If you’ve ever experienced a sudden blast of cold water while waiting for hot water to reach your shower or faucet, you’ve encountered what’s known as the cold water sandwich. This common phenomenon occurs in wall-hung combi boilers that rely on a brazed plate heat exchanger (HX) for domestic hot water (DHW) production. Here’s how it happens and why choosing the right boiler design can make all the difference.
What is the Cold Water Sandwich?
The cold water sandwich is a result of how brazed plate heat exchangers work. When you open a hot water tap, the heat exchanger starts working to heat incoming cold water on demand. However, there’s a lag between the initial flow of hot water (leftover from the last use) and the new hot water being produced. This lag creates an unwelcome burst of cold water in the middle of your hot water flow, disrupting comfort and wasting time.
The Solution: Built-In Indirect Water Heater
To avoid the cold water sandwich, consider a combi boiler with a small indirect water heater (WH) built into the unit. Instead of relying solely on a brazed plate HX for DHW, these models store a small volume of pre-heated water, ensuring hot water is available immediately when needed. When choosing a wall-hung combi boiler, look for a unit with this feature, such as the Laars Mascot, which ensures consistent comfort and performance for your customers.
Why Choose Laars with Rathe Associates?
Partnering with Rathe Associates means you’re not just getting a top-tier product like the Laars Mascot—you’re also gaining access to the exclusive benefits of the Laars Pro Program. We go beyond the sale with industry-leading support, offering: