Skip to content
heatexchangercleaning.co.uk
Arrange a clean

HVAC heat exchanger cleaning

Building services plant has to be cleaned around the people using it, and a district heating scheme has hundreds of small units, not one big one. Send the unit details and the scheme, and a specialist set up for that work will come back to you.

  • UnitsHIUs, calorifiers, plate exchangers, chillers
  • DepositsLimescale, magnetite sludge, biofilm
  • Worked aroundOccupancy and heating season

Submit a cleaning request

Four steps: unit, deposit, postcode, contact details.

  1. 01Unit
  2. 02Situation
  3. 03Site
  4. 04Contact
What needs cleaning?

01What gets cleaned

Heat interface units fail in hundreds while calorifiers fail one at a time

HVAC and district heating heat exchanger cleaning is planned around occupancy before anything else. A scheme cannot take its heating offline in winter, a hotel cannot lose domestic hot water, and a data hall or a hospital cannot lose cooling at all. That constraint, instead of the deposit, is usually what decides the method, and on a scheme with hundreds of heat interface units it also decides whether cleaning is the right answer at all.

01

HIU plate exchangers scale on the domestic hot water side and fail as a population

A heat interface unit takes heat from the network and makes domestic hot water instantaneously, which means a small plate exchanger holding a large temperature difference against mains water. In a hard water area that is close to ideal conditions for limescale, and once the DHW side has scaled the resident notices immediately because the water stops getting hot. The engineering problem is not one exchanger, it is that a scheme has hundreds and they scale at broadly similar rates, so complaints arrive as a wave and not one at a time.

Fouls with
Limescale on the DHW side, magnetite and debris on the network side
First symptom
DHW temperature falling, longer to run hot, resident complaints clustering
Watch for
Network-side strainers blocked, which produces the same symptom for another reason
02

Heating circuits fill exchangers with magnetite that came from their own pipework

Corrosion inside a heating system produces black iron oxide sludge, and it collects wherever velocity drops. Including in plate exchangers, in the bottom of calorifier shells and across every strainer in the system. It is a symptom rather than a cause: magnetite means the system water chemistry is wrong or the inhibitor has been lost, often after a repair that was refilled without redosing. Cleaning the exchanger without correcting the water schedules the next clean.

Fouls with
Magnetite sludge, corrosion debris, jointing compound and installation debris
First symptom
Circulation falling, strainers blocking repeatedly, pumps working harder
Watch for
Missing or depleted inhibitor, which is the actual fault
03

Chiller condensers and cooling circuits carry a legal duty as well as a duty loss

Water-cooled chiller condensers scale and biofoul on the water side, raising head pressure and pushing compressor power up for the same cooling. Where the rejection is through an evaporative cooling tower, the same circuit is also a controlled Legionella risk. Cleaning and disinfecting the tower and its associated plant is then a legal duty, set out in the Health and Safety Executive's approved code of practice. It is not a maintenance preference.

Fouls with
Scale, biofilm, airborne debris and silt in the condenser water circuit
First symptom
Head pressure and compressor power rising, approach temperature widening
Watch for
Legionella risk assessment and cleaning records, which are inspectable

02What has built up

Limescale comes from the mains and magnetite comes from the system itself

The two most common deposits in building services arrive from opposite directions, and treating one as though it were the other is the usual reason a clean does not last.

DepositWhere it comes fromHow it is removed
LimescaleHardness in the mains water precipitating on the hot side of DHW plate exchangers and calorifier coils.Inhibited acid circulation, or exchanger replacement where the unit is small enough that it is cheaper.
CIP / replace
Magnetite sludgeCorrosion inside the heating circuit itself, usually where inhibitor has been lost or never dosed.Powerflush or chemical clean of the circuit, then dose and keep dosing. Filtration keeps it out.
Flush + dose
BiofilmCondenser water circuits, cooling towers and any circuit sitting in the Legionella growth range.Clean, then disinfect, then maintain the treatment regime. This one is a legal duty as well.
Clean + disinfect
Installation debrisSwarf, jointing compound, flux and building dust left in a system that was never properly flushed.Flushing and strainer clearance. Common on new and recently altered systems.
Flush
Airborne foulingDry air coolers, condenser coils and AHU coils collecting dust, pollen, seed and leaf litter.Controlled-pressure washing from the outlet side back, with fin combing where flattened.
Wash
Glycol degradationOld or over-temperature glycol breaking down into acidic products that attack the circuit.Drain, flush and recharge. Cleaning a circuit and leaving degraded glycol in it achieves nothing.
Flush + recharge

03In place or off site

On a scheme with hundreds of units, replacing beats cleaning more often than not

This is the one sector where the recommendation is frequently not to clean. A domestic-scale plate exchanger is a low-value component, and mobilising to descale one can cost more than a new one.

  1. 01

    Descaling in place suits calorifiers and anything too large to swap

    Inhibited acid circulated through the unit on site, with neutralisation and flushing afterwards. It is the standard answer for calorifiers, plant room plate exchangers and anything where replacement is not a realistic option, and it can usually be done overnight or outside occupied hours.

  2. 02

    Replacing an HIU plate exchanger is often cheaper than descaling it

    At domestic scale the labour is the same either way, so a swap frequently wins. A new exchanger also arrives with no residual scale and a known starting point. Where a whole scheme has scaled, planning a rolling replacement is usually more economic and less disruptive than a descaling programme.

