 240v loads (elements) then you do not need a neutral. If you have both 240/120v loads ( lamps, temperature controller) then you need a neutral.

Some guys try to buy components that all run on 240v, that way a neutral isn't needed.

Oh and a breaker is a safety device, not a switch. A switch/ disconnect needs to be installed downstream of the breaker. I wouldn't do this. A SCR switched by a switch is a much better option. Just get ready for some temperature swings.

 

[Lennie]

Thanks for the info. I installed 10/3 Romex from the main to the spa panel so I have a neutral and a ground running into the box. I thought the additional gfci 50amp breaker in the spa panel would be OK to use as a switch since it isn't acting as a breaker other than being the GFCI. I did wonder if it would hold up to being used as a switch.

As for temp swings, All I'm doing is heating mash water to pump to a cooler MLT, and then boiling wort. So I don't know that I even need the SCR, but I bought it just in case I wanted to install it.

I suppose I will buy a 10/3 power cord and connect it as two hots and a ground since the element is 240v. I still have the issue of how to wire the SCR if I include it, it only has the two connections which I assume are two hots since its designed for 240V. I suppose if I locate the SCR very near the spa panel, I could run two hots from the spa panel to the SCR input, and then hook the two hots from the power cord to the SCR output and run the power cord ground on in the spa panel.

 

[Lennie]

Here's a drawing of the schematic I'm thinking of. It shows the main panel, four wire to the spa panel, then three wire to the element with the SCR inline on the two hots. I have to research how a GFCI works to make sure I am protected with this wiring setup.

 

[Lennie]

By the way, this is the SCR I bought. Two lugs for incoming power, two for outgoing. I can only assume it is meant to be wired with the two hots for 240V in and two wires out. I suppose this means it is not grounded either. I'm also trying to envision a way to enclose this thing since the end is relatively open. I suppose I need a project box that I can mount it in, with only the knob sticking out.


http://www.ebay.com/itm/10000W-AC11...r-Thermostat-/251251998263?fromMakeTrack=true

 

[doug293cz]

Here's a drawing of the schematic I'm thinking of. It shows the main panel, four wire to the spa panel, then three wire to the element with the SCR inline on the two hots. I have to research how a GFCI works to make sure I am protected with this wiring setup.

That's not the correct way to hook up an SCR, SSVR or SSR. Current flows in a loop. Breaking the loop anywhere will interrupt the current flow, and drop power to 0 (no current flow = no power.) One of the hot lines goes thru the SCR, and the other hot line connects directly to the element. You will still have voltage on the element with the power set to 0, so you still have a shock hazard. And, since solid state switches usually fail in the closed (on) state, if your SCR fails, you will have full power on the element whenever the main power is on. The safest designs place a DPST switch or contactor rated for the full element power. This is used to interrupt both hot lines so that even if the SCR fails, you have a failsafe way to remove power from the element.

Brew on

 

[Lennie]

OK I will put a DPST switch in the loop to be able to de-energize, although the 50amp spa panel gfci breaker would work for that right?

I only surmised that the wiring went this way because the SCR has two lugs for incoming power, and two for outgoing. I suppose this is for controlling two different loads/elements at the same time then? I'm half tempted to bag the SCR for the time being and just run the element at full power. Since its only for boiling and heating water, I didn't need the control anyway it was just a cheap unit and I thought if I could get away with lower power after bringing to a boil it would save electricity.

I'll consult my electrician friend again, he is coming over to brew tonight. Still using propane for this one, but I am getting closer.

 

[Lennie]

I'm looking at threads on wiring up SCRs and they seem to indicate the two hots go in to the SCR and two outputs go out to the element, like I drew in my schematic. I'm not done researching that yet though. My rudimentary understanding of 240V is that one of the two hots acts as the neutral for the other by being out of phase. The SCR is wired to full power, and simply dials down the amount going out to the element.

 

[doug293cz]

OK I will put a DPST switch in the loop to be able to de-energize, although the 50amp spa panel gfci breaker would work for that right?

I only surmised that the wiring went this way because the SCR has two lugs for incoming power, and two for outgoing. I suppose this is for controlling two different loads/elements at the same time then? I'm half tempted to bag the SCR for the time being and just run the element at full power. Since its only for boiling and heating water, I didn't need the control anyway it was just a cheap unit and I thought if I could get away with lower power after bringing to a boil it would save electricity.

I'll consult my electrician friend again, he is coming over to brew tonight. Still using propane for this one, but I am getting closer.

The spa panel breaker will work for that, but it is not recommended to use breakers for routine on/off switching.

Brew on

 

[doug293cz]

I'm looking at threads on wiring up SCRs and they seem to indicate the two hots go in to the SCR and two outputs go out to the element, like I drew in my schematic. I'm not done researching that yet though. My rudimentary understanding of 240V is that one of the two hots acts as the neutral for the other by being out of phase. The SCR is wired to full power, and simply dials down the amount going out to the element.

Where are you seeing wiring schematics like that? Can you provide links?

Edit: Ok, I looked at some of these controllers at on-line retailers. Some of them have pics of the actual circuit boards where you can see how the power connections in the device are wired. All of the ones where I could tell, the two outside terminal screws were simply jumpered together on the board, with absolutely no connection to any of the other circuitry on the boards. You could use the device with just one hot leg wired to the two inside terminals, and the other hot leg not connected to the controller. You can also wire as you show. If you wire as you show, do not wire anything other than the element to the output of the SCR, as you risk mismatching the phases and shorting things out.

Terminal block is to lower right in pic below.



Brew on

 

[Lennie]

Thanks, I will just be controlling the one element with this thing. And I did buy DPST 30amp switch so I won't be fatiguing the spa panel breaker. Also picked up a plastic single gang outlet box for the switch and a triple gang outlet for the SCR. Snagged 20' of 10/3 power cord and a set of 30amp plugs, so I think I have everything I need.

Thanks for looking up the wiring of the circuit board. I'll take the cover off and double check that mine is like this one before wiring it.

 

[RufusBrewer]

Use an On/OFf switch to turn power On and Off. Choose the proper tool for the job. A conventional GFI circuit breaker is not an On/Off switch.

 

[Lennie]

I sent the seller a question regarding this SCR. I asked if it was designed for 50Hz or 60 Hz. The answer came back 50Hz. There was no mention of this is the item description, but I read in another thread that it might be the case. I suppose this means I can look forward to this item failing in the not too distant future?

 

[Lennie]

Answering my own questions. Read that using a device designed for 50Hz unit at 60Hz means higher current, higher temp and greater chance of failure. Also you get 17% less power out if I understand it correctly, although with an SCR I don't know if that applies.

 

[RufusBrewer]

I do not think an SCR is frequency dependent. At least not in the context of 50 Hz Vs 60 Hz.

The 17% would come in play when there is an inductive power device involved, like a power transformer.

I doubt you will notice any problems.

 

[doug293cz]

The SCR will work at 50 or 60 Hz just fine. Also, the one you purchased is rated for 1.8 times the power of the largest common element used by homebrewers, and it has a built in fan w/heatsink. Just make sure you don't block the airflow over the heatsink. I don't think you should have any problems (unless the unit is defective.)

Brew on

 

[Lennie]

Glad to hear this SCR has a chance of working. I'll break most of the wire holes out of the gang box so it will be reasonably well ventilated.

 

[Lennie]

Got my electric brewery wired with the help of my friend. Boiled my first 5gal of water as a test, and we will brew a 10gal trial batch of stout today. I didn't have the SCR installed just yet, it appears that I can just heat and boil at full power without wasting much electricity.

 

[BowAholic]

How's the set-up working for you Lennie? I'm building one myself just for cold wet days...
MoJam is getting close...
Bob