We have a Daikin Altherma system and hot water tank (by Joule, 250L), installed by Octopus in March '24.
We were told that, when hot water cycle was active, then radiators would get heated too, but, as we have solar panels and battery/solar Boost fit, I wanted to run on Solar boost alone, at least initially. In June, we swapped over to run DHW from the ASHP BUT found it necessary to switch off all the TRV’s to minimise heat input into home during DHW cycles. Now we are on the cusp of winter, the additional heat input into the home during DHW cycles is welcomed once again, but I have a nagging question.
Is this installation normal, and, if not, how might I go about re-plumbing the system to minimise heat to radiators during DHW cycles driven by ASHP?
The solar boost system operates the tank immersion heater directly and can operate on a time basis, over-rule basis, or over-production basis. Any assistance/advise will be welcomed.
Normally the heat pump is plumbed to operate a 3 port valve to either heat the space heating loop OR heat the DHW cylinder, not both at the same time.
Do you have a 3 port valve?
I remember when we first had our cylinder installed but not the heat pump installed, so we were heating water just using the immersion, our radiators started getting a bit warm. I realised that there is a little lever on the valve to allow manual operation of it (I guess in case the actuator fails). However when this is pushed over the valve is in an in between state where some water goes to the heating loop and some to the DHW.
Maybe check your valve hasn’t had this lever pushed over.
No the daikins default to DHW priority, you can change it to climate priority but not both.
You should have an ESBE valve, which is similar idea to a 3 port valve except it only changes from climate to DHW and doesn’t have a both open position.
You could achieve the same with different valves if you wired it all up correctly but nearly all Daikin installs use an ESBE valve afaik.
If you have a ESBE rotary three port valve with a 2-point controlled actuator, then it maybe worth checking that the three ports have been connected to the correct pipes and that the internal valve shoe and actuator has been set correctly.
ESBE 3 port valve bodies for this application come in two basic configurations: VRG130 - the input flow would be connected to the either of the horizontal legs of the T, with the flow out to the heating/hot water to either of the other two legs. VRG230 - the input flow would be connected to the bottom vertical leg of the T, with the flow to the heating/hot water out of either of the horizontal legs of the T.
The valve shaft is splined and has a small scollop on the end of the shaft to indicate the shoe’s position, which closes that port and it’s important that this is aligned correctly when the actuator is connected and that the actuator is motored in the correct direction. Also make sure the whiterrather than the older style tapered shaft.
Also check that that actuator isn’t in manual mode - if it is you will see a red ring around the base of the round knob and it will turn by hand and it can be reset by pushing it in whilst turning it to engage the actuator.
Or you may have the VZC/D type ESBE valve - I’m not familiar with these or Daikin systems and only ever used ESBE rotary type valves for other applications.
You say the 3 port valve has a lever, which suggests it may be a Honeywell (or similar type) spring return valve. If so, when energised the valve opens against the spring, which then closes the valve when switched off - the lever is there to manually open the valve during filling etc and can be locked open by latching on a tab. When the valve is in the closed position (normally heating mode) you would feel some spring resistance if you tried to move the lever and when the valve is in the open position (normally hot water mode) the lever will freely move from side to side.
There are other types of valves and possibly the wrong one has been installed, or installed incorrectly?
If you’re still not sure maybe post a photo of the valve and its data plate.
Yes a Honeywell spring return valve. Looks like the flow (pump) in is in the correct (middle - AB) port, but can’t quite make out the other writing - normally for heat pumps you would connect the hot water cylinder to the normally closed port A, which will open when the valve is energized during the hot water cycle. It shouldn’t send water to both heating & hot water at the same time, unless it’s partially open/faulty - make sure the lever isn’t hooked up in manual mode and can you hear the valve wind closed by the spring when powered off when hot water cycle finishes.
Also, it is possible that water is short circuiting/bypassing by some other means if they have done something odd with the pipework etc?
Sadly, I am a Chemist, with little knowledge of plumbing.
Port A looks like “Cylinder” which matches the pipework I can see.
AB is from PUMP - not at all sure where the pump is - does this reside inside the ASHP unit maybe?
Port B looks like RH (which I interpret as Radiators/Heating)
I currently have the DHW cycle set at 0300 - 0400hrs, so am rarely awake/around to check radiator operation.
It does seem simplest (I think) to revert to the Solar Boost set up and almost ignore the DHW cycle all together?
I would still be inclined to get the installer back to check and rectify any faults - the 3 port valve/heat pump should only supply either the heating or hot water, but not at the same time!
Also, unless it works out cheaper overall with a lower time of use tariff, it’s better to charge the hot water at around the warmest part of the day, ie ~12:00-14:00, as this will generally achieve the best COP.
Unlikely I know, but our installer managed to plumb the DHW return into the emitter flow line, rather than the emitter return line, so whenever DHW started still-warm water ex the DHW tank coil flowed via the radiators . Soon fixed, but “schoolboy error” comes to mind…
. Soon fixed, but “schoolboy error” comes to mind…