2 ssr 1 pid

[gr3]

Will this work using a pid and a switch to go from 220v to 110v on element? I will auto tune on 110v.

 

[golfindia]

Don't know, but I do know that the SSRs I have all have a little "leakage" even when they are off, which could cause a problem with that design.

 

[gr3]

That's what I worried about. Maybe someone will ring in that knows.

 

[atoughram]

Your switching the ground on the 110V circuit, not really a good plan, I'd only plug and unplug the elements when there is no power hooked up for safety.

The leakage current shouldn't be a problem.

If for some reason you fire both SSR's at the same time, it could get exciting.

Make sure you have a GFCI and plenty of circuit breakers... It might work. How did Bobby M do this same thing? I remember a DPDT 20a switch?

 

[augiedoggy]

Why not just switch the other leg between neutral or 120v and use the same ssr for both 120v and 240v?

 

[atoughram]

I like this way better...

 

[Ravenshead]

Since you already have 220V service, why are you using 110V for anything? If you don't want to get another PID you could just use a PWD to control the boil. Or use one of these:

http://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=444

 

[augiedoggy]

I like this way better...

Exactly. Im assuming this is for a rims configuration? Thats the only scenerio where I could see this making any sense at all.

 

[jeffmeh]

I like this way better...

Agreed. And make sure the switch goes through open when switching back and forth between 120v and neutral.

 

[gr3]

I'm using this in a single pot to mash and boil. I thought it would be good to back power down on mash.

 

[Mista_Sparkle]

It may screw up your PID tuning depending on the load, though it would probably be close enough. Are you able to guarantee that the system is reasonably well mixed between your probe and heat source with a pump or something? If you are able to do that, you should be able to run an element at full power and your system should respond fast enough to avoid any problems. If you don't have any circulation you may have a problem both with high and low power.

If you have an SSR fail, they often fail closed, so that could be bad news per your original diagram...

 

[Ravenshead]

All else equal, your power will be the same regardless of the voltage. Power is voltage times amps and your element is going to pull the same power regardless of the voltage. It will however, draw fewer amps at 220V.

Also, all else isn't equal in this case. Heating elements are rated for either 220v or 110V not both. You can run a 220V element on 110V but there's no reason to. Your PID is going to control your duty cycle and thus regulate your power during the mash so there's no reason to reduce voltage. I'd just go with a straight 220V system and keep things simple.

 

[dyqik]

All else equal, your power will be the same regardless of the voltage. Power is voltage times amps and your element is going to pull the same power regardless of the voltage. It will however, draw fewer amps at 220V.

No, this is completely wrong.

The element has a fixed resistance. The current will be determined by the voltage: I = V/R
The element will draw twice the current at 230V as it will at 115V.

Since we have a current source (the supply voltage will stay at 115 or 230V, regardless of current supplied),the power will be determined by the voltage and the resistance of the element: P = VI = V*V/R = V²/R

The power will drop to one quarter when dropping the voltage from 230V to 115V.

Also, all else isn't equal in this case. Heating elements are rated for either 220v or 110V not both. You can run a 220V element on 110V but there's no reason to. Your PID is going to control your duty cycle and thus regulate your power during the mash so there's no reason to reduce voltage. I'd just go with a straight 220V system and keep things simple.

This is also somewhat wrong. The PID cycles on and off on a varying pulse width (PWM) to reduce the average power. During the "on" part of the cycle, the element will be running at the full power allowed by the supply voltage. If the PID PWM cycle is long (few seconds), there may be enough energy supplied to cause scorching, even if the average power is low.

 

[gr3]

I'm just going to get rid of 1 ssr and use a spdt mechanical relay to do switch. Thanks for all the comments.

 

[rudylyon57]

I'm using this in a single pot to mash and boil. I thought it would be good to back power down on mash.

I use the same approach except two DPST relays (switched by a common switch) are used to turn off both legs powering the heater. It works well. PID tuning parameters are optimized for 120V operation during mash. I will commonly kick back up to 240V (with higher mash flow to resist boiling in tube) for step mashing and mash out.

