Newest Threads

**Walker** · 03-03-2011, 02:20 PM

Quote:

Originally Posted by passedpawn

Yeah, that works, but is NOT a great way to do it. It's far better to totally cut power to the element. This also cuts power to the cord, which is probably where you'll see a fault if one happens some day.

I'll speak for the other camp here. I wouldn't rely on two SSRs to completely cut power to the element.

I use one SSR for my element for control purposes. If I want to turn the power off, I do manually do that with a BAS (big ass switch).

**Walker** · 03-03-2011, 02:21 PM

Quote:

Originally Posted by gunner65

I added a fan to my box after believing that a heatsink mounted to a metal backplane would dissipate the heat enough. After one test run to boil I burned up my 40a SSR (and they do fail in "closed" state) I mounted a computer fan to one side and cut slots in the other side for exhausting airflow. No problem since and lesson learned.

So far, I've not had any problems with one SSR and no ventilation (5500W element w/ 40A SSR and a headsink, connected to the backpanel). The SSR gets warm, but I don't think the temp inside the panel is too bad.

But, just because I can, I am going to add a couple tiny fans to the box. One blowing air in and one blowing air out.

gunner65 · 03-03-2011, 02:32 PM

Walker I thought the same thing when I was designing mine and poof the second test I ran the element was running uncontrollably "on" Checked the SSR with a lamp a sure enough no worky. Could have been a bad SSR out of the box but I had a pc fan laying around and used the guts of a walwort for DC power I also wired in a 120v panel mount bulb to the output so that I can see when the element is on and off that way if it fails again I can quickly look at the PID and SSR lamp to compare output.

samc · 03-03-2011, 02:38 PM

Quote:

Originally Posted by Walker

I'll speak for the other camp here. I wouldn't rely on two SSRs to completely cut power to the element.

I use one SSR for my element for control purposes. If I want to turn the power off, I do manually do that with a BAS (big ass switch).

Can't hurt to have two. I look at it this way - if one SSR fails I can still use the system with the other one.

**passedpawn** · 03-03-2011, 03:18 PM

Quote:

Originally Posted by Walker

I'll speak for the other camp here. I wouldn't rely on two SSRs to completely cut power to the element.

I use one SSR for my element for control purposes. If I want to turn the power off, I do manually do that with a BAS (big ass switch).

Well, the camp I actually represent is to use

2 SSR's to interrupt power to the element, then a
240V medium switch on my control panel (MAS) to cut just the element power, then a
big switch on the wall (BAS) to cut power to the the whole panel, including the 110 (from one leg of 240)

gunner65 · 03-03-2011, 05:54 PM

I use a 50 amp 2 pole contact relay to cut power to the element.

**Walker** · 03-03-2011, 06:13 PM

Quote:

Originally Posted by gunner65

I use a 50 amp 2 pole contact relay to cut power to the element.

yeah, me too. I just used shorthand there.

it's actually a TAS (tiny ass switch) that controls a BAC (big ass contactor).

**Walker** · 03-03-2011, 06:16 PM

Quote:

Originally Posted by gunner65

Walker I thought the same thing when I was designing mine and poof the second test I ran the element was running uncontrollably "on" Checked the SSR with a lamp a sure enough no worky.

LOL. I put a little 120v lamp on my panel, connected between the SSR output and the neutral to let me know when the SSR was allowing current to flow through.

Unfortunately, the SSR leaks enough current even when OFF than the little bulb is constantly illuminated. Confused the sh!t out of me when I first put the bulb in the control panel.

gunner65 · 03-03-2011, 06:47 PM

Mine is leaky too def illuminted somewhat but I can tell when the output is on noticeably brighter.