Strange DHW cycle behaviour

[KnightPhoenix (Zak Wilcoxen)]

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

[Timbones (Tim)]

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.

[Timbones (Tim)]

Related topics:

Kamstrup Multical 403 Stops Working During Hot Water Cycle (Interference?)

Here are a couple of other threads that discuss similar issues: Kamstrup Multical 403 Erratic flow readings - Hardware / Heatpump - OpenEnergyMonitor Community New emonHP install with strange readings - Hardware / Heatpump - OpenEnergyMonitor Community In my case it eventually resolved itself, especially after space heating started to run more often as we went into Autumn so it was probably dissolved air that was being released at higher temperatures when doing DHW runs. Hasn’t been a problem…

Advice from Marco:

Kamstrup Multical 403 Stops Working During Hot Water Cycle (Interference?)

Dissolved air in your system. Raise the fill pressure; get it good and hot; bleed the radiators; switch back and forth from DHW to purge the water with disoolved air from the DHW loop; bleed the radiators etc. Once there isn’t air in the flow sensor it will work correctly.

[tiger_cook (Neil)]

@KnightPhoenix

aav’s open on both DHW

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.

[KnightPhoenix (Zak Wilcoxen)]

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?

[marko (Marko Cosic)]

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

[borpin (Brian Orpin)]

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

Removing air from the system

I have just installed one of these: " DiSmart 28mm Swiveling Deaerator" It works utterly brilliantly. It removed all the air from the system over a period of a few days.

[KnightPhoenix (Zak Wilcoxen)]

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.