- Installing Heat Exchangers in Large-Scale Heating Systems: Key Considerations
If there’s one thing every heating engineer knows, it’s that a system is only as good as its weakest joint, valve, or fitting. The same applies to heat exchangers. In large-scale heating systems, getting them installed correctly can make the difference between smooth operation for decades or a string of callouts no one wants to deal with.
When you’re installing heat exchangers, you’re not just moving water from one circuit to another. You’re managing energy, pressure, temperature, and reliability in one go. The moment an exchanger goes in the wrong way, or the system isn’t balanced, you start losing efficiency, and that’s money down the drain.
At National Pumps and Boilers, we see the same pattern across schools, factories, and hospitals: it’s rarely the equipment that fails first. It’s the design, the setup, or the neglect of a few key principles during installation. Let’s break those down.
The Purpose and Function in Real Systems
A heat exchanger does one job very well: it transfers heat from one side to another without letting the fluids mix. In a boiler house or plantroom, that separation is crucial. It keeps chemicals, dirt, or high pressures from crossing circuits and damaging other components.
Think of it like a clutch in a gearbox. It transfers power efficiently but isolates one side from the other to prevent mechanical failure. A plate heat exchanger works in a similar way, thin stainless-steel plates sit close together, allowing excellent heat transfer while keeping circuits apart.
In commercial buildings, you’ll find them tucked behind control panels or next to buffer tanks, separating the main boiler loop from the distribution circuits. In an industrial plant, you might see larger shell-and-tube exchangers, handling tougher temperatures, steam, or process fluids that would ruin domestic-grade equipment.
The engineering logic is the same everywhere: control your flow, protect your components, and balance your circuits.
Choosing the Right Type
Heat exchangers aren’t “one size fits all.” You pick them based on duty, space, and what the system needs to achieve.
Plate Heat Exchangers
Ideal for tight plantrooms or retrofits. Compact, efficient, and easy to maintain. You can unbolt them, clean the plates, or replace gaskets on site. Perfect for schools, hotels, and district heating systems where space is always a battle.
Shell-and-Tube Models
Heavier, bulkier, but built to take abuse. These are common in industrial plants, chemical, food production, or power generation, where pressure and temperature loads are high. They’re easy to inspect internally and handle contaminated fluids better than most designs.
Brazed Plate Units
Completely sealed, smaller in footprint, and highly efficient. Common in modern condensing boiler systems or renewable setups. But there’s a trade-off, once fouled, they’re hard to clean. Great for closed, well-treated water systems only.
When specifying, match your exchanger to the wider hydraulic setup. Pair it with the right Expansion Vessels or Pressurisation Units so the pressures stay stable. Brands like Reflex and Flamco build excellent pressure management gear that prevents unnecessary stress on plates or gaskets.
Getting the Installation Right
A quality product can only perform as well as it’s installed. That’s not a slogan, it’s a rule. We’ve seen top-end plate exchangers underperform because the pipework was flipped, the flow direction ignored, or the commissioning skipped.
Flow and Connection
Always check your flow orientation before you bolt up. The primary and secondary flows should run counter-current to one another. It maximises heat transfer. Parallel flow looks fine on paper but you’ll lose efficiency immediately.
Isolation and Bypass
Valves on both sides of the exchanger are non-negotiable. You’ll thank yourself later when the plates need cleaning. A bypass loop lets water circulate if one side is out of service, keeping pumps safe.
Air and Shock Control
Air pockets are troublemakers. They cause corrosion, noise, and in severe cases, plate damage. Fit vents at the top and always fill the circuit slowly to avoid thermal shock. Steel expands; gaskets don’t. Rush it, and you’ll warp the frame.
Access and Insulation
Allow room to remove plates or tube bundles. Engineers need clearance to get spanners in without dismantling half the plantroom. Once it’s all sealed, insulate the casing, uninsulated exchangers waste energy and risk burns.
