Queries about district/community heating systems and HIUs

[@TonyC]

Last year, my wife and I viewed four apartments in a block of apartments that had a district/community heating system. Each apartment therefore had a heat interface unit (HIU). It was my first experience of this type of heating and I had never seen an HIU before.

In each apartment that we viewed, I was aware of a hum in a certain area of that apartment and it appeared to be coming from the HIU. If I was not in the vicinity of the HIU, I could not hear the hum. My main query is, do all HIUs make a hum and, if so, what is causing it?

Secondary to the main question is the following. Can the volume of the hum be turned down in any way? Can an HIU be turned off completely if hot water and room heating are not required? If an HIU can be turned off, does the hum cease?

Finally, which is generally considered cheaper, hot water and room heating provided by a district/community heating system, or hot water and room heating provided by a gas boiler?

 

[Chuck]

HIUs contain some electronics, which need a power supply that may hum all the time but this should be very quiet. There will also be a pump, often inside the HIU, that circulates water through the heat exchanger and around the radiators, etc. as necessary. This will sound like any other central heating pump; audible iif you listen for it but not loud enough to be a real problem.

In principle, HIUs should be cheaper to maintain than their boiler equivalent and the community may be big enough to buy its energy 'wholesale'. However, there will be community boiler / heat pump somewhere that you will presumably need to contribute directly or indirectly to maintaining. You may also have a more limited choice of companies who can service the system, which might increase costs a bit.

The only way to know, however, is to ask the vendor to provide details of the scheme: how it is funded, a history of charges to the apartment owner, and a schedule of planned maintenance and replacement/upgrades. Even then the price of energy and labour goes up and down over time so certainty is not really possible.

 

[@TonyC]

Thanks Chuck.

I would be suspicious of electronics humming or buzzing. Boxes of electronics like central heating control units and consumer units should not hum or buzz? Surely, this is indicative of a fault? But this hum was heard in all four apartments that we viewed.

I could understand the pump making a humming sound. We have a conventional boiler, radiator, and hot water cylinder system with a pump, and the pump does hum when the room thermostat or hot water thermostat is calling for heat. But the hum is not very loud, and you don't notice it most of the time. And, when neither thermostat is calling for heat, the pump stops and is completely silent. Does the pump in an HIU work like this? Or does the pump have to run continually? Like I said in my original post, all four apartments in the same block exhibited a continuous hum that never stopped while we were viewing. And some of the apartments were even vacant, which is the reason why I asked whether it is possible to switch an HIU off completely.

Is it possible that the hum could originate in the "plant room" containing the community boiler, pump, etc. and reverberate throughout the whole building?