What is Energy Integral

[J1mbo]

Would love an explanation of this term. Seems to be critical to heat pump operations.

Edited December 4, 2020 by J1mbo

[ProDave]

Give an example of the context of it's use

[J1mbo]

Vaillant controls - compressor starts at -60°min and stops at 0. DHW maintains -5°min.

[PeterW]

Got a link to the document this is in as it sounds like the rubbish Daikin use with their “Human Comfort Interface” which is really their thermostat ..!!

[Temp]

An integral is typically a total over a period of period of time.  So an "energy integral" could just be your total energy use over a period (day/week/year) etc. On the other hand it could be marketing BS.

 

If there are any graphs involved an integral is usually the area under the curve.

Edited December 4, 2020 by Temp

[J1mbo]

Thanks, HP control interface manual is available here: 0020291573_00.pdf (vaillant.co.uk)

 

e.g. "Compr.start heat. from" on pg 26

[Temp]

On page 10 it says the units of Energy Integral are degrees. So its not energy consumption.

 

See para 3.6 on page 15.

Edited December 5, 2020 by Temp

[Temp]

It looks like some sort of anti short cycling feature.

 

It monitors actual flow temperature and target flow temperature and treates the difference as an "energy deficit" that it counts up. So if the difference was say 5C for 3 mins that would be 15 units of deficit. When that deficit reaches the level set in the Energy Integral parameter it turns the heat pump on. When the deficit has been eliminated it turns it off.

 

I've made up these numbers, I've no idea what value the Energy Integral should be set to.

[dpmiller]

Ask Zoot?

[SteamyTea]

Integration is the opposite of differentiation.

 

So if you know the curve, you can calculate the area under it with integration, differentiation allows you to calculate a value on the curve (there is more to it than this).

 

I suspect that it is a marketing term that is based on the performance in different conditions, so could be weather compensation or ramp up times.

[ProDave]

I have declined from answering as I don't have a clue about some made up unit.  I strongly suspect "Energy integral" bears little relationship to the true meaning of Integral in mathematics.

 

Differentiation will give you the rate of change of a parameter.  Integral gives you the sum over time.

 

All I can remember is "integration by parts" was one of the most difficult areas of maths that I found difficult to understand.

[SteamyTea]

2 minutes ago, ProDave said:

"integration by parts"

Was that Euler's Method

https://en.wikipedia.org/wiki/Euler_method

[pdf27]

5 hours ago, Temp said:

It looks like some sort of anti short cycling feature.

 

It monitors actual flow temperature and target flow temperature and treates the difference as an "energy deficit" that it counts up. So if the difference was say 5C for 3 mins that would be 15 units of deficit. When that deficit reaches the level set in the Energy Integral parameter it turns the heat pump on. When the deficit has been eliminated it turns it off.

 

I've made up these numbers, I've no idea what value the Energy Integral should be set to.

 

Quote

The energy balance is the integral from the difference between the flow temperature actual value and target value, which is added up every minute. If the set heat deficit is reached, the heat pump starts. If the supplied heat volume corresponds to the heat deficit, the heat pump is switched off.

Assuming that the flow rate and heat capacity of the water is constant, then temperature difference is a pretty good proxy for heating power, and then multiplied by time gives energy.

Essentially it sets the size of the lumps in which the heat pump delivers energy - the idea is probably to reduce short-cycling without affecting comfort too much, and changing the parameter allows you to vary whether you prioritise avoiding short-cycling (big number) or achieving a very stable temperature (small number). Basically you want the biggest number where you don't notice any issues with comfort.

[J1mbo]

For the benefit of the search:

 

Vaillant controls calculate energy integral from a starting point of -180° minutes. As each minute passes, the average °C that the flow temperature deviates from the target for that minute is added to the running total, subject to a floor of -180° minutes.

 

i.e. once the target flow is reached, and the HP starts to overshoot, it it were 1°C above the target for 1 minute, the energy integral would then read -179° minutes.

 

Therefore the set range controls the cycle length mid-season, where the ASHP minimum output exceeds thermal load. The default is to turn on compressor at -60° minutes and off at 0° minutes. If that were to be changed to say -90° minutes, then the HP will allow the circuit to cool more leading to a longer cycle period.

[Dan F]

On 07/03/2021 at 10:01, J1mbo said:

If that were to be changed to say -90° minutes, then the HP will allow the circuit to cool more leading to a longer cycle period.

I've tested this, but doesn't work on my arotherm+.  It seems to just ignore the configuration and fire up the compressor at -60 ° minutes anyway. Have you happened to have tested this?

Edited February 15 by Dan F

[JohnMo]

Just sounds like rubbish complication no-one really needs. May be ok for a very low inertia heating system, but absolutely rubbish with UFH for example.

