Posted by: @damonc

↑

yes about 1-1.2 kw. I’d expect the same I don’t get why it can’t modulate smoothly it’s almost as if it has modulation steps. Maybe something Grant can advise on?

@damonc, thanks for confirming that detail, really helpful for me. I will contact Grant technical support tomorrow to discuss my obesrvations and seek their advice. I will of course share in due course.

@JamesPa, thanks for your input, but my cycling is not related to defrost. When in defrost temperature range it defrosts once per hour, you can set your watch by it and its very easy to confirm on the control panel.

@steam-powered do you know if you also have the immersion heater plumbed in on your volumiser that probably isn’t part of your issue but it is a 3Kw heating element! fortunately ours isn’t wired up. 

Also can I ask was this an ECO4 install or did you contract a company to install it? Just wondering as you probably have grounds to ask them to remove it and install a correctly sized unit. 

@grantmethestrength wow that's quite the project, very interesting but my Aerona is 2021 and so I don't think has the required modbus bits as when I enquired about retrofitting the smart controller it wasn't suitable.

Posted by: @jamespa

↑

Posted by: @damonc

↑

@jamespa that’s possible I guess, is there an automated defrost limit temp?

There is, you cant change it.  

Expect regular defrost at any temperature less than 5, until it gets really cold and the air dries out (-5~-10 or less).

You can tell its defrost because 

• the fan stops working temporarily
• the flow temperature drops sharply, even to below the return temperature
• at the end of the defrost cycle you will see a (often quite impressive) cloud of water vapour being pushed out the front of the unit
• the compressor will often ramp up to max immediately after in order to recover as soon as possible

Frost builds up on the evaporator fins at the back of the unit and needs to be cleared from time to time.  Thats what the defrost cycle does, by robbing a bit of heat from the circulating water to melt the ice.

 

thanks , that makes sense and I have seen that cycle happen but I agree with @steam-powered though, my cycling definitely isn't always defrost, the defrost symbol doesn't show in the display 

@damonc if you have the R32 ASHP it will have the modbus connection on the PCB if you want to chat a bit more about it pop over to this thread so we don’t hijack this one.

Posted by: @grantmethestrength

↑

@steam-powered do you know if you also have the immersion heater plumbed in on your volumiser that probably isn’t part of your issue but it is a 3Kw heating element! fortunately ours isn’t wired up. 

Also can I ask was this an ECO4 install or did you contract a company to install it? Just wondering as you probably have grounds to ask them to remove it and install a correctly sized unit. 

@Grantmethestrength, the LLH immersion heater is fitted but not connected. With my oversized HP I don't think I need it 😢 

The HP installation was managed by my house building contractor (complete new build). The heating was about the only aspect of our house design and build that I didn't get closely involved with, thinking the "experts" would sort it. A big mistake however! Our builder had his own plumber do all pipework and he subcontracted the HP connection. Initially the proposal was for a 10kW Vailant unit, but he later switched supplier to Grant for a small cost saving, but I think mainly because the local Grant engineer was a mate of his plumber. The spec. then changed to 17kW, but I have an email record that Grant were involved in the heating calculations as they requested details from our builder. 

I will see how my discussion goes with Grant technical support and ask them to provide their calculations as part of that.  

I’ve made a web app which allows you to visualise the effect of changing weather compensation parameters on the WC curve/slope. You can install it on your phone/tablet if you want and your settings will be saved for you. https://heat-curve-plotter.lovable.app

@damonc this is a great little tool I have been using WC Ready Reckoner that @allyfish created but I am a visual person so this is great. i have fully extended my WC curve to the limits of the ASHP 23c to 55c and the house is roasting lol but I can see the flow temps and the various room temps so can work back from that. This lets me work out where to put those min and max temps currently -15c and 20c gives me a flow temp of 31-32c so I can now test and adjust on the visualisation before making changes. So cheers!

@damonc I have been playing with this and it is pretty accurate compared to my real world results on a Grant Aerona3 R32 13kW I made my curve a ridiculous 55c@-20c and 23c@20c and the chart said 30c flow rate @ 11c AOT and 31c @ 10c  AOT and that is what I was getting, so good job!

Obviously most normal people would look at this and use 41.5c @-3c but where is the fun in that!