Balanced operation of two parallel Aquarea split heat pumps (load balancing)

[DanieleB7]

Hi everyone,

We are considering implementing a system with two aquarea split heat pumps heating a single DHW tank in parallel.

Each heat pump will work independently for space heating, with separate buffer tanks to heat two separate apartments.

Using a separate heishamon controller for each heat pump and a centralised nodered/home assistant controller, what we would like to know is the following.

1. is it possible to control the two heat pumps to modulate/work synchronously such that each pump equally heats the hot water tank? Since the DHW tank is shared between two neighbours it is important that each pump heats the water equally.

2. Is it possible for both DHW and space heating to modulate the heat pumps to track solar production ie can you directly control the % of modulation of the heatpump at any one time or can this only be done indirectly by changing the temperature setpoint.

any help from someone with direct experience would be much appreciated

thank you

Daniele

[stumbaumr]

There are people running more than one Aquarea in their homes, see
http://aquarea.smallsolutions.de/index.php?title=Referenzinstallationen#Installation_von_mehreren_Geishas_bei_einem_Objekt

[gvzdus]

Hi Daniele,
with little, but intensive experience:
No: You can not control the % modulation. You can influence it with "QuietLevel" (especially to go up pretty fast to max performance). But beside of the target temp, you can set the pump duty. Enforcing that the HP uses the max. assigned pump duty, you can control both target temp. as well as pump duty.
Regarding the equality problem of 2 neighbors in heating the shared DHW: I would tend to say: Yes. Simple approach for a ~99,9% solution: You count the input energy at both heatpumps on the long run during DHW, and when DHW heating start, you only start the HP with less energy consumed, and once it reaches the kWh consumed by the other HP, you start he other HP as well. That should really be 99,9% fair on the long run.

[DanieleB7]

Hi Gvzdus

thank you for your insight. If I am not mistaken from your posts you are also running two heatpumps in parallel. I would be interested in knowing how exactly your are managing them and for what scope you have two pumps. I have attached a schematic of how we planned to use ours, if you have any further help regarding this it would be much appreciated.

[geduxas]

all pumps should connect to common buffer tank and from there heat should be taken to heat the house, also all heat pumps should have own 3way valve to heat DHW. and with help of node-red or some automation tool you could control all pump's in parallel. Your main goal would be to maintain temperature in common buffer tank..

[gvzdus]

I have updated my system description (#565) with the diagram.
Your intention with one heating circuit per HP will be much more stable than my solution with the shared pipes. Defrosting of one HP caused with a > 50% chance a H62 error in the other heatpump. The installer changed the max pump duty to 0x7C (~22-25l/min), which somehow helped. My current solution is to have the pump duty of all active HPs roughly at the level of the seperate heating circuit (~23 l/min), to have roughly similar temperatures. Whenever Heishamon indicates Defrosting_State==1, I set the pump duty to 0x7c, and back to normal when Defrosting_State==0.

[geduxas]

regards H62, i noticed your schema, and one question is who controls circulating pump? and also do you really have that kind of mixing system installed as shown in schema?

[gvzdus]

Originally, the (heat circuit) pump was controlled by HP1. I changed this to direct control via a Shelly (probably Heishamon relay next), to:
a) be able to run on HP2 only, without HP1 turned on
b) continue to run the heat circuit during DHW operation

The mixer unit is installed, but it makes no sense: I manually set it to "max". Why should I want to have an (even) lower temperature in the circuit than in the buffer? IMHO it would only make sense if there were multiple circuits: One with floor heating, one with radiators.

[geduxas]

Ok, so yes... It's wrong, and that's why you get error...

[gvzdus]

IMHO the H62 error is due to "usage conflicts" of the shared pipes for the 2 HPs to the buffer. If one HP goes to deicing, you see variations in the other HPs flow & temperatures. Anyway, the last H62 is quite some days ago since I increase the pump duty on deicing.

[geduxas]

I think you need bugger pipes, and get rid of circulation pump before buffer.. that's your problems.. maybe even getting rid of circulation pump is enough.

[gvzdus]

The reason why I have 2 HPs: I simply knew that I need 18 kW of heating power. Also, I wanted a R290 HP because of subsidies in Germany compared to R32. Having found out that the cascade manager of Panasonic is not that helpful (and - together with the Modbus HW also pretty expensive), I would not build the system like this again. The pain with the H62 errors together with having mono-block HPs (so: Water outside) makes me really nervous that the system might get into a situation where frost kills either a heatpump in error state or at least the heating water is lost by opening of the safety valves.