240VAC Toolbox Control Panel with Pics

[ScubaSteve]

Yeah, that's about right from when I remember. You can find 240V, 30A DPST switches at mouser.com for a little cheaper than $10.

When I looked at 2-pole contactors (which take up a lot of space in the box) I found that the price of a 2-pole contactor and a simple SPST switch was about the same as a big burly 240V,30A DPST switch, so I went for the contactor. Overly cautious and all...

Looking on mouser.com for relay contactors rated at 240vac/30A, they're all pretty expensive, like $20-$50. I know it's for safety reasons, but it could sure add up I guess you'd only use this for the "main" power swtich, right?

 

[IrregularPulse]

I feel like I've hijacked the thread enough and know enough to get started. I'll likely post a new thread once I get a parts list together for my own build. I think I too was confused o the switches not coming with the contactors.

 

[Walker]

Looking on mouser.com for relay contactors rated at 240vac/30A, they're all pretty expensive, like $20-$50. I know it's for safety reasons, but it could sure add up I guess you'd only use this for the "main" power swtich, right?

I did not get my contactors from mouser.com.

I found the contactors on ebay. They were $6 each. $5 shipping for the first one, and $1 shipping for each additional.

I ordered three of them, so my total price was $25 ($8.33 each).

edit: oh, and the contactors I got handle either 40A or 50A.

 

[Walker]

Here's the ones I bought (40A, 120V coil):
http://cgi.ebay.com/DEFINITE-PURPOS...tem&pt=LH_DefaultDomain_0&hash=item33581a4caa

The price has gone up since the time I bought them. They are $10 now. Shipping is still the same.

The same seller has other contactors with different load ratings and coil activation voltages.

The cheapest ones are here:
http://cgi.ebay.com/DEFINITE-PURPOS...tem&pt=LH_DefaultDomain_0&hash=item33581a293c

30A load and a 24V coil.... so you would need a special power source to get the 24V.

Anyway.... even for $10 (the ones I bought) they are still a pretty good deal. Remember, the other option is a DPST switch capable of handling the load, and those things are looking like something in the neighborhood of $15 to $20 anyway, so the contactor is still a price win.

 

[passedpawn]

Quick Test Results...

Brewed two large batches today. Everything worked flawlessly. I'm very happy with this new box.

 

[ScubaSteve]

SO I got two D2425's for 15 bucks each I've sourced some dryer cords for my elements, but I can't tell from your pics or schematic; are you using a 3 or 4 wire cord for your main line?

 

[passedpawn]

SO I got two D2425's for 15 bucks each I've sourced some dryer cords for my elements, but I can't tell from your pics or schematic; are you using a 3 or 4 wire cord for your main line?

Err... that is a GREAT deal. Those are the singles, right? I think the duals have a "D" after the number.

I'm using 3-wire, but you should build it with a 4-wire. I didn't have a ground wire in my 240 service (I will fix that later....). Neutral is only used for the 110V stuff, and the earth ground should not be used to conduct any current.

Take pics along the way and post them here after you've built it.

 

[ScubaSteve]

Just checked my dryer outlet, it's 4 prong, so I guess I just answered my own question On another note, I see that you used thermocouples with 2 wires and switched them. I'd like to use RTD's because they're more accurate and aren't affected by heat in the enclosure.....BUT, they have 3 wires. What should I do?

EDIT: I think I answered this too; a 4PDT switch...with on-off-on configuration....about the same price on digikey (I hate searching for stuff on there, they should take a cue from McMaster-Carr)....

EDIT SH!!!!!!!!!!T!!!!!! I ordered the wrong relays! You're correct, the RIGHT part number is D2425D....I just bought single ssr's.

 

[passedpawn]

Just checked my dryer outlet, it's 4 prong, so I guess I just answered my own question On another note, I see that you used thermocouples with 2 wires and switched them. I'd like to use RTD's because they're more accurate and aren't affected by heat in the enclosure.....BUT, they have 3 wires. What should I do?

Yea, that's a problem. RTDs are actually 2-wire devices, so you can use it that way (just leave one of the wires unconnected). However, when the wire to the RTD changes temperature, the wires resistance will change and affect the reading. I can't say how significant this would be. In an electric keggle, it might not be very much. Maybe someone out there has done some tests.

Or, maybe you can find a 4PDT switch. That'd be nice. Do a search on Digikey.com.

Or, just do your best to keep the inside of your control box the same temperature and stick with the thermocouples. Getting the heatsink and SSRs outside the box will help here.

 

[HoboJoe]

Do you have a parts list for this build?

 

[passedpawn]

Do you have a parts list for this build?

No, only what is in the schematic in the original post.

 

[RootvonRoot]

craziness, never seen anything like this before

 

[dutch-brew]

Say PassedPawn, i'm trying to understand something here..
I am looking at the toggle switch you got from digikey, and looking at the specs it says it's rated 25A-125V
How is that able to work for us then, if we run about 23A with a 5500W at 240V element?

