@netdonkey I think you have an air lock, a restriction or for some reason a lack of flow.

@netdonkey 

We have a Evosta 3 set to fixed curve regulation mode level3.  Is this correct?

It looks like the Evosta has been installed upside down but I assume it was done this way due to the flow direct?

At the beginning is this the main pump you are talking about? can you check that the face is in the correct orientation or it could air lock or not circulate correctly.

@netdonkey 

I am sorry to say, but I have just gone through the pictures again and although I cannot see the face of the pump I can clearly see the cable coming out the top and it very likely that is incorrect according to the sections I sent you from the manual. most pumps need to have the shaft vertical and the writing on the face of the pump the correct way up. although your pump needs to point down, what should happen is the face (head) is taken off and refitted the correct way up, this allows the self priming and bleeding to work and prevents the pump form air locking.

@ashp-bobba Or in the case of the Wilo Pico pump, just loosening the case screws enabled the fitter to turn the face around the ‘right’ way; this had to be done by my fitters. Regards, Toodles.

@netdonkey

Reading the manual it looks like rotating the face is just to be able to read the interface, this instruction manual says to bleed to pump you unscrew the centre screw allow the air out and tighten again. I have attached the whole manual.

@ashp-bobba We are on high constant curve 3 and will check the orientation.  I believe it was set that way due to the way the flow worked

@netdonkey Yes, the pump body is installed the correct way but the head (front of the pump is the wrong way), before the pump is installed it should have the head taken off and rotated so you have the body and the head correct. I sent you the installation manual to show you. Its worth giving the pump a bleed as its not self priming, thats in the book too.

Posted by: @netdonkey

↑

We are on high constant curve 3

Just before we jump to the conclusion that the pump is effectively "full on", there are occasions when a pump must be put into that mode so that its speed can be governed by a PWM supply.

It's now rare, because pumps with a separate Control Connector for PWM signals are also readily available.

I have a Grundfoss pump with the Selector set to "3" but pulsed by the controller for my solar-thermal panel on the roof.
That allows its speed to be dropped down to 40% which is adequate for that job.

@transparent There is a Grundfoss UPM3 Flex As (bottom right of the pics) that is set to level2 and seems to be in working order

@ashp-bobba Bled it and there was a fair bit of air in there before water started to come out but still hasnt made a difference. Although the E911 error isnt coming up as often, the circulator keeps going off ever so often.

The installer (an electrical company which subbed the heating out to someone else) and telling us to get in touch with Samsung as they seem to be washing their hands of it as "it has been working fine for 6 months".  Samsung want £550 ex VAT (which they will refund if it is a Samsung fault) but I'm not confident if the fault lies with the Samsung or the rest of the plumbing.

The company are registered with RECC, do you think it is worth raising a formal complaint with them?

@netdonkey I think if what you did just now made the system run for longer then it is air in the system and your flow may now have improved.

As with reporting the issue, this is up to you and your right to do so but I think I would push the installer to make a further effort to take another look, but this time get them to show you and confirm they got the flow rate up to 24 lp/m if an 8kW system or 32 l/pm if 12Kw and that it is stable there. your issue is very likely flow rate.

To help out a very good heating company I know that installed a 12kW Samsung system it took me 5 attempts over 2 weeks to get it running correctly and every time it was air in the system and every time I helped the company assess, bleed and proved the flow rate which by the way was 29l/pm so only just under design, within 1 or 3 days it would lock out again on air. What I did the last time we went which fixed it was to break the connections on the condenser, use a flushing pump to blast the long pipe run and drive the air out and then place the condenser back, bleed locally, open the valves and from then it was good as gold. what was wrong with this system was missing air bleed points on sections of the pipework where it ran flat or rise and fall. 

I think you may have some closed AAV's further up the line or just some air that built up over time from little pockets. Its worth reading the water flow again now if you think it runs for longer to see if thats improved.

Oh and don't be afraid to bleed that pump every day for a week, if its going to collect there then at least you can release the air. 

Posted by: @netdonkey

↑

Bled it and there was a fair bit of air in there before water started to come out but still hasnt made a difference.

Then there's likely to be more air in the pipes somewhere.

The amount of air which came out from that bleed position was "a fair bit", but it's limited by just how much air can be trapped at that location.

Bleed it again 20mins later and you might get more air out.

Equally, you have other air-release valves which are worthwhile looking at.
Even the ones which are meant to be "automatic", can sometimes be less optimal at the job.
Unscrew the plastic cap on the top and press down the brass plunger.
You may get a mixture of air and water before you see just water trickling out.

2: As I understand it, that cylinder has a 50-litre buffer tank at the base, and a 220-litre DHW tank above it.

The photos show that each compartment has its own immersion heater, which I'm going to assume is the usual 3kW rating at 240v.

We've previously discussed on the forum how the immersion heater in the DHW tank is used at intervals to run an anti-Legionella cycle.

If you're wanting to run this (and some people decide not to), then it does need to be effective.
The usual sequence is for the ASHP to raise the water temperature to 50°C.
The immersion heater then takes over for an hour to reach the 60°C required to kill the bacteria.

For a 3kW heater to raise 220-litres of water by 10°C in an hour, is a borderline case.

Your cylinder would need to be well insulated for that to succeed.

For comparison, a 250-litre tank is impossible because the efficiency of the insulation would have to be 100% perfect to achieve a 10°C rise in an hour!
So it would require longer time or a more powerful immersion heater.

I've done the calculation over here on another topic if you'd like to check the physics and my arithmetic!