I’ll check in with Daikin to see if they can help answer your question.

@gajolos I heard back from Daikin, and they explained that field setting 9-02 controls the heating operation prohibition. In simple terms, it sets the outdoor temperature above which the system will stop allowing heating.

The calculation is: 24C + the value set in 9-02

So for example:

• +0.5 → heating stops above 24.5C
• -0.5 → heating stops above 23.5C

It’s mainly there to stop the system accidentally running heating during warmer weather.

Regarding 9-03 and 9-04, Daikin said those aren’t active settings for this controller/system combination. If you’re seeing them in the menu, they’re essentially unused or blank entries, so they don’t control anything on your unit.

Good morning. After many days and trials I managed to find out what happens at least with the code 9-02 (Thermo on-off admission). If, for instance, I set the 9-02 at + 0,5 °C and have set the room thermostat at 22°C, the pump will continue functioning until the thermostat reaches 22 and will restart when the thermostat drops at 21,4°C. That's what I was thinking this code does.

However, the problem is that you need to have the BRC21A52 controller of the Daikin pump in your house as a room thermostat. This code doesn't work along with another room thermostat. This BRC21A52 controller is next to the inner unit of my heat pump, so it can't be used as a room thermostat. The heat pump is connected to two houses, so even if I wanted to put it in the main house, the heat pump won't work properly for the other house.

There is another code 8-00 in this controller that is

"[8-00] Remote controller temperature control - leaving water control

When using the remote control delivered with the unit, 2 types of temperature control are possible. Default [8-00] = 1 which means that the remote controller is used as room thermostat, so the remote controller can be placed in the living room to control the room temperature. Set [8-00] to 0 to use the unit in leaving water temperature control. "

So, to use the BRC21A52 controller of the heat pump as a room thermostat you need to set code 8-00 at "1" and put it in your house. If you set the 8-00 at "0" then the settings in code 9-02 don't matter.

That's all I have find out after searching and many trials with the controller.

I would like to ask another question if anybody knows. My heat pump is connected to two houses. One on the second floor (130sq.m) and another one on the ground floor (45 sq.m). The heat pump in on the ground floor. Is there a possibility that the heat pump sends more easily the leaving water for heating to the ground floor apartment and the leaving water to the second floor apartment can't reach the radiator panels easily, resulting in loss of heating of the radiators? If so, what could I do to fix this? Is there anybody that confronted such a problem and solved it? Thank you.

@gajolos Are you implying there are two totally separate pairs of primary pipes? I would have thought that the 2-level pipework should be no different than the usual one circuit feeding the heat to a home with an up and a down stairs. The primary pump requires enough head to be able to circulate the water through the whole system (or as far as a low loss header if fitted, where a secondary pump would take on the circulation within the property*) and then back to the heat pump. Our Daikin Altherma 3 monobloc is at ground level at the back of the house and only feeds the primary to the airing cupboard upstairs and then supplies the LLH where a Wilo Pico pump takes over for the secondary circuit. The circulation pump in the heat pump should have sufficient head for the job of supplying first floor needs.

*Not that I am suggesting you ought to have an LLH, in fact most systems work better without one!

Regards, Toodles.

@toodles There is one primary pipe in the inner unit for leaving water and another for returning water. The primary pipe for the leaving water is divided into two secondary pipes. So, one is for the second floor apartment and the other is for the ground floor apartment.

That's why I asked if the ground floor apartment because of the pipes that end to the radiators from the pump are shorter ( due to the fact that the heat pump is on the ground floor), affect the leaving water that end to the second floor apartment through the pipes from the pump (that are obviously longer), resulting in loss of heating water in the second floor apartment.

@gajolos The circuit is very similar to a conventional house then, the pumped water is taking the line of least resistance, the lower circuit.

I would suggest that you check the TRV’s are not preventing the flow by opening the upstairs valves to Max and see if this helps first. If the heat is still not flowing uphill to those radiators, check the Lockshield valves on the opposite ends of the radiators to the TRV’s. Try opening these a little to increase flow. I have written an article on setting up LSV’s which you will find here: 

https://renewableheatinghub.co.uk/radiator-balancing-lockshield-valve-guide/

You may find that the downstairs circuit needs some tweaking later but carry out any adjustments in small stages.

Regards, Toodles.

@toodles  Thank you for your reply. There are no TRV 's on the radiators, just the lockshield valves. 

Something else I'd like to ask. Maybe a buffer and two different circulators, one for each one of the two houses, will be better for the circulation of the water to the radiators of the second floor apartment? Or, maybe, a circulator just for the second floor house? I don't know if this is possible, to use a buffer in parallel connection to the inner unit of the pump and have a circulator just for the second floor apartment. Just thoughts, maybe someone who has done it  know better.

@gajolos Sorry but, I am not sure of your terminology; by ‘circulators’ are you talking of pumps? I notice you have referred to the spaces to be heated as ‘houses’ now and I am beginning to wonder if this is really two separate properties sharing a heat pump?

I think advice from someone more knowledgable than I is required for this setup. I will say that the use of buffers is to be avoided whenever possible but whether such a system as yours would benefit from using a buffer might help is something a more experienced reader of the forum might be able to advise on.

May I suggest to help anyone who might advise you, that you provide a sketch or schematic with approx. lengths of pipe runs along with their diameters where known please? Also, if you have the details of heat loss calculations, this would help greatly.

Is this a new installation, or has one ‘house’ been added to an existing working system and if so, did the system previously provide the level of heating required? Any relevant details might help to establish what is going on when the system is attempting to heat both ‘houses’. Regards and sorry, I can’t help you. Toodles.

Yes, by circulators I refer to installing one or two secondary circulators for the heat pump ( if I install a buffer). The two apartments share one heat pump 16kw. Firstly the pump was installed for the second floor apartment (130 sq.m) and after 3 years the ground floor apartment (45 sq.m) was connected to the heat pump too. I don't know if the second floor apartment was heated satisfyingly because I wasn't living then. As for the buffer, I have read that a buffer may work in benefit for a pump because the pump heats up the buffer tank which is next to the pump and then the secondary circulator sends the heated water to the apartment or apartments whenever it is demanded. I don't know if this is true, that's why I asked here.

I'm more interested in trying to find out if by heating the ground floor apartment ( 45sq.m), the second floor apartment (130sq.m) "loses" somehow due to the ground floor apartment and if a buffer and a secondary circulator will work better and in a more cost-effective way for the whole function of the heat pump.

@gajolos Ah, unless the occupants of the first floor apartment were cold blooded or didn’t like to complain, it sounds as though the original installation took care of all the heating needs before the addition of the ground floor accommodation. As discussed, the pumped water will take the least line of resistance, hence the ground floor in preference.

The next question then is, does the ground floor overheat? Were this the case, some adjustment to the flow downstairs may encourage more flow to the first floor. You could easily find out if upstairs could still be served when the ground floor area is restricted a little (but not to the degree that the ground floor becomes colder than required) by reducing the flow with the TRV’s (if fitted on ground floor). If no TRV’s but less heat is tolerable, try reducing the flow via the LSV’s by turning slightly clockwise to shut them off a little.

Please bear in mind what I stated before, I am not an expert! If the temperature at present in the ground floor rooms is as you require it to be then leave the LSV’s alone! Some other means of encouraging the water flow to the first floor is required and perhaps someone with plumbing experience might be able to advise further. Regards, Toodles.