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[Solved] Daikin high temperature heat pump

gajolos · 2026-03-14T10:56:09Z

Hello, I have a DAIKIN ERSQ 016AAV1 16KW. I have a BRC21A52 controller and there is a code in the service manual 9-02 that is indicated as Thermo on/off admission with a range -5 till +5. What exactly does it do? For example what's the difference between setting it at +0.5 and -0.5? There is also another code 9-03 that the step is every 0.2 and it can be set either until +5 or -5 but there isn't any explanation in the manual what is this code about. The same for 9-04 with a step of 10, until 60. Any help would be nice. Thank you in advance.

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Air Source Heat Pumps (ASHPs)

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JamesPa

(@jamespa)

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22/03/2026 10:02 am

Posted by: @toodles

↑

@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.

@gajolos

I havent fully followed this but as I understand it you have two apartments, the downstairs one is heating sufficiently, the upstairs one not. Im presuming that there are no operational thermostats or TRVs (ie they are all set to max), its all open loop and operating 24x7.

Assuming that my assumptions are correct then @toodles is right, this is about balancing, ie shifting the balance of water flow (and thus heat transfer) between the two. First make sure that the flow overall is as high as it can be by maxing out any pump adjustment available and ensuring at least one LSV is fully open. Then reduce the flow downstairs to increase the flow upstairs until they are at the same temperature. They might both settle at a temperature which is too low in which case you may need to edge the flow temperature up a couple of degrees.

Dont get involved with buffers, it will simply amplify your problems. If the upstairs pipework is too restrictive for some reason so that a balance cant be achieved then an auxiliary pump for the upstairs might be needed, however this is a bit of a last resort not least because you then have to think carefully about pump control etc. but also because it shouldn't be necessary if both have been similarly plumbed and radiators have been similarly sized, unless the pipework connecting upstairs to downstairs is very long or very contorted. Are you sure radiators have been sized correctly upstairs and downstairs or is it possible they have been sized with different flow temperatures in mind?

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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