Tell Me About Steaming


How Silvia Controls Steam

The internal wiring on your Silvia is configured so that all current to the heating element must pass through the steam thermostat. This is the case while in either brew mode or steam mode.

When the steam switch is turned on, a "jumper" circuit around the brew thermostat is created. This jumper circuit makes the machine behave as though the brew thermostat is locked in a closed position, i.e., always calling for heat.

So when the steam switch is on, the temperature is limited only by the steam thermostat, regardless of the setpoint on the brew thermostat.

Conversely, when the steam switch is off, the temperature is limited by EITHER the brew thermostat OR the steam thermostat, whichever has the lower set point.

How a Basic PID Kit Will Improve Steaming

Most MLG kits replace only the brew thermostat, so they control your espresso machine only when it is in "brew" mode. Unless you have also installed one of our steam control packages, the original steam thermostat will continue to control boiler temperatures when the steam switch is on.

But, even though the PID will not directly control the steaming temperature, it still offers a chance to make significant improvements in your machine's steam quality and capacity.

Without a PID, right after you pull your shot, you will normally turn on the steam switch and watch the "ready" light. When the light turns off you know that the boiler has reached steaming temperature. (Although we have seen wide variation in this temperature, the ready light typically turns off somewhere around 290F-300F.)

Unfortunately, when the ready light is off the heating element is also off. As you draw down the steam in the boiler, no new steam is being created to take its place. Not until the boiler temperature has dropped 40F or more will the stock steam thermostat start calling for heat again.

A more effective method of steaming would be to open the wand just before the steam thermostat is "satisfied." This way, as the boiler temperature is dropping, the steam thermostat remains "unsatisfied" and allows the heating element to remain energized. As steam is used up, more can be created by the energized heating element.

The trick, obviously, is to find the "satisfaction" temperature for your steam thermostat. This is where the PID comes in. Whether in brew or steam mode, you can always read the current boiler temperature on the display of the PID. After one or two steaming sessions, you will figure out exactly the temperature where the steam thermostat shuts off the element (on our machine it is a low 285F).

Once you know this temperature for your machine, then for all subsequent steaming adventures you just watch the PID display, wait for the boiler to get close to the "magic" steaming temperature, but open the wand and start steaming 1 or 2 degrees before it gets there.

This procedure maximizes both the steam quantity and quality with your machine. Customers have told us that following that procedure makes a dramatic improvement in their stretched milk.

Sorry, Not Good Enough, I Want More!

Another strategy for improving steam capacity is to make a temporary change to your PID setpoint, say up to around 295F, instead of turning on the steam switch. This works, but has some disadvantages.

First, if you recall our earlier description of how Silvia controls steam, regardless of where you set the PID (i.e. the new brew thermostat), the current must pass through the old steam thermostat before reaching the heating element. So as soon as that old steam thermostat thinks things are hot enough, thank you, it will open its switch and turn off the heating element, no matter what the PID is calling for.

Second, even though all of our customers are unusually bright people, it would be very easy for the temporary PID setpoint to become accidentally permanent if you forget to change it back. This wastes a lot of energy and has the potential for damaging your machine. Even though we pre-set the PID's in our kits so the maximum setpoint is 300F, there is nothing that can be programmed into the PID to help you remember to set it back.

The Solutions

We have already discussed how to achieve a significant improvement in steaming using "just" a basic PID kit. For the vast majority of Silvia owners, this will be enough. But for those of us (we know who we are) who really obsess over our stretched milk, MLG can now offer a couple of solutions.

First, and most straightforward, we offer a dual setpoint Watlow Series 96 controller. By including a small mechanical relay with your kit, wired directly into Silvia's steam switch, you will be able to have the PID take the place of both the brew and the steam thermostats. This gives you complete control over the boiler and allows you to set the steam temperature anywhere you want (up to 300F). The best strategy for steaming with this kit is to begin steaming at between 290F and 295F. As the plot below shows, the boiler will reach this temperature approximately 100 seconds after turning on the steam switch.

The second option works with our 935A controllers and is still in the development stage.

Either of these options results in totally transparent steaming operation for the user. If you follow our recommendations for installation, you will be able to operate your machine exactly as you do now. When you want to steam, you flip the switch. (Even the little switch lamp will come on to remind you that the switch is on). The PID will automatically change setpoint and bring the boiler quickly to steaming temperature, and hold it there until you finally find that new carton of soy milk in the fridge, open it, and prepare your pitcher.

Hang On - This Can Get Tricky

Installation of any MLG steam control package adds complexity and time to your kit installation. The steam packages are not for everyone! But, like all of our kits, they are totally reversible. You will need to access the steam switch to complete the wiring rearrangements. Unless you have unusually long, skinny fingers, this will almost certainly mean temporarily removing the front panel.

In addition, the 935A steam package introduces another electronic component (power supply). But if you simply must have the best steam possible you would probably be satisfied with either of these options. (Yes, the steam package can be added at any time later, as long as you purchase a compatible Series 96 or NIB 935A kit).


Copyright (c) 2006 MLG Properties, LLC