HIU - Heating Interface Unit
A number of residents have had issues with the heating. It’s usually the heat interchange unit (HIU) that’s the issue or the thermostat.
The HIU is the responsibility of the Managing Agent to repair and we have had a few of them repaired by Unitary under the direction of Encore.
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Unless you are confident with removing the cover to the HIU we strongly suggest you get professional help.
We recommend Alex Derrick, Switchsafe Environment, switchsafe.uk.com, 07545 308730, 01179730029
The HIU cover is located over pinns on the back plate, to remove the cover push it upwards to clear the pins and pull towards you to remove, there are no fixing screws involved - the covers can be a little awkward to remove or replace.
The first thing to check is that the central boiler water is reaching the HIU.
If you feel the pipes on the upper left they should be boiling hot.
If they are not then it is a system heating issue and someone must have turned off a valve to the property. If you have hot water then these pipes will be hot anyway.
The next thing to check, looking through the boiler window, when the heating is turned on you should see the green light on the circulation pump come on. This means the heat thermostat and switch are working. If this is the case and there is still no heating then it could be that the circulation pump has ceased to function - a very common problem - (note you might not be able to see the pump without removing the cover of the HIU).
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Sometimes a gentle tap on the circulation pump casing can restore its function, the impeller within the pump can become stuck which renders the pump inoperative and a gentle tap on the pump casing may free up the impeller.
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The only other issues we have encountered are motorised valve failures. This is a tenant responsibility I believe. The motorised valve switches water from the HIU to the radiators and is usually located above the HIU - (note you might not be able to see the pump without removing the cover of the HIU).
If you look at the little lever by the wire this should move backwards and forwards as it diverts hot water to the radiators. The lever should be all the way to the right to send water to the radiators.
For the extremely technical here is a diagram:
MEV setup instructions
Mechanical Extraction Ventilation
