Where do I start, well its taken 14 months for my installer (who shall remain nameless for now due to on-going issues) to get this far, a couple of months ago they left me in this state with the Daikin 16KW set on 50C (which I lowered after a huge bill) and said they would come back to finish the DHW. The installer is a very large UK-wide company whom said they had done thousands of installs, yet they couldn't work out how to commission the DHW! That included a visit from a Daikin engineer who also seemed clueless.
Anyway, they have let me down 3 times in the last two months on cancellations due to "Covid" etc (easy excuse nowadays) but I want to be able to fire a list of what is wrong to them as a final chance. The good thing is that I have only paid the 10% deposit and if they fail to get everything done including registering for RHI before which closes on 31/3 I wont be paying another penny.
So here is the schematic which I drew up today, prompted by me noticing that there is a 5C drop from the HP flow before it even gets to the radiator circuit. Amazingly, the majority of the house is getting up to temperature but there are some undersized rads causing some issues (that's for another thread).
I am new to ASHP, so I'm still learning about the theory, but here is what look wrong to me.....
Please comment/correct me if I am wrong.
1) The BoilerMag filter is fitted to the flow from the HP and not after the last Radiator, with the HP being at the lowest point of the whole install I would assume it is currently filling up with gunk.
2) The Daikin backup heater EKMBUHCA plumbing seems to be reversed according to the install manual.
3) The buffer flow is incorrectly plumbed into the bottom and therefore HW is mixing with cold return from the Rads and DHW, thus causing temp loss before it gets to the Rads.
3a) It actually looks like there is a return loop that doesnt get back to the HP for heating, the accumulator is blending the water instead.
i'm trying to find a schematic of how it should be done but not found one yet.
1) The BoilerMag filter is fitted to the flow from the HP and not after the last Radiator, with the HP being at the lowest point of the whole install I would assume it is currently filling up with gunk.
2) The Daikin backup heater EKMBUHCA plumbing seems to be reversed according to the install manual.
3) The buffer flow is incorrectly plumbed into the bottom and therefore HW is mixing with cold return from the Rads and DHW, thus causing temp loss before it gets to the Rads.
3a) It actually looks like there is a return loop that doesnt get back to the HP for heating, the accumulator is blending the water instead.
i'm trying to find a schematic of how it should be done but not found one yet.
Hi Saf1973,
From looking at your schematic it would appear that the water connections are reversed at the ASHP, and of course that would mean that the flow through what you have described as the BoilerMag is also in the wrong direction.
Swapping the water pipes at the ASHP and turning the BoilerMag around should correct the main problem. It may also correct the problem with the DHW, if there is a none return valve somewhere in the water circuit.
@derek-m Great spot! It is really that simple isn't it, then the flow would traverse through the top of the buffer and the return through the correct path of the BoilerMag (once reversed). I did tell them months ago about the BoilerMag being in the flow but they have never come back since then.
As for the DHW, I don't know what they think the issue is, at the moment the DHW valve is not connected electrically so I am manually opening it (and upping the flow temp). They said they had to get "more parts" and left it at that.......watch this space on that one.
I cant see any non-return valves either, which was another thing I was thinking about. Where would you like to see them in the circuit?
@derek-m Great spot! It is really that simple isn't it, then the flow would traverse through the top of the buffer and the return through the correct path of the BoilerMag (once reversed). I did tell them months ago about the BoilerMag being in the flow but they have never come back since then.
As for the DHW, I don't know what they think the issue is, at the moment the DHW valve is not connected electrically so I am manually opening it (and upping the flow temp). They said they had to get "more parts" and left it at that.......watch this space on that one.
I cant see any non-return valves either, which was another thing I was thinking about. Where would you like to see them in the circuit?
many thanks for your help
Hi,
I think the fact that the motorised valve for the DHW not being connected to the controller may have something to do with it not working correctly.
The Daikin manual only shows a 3-way valve for selecting DHW or CH, not the two 2-way valves that you have fitted. It may therefore be necessary to install an interposing relay. I would suggest that you contact Daikin and ask them to provide the wiring diagram for your system, you could also ask your installer what addition parts are required to get the DHW functional. Though since it would appear that they cannot get two pipes the correct way around, some electrical wiring may be well beyond their comprehension.
i stop looking when i see two port valves and i’m a 62 year old heating engineer. high efficiencies can only be delivered with constant flow and variable temperature. that’s true on gas boilers as well as heat pumps..
The key to optimising energy efficiency with a heat pump and condensing boiler is constant flow with variable temperature. Thus as room temperature rises to meet set point, flow temperature has to decrease enhancing heat generator efficiency.
if that is not happening then opportunities for efficiency are lost
two ports create standing losses ie wasted heat
they can be used with the right controls but the hydraulic layout suggests it is not from a daikon design manual
Hi Alec,
I agree with your sentiments, and I also become frustrated by the inability of so called system designers to follow manufacturers recommendations, but at the end of the day the customer wants a working system, even if it is not perfect.
The advice I try to provide is to get a working system, with the minimum amount of disruption, rather than rip everything out and do the job correctly.
Perhaps the system designers and installers should be forced to read through forums such as this, so that they may then realise what an appalling service many of them are providing.
Just received this feedback from a credible source:
"The installer doesn’t know what they are doing. The manufacturer has probably told the installer what is wrong, but they won’t ‘discredit’ the installer to the homeowner, so they probably shrugged their shoulders and said they would discuss it with the installer. Installer probably knows that it is going to be expensive to put it right and so is prioritising other work at the moment. The best thing that the homeowner could do is to go to MCS with a complaint."
I think the advice about going to to the MCS is a good idea. As an extra point, if your installer is MCS accredited you will have insurance, probably from HEIS, that is in place to get these kind of sagas sorted out. I'd flag this with MCS.
a bit more testing/checking on the pipework..... so it looks like the plumber has correctly connected the F&R at the heat pump but made the mistake inside. The higher temperature is on the bottom right pipe (b) and the lower temperature on the top left pipe (a). So the plumber has switched the pipes at the backup heater and accumulator, and of course still messed up on the filter.
As for the DHW, it looks like the plumber still has a Boiler S-Plan mindset. I will create another thread re the controls being used, but as they have "promised" to come back with new parts (whatever) they are, that thread could be redundant. They have told me Daikin have instructed them to fit these "new parts", so its a wait and see. I shall put together a final warning email today with dates and expectations.
I forgot to mention, either disable your backup heater, or adjust the setting for its use to be required to something like -15C, otherwise you could end up with rather high bills. If the outside air temperature should fall to -15C and your heat pump is struggling, then just by a couple of electric fan heaters, which would probably be much more effective.
I cannot understand why any system designer would contemplate installing a backup heater in the UK, unless it is just a further way to bump up the cost of the system.
