Since having our Daikin heat pump installed we regularly get woken up in the middle of the night by the central heating pipes creaking.
Its happening at the end of the DHW cycle (45C) and this morning I checked my watch and it was 02:44.
Currently the hot water cycle start is set to 02:00 as
Its in our IOG cheap rate
I often have to get up at silly oclock to catch a flight and its nice to wake up with a hot shower
Usually by this time my home batteries have fully charged and there is less demand from my house on the grid.
Now I could move the DHW cycle out of sleep time, for example at lunch time but then I am likely using precious home battery energy and in the depths of winter I dont have enough battery to get the heat pump through the day so added a kW/h or two will only make that worse.
Maybe I could split the DHW into 2 cycles, one at 23:20 at the start of my cheap rate and then another at 05:30.
Could anybody confirm why my central heating pipes are creaking after the DHW?
Suggest any strategies to mitigate it with heat pump settings?
Or is it a physical job for a plumber?
My heating pipes have always creaked and groaned when heating turns on or off. Happens a lot less under HP than it did under gas, since HP tends to be on all the time.
There was a thread somewhere talking about it being better (more efficient) to heat the water in two halves, rather than all at once, counter-intuitive though that may be.
Perhaps a dumb suggestion, but overnight power on IOG is so cheap that you could just use the immersion overnight, rather than the HP. (I was doing that during the freezing nights to try to reduce HP defrosting.) Or use HP to heat to eco temperature at 23:30, then immersion to raise it to comfort temperature when you need it.
Creaking pipes are usually a sign of poor installation. Pipes just laid directly in notches cut out of rafters, installed under strain, tortuous bends with no allowance for expansion. The pipes should be held in place by clips with rubber inserts to allow the pipes to smoothly expand and contract.
In the bad old days when I ran my boiler at 82degC and pump at full wack, the pipes would creak and bang as the system warmed up. Now with lower flow rates and temperatures, not a sound. So it can be mitigated by reducing the rate at which heat is forced into a cold system, gives the pipes time to creep rather than jump as they expand.
we get a brief pipe creaking noise briefly as the hw cycle finishes and the valve turns over to central heating ( hotter water suddenly going in to cold pipes
Its an old house, 1920s. Ground floor rads are fed by surface pipes that drop from the ceiling. Upstairs are all under the upstairs floor. The pipes will be 30+ years old, which is as long as we have lived here.
Octopus did the heat pump install, without needing to lift a single floorboard, pretty much everything is copper apart from the new extension and not so new bathroom. Dont ever recall seeing any pipe clips when the floors have been up.
It was never an issue before as we had an oil combi with on demand hot water. Before that we did have a coal Rayburn and immersion but that was decades ago.
So its only really been noticeable since the heatpump went in and we now heat the water overnight on IOG.
The creaking is definitely immediately after the valve turns to DHW to CH. Like I say its loud enough to awaken anybody sleeping.
Will likely have a look at it next time the upstairs floorboards/carpets come up.
Probably not relevant, but just in case… in another thread (today, I think), someone mentioned that their DHW circuit included the volumiser, which meant that, at the end of the DHW cycle, the volumiser was full of very hot water, which would presumably then get pumped through the radiators.
On my system, volumiser is in the radiator circuit only.
Hunt the creak, and if you are lucky, the evidence will be a shiny spot on the underside of the floorboard, you can resolve it by cutting the notch a few mm deeper, happy hunting !
