If you have a plate heat exchanger in your system—or are planning to install one—check out the most common installation mistakes to avoid errors and time-consuming corrections. This way, you can ensure your plumber connected it correctly. Or maybe you already have a heat exchanger, and your system isn’t working properly? Read the article, learn more, and diagnose the issue.
A common issue is purchasing a heat exchanger "by eye" without precise sizing for the required thermal capacity of the system. An undersized heat exchanger won’t transfer enough energy, leading to insufficient heating or problems with domestic hot water (DHW). This post doesn’t focus on equipment selection but rather on installation mistakes—however, even a correctly connected unit won’t help if it’s poorly sized. Learn more in the article below.
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Plate heat exchangers are highly efficient devices used in heating, cooling, and sanitary systems. However, their proper operation largely depends on correct installation and connection. Unfortunately, installation errors are quite frequent because these aren’t everyday devices, and even plumbers often lack experience in selection or connection. This can reduce efficiency, cause failures, or even damage the unit. Here are the most common mistakes when connecting plate heat exchangers.
Most plate heat exchangers are counterflow devices. A counterflow heat exchanger must always be connected in a counterflow arrangement—meaning the media flow in opposite directions (relative to each other). This ensures maximum heat transfer efficiency. A frequent mistake is parallel-flow connection (media flowing in the same direction), which significantly reduces efficiency. This error can lead to a 30-50% loss in plate heat exchanger performance, obviously preventing the system from working correctly. Unless you install a massively oversized exchanger (e.g., 2-3 times larger than needed), the excess capacity might compensate for the efficiency loss from skipping counterflow.
For Nordic Tec exchangers (and most other brands), plate heat exchangers have arrows on the nameplate indicating counterflow.
Important: Nordic Tec exchangers allow free flow direction adjustment (while maintaining counterflow). This means the flow direction in one channel doesn’t matter as long as the other channel flows oppositely. However, this may not apply to other manufacturers.
Strainers (min. 500 microns) should be installed upstream of the heat exchanger (on both sides) to protect it from contaminants: metal particles, rust, sand, or deposits. Missing strainers lead to clogged channels, reducing efficiency or permanently damaging the exchanger. A clogged unit can often be cleaned—but there’s no guarantee, so forgetting strainers risks irreversible damage.
In our work, we’ve seen questionable approaches—e.g., one plumber tested the exchanger first and only added strainers afterward. Unsurprisingly, pump startup (sudden water movement) poses the highest contamination risk. Later, he wondered why the exchanger failed after weeks or a season, insisting it couldn’t be clogged. Clearly, strainers must be installed before the first test run.
As a curiosity: another plumber suspected flow issues and "fixed" them by... removing the strainers. We’ll leave it at that.
Remember: even with strainers, periodic cleaning (e.g., every 1–2 seasons) is recommended.
Manufacturers don’t specify exact strainer types. Assess the system’s condition—a mesh strainer is typically the bare minimum. In old open systems, a magnetic filter or separator may also be justified. Experience and on-site evaluation are key.
✅ Note: Strainers are also essential for plate heat exchangers in new, closed modern systems, not just old pipes.
A plate heat exchanger must be mounted vertically for proper venting. Exceptions (e.g., some DHW stations or logo-therms) are carefully designed. Never mount it horizontally, sideways, or—worst of all—"on its back" (connections facing up), which causes immediate clogging.
Summary: If not vertical, airlocks and flow blockage are inevitable—sooner rather than later.
Plate heat exchangers have strict operating limits (pressure/temperature). Exceeding them (e.g., in steam systems or with overpowered pumps) causes leaks or permanent plate damage. This is more a selection than installation issue, but worth noting.
In liquid-liquid systems, overpressure is rarer—but possible if using a standard exchanger for refrigerant instead of a dedicated high-pressure refrigerant model.
Again, this is a selection issue. A common mistake is using standard liquid-liquid exchangers (e.g., Nordic Tec Ba-12, Ba-23, etc.) as heat pump condensers with refrigerants. Standard liquid-liquid units aren’t certified for refrigerants, risking leaks and voiding the warranty.
Similarly, using standard exchangers for pools instead of pricier pool-grade models risks leaks—copper-brazed plates aren’t resistant to high chlorine or pool chemicals long-term.
The same applies to untreated media like groundwater, well water, or river water—minerals and elements differ from treated water, potentially voiding warranties unless approved by the manufacturer.
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