Reason i am asking, at the hardware store they have 25A-125W toggles for about 6 bucks or so.. I just wanna make sure they'll work.


edit:
Really what i am looking for is a switch to only switch one leg of the 240V, i would be open for any other suggestions I am not going to switch the thermocouple cable, just unplug/plug different one in.

 

[passedpawn]

That switch only has the low-voltage low-current control signals to the SSRs. The SSRs do the heavy lifting here.

In other words, I'm just routing the control signal from the PID to whichever relay (SSR) I want to be on. The switch also routes the correct thermocouple signal back to the PID.

 

[dutch-brew]

Oh man, i am an idiot.. looking at so many of these threads i am getting 'em all switched up..

sorry

 

[SpottedDogBrewing]

Very, confusing! Im trying to just connect a PWM to a SSR 40a that will run by BK using a 5500w element

 

[KEG99]

It helps to consider the water analogy again:

voltage (volts) = pressure, (psi)
current (amps) = flow (gpm)
resistance (?) = resistance (ohms)
​

I.e., I = 5500W / 240VAC = 23A.​

I liked the water analogy. Would it give a better picture by stating it this way?

voltage (volts) = pressure, (psi)
current (amps) = flow (gpm)
resistance (ohms) = resistance (pipe diameter)
​

 

[passedpawn]

I liked the water analogy. Would it give a better picture by stating it this way?

voltage (volts) = pressure, (psi)
current (amps) = flow (gpm)
resistance (ohms) = resistance (pipe diameter)
​

Yea, my analogy fell apart at resistance. Prolly was drinking, as usual.

 

[Stevo2569]

Hey Passedpawn, I'm trying to put together something similiar for a friend. He has 4 5500W elements all on their own 240V-30A breakers. Planning on putting 1 PID to control all 4. Will we need 4 or 2 D2425D SSR's to handle the load. I like the idea of having both legs being controlled. Is the D2425D rated for 25AX2? Also a single SSR has 4 connections, Does the dual have 6? Having trouble understanding the Dual SSR. Thanks

 

[rjsnau]

Does anyone know if an electric system can be done safely on a 3 prong system? We have an old 1950's house and they only have 3 prong 240v outlets. If I have an electrician install a GFCI breaker in our panel would this provide the protection I need?

 

[passedpawn]

Does anyone know if an electric system can be done safely on a 3 prong system? We have an old 1950's house and they only have 3 prong 240v outlets. If I have an electrician install a GFCI breaker in our panel would this provide the protection I need?

It will work fine in a 3-prong 240VAC outlet. There are some instances where it might not be as safe as a 4-prong (Line-Line-Neutral-GND). I would strongly suggest that the electrician change the outlet to add the safety ground. Shouldn't be a big deal do do that if he can pull a ground from nearby wire.

 

[passedpawn]

Hey Passedpawn, I'm trying to put together something similiar for a friend. He has 4 5500W elements all on their own 240V-30A breakers. Planning on putting 1 PID to control all 4. Will we need 4 or 2 D2425D SSR's to handle the load. I like the idea of having both legs being controlled. Is the D2425D rated for 25AX2? Also a single SSR has 4 connections, Does the dual have 6? Having trouble understanding the Dual SSR. Thanks

The pinout of the dual SSR is just 2 of everything, like this:

Some of the duals have screw terminals for the outputs, others (like mine) have Faston lugs. They all work fine in our application. The control side has pins on 0.1" spacing for standard connectors, or you can solder to them or connect to them in a bunch of ways, or some models also have lugs for the control signals.

Here's the derating curve. This is Combined Output Current, so it is the sum of the current on both channels. With a poor heat sink (the chinese varieties) The heat conduction is poor (i.e., 5°C/W) and you won't get to run the SSR very hard. With a good heat sink (mine is 0.7°C/W) you can run it full tilt. I use a 5500W element, and it goes through this dual, so both channels are geting about 23A, for a total of 46A. You can see that at an ambient temp of 20°C, I'd need a heat sink of 1.0°C/W or better. I got one. You can see my heat sink somewhere earlier in this thread (I think).

 

[Stevo2569]

Got it. Great explanation. So to run 4 5500W elements on 1 PID: Jumper the inputs to 4 25A- DSSR's. Will we need 2 of the heatsinks you posted?

 

[passedpawn]

Got it. Great explanation. So to run 4 5500W elements on 1 PID: Jumper the inputs to 4 25A- DSSR's. Will we need 2 of the heatsinks you posted?

Yes.

and maybe (if you are driving all the DSSRs at the same time). My heatsink carries two SSRs (or DSSRs). It (the heat sink) is properly spec'ed for one of those DSSRs going full tilt, but not both at the same time - that would be double the heat dissipation needed from the heat sink. You could probably do it with a fan over the heat sink, but with just passive cooling on the heat sink I think it's not gonna keep the SSRs cool enough.

 

[Stevo2569]

Definitely add a fan then. Thanks..