Posted by: @jamespa

↑

Your heat pump cycles because the demand is less than it's minimum output.

@ajbevster - look back at the diagram I posted here a couple of pages ago

Posted by: @ajbevster

↑

Sadly the dhw thermostat wasn't installed correctly either so that gauge is way off currently.

If the heat pump is getting incorrect data on DHW temperature, how is it 'deciding' when to heat that cylinder?

Can the temperature sensor not be re-positioned?
Any chance of a photo?

Posted by: @ajbevster

↑

hot water temp is more like 50c coming out of tap (separate issue) 

That can and does happen and its a good thing!  The tank will be stratified, meaning it will be hotter at the top than the bottom (because hot water rises).    So as you draw water the top layer stays hot whilst the bottom cools.  This means that you can continue to draw water from the top (of the tank (which is where the take off point is) until the tank is nearly full of cold water.  The sensor will be about half way down, so will show a drop in temp before the tap does.

Posted by: @ajbevster

↑

Posted by: @ajbevster

↑

Sadly the dhw thermostat wasn't installed correctly either so that gauge is way off currently.

 

 

If the heat pump is getting incorrect data on DHW temperature, how is it 'deciding' when to heat that cylinder?

How do you know that its getting incorrect data?

Posted by: @ajbevster

↑

I get the feeling that the only real way to figure out most efficient for my property is trial and error. Especially if the system hasn't been surveyed properly. A lot of cowboys on the eco4 scheme sadly. 

Thats true, of your property and every property.  Surveying is not an exact science, there are too many unknowns.  That means that field adjustment will always be necessary if you want the absolute best performance. 

There are various ways to do it but the ultimate one is inevitably for the householder to tweak settings over a period of time as they get used to the system.  Unfortunately this is infrequently explained.  Most installers set up a basic configuration that will work, but may be 10-20% less efficient than is optimum.  Incidentally its been that way with condensing gas boilers too, since they were first introduced in the early 2000s.  

With due regard for the title of this topic…

This debate has been brewing for quite a few weeks now. It certainly asks some questions of the standards of the industry.

So is the designer/installer charged with the responsibility for achieving the most economic operation? If not why not? And is the low and slow catchphrase the essential purpose of every installation? Who is protecting the homeowner? 

If radiators are under sized or HPs are over sized for operation at a specified low flow (say 32c) shouldn’t this be automatically failed as an installation. 

would this eliminate problem cycling?

Perhaps we have just turned a corner?

Posted by: @sunandair

↑

This debate has been brewing for quite a few weeks now. It certainly asks some questions of the standards of the industry.

So is the designer/installer charged with the responsibility for achieving the most economic operation? If not why not? And is low and slow catchphrase the essential purpose of every installation? Who is protecting the homeowner? 

If radiators are under sized or HPs are over sized for operation at a specified low flow (say 32c) shouldn’t this be automatically failed as an installation. 

Perhaps we have just turned a corner?

I think the answer to this is because we, as consumers, arent prepared to pay for installers to revisit properties multiple times to optimise the set ups, which is what is necessary (in the absence of tweaking by the consumer) to optimise installations.  Until we have auto adjusting LSVs linked to the heat pump (as Adia are developing) we are stuck with manual adjustment over several days/weeks, which no installer will do.

Im not saying that there arent cowboy installations, there clearly are, but I think we have to be realistic about what to expect in terms of getting the absolute best out of a system.

Posted by: @ajbevster

↑

My thoughts are running it at a lower flow rate will help heat transfer...only way I can achieve is by reducing max pump speed (seems to only ever run at 100%) the compressor modulation sorts itself out. 

I have temp sensors on the flow and return of the DHW circuit. I've reduced the pump speed from 3 to 1 for todays cycle/test (roughly 23L/min to 10L/min).

DHW schedule will start at 12:00 and you'll see the data here. We can compare this with previous DHW production cycles and see if it makes a difference, OAT temp should be similar to previous days as well... trying to reduce variables in the test...

Posted by: @ajbevster

↑

Posted by: @ajbevster

↑

My thoughts are running it at a lower flow rate will help heat transfer...only way I can achieve is by reducing max pump speed (seems to only ever run at 100%) the compressor modulation sorts itself out.

Why, sorry but this is not logical so far as I can see.

Test 1

Posted by: @stuartornum

↑

I've reduced the pump speed from 3 to 1 for todays cycle/test (roughly 23L/min to 10L/min).

Is this on the ch pump? I've got a wilo pump and changing this pump speed from 3 to 1 doesn't change flow rate I don't believe...probably wrong though. I'm talking about changing the max condenser pump speed. 

Posted by: @transparent

↑

Any chance of a photo?

Here's the thermistor for dhw

Posted by: @jamespa

↑

Posted by: @sunandair

↑

This debate has been brewing for quite a few weeks now. It certainly asks some questions of the standards of the industry.

So is the designer/installer charged with the responsibility for achieving the most economic operation? If not why not? And is low and slow catchphrase the essential purpose of every installation? Who is protecting the homeowner? 

If radiators are under sized or HPs are over sized for operation at a specified low flow (say 32c) shouldn’t this be automatically failed as an installation. 

Perhaps we have just turned a corner?

I think the answer to this is because we, as consumers, arent prepared to pay for installers to revisit properties multiple times to optimise the set ups, which is what is necessary (in the absence of tweaking by the consumer) to optimise installations.  Until we have auto adjusting LSVs linked to the heat pump (as Adia are developing) we are stuck with manual adjustment over several days/weeks, which no installer will do.

Im not saying that there arent cowboy installations, there clearly are, but I think we have to be realistic about what to expect in terms of getting the absolute best out of a system.

not sure I agree… most of the sizing issues can be done at the design stage as a calc exercise. And as you and I have discussed previously… the design stage tends to focus on max output at -3 where there is not a cycling issue. The problem of size and volume occurs at low flow temps and min outputs. Yet that is also where heat pumps can be at their most efficient.

the infrastructure of the installation needs to be right at the design stage. That would then allow the tweaking and fine adjustments post-installation doesn’t that make sense? 

@jamespa how else can I increase my delta t? When I reduce flow rate (condenser pump speed) the delta t increases to around 5c.

Posted by: @jamespa

↑

Why, sorry but this is not logical so far as I can see.

Lets prove it with a fairly simple test. We do a lot of talking about this stuff in this industry, yet I do not see much empirical evidence... anywhere. Maybe we should start here. I would love access to this!

Posted by: @ajbevster

↑

Is this on the ch pump? I've got a wilo pump and changing this pump speed from 3 to 1 doesn't change flow rate I don't believe...probably wrong though. I'm talking about changing the max condenser pump speed. 

I have an NRG Zone and the DHW circuit is taken off one of the "zones". This "zone" has a dedicated circulation pump which I have reduce the speed on. It's completely separate to the CH "zone". The pump within the HP itself will modulate accordingly to maintain an optimal dT.