SSR or contractor.

[ej1332]

Has anybody used a mechanical relay instead of an SSR?
I'm planning a build for a 5500 watt BK. I have a few that I found on a job and with hearing about SSR burning out I thought this might be a better way to go.


Sent from my iPhone using Home Brew

 

[iijakii]

If youre going to use a PID to control the element you will need an SSR because the very frequent cycles wears out mechanical relays quickly.

 

[KEG99]

Agree. With a PID set at 80% or 70% during the hard boil, you save a bit on the electric while keeping the boil going. But to do so, the SSR is constantly switching the element on and off.

If you plan to just turn on the element and leave it at 100%, a mechanical switch might work fine - for a while.

In my last post my problem turned out to be the mechanical selector switch that went bad. This was the second time (I should have suspected it). and I (try to) only switch it with power off. I must have done it with power on and it fried. Mechanical is sensitive to heavy voltage switching.

 

[geoffey]

I actually did this on my build a year an a half ago, but used commercial grade 30amp lighting relays instead of contactors. It worked ok, and I did about a dozen batches that way. You have to change you PID settings so that your cycle rate is not the typical default of 2 seconds. I used 10 seconds or 20 seconds. But your contactor needs to be rated to switch that often. Wasn't an issue in my build. What became an issue was response rate. I found it to be slower than I preferred (though this of course could have been related to other parts of my build). The other issue was that even with a 10 second cycle rate I didn't have much control over my boil-off rate. When I tried to set it for 80% the contactor couldn't really see the difference between that and 100% or 60%. So ultimately I decided to opt for an SSR. In the spirit of buy once, I'd say go with SSR's. They have just proved to work so well with so many others that it's a solid choice. I HAVE found that they are prone to burn out if your connections aren't clean and have gone through three of them to figure that out. But once you get them installed correctly they should last a LONG time.

 

[ej1332]

Thank you for the input


Sent from my iPad using Home Brew

 

[kal]

Has anybody used a mechanical relay instead of an SSR?
I'm planning a build for a 5500 watt BK. I have a few that I found on a job and with hearing about SSR burning out I thought this might be a better way to go.

As others have said, it's the mech relays (or contactors) that wear out, not SSRs.

Use SSRs when frequent/continual switching is required. In my panel I use SSRs to control the heating elements - sometimes they switch more than once a second. I also use relays (or contactors) to physically disconnect power from the elements for safety / process control reasons. They only switch 2-3 times during the entire brew day.

Kal