@heatgeek Isnt the DT steady at 5C? The only time I can percieve it isnt is when starting up and its trying to get to temperature. The flow and return temperatures seem to track well. Or am I missing something?

I am curious as to what would be the effect of choosing a different DT. I think 3C is selectable in the menus somewhere.

@bontwoody If you look at the diagram, at 19.00 when power is over 3kW, the DT is 5C. If you look around 11.00 when power is ~2kW, then DT is 3C. In both cases, flow is constant around 9 l/min.

@jamespa 

I think I basically understand the principle, but I still feel like there's something I'm missing. 

I've just been there, it's 17° outside, the controller (in the cupboard in the coldest part of the house) is reading indoor temp of 26°, and the radiators are still getting heat.

I don't understand what 'high OAT end of the WC curve' means in your explanation.

I assume WC means weather curve and FT flow temperature? 

Where can I find flow temp adjustment? 

I already adjusted the weather compensation as described in the video bontwoody linked to Outdoor temp for water law. Low 13°. High -2°

Is this what you are referring to in your explanation?

I've lowered them again, this is what I see.

Posted by: @pooneil

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I think I basically understand the principle, but I still feel like there's something I'm missing. 

I've just been there, it's 17° outside, the controller (in the cupboard in the coldest part of the house) is reading indoor temp of 26°, and the radiators are still getting he

Assuming your system is running on water law only the indoor temperature registered by the controller doesn't matter.  It goes solely (in this mode) according to the value of the temperature registered outside.  Days like today when its cold but there is high solar gain can definitely cause an6y heating to heat too much during the daytime, hence using either the temp sensor in the controller or TRVs as a limiter (ie setting them a couple of degrees above the desired temperature). Days like today are also  lousy days to adjust weather compensation!

You currently have your WC curve set at 17 @ 10C OAT and 30 @ -2C, thats assuming you are running on water law 1 (there are 2).  In the installer menu you can tell which water law you are running on by the value of FSV (field setting value - essentially parameter) 2041.  Alternatively if you can tell what the outside temperature is (in the shade) we can check its following the curve.  If its running on WL1 and the outside temp is >10C you would expect the rads to be at 17C which wouldn't feel warm, so Im a bit suspicious its either not running on WL or it is running on WL2.

17@10COAT is a bit weird.  More normal would be something like 25-30 (water temperature out) @15-20 (OAT).  Do you have UFH?  Im guessing this property is rather well insulated and/or a flat so contributions to warmth other than the heating can make a big difference.

If you send some more screenshots it may be possible to work out whats going on.  

Posted by: @jamespa

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17@10COAT is a bit weird.  More normal would be something like 25-30 (water temperature out) @15-20 (OAT).  Do you have UFH?  Im guessing this property is rather well insulated and/or a flat so contributions to warmth other than the heating can make a big difference.

It was originally set at the numbers you suggest are normal. I've adjusted them down, in increments, to where they are now as per the video link.

It's a 3 bed house, about 90sqm over two floors. It's very well insulated. No UFH.

Posted by: @pooneil

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Posted by: @jamespa

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17@10COAT is a bit weird.  More normal would be something like 25-30 (water temperature out) @15-20 (OAT).  Do you have UFH?  Im guessing this property is rather well insulated and/or a flat so contributions to warmth other than the heating can make a big difference.

It was originally set at the numbers you suggest are normal. I've adjusted them down, in increments, to where they are now as per the video link.

It's a 3 bed house, about 90sqm over two floors. It's very well insulated. No UFH.

 

OK, quite small, well insulated.   In terms of setting up the heat pump at present solar gain is your enemy.

A few more questions, if you are able

• Detached, semi/end terrace or terraced?
• Does it get lots of solar gain?
• Can you confirm the value of FSV2041?
• Can you send some screenshots of the controller.
• When you say the rads are feeling warm, how warm?  If its running on WL1 and OAT is 17 (in the shade) they shouldn't feel warm at all.

This is the current status. 

Semi detached. One side is south facing, with large windows in the living room and main bedroom. There's definitely some solar gain.

I think it on WL1, see above. But I don't know if the 'floor' bit is right. The only other option was WL2

The rads don't now feel as hot as they did before I reduced the WC. 

What pics if controller would you like?

@pooneil Here are my settings. Keep 201* at 17C and -2C and just lower 202* a little. Notice in 202* at the top it says "For WL1 Heat" and my 2041 setting is WL1 so you know you have the right Water Law.

As James says its difficult on days like today to get it right. Remember the higher flow temperature is when its -2C outside and the lower is for when its 17C outside.

@heatgeek I see what you mean, I couldnt read the figures when looking at my phone screen and I assumed the gap was a DT of 5C which it has been through the winter. My best guess is that my radiators are struggling to lose enough heat at the moment to maintain a DT of 5C. There is also a fair bit of noise as the control system tries to adjust to the most recent data which makes reading difficult at times.

Posted by: @bontwoody

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Keep 201* at 17C and -2C and just lower 202* a little.

But isn't that what it was before, when it was too hot and the rads were still throwing out heat?

What would you suggest I set 202* to?

I still don't understand, if there's a full tank of water and the house is hot, why the system has to operate at all.

Say it's mid summer and 28° outside, plus solar gain inside, is the system still going to be running 24/7 ?

@pooneil OK, I dont think you have really got the understanding of how weather compensation works yet.

The 17C and -2C are markers for when the heat pump is heating your house. Above 17C outside it wont turn on. At 17C it will and the flow temperature in my system will be 33C. At -2C outside the flow temperature in my system will be 40C. Between those two outside temperatures the flow temperature will be somewhere between 33 and 40C in my system.

If you house is too warm you need to drop the 33C and 40C settings FSV 202*. Try 30C and 35C and see how you get on. 

If its still too hot then lower them a bit more. I will attach a file explaining things in more detail in another post.