 

[Bellybuster]

with only two wires and ground you have no correct access to 120volts. You need three wire (2 hots/neutral and ground) Neutral and ground are not the same thing.

atoughram's diagram would work but I'd be using a contactor instead of a switch. You also need to work in grounding as well.

 

[doug293cz]

I'm just going to get rid of 1 ssr and use a spdt mechanical relay to do switch. Thanks for all the comments.

This will work, but you need to make sure the NC contacts on the SPDT relay are rated for the same current as the NO contacts. For most xPDT relays (especially the cheaper ones), the NC contacts are rated for much lower current (often about 10X less.) @rudylyon57 's solution may be cheaper even though it uses two contactors.

Brew on

 

[atoughram]

I'm just going to get rid of 1 ssr and use a spdt mechanical relay to do switch. Thanks for all the comments.

You will be happier...

 

[gr3]

I have 3 wire 220v, 110v, 110v and ground. So I have to use ground for neutral is that a problem?

 

[doug293cz]

I have 3 wire 220v, 110v, 110v and ground. So I have to use ground for neutral is that a problem?

How did you determine that you had ground vs. neutral?

Brew on

 

[gr3]

In my fuse box the bare wire going to my range rect goes to ground.

 

[doug293cz]

I my fuse box the bare wire going to my range rect goes to ground.

If it's a bare wire, it better be ground.

Brew on

 

[Bellybuster]

Neutral is only required if you plan on tapping 120v off of the 240v.
The proper wire for a 240v with 120v application is called "3wire" which actually has 4 wires. Two hot wires (black/red), a neutral (white) and a ground (green or bare) Th ground is not counted as a wire because it should never carry current.

 

[Bobby_M]

Agree with others that you should not derive 120v between l1 and ground. You need a neutral. If you can't do it that way, some PIDs have a parameter of max power output. You can set that to 20% and it will never allow the element to get to the scorching temps. The down side is needing to get into the programming before you are able to boil. You can also wire an SSVR in series with the PID SSR to do the same with an external knob.

 

[augiedoggy]

I would just invest in an ULWD element (like this stainless based one http://www.ebay.com/itm/321917164405?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT )
and let the pid do the rest.... Why complicate things for no gain? I use a 4500w 240v element in my bk and never in over 60 brews has it caused scorching or any type of over boiling situation... the pid will hold any temp below 212 I want and the ultra low watt density prevents any denaturing or scorching...

 

[augiedoggy]

All else equal, your power will be the same regardless of the voltage. Power is voltage times amps and your element is going to pull the same power regardless of the voltage. It will however, draw fewer amps at 220V.

Also, all else isn't equal in this case. Heating elements are rated for either 220v or 110V not both. You can run a 220V element on 110V but there's no reason to. Your PID is going to control your duty cycle and thus regulate your power during the mash so there's no reason to reduce voltage. I'd just go with a straight 220V system and keep things simple.

I accidently liked this ... as already stated running a 240v element on 120v will quarter the power output... I agree with the point of the second comment though. Using a quality pwm controller like a pid with manual mode with a short cycle time will do the same thing in practical terms...

 

[Ravenshead]

No, this is completely wrong.

The element has a fixed resistance. The current will be determined by the voltage: I = V/R
The element will draw twice the current at 230V as it will at 115V.

Since we have a current source (the supply voltage will stay at 115 or 230V, regardless of current supplied),the power will be determined by the voltage and the resistance of the element: P = VI = V*V/R = V²/R

The power will drop to one quarter when dropping the voltage from 230V to 115V.



This is also somewhat wrong. The PID cycles on and off on a varying pulse width (PWM) to reduce the average power. During the "on" part of the cycle, the element will be running at the full power allowed by the supply voltage. If the PID PWM cycle is long (few seconds), there may be enough energy supplied to cause scorching, even if the average power is low.

You're right and that's what I meant. I don't know what I was thinking.

As far as the PID cycle goes, every one I've used cycles way faster than once per second on 220V. I have seen some scorching on 110V systems though I wasn't watching the cycle time.