Posted by: @grahamf

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Your system is constantly cycling, but fortunately the frequency of cycling is not very high.  Have you tried lowering the weather compensation curve to try to reduce the cycling?

My system design was 45c @ -3c which was way too hot for us. I slowly adjusted it down as we went through the end of last heating season to 32c @ -3c OAT on the other end it is 23c (the lowest the unit will go to) @ 20c OAT (I did have this at 16c as we really don't need heat when it is about 16c outside, but having seen other peoples settings I thought I would try 20c. I was hardly getting any DeltaT maybe 1-2c but the house was warm. I have just changed over to medium pump speed and holy cat poop Batman, Grant don't do things by half! my flow rate is now 37 l/min. I will monitor it and see what that has done if anything (well apart from doubling the power consumption of the pump!!).

I get what you are all saying about the cycling which I am not too concerned about as it is still mild out, even here in Pembrokeshire, and it is not being caused by defrosts which is a good thing. I may have a look at using night mode to throttle the compressor (if that is the right word to use) maybe limit it to 75% see where that gets me. 

I too felt the podcast was useful but think it could do with a bit less on the "bad design, installation, commissioning = bad system" as it's been done to death now!  @pirate-rich mentioned something about balancing rads, quarter-turn adjustments, flow rate impacts etc but didn't really go into much detail - IIRC, he mentioned a video he did so if it's useful in this context could we have a link?  I'd be interested in hearing how balancing the system, by adjusting the LSV, affects the flow rate and thus the efficiency of the system.  Also, that but with a comparison to making adjustments using TRVs.  How does a homeowner know there is an issue with the flow rate?  I can't see mine (Octopus provides very, very limited data to the homeowner) so I guess it would be something an engineer would have to check and maybe adjust.

I've been thinking about this over the last few days, following the latest Podcast where flow rates are discussed - this was mentioned in passing but not followed through unfortunately.

If the flow rate is critical, then how is that affected by balancing the system by turning up/down the LSVs?  Or turning down the TRVs which could prevent any flow through the radiator?  Does it require an adjustment to the flow rate to compensate or does that just unbalance the system again?  What happens if the flow rate is negatively impacted - how do I tell?

Perhaps a heating engineer can discuss this in some detail.  Incidentally, I have no access to my system's flow rate so I can neither see what the current value is nor change it.  But the system does need balancing as upstairs is running 1.5=2.0c warmer than downstairs, and even downstairs room temps span 19.5 to 22.2c.

Im noit a heating engineer, but I will have a go anyway (I think you are overthinking a bit)

Posted by: @andrewj

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If the flow rate is critical, then how is that affected by balancing the system by turning up/down the LSVs?

If you turn down all the LSVs then you will restrict the flow.  If you turn some up and some down the main effect is to redistribute the flow (thats what you are trying to do).  Overall you want the flow as unrestricted as possible consistent with the system being in balance.  So at least one LSV (often the one furthest from the heat pump, unless that's a towel rail) should be fully open.  Towel rail LSVs should, I believe, always be restricted otherwise its virtually a short circuit.  

Posted by: @andrewj

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 Does it require an adjustment to the flow rate to compensate or does that just unbalance the system again?

Not normally.  The water pump will just keep going, the flow rate may change a bit, DT may change a bit and the system will simply reach equilibrium at a slightly different point.  Flow rate is critical, but only in the sense that it has to be high enough to transfer the energy required with a reasonable dt across the emitters, and not so high as to cause noise in the system.  It doesnt have to be a precise figure.

Posted by: @andrewj

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What happens if the flow rate is negatively impacted - how do I tell?

Your heat pump will normally monitor flow rate, if it doesnt then you cant easily tell whats happening.  Almost all, probably all, heat pumps will complain and stop working if the flow rate goes too low.

Posted by: @andrewj

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But the system does need balancing as upstairs is running 1.5=2.0c warmer than downstairs, and even downstairs room temps span 19.5 to 22.2c.

There is an article on balancing radiators elsewhere on the forum https://renewableheatinghub.co.uk/radiator-balancing-lockshield-valve-guide/

@jamespa Thanks James.  I already have the article on balancing and I don't think that, overall, the system is that far out: tweaking LSVs now rather than major changes.  Do you think it would be better to open up the LSVs downstairs to increase flow there - even though mostly these are at the room temp I want - before closing down upstairs?  I'm thinking that getting more flow downstairs will naturally reduce the temperature upstairs and then I can tweak the flow temp to bring any overshoot down.

I have a related query, feel free to move it to a new thread if preferred.

I have an Ideal Logic Air 10kW.

