I signed up here due to finding this question via a Google search.   I've been looking into this with my Aerona R32 for some considerable time. I've had long conversations with Grant and tried various settings. I've been running with 'Pump Blockade On' for over 9 months without any issue except now that winter is upon us. Because Pump Blockade also turns off the 2 port valve on the rad circuit, when the outside temperature drops below 4 degrees the circulator pump kicks in for frost protection, and is restricted by the closed 2 port valve - which can't be good for it. Therefore, I've had to turn 'Pump Blockade Off' over the winter.

Despite speaking with Grant and showing them a range of graphs and scenarios, I feel they don't fully understand what the concerns are over a pump running almost 24/7 (these pumps are not cheap). I was one of the first to adopt the smart controller, so very few Aerona owners understood the issue I was having last year. Now more of these are being fitted, this question keeps coming up across the net.

We recently (Aug 25) had a Grant Aeorana 3 installed under a Eco  grant.

Initially set with 48degC fixed flow temp for space heating no schedule just to be controlled by turning room stat up/down as required, but I've since changed this to WC.

 DHW at 50degC which reheats when it drops to 45degC, again no schedule.

I've noticed the following regards the regards circulating pump (integrated in to the ASHP unit );

For space heating in 'day' or 'night' mode the pump appears to run all the time regardless of Pump Blockade setting.

For space heating in 'holiday' mode the pump stopped once the room stat was satisfied, but I don't remember the blockade setting at the time.

In Aug/Sep with only DHW enabled 24hr no schedule and the heating set to off the following seemed to happen;

DHW drops to 45degC

ASHP Target goes to 55degC

ASHP (and circulating pump) start up, valve goes to DHW

ASHP flow/return get to 55degC (tank stat ~49.6degC)

ASHP shuts down

Valve goes to CH

Circulating pump runs indefinitely on the CH circuit.

Tank drops to 45degC

ASHP fires up and the cycle repeats.

I noticed that after a Legionnaires'  cycle the circulating pump had stopped.

I checked the stat in the the DHW tank and it was just dangled in the pocket so I packed it with a little fluffy insulation and the following happens;

DHW drops to 45degC

ASHP Target goes to 55degC

ASHP (and circulating pump) start up valve goes to DHW

ASHP flow/return aim for 55degC

Tank stat hits 50degC

ASHP shuts down

Valve goes to CH

Circulating pump runs for a few minutes then stops

Tank drops to 45degC

Cycle repeats.

My conclusion after all that, the ASHP decides when it needs the circulating pump running and it's dfficult to work out what triggers it or the logic behind it.

there's a detect cycle setting (4200) on the old grant controller which controls the internal pump. It means the internal pump only runs when the compressor is running then runs a 'detect cycle' every 5 mins or so to circulate the primary water to allow a temp check, if it's below what the curve setting requires the compressor starts up. That's my reading of it anyway, has anyone tried this setting on an Aerona3?