That sounds like a horror @saz. Like you, we suffer from regular low flow errors. Nightmare. I'll put some feelers out tonight on your behalf and see if some of heating engineer contacts have any thoughts. 

Posted by: @saz

Hi there,

I an living in a heatpump nightmare at the moment. New ASHP installed last year, endless leaks and pressure drops occuring daily led to repair that involved removal of buffer vessel, PRV and the system being injected with a leak sealer. Then the pump broke down completely with error messages appearing 'compressor blocked/flow rate too low'. Repair people been out to check filter, not that. I have no heating and hot water so was told to use the immersion. It is run via the heat pump power supply and this switch (picture attached). However, I have noticed that the tank temp sensor is dropping, the circulation pump that generally only comes on when heating is being called for is now running constantly (for no purpose because the heatpump cannot provide it at the moment?). Is this pump running cool water through the coil in the tank and cooling the water that the immersion is trying to heat? Help! I am so cold and fed up. (the immersion is not wired in to its own separate supply.

Hi Saz,

Sorry to hear about your problems.

What is the make and model of your heat pump? It may be possible to change the settings within the heat pump controller to stop the water pump from running, and only use the immersion heater.

If the circulation pump that you mention is external to the heat pump, then it may have a plug and socket connection, so can be unplugged. Who is the manufacturer? The circulation pump may be running continuously because the indoor air temperature is low, so the system is continually asking for heating, so the water may be just being pumped around the heat emitters. Try turning the thermostat right down and see if the water pump stops.

Hi Derek,

It's a Vaillant Arotherm plus. The ciculation pump is a Wilo. The UFH is off, and so are the rads, so I don't get why it's even running, the heatpump is not working and I don't understand why the tank temp sensor is not working either, temp doesn't increase when immersion is on, it drops. I can't turn the heat pump off to stop the circulation pump because the immersion power supply runs off it.

Posted by: @saz

Hi Derek,

It's a Vaillant Arotherm plus. The ciculation pump is a Wilo. The UFH is off, and so are the rads, so I don't get why it's even running, the heatpump is not working and I don't understand why the tank temp sensor is not working either, temp doesn't increase when immersion is on, it drops. I can't turn the heat pump off to stop the circulation pump because the immersion power supply runs off it.

Hi Saz,

Look at the controller fitted to the circulation pump and see is it can simply be switched off. If not, then see if the power supply can be unplugged at the pump controller.

Have two responses. They may not be overly helpful, but I have to agree that you need to get the installers out, despite them not being very good. If you don't want to go down that route, you will have options if they were MCS certified. Were they?

Your other option is to call Vaillant – by all accounts their support team is usually very good.

Response 1:

First thought would be that it's a really bad install and talking to the manufacturer of the heat pump first may put some light on the issues as I would assume the heat pump is still under some kind of warranty.

Loss of pressure and control issues don't help but understanding if the pump has been designed and installed correctly would help.

Response 2:

Well the fact a buffer was present tells you there was issues with flow in the first place, removing will not help.

My advice is get the manufactuer out to check over, complete heat loss and diagnose the issue. Would help to know the installer and manufacturer and we might be able to help using our connnections and reach.

@derek-m I've turned the whole system off now as that pump starting to make strange noises and I was getting quite freaked out. This does however mean I have no immersion now so no hot water 🙁

Sounds like a big mistake having leak sealer put into your heat pump. Did you installer do that ?! Surely that's the reason for 'compressor blocked'.

@editor Sorry, I should have said they replaced the buffer but altered some pipework I think. That latest repair has caused the whole system to break down. My immersion is not on it's own power supply so now I have no hot water either. It's just all going from bad to worse! I hope a visit by a senior engineer from Vaillant will at least start to get to the bottom of it as otherwise I think I'm going to crack up. I'm at the point where I feel like I may need to get legal advice but I'm not sure where to go. There are lots of strange things going on with this set up, it's been like it since installation but I have never had any satisfactory answers by the installers.

@heat-pump-newbie Yes, the installer did it. Well-meaning I guess as they were fed up repairing leaks but Vaillant seem to think it's affected the flow rate somehow. I'm not sure what compressor blocked means. It might not mean an actual blockage as such, just that the compressor has been blocked from working due to low flow. I won't know until someone competent looks at it.

@saz 

If you unplug the pump controller as I suggested, you should be able to switch the system back on and set the immersion heater to operate.

Posted by: @heat-pump-newbie

Sounds like a big mistake having leak sealer put into your heat pump. Did you installer do that ?! Surely that's the reason for 'compressor blocked'.

Hi Newbie,

I suspect that you are probably correct.