@netdonkey The model number for your Samsung indicates it is an 8kW system? The flow rates you are indicating only provide around 2.5kW and the code E911 is related to lack of flow, airlocks, restrictions on flow or other flow sensor issues. 

Samsung send an inline strainer with their systems, if this was fitted it will collect debris from the system and block (this is its job) this will need checking 1st, also its worth confirming the length of the primary pipework from the condenser to the plant room (from the condenser to the manifold or plant room, buffer or 1st secondary distribution pipework valves). It worth making sure this pipework is the correct size for the flow rate and distance it serving. 8Kw will need a minimum of 28mm on a short run.

@ashp-bobba Thanks. The pipework run from the ASHP to main plant is around 13m.  Would the strainer be near the pump or the main plant?  I assume the strain would be on the return to protect the pump?

@netdonkey The strainer can be anywhere on the rerun line from the airing cupboard / plant room to the ASHP condenser, so this could be in that room or at the condenser, they look like a Y shape: linked here for you to see.

Please clarify 2 things if you can?

13m from the condenser to the plant room as the main ASHP pipes 

What size is the pipework from the condenser (most manufacturers need you to limit the run to a max 10M or calculate an upsize in pipework and pump to cope with the length of run).

Posted by: @netdonkey

↑

Would the strainer be near the pump or the main plant? 

On our system, originally, it was inside the heat pump unit (we don’t have a Samsung). It was a bloody stupid location because we had to remove heat pump side panels to access it, so we had the installers move it into our plant room. See photo.

I asked installers specifically about Y strainers on a recent podcast and they should be fitted on every installation, so you should have one somewhere. 

@ashp-bobba 28mm I believe but will get the tape measure out tomorrow.

@editor will have a look for it tomorrow.  How hard is it to open and clean?  I assume there will be a stop valve/cut off either side of it?

@netdonkey Should be shut of valves either side. the nut can be a bit tight on some of them, be sure to support the pipe when you try.

A new symptom this morning. 

The HP shut off overnight with the E911 error.  I have reset everything as usual and now the HP isn't coming on but the MIM is still reporting 7.4lpm and the radiators aren't getting warm at all

@netdonkey do exactly what @ashp-bobba says above.

Cleaning it is really easy once you've popped the nut off. It's got a little gauze filter/mesh inside. Give that a rinse under a tap, but before you do, check to see how many corrosive bits are in there as a reference. 

@editor Can't see anything that resembles a Y filter.  There does seem to be a big black fillter (pic attached) which might be a filter?

Before and after the Evosta3 circulation pump there are valves.  Is it worth making sure those are fully open?

 The heat pump has just came on, the pipes near the water tank start to get a bit warmer and then the HP goes off again so sounds like it might be cycling?

@netdonkey The filter in the first photo looks saucespiciously like a ‘MagnaClean’ type filter; as the flow passes through this, the larger volume of the chamber reduces speed of flow and allows a magnet to attract and retain any particles of ferrous material that passes through the pipework. This chamber is normally cleaned out during any servicing work. Regards, Toodles.