  3. 03

    Flushing the circuit treats the magnetite that keeps refouling the exchanger

    Powerflushing or chemical cleaning of the heating circuit removes the sludge at source, and it only holds if the system is then dosed with inhibitor and fitted with filtration. Cleaning the exchanger alone, on a system that is making magnetite, is a repeat visit booked in advance.

  4. 04

    Cooling tower cleaning and disinfection is scheduled as compliance, not maintenance

    Tower cleaning and disinfection is a duty under the approved code of practice for Legionella control, carried out at a defined frequency with records kept. The condenser and interchanger cleaning that goes with it is normally planned into the same visit, because the access and the isolation are already in place.

04What happens next

Four steps take a fouled unit from enquiry to a tested return

The enquiry goes straight to a contractor who cleans that unit type. There is no qualifying call in between.

  1. You send the unit details, the deposit and the postcode.

  2. The enquiry goes to a specialist set up for that unit type and that fouling.

  3. They come back with method, timescale and price.

  4. The clean is carried out in place or off site, and the unit is tested before it goes back.

05Questions

Occupancy, unit count and system water decide how building services plant is cleaned

Our HIUs are not reaching hot water temperature. Is it scale?

Often, particularly in a hard water area and on a scheme more than a few years old. Instantaneous DHW production across a small plate exchanger is close to ideal conditions for limescale. The symptom is what residents report: water taking longer to run hot, or not getting properly hot at all.

Rule out the alternatives first, because they present identically. A blocked network-side strainer, a failed differential pressure control valve, or a network flow temperature that has drifted down will all produce the same complaint without any scale being present.

Is it cheaper to clean an HIU exchanger or replace it?

At domestic scale, replacement usually wins. The plate exchanger in an HIU is a low-value component, and most of the work either way is getting an engineer into the flat. Fitting a new one instead of descaling the old one adds very little.

Replacement also gives a known starting point instead of a partially descaled unit. Across a scheme the case is stronger still. A planned rolling replacement is far less disruptive than descaling several hundred units in place.

Can this be done with the building occupied?

Almost always, because it has to be. HIU work is done flat by flat with a short interruption to that flat only. Plant room work is planned for evenings, weekends or outside the heating season, and on systems with duty-standby plant one side is cleaned while the other carries the load.

What needs planning is access and not the work. On residential schemes, arranging entry to individual flats is routinely the longest part of the programme and is worth starting well before the engineers are booked.

Where does the black sludge come from?

From the inside of the system. Magnetite is iron oxide produced by corrosion of the circuit's own steel, and finding it means the water chemistry is wrong. Usually inhibitor that was never dosed, has been depleted, or was lost when the system was drained for a repair and refilled without redosing.

Which is why removing it is only half the job. Clean the exchanger, flush the circuit, then dose the inhibitor and fit filtration, or the same sludge will be back in the same place.

What are our duties on cooling towers?

Evaporative cooling towers are a controlled Legionella risk, and the duty holder is required to have a risk assessment, a written control scheme, and cleaning and disinfection carried out at defined intervals with records kept. The Health and Safety Executive's approved code of practice sets out what is expected.

The practical point for cleaning is that the associated condenser and plate exchangers are best done in the same visit, since the isolation, access and permits are already arranged. Records from that work form part of the compliance file instead of sitting in a maintenance folder.

How long does a chiller condenser clean take?

Brush cleaning or lancing the condenser tubes on a typical commercial chiller is usually within a day, with isolation and refrigerant-side precautions taking a fair share of that.

Scheduling is the harder part. It needs the chiller off. On a site with no redundancy that means out of season or overnight. On a site that cannot lose cooling at all it means one machine at a time, with the others carrying the load.

What does building services exchanger cleaning cost?

Access and unit count, more than deposit. A single plant room calorifier descaled overnight is straightforward to price; several hundred HIUs across a residential scheme is a programme, and the cost is dominated by getting into the properties.

For schemes, ask for the replacement comparison alongside the cleaning quote. It changes the answer often enough that it should be a standard question rather than an unusual one.

How often should this plant be cleaned?

DHW exchangers in hard water areas are condition-driven, and the useful trigger is the DHW temperature the unit achieves, not an interval. Softening or scale-reduction on the incoming main extends it considerably.

Heating circuits should not need repeat cleaning at all. If they do, the inhibitor regime is the thing to fix. Cooling towers and their associated plant are the exception: those are cleaned at the frequency the control scheme specifies, regardless of how they look.

06Other industries

Fouling follows the process, so every sector fouls its exchangers differently

Data centresMineral scale in chiller condenser tubes, biofilm in cooling tower interchangers, particulate on coils.data centre heat exchanger cleaning →Water and wastewaterStruvite, rag and sludge solids on digester heating loops and heat recovery exchangers.water treatment heat exchanger cleaning →Energy from waste and biomassAsh, slag and acid-side deposits on flue gas coolers, economisers and condensers.energy from waste heat exchanger cleaning →Refrigeration and cold storageScale on evaporative condensers, oil fouling on ammonia chillers and plate evaporators.refrigeration heat exchanger cleaning →

A specialist who cleans that unit type answers the request

Unit, deposit and postcode are enough to start. Your details go to a specialist who cleans that unit type. No obligation.

Arrange a clean