Not really.

The only parallel I have is last summer I had a slew of apparently unrelated faults (including compressor blocked) and the compressor would start then stop a few minutes later.  Installer turned up, cleared the fault list, cleaned out both of the filters, problem fixed.  He said that 90% of callouts are due to blocked filters.

Clearing the fault list appears to matter, I get the impression that certain faults are fatal until cleared.

Posted by: @jamespa

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Not really.

The only parallel I have is last summer I had a slew of apparently unrelated faults and the compressor would start then stop a few minutes later.  Installer turned up, cleared the fault list, cleaned out both of the filters, problem fixed.  He said that 90% of callouts are due to blocked filters.

Thank you. Will let you know when fixed.

@jamespa Should I assume that cleaning those filters has to be done by a Vaillant technician and would be included in an annual service?

Posted by: @davidb

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@jamespa Should I assume that cleaning those filters has to be done by a Vaillant technician and would be included in an annual service?

It should be included in an annual service.

The filters are external to the unit.  You may only have 1.  I have a magnetic filter branded valiant and an unbranded mesh filter.  The latter is cylindrical about 75mmx40mm and closer to the unit than the mag filter (it's finer).  It was the latter that was the cause of my problem, I didn't even know I had it until the installer pointed it out, it's just behind my outdoor unit.

I would say that learning how to clean these is a useful householder skill!

@jamespa Thanks for that info.  I had looked at the functional diagram (p87j of the Aerotherm plus instal and maintenance manual and noted items 2 and 26 namely filter and filter / dryer respectively and assumed those were the items mentioned and, being inside the casing, needed a specialist.  The filters I have outside of the external unit are a mag filter and inline strainer - additional to the ones mentioned but are inside our house.  If there is an external filter just outside the casing, it’s not evident with everything covered by pipe insulation.

i am specifically interested in this routine stuff as my installer (who is on the mainland) says he may struggle to get to us due to difficulties with ferries to the Isle of Arran. I am hopeful I will get a visit but it’s definitely not guaranteed so I am wanting to understand what is allowable DIY.

Posted by: @davidb

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 The filters I have outside of the external unit are a mag filter and inline strainer - additional to the ones mentioned but are inside our house.  

Sounds like the same as me.

Posted by: @davidb

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 I had looked at the functional diagram (p87j of the Aerotherm plus instal and maintenance manual and noted items 2 and 26 namely filter and filter / dryer respectively and assumed those were the items mentioned and, being inside the casing, needed a specialist

I havent touched those and dont know if they are a regular maintenance item or not.  There is a maintenance schedule at the back of the manual.

Posted by: @davidb

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i am specifically interested in this routine stuff as my installer (who is on the mainland) says he may struggle to get to us due to difficulties with ferries to the Isle of Arran. I am hopeful I will get a visit but it’s definitely not guaranteed so I am wanting to understand what is allowable DIY.

Ah, yes its probably best to be as self-sufficient as possible.  I cant see why the two filters external to the unit would not be DiY, my mag filter came with instructions but not the strainer (which is isolate, unscrew the end, remove, wash the mesh, reinsert)

Posted by: @davidb

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@jamespa Aerotherm plus instal and maintenance manual.

I looked online for this manual but didn't find.  Can anyone provide a link?

I’m not a Vaillant owner, so take this with a pinch of salt, but I did a quick bit of Googling and had a look around some of the Vaillant fault information.

The thing that jumps out at me isn’t actually the "DHW compressor blocked" message, it’s the "Frequency converter not recognised" fault. Thinking about it logically, if the controller can’t see or communicate properly with the frequency converter (inverter), then it wouldn’t be much of a surprise if the compressor refuses to run afterwards.

Given that the unit is only a few weeks old, my mind immediately goes to something relatively simple such as a connector, wiring issue, PCB fault or a component that’s failed prematurely, rather than anything you’ve done or a system design issue.

If it were my system I’d be straight on to the installer and Vaillant support. A three-week-old heat pump really shouldn’t be throwing faults like that.

Out of interest, has the heating side of the system been working normally (I know it's been pretty warm, but worth asking) and the fault only appears when it tries to produce hot water, or has the whole heat pump stopped operating?

Posted by: @editor

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If it were my system I’d be straight on to the installer and Vaillant support. A three-week-old heat pump really shouldn’t be throwing faults like that.

Out of interest, has the heating side of the system been working normally (I know it's been pretty warm, but worth asking) and the fault only appears when it tries to produce hot water, or has the whole heat pump stopped operating?

The installer has just called and noted an error code of F.753, which means there is fault with the outside unit (communication has been lost between the main heat pump control board and the inverter/frequency converter board).  Vaillant have been contacted and will attend site on Wednesday.

@trebor12345 

Silly question but I presume the ODU is turned on/breaker hasn't tripped

If not then sounds like the bus may have come disconnected