Heat Exchangers with PIDs: Are They Worth It?
Heat exchanger espresso machines are loved by home baristas and cafe owners alike for their combination of simplicity, power, and cost-effectiveness. Over the past few years, more manufacturers have been upgrading their heat exchanger models with the addition of a PID. Many are familiar with the purpose of a PID on espresso machines with dedicated brew boilers where they allow for direct, precise control over brew temperature. On a heat exchanger, the story is a little bit different. Watch the video below to get a quick understanding with the full text transcipt below.
Because HX machines heat water for brewing by passing it through a tube within the steam boiler, it isn’t possible to directly control brew temp. Instead, the PID on machines like the Profitec Pro 500 PID is solely controlling the temperature of the steam boiler. When compared to the thermostat based temperature control mechanisms on more traditional HX machines, this represents a substantial upgrade. Not only will steam boiler temperature, and therefore pressure, be more consistent - but controlling it means that you can modulate steam power. If you prefer large milk drinks you can bump up the temperature to steam milk even faster. If you prefer small cortados or cappuccinos, reducing the steam power will help keep that milk in the pitcher and give you a bit more control.
When it comes to brew temperature, the relationship between steam boiler temp and brew temp is a bit less direct. Because the water headed to the group is only in contact with the heat exchanger mechanism for a brief period of time, a large variation in steam boiler temperature only creates a small difference in the temperature of the water leaving the group head. In order to quantify this difference, we did tests using a scace device. This simulates the flow rate of a shot of espresso and has a temp probe in the middle, allowing for precise simulation and measurement of brew temperature over the duration of a shot.
As a baseline, we used the ECM Mechanika V Slim which uses a thermostat to maintain steam boiler temperature. We compared this to the Pro 500 PID with its steam boiler set to 250, 255, 258, and 262 degrees Fahrenheit to get a clear picture of how much control over temperature you can get. With each, we started with a 7-second cooling flush, followed by three 30-second shots with 1-minute resting periods between them, taking the temperature every 5 seconds.
Our findings show that, while the relationship between steam temperature and brew temp isn’t linear, it’s certainly close. While both machines are quite temperature stable after a cooling flush, the Pro 500 PID gives you the ability to control temperature in a way that non-PID heat exchangers just don’t. Being able to get fairly consistently target temperatures anywhere between 195 and 203 degrees is super powerful. The ability to get temperature control nearing that of a true PID’d brew boiler is, in our eyes, well worth the money.