cafeIKE wrote:You will need a RESET on pin 5 to stop the pump.

According to the info sheet, the timer will also reset upon power interruption.

erics wrote:To properly "break" 240 VAC, you need to interrupt both "hots". That type of delay relay may be a tough find.

This is what I thought but the salesman told me that wasn't true, that simply interrupting one leg would work. What makes me think he may be right is my PID uses an SSR with one leg interruption to control the heating element which is 220v.

But if I have to interrupt both HOTS, I could simply use two SSR's, both controlled by the timer to do that.

And that's why I used the word "properly". Yes, a 240V circuit is halted when you open one leg but if you check out the Linea wiring diagram here: /downloads/ , you'll see that LM opens both hots in several spots. If you want a better rendition of that drawing, you can email me at erics at erols dot com .

I certainly remember your PID adventure and am familiar with that wiring . However, I do not have a good answer for you on why its "OK" to do it in different ways in different situations. It can (obviously) work as Dave Stephens did with his Faema and that, to me, would be the least intrusive (and safest) method - either that or the DPST switch I previously suggested.

Granted, it would not provide 0.1 second capability but . . .. I have not spent any time in determining whether you would need to "get into" the ribbon cable wiring between the push button panel and the control box or other circuitry within the control box itself when using the digital timer. If that were the case, the big red light would illuminate strongly.

mitch236 wrote:According to the info sheet, the timer will also reset upon power interruption.

True, but inelegant. Presumably if using power to control stop, also using power to initiate. How long is 'boot up'? All the diagrams show an interval between power and delay start. Will the unit power on and immediately enter the delay interval, in less time than your pre-infusion interval? Would like to see a blank display until power on or have the interval displayed any time the machine is on?

A small SPDT relay controlled by the pump motor power control from the Linea will do the trick.

Definitely interrupt both legs of 220 with a Dual Output SSR

Eric,

If you look at the wiring of the pump motor, there are three wires. The black wire appears to be connected through the distribution block to the main power switch and therefore I have to believe it is always on (as long as the machine is on). If that is true (and it can be tested), then if insert the relay inline with the white wire at the pump, it should work.

Of course I'll check it all with a meter, but based on the wiring diagram, it should work.

What do you think?

cafeIKE wrote:True, but inelegant. Presumably if using power to control stop, also using power to initiate. How long is 'boot up'? All the diagrams show an interval between power and delay start. Will the unit power on and immediately enter the delay interval, in less time than your pre-infusion interval? Would like to see a blank display until power on or have the interval displayed any time the machine is on?

Ike, the power interruption occurs on the sensing inputs, not the units main power inputs so the unit stays powered up even when the pump is off.

What do you think?

I agree with what you have said but I still prefer the less elegant solution as a TRIAL.

Point well taken. Thanks!

Breaking either leg of a circuit will stop the flow of current (if we are talking single phase) the problem is safety: someone working on the machine with the power on might assume that, lets say, the heating element is off and safe to work on while one leg of power is still supplied to it. In most cases it is far better to unplug the machine for testing but some measurements require power to be connected. In many cases a single pole thermostat is allowed on a 220v heater if there is also a two pole disconnect "within sight" of the device. Otherwise there is no advantage to break both legs for control as long as the relay, or solid state device has enough capacity.
KDM

Of course breaking both legs on 220v is for safety.
What's 'permitted' or 'required' is not always the safest solution.
Safety 1st, 2nd & damn soon afterwards was my Gramps' credo.

Whether one contact / SSR or two, the current capacity doesn't change.
The TOTAL current flows through 1 or 2 devices.
What does change with an SSR is the power dissipation as there are two junctions rather than one dissipating heat.

Do it right. There's great satisfaction in doing it right and none in Mickey Mouse.

Breaking both legs on a standard relay divides the current between two sets of contacts. Breaking the same circuit with one contact puts the full current on one. To increase contact capacity you can feed the circuit through both sets of contacts (loop) and create a "double break" set up which lowers the load on each set. Some open "power" relays use double break to withstand more opening current. To be fair a resistance load like a heater is not as tough on contacts as a motor load or transformer load where inductance "works" the contacts harder.
KDM

So if I understand this correctly, I should get two SSR's, one for each leg, and the input side of the SSR can be a common set of wires in parallel and each output would control each leg? That should be easy enough to do. Is there any downside to ordering higher amperage SSR's? I could order two 50A units which would easily handle the motor.