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.

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.

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.

Thanks Dave. I was a bit afraid of that too. It feels a bit like diagnosis by exclusion at the moment, which I guess is fine up to a point, a couple of new pumps and flow switch don't break the bank but new a PCB on an ageing system feels like a punt at best. I guess what I'm struggling with is that if the system had an inherent design flaw (lack of bypass valve etc) I'd have expected a multitude of issues before now? Given its age, would it make more sense that something is actually worn out and broken...🤔 Am I right in thinking the call for heat actually goes first to the zone valve in the garage, which then opens and sends a signal to start the heat pump? If this was faulty (even though it's in theory been checked) and wasn't opening fully or quickly enough, it might be enough to trigger the fault? If he's going to replace anything, would this be a more sensible starting point?

There's a mezzanine in the garage above this stuff. I'll check when I get home later what's up there (my partner has sent these through to me). Is it possible there's an inherent problem with the actual setup after all these years? The plumber seems to think it's the PCB and is pricing a replacement. On a more general note, what's the life expectancy (on average) of these systems? It's approaching 10 years and if it needs a lot spending on it I feel like I might be throwing good money after bad.

Or this red one next to the cylinder?

Is this a buffer tank?

In this photo, this is literally all there is the cupboard. The water pipes disappear into the wall and I'm not actually sure where they emerge... 🤦‍♂️

I see what you are saying. Would a blending valve and pump be located close to the manifold? If that's the case, I don't think there is one. Where's the most likely spot for the bypass valve if there is one? If this was the issue though, would it not have flagged up long ago? The system worked fine all last winter after the flow switch was replaced.

The manifolds are both it cupboards with no other pumps etc near them that I can see. All the pipework from them just disappears into the floor. The remaining pumps/system is all situated in the garage. I think there's a buffer tank. This is the other pump in the garage that supplies the UFH loop that has just been replaced I'll get another picture of the other bits in the garage

There's the pump you can see on the first pic plus another one for the UFH. Both are brand new. We've not had a persistent error like this before so I'd assume the setup has been sufficient up til press? The metal lever does go up and down but I'm not sure how 'smooth' it should feel.

Not sure why the photos get rotated when I upload them...🤔🙄

In between the flow errors the UFH has been working. Thermostats seem to be communicating with actuators OK and these are opening and there is flow through the various zones, just not warm water. There's a manifold upstairs and downstairs. Separate pump for UFH which has just been replaced. The heating zone valve in the first pic (top one) has been checked by the plumber (he changed the motor?) and said he thought it was OK. The heating zone valve feels warm to the touch, even with no flow, wheras the hot water one doesnt. I don't know if this is relevant or not.

I can try and get a better one later but this is one of them when calling for heat.

As above... We have a Samsung ASHP mated to an Upunor UFH system. E911 errors last winter were resolved by a new flow switch. The system is about 8-10 years old. The house was a very high spec new build from an insulation POV. We have had persistent problems/errors the last few weeks that two plumbers have so far been unable to resolve. The ASHP seems to make a full tank of hot water without triggering an error but when the UFH system calls for heat we very quickly get E911 flow error. The flow switch has been replaced again, both pumps (old Grunfos ones) have been replaced by new Wilo ones and this has pushed the flow rate up over 20 l/m (it was previously around 15) but we still get the same error. The plumber checked the zone valve for the UFH and thinks this is working as it should. Filters have been checked/replaced. We are at a bit of a loss. The plumber has said the PCB may need replacing but we font want to go the expense of this on a hunch. The call for heat from the UFH only seems to come inconsistently (it should trigger a sun symbol on the Samsung LCD) so the system can run happily producing hot water for a few days but no UFH. If you switch the Samsung control unit off at the mains, when it reboots the sun symbol comes on and triggers the E911 within 15-30 seconds. And occasionally we get a random E912 error message, just for fun and to mess with our heads! Could this be some sort of electrical/communication issue between the UFH and the Samsung bits? It's just wierd how it can make hot water with seemingly no dramas. Any experiences with this or help would be very appreciated!