[JamesPa]

1 hour ago, JohnMo said:

Just sounds like rubbish complication no-one really needs. May be ok for a very low inertia heating system, but absolutely rubbish with UFH for example.

So is this just the 'i' in a pi or pid control system, the gain of which they have made adjustable to account for the varying system inertia.  (How many installers could cope with that?)

[JohnMo]

38 minutes ago, JamesPa said:

So is this just the 'i' in a pi or pid control system, the gain of which they have made adjustable to account for the varying system inertia.  (How many installers could cope with that?)

Not sure its either.

Thinks it works like this

Target flow temp of 35 deg.  Every minute above or below this it calculates how much more running time it needs to do or not do to compensate.

 

Example - My target flow temp is now fixed at 35.  The heat pump runs UFH in a thick slab of concrete, it never actually goes above 33 and bit, it runs for around 8 hrs +/-. So in my case the heat pump would never actually stop, it would for ever chase its tail.  Fan coils with a small system volume it may work to compensate for defrosts etc, but the fan on the fan coil does that for you anyway if room temp drops, it just increases fan speed.

[SteamyTea]

6 hours ago, JohnMo said:

Not sure its either.

Thinks it works like this

Target flow temp of 35 deg.  Every minute above or below this it calculates how much more running time it needs to do or not do to compensate.

I seem to remember this topic has been discussed before, and what you describe is the gist of it.

[sharpener]

19 hours ago, Dan F said:

I've tested this, but doesn't work on my arotherm+.  It seems to just ignore the configuration and fire up the compressor at -60 ° minutes anyway. Have you happened to have tested this?

 

How do you change this parameter? I have played with the VR720 simulator but don't remember seeing it in the settings.

 

9 hours ago, JamesPa said:

So is this just the 'i' in a pi or pid control system, the gain of which they have made adjustable to account for the varying system inertia.  (How many installers could cope with that?)

 

IIRC where there is a finite proportional gain you classically need an integral term as well to stop there being a long-term error as a result. Not sure why it would need to be adjustable.

[Dan F]

15 minutes ago, sharpener said:

How do you change this parameter? I have played with the VR720 simulator but don't remember seeing it in the settings.

It's via installer settings of the controller or hydraulic unit (not the sensocomfort).

 

15 minutes ago, sharpener said:

IIRC where there is a finite proportional gain you classically need an integral term as well to stop there being a long-term error as a result. Not sure why it would need to be adjustable.

I don't know much about control theory or PID's, but Vailant use this for couple of things I believe:

- To decide when to turn on the compressor based on deficit degrees/min (vs. desired flow temp)

- To decide when to turn off the compressor based on excess of degrees/min (vs desired dlow temp)

 

This approach is preferable to a simple hystersis, especially when combined with compressor modulation (25-100% on the vaillant heat pumps).

 

You are right, typically there is no need to adjust this and the default -60 degree-minutes is fine.  But, if your ASHP is slightly over-sized and/or it is spring and you have low heat-demand, the theory says that decreasing this theshold this will result in longer cycles which should be slightly more efficient.  This is because more deficit (if that is the correct term) is allowed to accumulate before the compressor kicks-in.  This in turn means that the cycle should be longer as it's starting from e.g. -100 rather than -60.

 

Edited February 15 by Dan F

[Dan F]

This shows this working, along with the compresor modulation:

 

1. Target flow temperature increases (red)
2. Nothing happens immedialty, as there is high integral from pevious low target temp.
3. integral (deg.min) gradually reduces from 99 to -60 based onthe delta between actual and target flow temperatures.
4. Once integral hits -60 heating pre-run starts and pump power increases (brown)
5. Shortly afterwards compressor starts (purple)
6. Compressor modulates trying to match desired flow temp (yellow)
7. Integral increases if actual flow temp is above desired flow temp, and decreases if actual flow temp is below target.
8. If the heat demand < min output, then (even at min compressor) the actual flow temperature will generally be above the target.
   1. If this occurs, then integral gradually increases based on excess deg.minutes.
   2. Once integral reaches 0, compressor is turned off.
9. If the heat demand > min output then integral chaneg slightly, but won't increase to 0 over time  and the unit continues to run.

 

 

 

Edited February 15 by Dan F

[HughF]

The Carel platform that’s used on the Cool Energy units has full adjustment of the PID parameters available.

[Dan F]

On 15/02/2024 at 01:56, Dan F said:

I've tested this, but doesn't work on my arotherm+.  It seems to just ignore the configuration and fire up the compressor at -60 ° minutes anyway. Have you happened to have tested this?

 

@J1mbo I resolved this in the end, it was a firmware bug. The old firmware doesn't respect the "-100degmin" setting, it also double-counts the change in integral resulting in increased cycling! New firmware works as expected.