Air Source Heat Pump Noise

nxdmsandkaskdjaqd

Is it normal for a Air Source Heat Pump to sound louder/rattle a bit when it's 5/10 minutes before the de-ice cycle starts (the fins are iced up at this time).  

matelodave

Mine gets slightly noisier and rattles a bit when it's about to defrost, but as it's been doing it for 14 years I don't take any notice.

I think its only natural that when you get summat that's new or you don't fully understand that you'll worry about anything that looks or sounds a bit different or out of the ordinary.

When people first got condensing gas boilers many were concerned or worried when great plumes of steam started coming out of the flue until they understood why. Similarly heatpumps have their own little foibles that might make you sit up and take notice and these might seem more important the more you try to analyse what might be going on.

If its been chuntering away quite happily, keeping your water hot and keeping the place reasonably warm and comfy during the summer and autumn months and then there's suddenly a cold snap, the unit will behave a bit differently.

It has to work harder the colder it gets, it will probably frost up, when it gets cold and dampness makes it worse, the unit has to then do a defrost cycle which requires the circuits to be reversed inside the unit to get heat into the bit thats normally cold - that will change pressures and temperatures and may make the unit a bit noisier when doing it, but it doesn't mean that its falling to pieces or about to explode.

I have a mate who used to work for both Daikin and Panasonic and he reckons that the defrost cycle is based on time and temperature but the unit really has no idea of how much actual frost or ice gets deposited.  So under certain conditions it could seem to defrost when it doesn't really need to and sometimes not as often as you think it should, especially when its foggy and misty outside.

Fiddling with controls or shutting the system down when it's trying to do what its been designed to do will just stop it it working properly.

I also think that having room stats or TRV's can slow down or even might curtail a full defrost cycle if it shuts down the circulating pump or restricts the system water volume if TRV's close off radiators.

My system work much more efficiently (insofar as we are comfortably warm all day without temperature swings) and uses less electricity since I disabled all the underfloor flow actuators (like TRV's on rads, actuators control underfloor loops).

I initially thought that having temperature controls in each room would make the system more efficient.

However it seemed to do the opposite by making the heatpump short cycle which not only affected the comfort levels but significantly increased the energy consumption. It took a couple of years before I got it right, but I've managed to get my annual electricity consumption down by around 1600kwh a year (approx £400 at todays prices)

The  unit uses weather compensation to control the house temperature rather than using room stats etc. It also seems to defrost less frequently than it used to and the house doesn't get cold overnight eother.

nxdmsandkaskdjaqd

matelodave said:

Mine gets slightly noisier and rattles a bit when it's about to defrost, but as it's been doing it for 14 years I don't take any notice.

Thank you for the feedback