Electrical Question

[GumbyOne]

Hey all, I'm in the process of building a control box for my new brew stand and have only a 10A outlet to play with. This is ok at the moment but I want to upgrade to herms in the near future and wont be able to run the HLT and heat exchager at the same time. Is there a way give the exchanger element priority over the hlt, switching the hlt off automatically when the exchager is running? Has anyone done this before? Thanks for any help.

Gumby

 

[mxd]

yeah there is, the ssr or pid will have a normally open/closed type connection so what you want to do is wire the HX so it has priority, when the HX doesn't want power it will provide power to the HLT.

N.B there will be a proper elect person who can answer this.

 

[GumbyOne]

Cool, sounds simple enough, I'll just be using on/off controllers initially, i'm assuming a mechanical relay will be sufficient for this application? Any advantages to an ssr?

 

[browndog]

I'm no electrican, but if it were me, I'd be using a DPDT switch and manually setting which circuit you want to run. HLT or HE. I have a bit of experience with PIDs and can't see how you could have it switch between the two as MXD suggested.

cheers

Browndog

 

[GumbyOne]

I'm no electrican, but if it were me, I'd be using a DPDT switch and manually setting which circuit you want to run. HLT or HE. I have a bit of experience with PIDs and can't see how you could have it switch between the two as MXD suggested.

cheers

Browndog

Yeah thats what I was going to do but I thought I may be able to throw a DPDT relay (or something) in there instead and have it switch automagically, minimising HLT downtime. But I've never really used relays before so dont really know how to go about it.

 

[schooey]

The reason we use SSRs is that they can handle multiple switching in a short period of time without failing, but they are like an on/off switch; they aren't a changeover relay. The problem with most changeover relays is that they are mechanical, and don't really like being pulsed 40 times a minute by a PID controller.

If you were to go with a changeover relay setup, you don't necessarily need DPDT (double pole, double throw) because you really only need to switch the active side. You will need to source one that will handle the rate of switching that your PID will throw at it, and it will also need the ability to switch the full (~10A) load of the elements.

If you were going to go down the changeover relay path, it would probably be best to get an SSR for each element and use a changeover relay in between the PID and those; hence only changinging over a small DC voltage

edit: The thing is though, you'll have one temp probe mounted in your HEX, so your HLT will be at the mercy of the gods temperature wise unless you put in another PID and another SSR in line to control the temp for it.... :blink:

 

[mxd]

I was working on 2 pids and 2 ssr's,

Pid 1 -> HX
Pid 2 -> HLT

When PID is using power, nothing is given to pid 2 (I think my PID (or something else I have) has the ability to pass the power off when is is not using (normally open/normally closed is what I think it is), so if the HX doesn't want to heat then PID2 can heat the HLT (if required)

 

[GumbyOne]

The reason we use SSRs is that they can handle multiple switching in a short period of time without failing, but they are like an on/off switch; they aren't a changeover relay. The problem with most changeover relays is that they are mechanical, and don't really like being pulsed 40 times a minute by a PID controller.

If you were to go with a changeover relay setup, you don't necessarily need DPDT (double pole, double throw) because you really only need to switch the active side. You will need to source one that will handle the rate of switching that your PID will throw at it, and it will also need the ability to switch the full (~10A) load of the elements.

If you were going to go down the changeover relay path, it would probably be best to get an SSR for each element and use a changeover relay in between the PID and those; hence only changinging over a small DC voltage

edit: The thing is though, you'll have one temp probe mounted in your HEX, so your HLT will be at the mercy of the gods temperature wise unless you put in another PID and another SSR in line to control the temp for it.... :blink:

I'm not using a PID, just a couple of mashmates. This all sounds more complicated than I thought it would be :blink: :lol:

 

[mxd]

untill you get to herms there is no issue, but if your going to herms you "should" go for a PID to get full control, other wise leave you hx coil in the HLT and you have the same, just turn the pump on and off by hand.

I'm not using a PID, just a couple of mashmates. This all sounds more complicated than I thought it would be :blink: :lol:

 

[schooey]

I'm not using a PID, just a couple of mashmates. This all sounds more complicated than I thought it would be :blink: :lol:

Oh ok... well then you can just use a changeover relay as the inbuilt delay in the mashmate will stop it from changing too quickly. just put the output from the tempmate to the input of the relay and then you have your two lines out. The NC one goes to your HEX and the NO goes to the circuit of the Mashmate controlling your HLT. Unless you want to be turning the HLT mashmate on and off completely all the time, you'll still need a second changeover really on it's circuit.

If you wire it all in a jiffy box with plugs and sockets, it'll be easier to change later if you end up with more available power.

edit: And yeah... controlling a HEX HERMS system with a mashmate is going to be a bit of a challenge...

 

[Brown_hound]

Gumby,

Sounds like a fair bit of effort...

Would it be worth your while just getting a 15A circuit installed for the purpose?