Strange DHW cycle behaviour

Good evening all,

I am seeing some weird behaviour with the DHW cycles following some radiators swaps recently.

Before I go back to the installer again I was wondering if anyone here had any thoughts. I have tried an air purge with all of the aav’s open on both DHW and heating circuits and it did let some air out but not much. It has done this for the last few days but before this I was seeing around 3.x for DHW.

Any and all ideas greatly appreciated

The drop in heating power is likely due to air messing with flow rate sensor, as the temperature continues to rise as expected. Keep running the system and bleeding the rads and valves.

Related topics:

Advice from Marco:

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We (Octopus) removed (on my request) the aav and added a manual air vent for the DHW loop as we could not purge the air from the DHW loop, and I could hear gurgling at night on startup. Even now every week I let a little air out of the DHW loop.

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Hey Tim,

Thanks for this,

Unfortunately after lots of attempts to purge air and running the system at 2bar and 50°c switching from heating to hot water and back I am still seeing this weird behaviour.

I have bled all the radiators and all the aav’s are open. No more air is coming from the radiators but still the meter is having issues reading only in DHW cycles.

This was working perfectly up until 4 radiators were swapped last month by the installer.

Any ideas on how to proceed?,

Any benefit to draining and refilling the system again?

Draining and refilling will make this worse

You need to work out where your air is trapped and a way to release it I’m afraid

Someone posted a llink to a device to help purge air. I’m sure it was a specific topic, but I can’t find it now.

Found it

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Bit of an update on this one.

Issue seems to have been the lack of inhibitor in the system.

Following a radiator swap the plumbers did not replace the x100 and this caused the dissolved air to stay in the system (and not be scavenged /removed)

I replaced this a couple of weeks ago and we are back up to a COP of 3.x for DHW cycles and things are looking up again.

Thanks for all the help and guidance with this.