HIU & CIU servicing in London
No heating or hot water in a flat on a communal heat network, or cooling that won’t cool? We service and repair heat interface units (HIUs) and cooling interface units (CIUs) for landlords, letting agents, managing agents and residents.
What we do
- HIU servicing and repairs
- CIU (cooling interface unit) servicing
- No heating or no hot water fault finding
- Circulation pumps and expansion vessels replaced
- Strainers cleaned, isolation and pressure valves checked
- Actuators, set points and controls checked
- Heat meter displays and sensors checked
- Underfloor heating manifolds checked
What an HIU service covers
- All strainers cleaned
- Pressure and isolation valves checked
- Pump checked and air removed if needed
- Actuators checked and set points verified
- Insulation checked
- Heat meter display and sensors checked
- Primary flow and return temperatures recorded, and the difference between them
- Flow rate recorded with the valve fully open
- Heating expansion vessel pressure checked
- Hot water temperature recorded after two minutes of running
A CIU gets the same checks on the chilled water side, with the chilled flow and return temperatures and flow rate recorded. You get every reading in the report, with photos.
Who it’s for
Tenant reports of no heating or hot water, fixed with a report.
Servicing across flats, with readings for each one.
Your heating, hot water and cooling checked properly.
Recent HIU and CIU jobs
- Trace heating alarm, White City (W12). A Raychem trace heating system on the pipework by a flat’s HIU kept showing a low or no current alarm. We disconnected the load and reset the controller, which then failed to alarm with nothing connected. Tested on its own, the heating cable drew about 1.2A and warmed up as it should, so the fault was in the controller’s current monitoring, not the cable or the pipe insulation. We recommended a new controller module and quoted for it.
- HIU repair, no hot water, Canary Wharf (E14). A flat on a communal heat network with a failed pressure valve on its heat interface unit. We replaced the valve, tested the hot water at the shower and kitchen tap with a thermometer, and checked every joint we had disturbed for leaks. Hot water was back on the same visit.
- Full heating and cooling service, Islington (N1). A new-build apartment on a communal heat network. We serviced the heat interface unit, cooling interface unit, fan coil units, MVHR and underfloor heating in one visit. We found the HIU’s heating pump and expansion vessel had failed, a faulty pressure gauge on the CIU and a failed MVHR supply fan with worn-out filters. After cleaning the CIU strainer the chilled water flow stayed low, which pointed to the building’s communal system rather than the flat, so we said so in the report. The fan coil filters were cleaned and disinfected, and the managing agent got the readings, photos and a quote for the repairs.
Related services
Good to know
Common questions
Why is my trace heating showing a low current alarm?
A low or no current alarm means the controller thinks the heating cable is not drawing power. That can be a damaged cable, a tripped supply, or a fault in the controller itself. We test the cable on its own with a clamp meter to see whether it heats and draws current normally, so you only replace the part that has actually failed.
Why have I got no hot water from my HIU?
On a heat network flat, no hot water is often a failed valve, actuator or sensor inside the HIU, or low pressure or flow from the building’s communal system. We test the unit to find which, replace the faulty part where we can on the day, and tell you if the problem is in the communal plant instead.
Can you replace parts inside an HIU?
Yes. We replace valves, actuators, pumps, expansion vessels and sensors in heat interface units, then test the hot water and heating and check the joints for leaks before we leave.
What is an HIU?
A heat interface unit is the box in your flat that takes heat from the building’s communal heating system and turns it into heating and hot water for your flat. It does the job a boiler would do in a house.
What is a CIU?
A cooling interface unit does the same job for cooling. It takes chilled water from the building’s central plant and feeds the fan coil units that cool your flat.
Why has my HIU stopped giving heating or hot water?
The faults we find most are blocked strainers, a failed pump, a failed expansion vessel, or a valve or actuator that has stopped working. Sometimes the problem is on the building’s communal side. We take readings so you know which it is.
Can you fix problems on the communal system?
We fix faults inside the flat. If the readings point to the building’s communal system, we say so in the report so the managing agent or heat network operator can deal with it.
Do you work for landlords and letting agents?
Yes. Most of our HIU and CIU work comes from landlords, letting agents and managing agents. We arrange access with the tenant and send the report, photos and invoice together.
Got a job that needs doing? Let’s get it sorted.
Tell us what you need and you’ll get a clear, written price back.
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