PID and relays. SSD or Coil

Hello everyone.
I have a SYL-2342 and am going to use 120v coil 220 contact relays. I will be using a rtd type thermo couplier. Will this setup work to run 2 4500 watt heating elements. It is needed to keep 300 gallons of water at 85-90 degrees.

I hope someone is willing to help out with this subject. I am having a hard time getting help simply b/c i am not "Brewing".
If no one wants to help i understand. No hard feeling. Again thank you.

You say you're using a 220v contact relay, so I take that to mean your using 220v power source.
4500w x 220v = 20.45 amps x 2 elements = 40.9 amps

Your solution will depend on your breaker and wire size if you can run them both on 1 circuit. A 50 amp 220 service should get the job done. Make sure you use appropriately sized wire to your controller - 6 AWG.

And appropriately sized wire to your elements - 10 AWG.

Also - check out this page - http://www.gnipsel.com/beer/software/beer-software.html. Find the "Electric Heat Spreadsheet"

Ignoring the part on "Time it takes to boil water..." and focusing on the "Time to Temperature..." it looks like for 300 gallons at 9000 watts you'll get from 60*F to 90*F in 2 hours and 34 minutes. If your element is rated for 240 and not 220, then it will take 3 hours and 4 minutes.

Are you using an insulated tank and do you have anything to stir or otherwise mix the water? I think you'd get stratification in there pretty easily. Just something else to think about.

300 gallons of 85-90° water?

Well, that's too cold for a hot tub and not big enough for a swimming pool...

Please tell us some more. This group is great at doing mind jumps and will be able to help you in your mission.

Your mission seems to be something that we can assist in planning.

P-J

Sounds like he is building a hydrographic dipping tank. Its the same application as me, and what is currently kicking my butt.

tried to run two heating elements off one ssr....

i guess he is trying to do something similar?

My question is are you wanting to control the water to be somewhere between 85-90°, or at a set point which happens to be somewhere in the range of 85-90°? If it only needs to be between 85-90° the contactor should be fine, just make sure that the loads you are palcing on it are under the equipments specs. The 120 control through the PID to the contactor coils should be ok, just check the contactor can take 10kW or get two at 5kW each.
As mentioned temperature stratification could be an issue. This would need mixing if using a single probe PID.
Also have you checked on heat loss from the tank and if 9 kW will be enogh to keep it at temp?

the water has to be kept 85-90 degrees. how this happens exactly, i dont think anyone cares. it doesnt seem that temp is super critical just stable within that range.

originally i wanted to run a contactor, because of the size of the load involved. i just dont trust a "chip" to handle this kind of current.

but i drank the ssr koolaid and now im stuck.

by temp stratification do you mean the heat not being distributed evenly?

stratification kind of means that. in essence, you see different temps at different depths.

to combat stratification, stirrers and water recycling help.