Pump Coordination
Pumps drive the circuit, but their discharge connection must be thought through. Ideally, the pump outlet connects to the lower exchanger port. It helps purge air and balance flow. Reliable pumps from Wilo, Grundfos, or Lowara are designed with this coordination in mind.
A Story from the Field
A hospital retrofit not long ago used new plate exchangers tied into existing boilers. Beautiful bit of kit. But a month later, half the wards were running cool. The problem wasn’t the equipment, it was balance. The contractor hadn’t accounted for the secondary head loss. Once recalculated, with proper valve throttling and a small adjustment to pump speed, the system levelled out.
That day reminded everyone involved that hydraulics don’t forgive shortcuts.
Integrating with Pumping Systems
The link between pumps and exchangers is one of those details that gets ignored until the phone starts ringing. If the pump’s curve doesn’t match the exchanger’s pressure drop, efficiency plummets.
When installing, confirm the exchanger’s pressure loss and pick a pump that delivers flow within ±10% of the required duty. Too strong and you risk erosion; too weak and you lose temperature difference.
Commercial installations often use Commercial Circulators, Wilo or Armstrong twin-heads are popular. Always use proper Pump Valves so you can isolate without draining the system.
Cavitation is another silent killer. You’ll hear it first, rattling, a sound like marbles in the impeller. It’s usually because the system pressure isn’t stable. Correct this with the right Expansion Vessels and Pressurisation Units. A small adjustment here saves thousands in repairs.
Keeping Systems Healthy
Once a system is up and running, the real work begins: maintenance. You can’t just install and forget.
Water Quality
Poor water quality will ruin the best heat exchanger in under a year. Follow BS 7593, flush, dose, and monitor. Add inhibitors and magnets where needed. Dirt separators can make all the difference.
Cleaning and Descaling
Over time, plates foul up. Backflush first. If that doesn’t work, use a mild acid descaler. Avoid anything aggressive, too strong, and you’ll lift the gasket. Regular cleaning restores temperature differentials and keeps your pumps happy.
Monitoring
A well-set system should hold a consistent ΔT (temperature difference). If it starts to narrow, that’s your first clue something’s clogging up or a valve’s drifting. Link sensors into your BMS to catch it early.
Regular checks keep the rest of the system running too, Central Heating circuits, DHW Pumps, and expansion vessels all depend on one another staying in balance.
Commissioning and Testing
Commissioning isn’t paperwork, it’s proof that the system actually does what the design promised. Here’s what good commissioning looks like:
- Flush everything before connection. Debris kills efficiency.
- Pressure test to full system pressure and hold. Look for leaks, gasket distortion, or alignment issues.
- Balance the circuits. Adjust valves to achieve the designed flow and temperature difference.
- Control Integration. Ensure sensors feed accurate data back to the BMS.
- Document results. Include flow rates, pressures, and system ΔT in the handover file.
If there’s any uncertainty, especially on high-duty systems, it’s best to contact National Pumps and Boilers for commissioning support or verification testing.
Common Errors Worth Avoiding
- Reversed Flow: Always check the flow arrows. Counter-flow, not parallel.
- No Isolation: Future you will regret skipping valves.
- Misalignment: Stresses gaskets and causes leaks.
- Ignoring Pressure Drop: Oversizing leads to wasted pump energy.
- Poor Service Access: If you can’t reach it, you won’t maintain it.
None of these are complicated. They just need forethought.
Final Thoughts
Heat exchangers don’t shout for attention. When they’re installed correctly, you hardly notice them working. But if they’re undersized, misfitted, or neglected, they’ll remind you with low heat output, high bills, and pressure alarms.
Getting it right means understanding the whole picture, hydraulics, pump duty, system pressure, and water treatment. That’s where experience counts.
For engineers handling large-scale heating systems, investing the time to install exchangers properly is what keeps everything else reliable. Combine them with trusted components from Wilo, Reflex, or Mikrofill, and you’ll have a setup that runs quietly and efficiently for years.
For more advice or to plan your next installation, get in touch with National Pumps and Boilers.