Relay question

[djcorbetto]

My control panel is set up using the electric brewery as an inspiration. Since planning and initial build in have added an extra element to both my hlt and boil kettle, however i have realised the planning didn't involve any parts that would accommodate he extra elements, thus there are only two relays, one for the hlt and one for then boil kettle, in a state of panic I've installed and wired up two ssr's for each pot but there's only one relay. My question is, can both the feeds from the ssr go through one relay?

Just for the safety, I'm in the UK so my electrics are different

 

[schematix]

What is your element wattage? What is your voltage? How many amps are your SSRs good for? How many amps are your relay/contactors good for?

Do you have a diagram of your system, or can you link to a PJ diagram that is close?

 

[djcorbetto]

Sorry I forgot to add that

5kw in total
240v
Ssr can cope with 40amps

I'm on my phone at the moment so will need to draw one and upload it

 

[djcorbetto]

Oh and relays are for 40 amps too

 

[jeffmeh]

5000w / 240v is less than 21a. 40a SSRs and relays should handle it fine.

 

[djcorbetto]

The question was wetter I could run the outputs from both the ssr's through the mechanical relay? As I have two sockets at the other end?

 

[BadNewsBrewery]

Your relay doesn't "know" nor "care" how many wires are connected to it downstream. If you have a relay rated at 40 amps, you could have one 40a load, or forty 1a loads - the relay doesn't know the difference. So if your combined load downstream of the relay is less than what the relay is rated for - you're good to go.

Now - if your question is, can you run TWO separate SSRs to ONE relay and then back to TWO outlets. Well... no. How would the electricity from one SSR know which outlet its supposed to go to if you run it to one combined point with the other SSR on the relay?

Soooo... Relay to SSRs to Outlets - good to go. SSRs to Relay to Outlets - no dice, unless your relay has 4 or more separate poles.

-Kevin

 

[djcorbetto]

In that case then I think I have too many ssr's in my build

 

[schematix]

Whether or not you have too many SSRs depends on whether or not you need independent control of the elements in the same kettle or can they be run as a pair? If you control them together you can wire them in parallel:

The PID will control the coil on 1 SSR. The 1 SSR will feed the contacts on 1 contactor/relay. The load side of 1 contactor/relay can feed the 2 outlets.

Other options exist though. It just depends on what you're trying to accomplish.

 

[djcorbetto]

Because I had two elements I have installed 2 ssr's to each pid

 

[schematix]

You can put multiple elements on an SSR, so long as the total current draw doesn't exceed its rating.

The only function of the SSR is to switch the main supply power to the load at a relatively high frequency.

The function of the relay is just an additional interlock. I left it out on my own design but it doesn't hurt anything.

 

[BadNewsBrewery]

The PID will control the coil on 1 SSR. The 1 SSR will feed the contacts on 1 contactor/relay. The load side of 1 contactor/relay can feed the 2 outlets.

Are you saying that the SSR feed the COIL on the relay? If so, that's not how an SSR works... The SSR doesn't control the coil on a relay - you'd have one relay switching another and gain nothing. The SSR is the relay (the R in SSR) that cycle whether the element is heating or not - it gets its signal from the PID (to the "coil" if it had one) and its output is full power. The contactor / mechanical relay, while optional (though highly suggested) is there to serve as a brake in the power supply from the SSR to the element. The contactor is triggered by a switch on the panel that powers the coil.

If you're proposing that a single SSR supply power to the LINE side of a contactor and then two elements are attached to the LOAD side, then you are absolutely correct, assuming that both the SSR and contactor are rated for the combined load of the two elements, and if you don't give a crap that both elements are firing at the exact same time.

I assumed the reason OP wanted 2 elements was to have them under separate control for whatever reason.

EDIT - I noticed your other reply, so I'm guessing you meant more of the second condition in which case we're saying the same thing. - EDIT

 

[djcorbetto]

Hi, yeah the elements will be controlled together as they are the exact same element, I have two elements because it's a 100litre pot being heated.

Thanks guys, I will just not connected up one of the ssr's on each of the circuits and then split the power at the end after the mechanical relay.