The flow rate showing on the Halo was 25 – 30 l/min, but often quite a low dT, maybe 2 - 3C.

I’ve noticed that it is possible to set the pump to modulate to maintain a dT of a variable number so as an experiment I’ve set it at 5C, (default is off for this setting, 5 if it's on).

It’s also possible to set the minimum pump speed %, I’ve set it to 50% (default is 70%), it’s unclear when this actually operates if the Modulation is off.

The pump is now generally running slower, currently 16l/m. House still maintaining temperature.

I’m really asking if there is any value in doing this, on the face of it, it seems logical to run the pump slower and maintain the dT. The problem is the Halo Stat data is worse than useless, for example it suggests in the last day it used 32kWh, which is difficult as the whole house use for the last day was 22kWh!

So, I don’t know if it more or less efficient.

Any observations appreciated.

Note it's on full WC mode.

Thanks

Simon

Posted by: @andrewj

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 Do you think it would be better to open up the LSVs downstairs to increase flow there - even though mostly these are at the room temp I want - before closing down upstairs?  I'm thinking that getting more flow downstairs will naturally reduce the temperature upstairs and then I can tweak the flow temp to bring any overshoot down.

Its very difficult to be prescriptive without being in the house.  The answer to your question as asked is however 'yes'.   A way of thinking about it, which might help, is this

• The aim of balancing is to adjust the relative temperatures of rooms, not the absolute temperatures.  You want to achieve balance with the LSVs as open as possible and at least one (not one on a towel rail) fully open.  Don't worry if this makes all the rooms too warm, as long as they are too warm by roughly the same amount
• Once the relative temperatures are right, turn the flow temp up or down to achieve the right absolute temperature

In practice this is a bit iterative, but the aim is to achieve the right room temperatures at the lowest possible flow temperatures, which will occur when the radiators are balanced with the maximum flow through them consistent with they landing at the right relative temperature.

Hope that helps, if not feel free to ask again.

Posted by: @simonwig

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I have a related query, feel free to move it to a new thread if preferred.

I have an Ideal Logic Air 10kW.

The flow rate showing on the Halo was 25 – 30 l/min, but often quite a low dT, maybe 2 - 3C.

I’ve noticed that it is possible to set the pump to modulate to maintain a dT of a variable number so as an experiment I’ve set it at 5C, (default is off for this setting, 5 if it's on).

It’s also possible to set the minimum pump speed %, I’ve set it to 50% (default is 70%), it’s unclear when this actually operates if the Modulation is off.

The pump is now generally running slower, currently 16l/m. House still maintaining temperature.

I’m really asking if there is any value in doing this

Not particularly unless you have a problem with noise in the pipework

Posted by: @simonwig

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it seems logical to run the pump slower and maintain the dT.

No, but there is a bit of a trade off and its not straightforward. 

The heat pump will be more efficient at lower deltaT.  However the water pump will consume less energy if its operating at a slower speed, which will mean less flow so higher deltaT.  Since the heat pump is likely to bne consuming 100s of W and the water pump 50W max, the heat pump will usually dominate. 

The sweet spot is dependent principally on your house loss.  The folks on openenergymonitor did a calculation and, for their particular set of circumstances, the optimum deltaT at the design OAT was ~2C (which implies that deltaT will be less at higher OATs).  Im pretty certain this was a ~5kW house.  The upshot of this, given that normally heat pump systems are designed for DT5 or thereabouts, is that for most cases the optimum is going to be to run the water pump at the highest comfortable speed, which likely will give a DT between 2-5 if its been designed correctly.

In short if its operating at 2-3C most of the time dont worry about it.

@jamespa thanks appreciate the comments.

Simon 

@jamespa They are indeed mysterious devices!!! I have only just discovered this thread and have been observing what I believe to be a change in the MO of my Daikin 8 kW Altherma 3 system. In previous times (last 2+ years, I have noticed flow rates that vary between ~28 lpm and ~14

lpm. Of late (during the last month) I have noticed that a flow rate of ~ 7 lpm has become the popular rate for the majority of the time once the system has settled down from starting up. I have now adjusted my Wilo Pico secondary pump on the flow from the LLH down to ~7 lpm from the former setting of ~14 lpm. What (if any) difference this will make to the running efficiency I don’t yet know though. I attach a Homely plot for the month and also for the last week only. Regards, Toodles.

@toodles 

Firmware updates? - do Daikin do that

@jamespa Ah, they do indeed do firmware updates very occasionally, they carried out one a few months back ISTR. Maybe that is the reason then! Regards, Toodles.