Samsung ASHP Gen 3 issues E911 errors

[Mark Harrison]

14 minutes ago, ProDave said:

There are a number of ways to wire a heating system,buy typically the programmer an room thermostats will call for heat to the manifold control box, that little grey box that the UFH actuators connect to.  When one or more of the UFH zones have been activated, that box will tell the motorised valve for the heating to open, and the feedback contacts from that will call for heat from the ASHP.

This is my understanding of how it works... But yes, I get what you are saying, if all the plumber related bits have been replaced then some sort of electrical issue or gremlin seems feasible. 

[Mark Harrison]

Ok, so I can't see a buffer vessel. 

 

The pic shows the heating water pipe going into the top of the big tank, it then exits even higher at the top and there is the pump and it goes into the house. 

 

This evening the system would do nothing due to an E912 error but after rebooting it and messing about with the levers on the heating zone valve (I pushed it down from auto to manual override) it's now producing hot water again. 

 

Not sure if relevant but the heating zone valve lever (when the system was showing a fault) was completly slack and could be moved up and down freely. At the same time, the hot water was stuck in the up (auto) position and could not be moved down. 

[ProDave]

55 minutes ago, Mark Harrison said:

Not sure if relevant but the heating zone valve lever (when the system was showing a fault) was completly slack and could be moved up and down freely. At the same time, the hot water was stuck in the up (auto) position and could not be moved down. 

A floppy lever means that valve is energised and the actuator is holding it in the open position.  A stiff lever means the valve is closed, either waiting for it to be energised to open, or for you to push the lever to manually open it.  So when you did that test, it was demanding heating.

 

 

[Mark Harrison]

Fault still ongoing... 

 

Given the age of the system we are thinking of just biting the bullet and replacing. 

 

Plumber one says ASHP systems inherently unreliable/complex and to rip out and install A rated oil boiler. Costs like around the £6k mark all fitted with tank etc

 

Plumber two says actually a brand new Mitsubishi Ecodan system (£8k) should be reliable and effective/efficient and would be daft to go 'backwards' and install oil boiler. 

 

Aaarrrggghhh! 

 

Any views on the above scenarios?!

 

The house is very well insulated. 

[markocosic]

Figure out / draw the schematic first. Follow pipes or find the original installer / drawings etc. Then we can give wound advice free of charge.

 

It sounds like a flowrate issue, possibly transient.

 

I wouldn't be surprised if the UFH flowrate is high but the flowrate through the heat pump is low.

 

I wouldn't be surprised if a filter on the heat pump primary is clogged; or the heat exchanger if there isn't a filter.

 

There may be a buffer vessel built into that simplex "cylinder" - phot all the labels.of all your kit and Google the datasheets.

 

As regards replacement:

 

There is nothing exotic about heat pumps. Your own unit is likely fine. Worst case needs a heat exchanger flush.

 

If you're running UFH at low temperatures there's les ls to be gained from a new unit (in efficiency) than there would be if you were running high temperatures into rads.

 

A new boiler for £6k is a joke. Tell them to shove it. 

 

Ecodan units are a crock of poop. There's a reason they're marketed heavily rather than selling themselves and there's a reason they're used in social housing developments. Minimum flowrate on those unit in particular is enormous and unhelpful.

[HughF]

Please don’t just rip this out and replace it, that’s the standard answer given by ‘engineers’ who don’t want to be bothered with a bit of fault finding. Provided your outdoor unit isn’t a rusty mess that’s leaked all its refrigerant there is no reason to just replace it. 
 

I’d be replumbing it with a pwm controlled primary pump and a small buffer or llh. Sort the wiring out too, perhaps change the actuators for something more modern. You should easily be able to get this working nicely again.

[Kelvin]

We had exactly the same system in a previous house. The main Grundfos pump failed and was replaced by a different Grundfos pump as we couldn’t get a hold of the original pump. We then had regular E911 errors (and occasional E912 errors) The flow rate was above the minimum needed going by the meter. 
 

Our system was designed as is being described here. No buffer tank but had a pump and mixer at each manifold. I eventually figured out that the errors were only being triggered when the living room was calling for heat. In our case it turned out to be a failing manifold pump. It was still running but not at the required flow rate. We also had various valves all fail at the same time too so the fault was hard to diagnose as we had several failures. System was 8 years old.
 

None of these pumps/valves are specific to heatpumps so could happen just as easily with any other heat source.