Another 'Cool Energy' heatpumps thread

[ReedRichards]

4 hours ago, JohnMo said:

Yes runs loose in the outer duct. There is an air space, between the outer of the insulation and inner of the outer duct. I actually wrapped the insulation in aluminium tape also. The armour flex is close cell foam so shouldn't absorb water, the outer casing is mechanical protection and stops the insulation being compressed by the weight of the soil, sand etc.

The field mice that like to overwinter in my loft love to chew on pipe insulation but don't seem to like the stuff with an aluminium surround.  So aluminium foil may be a good idea if there is any chance of rodents getting inside the duct.

[Marvin]

10 hours ago, ReedRichards said:

The field mice that like to overwinter in my loft love to chew on pipe insulation but don't seem to like the stuff with an aluminium surround.  So aluminium foil may be a good idea if there is any chance of rodents getting inside the duct.

yes its the effect on their fillings

[HughF]

Weather compensation set, timers set, analog stat wired in (for now)….. we have heating and hot water. 

Once my programmable stat gets wired in then I’ll switch the timers off and use the stat to take care of things.
 

Doesn’t seem to be running up my smart meter too fast, even with the short cycling that I’m experiencing in this mild weather, with only 5 rads in circuit and the bottom of the weather comp curve set to 37…

 

It’s probably a bit too big by a kW or so, but I guess it’s better for it to be ticking along in the middle of it’s modulation curve than running flat out.

 

Tech note, if you plan on using it like a system boiler and just rely on the pump in the unit, without a buffer or header, you need to change the pump settings from ‘demand’ to ‘normal’ , otherwise the pump will stop when the buffer/flow sensor reaches temperature.

Edited October 4, 2023 by HughF

[SteamyTea]

On 03/10/2023 at 08:13, Marvin said:

yes its the effect on their fillings

Could solve the energy storage problem if they made batteries from filling amalgam and aluminium foil.

[HughF]

Siemens programmable room stat has been in for a week, 17 deg setback from 23:00-06:30, 21 the rest of the time.

 

weather comp is 37@15, 47@0

 

Seems to sip electricity in this damp but not too cold weather and the residents haven’t frozen to death.

 

UFH to get running in the extension now, currently just running a few rads and a couple of fan coils.

 

 

[HughF]

DHW update, the 1m2 coil is no issue whatsoever. I can recover the bottom half of the tank from 20-48.5 in about 20 mins, whilst pulling around 2.1kW off the mains.

 

Getting good delta-t across the coil.

 

[dpmiller]

what pump modulation are you seeing and what deltaT are you set to?

[HughF]

Delta-t 5, pump pwm set to auto.

 

I don’t get a delta-t on heating as my connected emitter volume is small compared to the size of the heat pump, it’s short cycling the compressor quite a lot (probably 20% duty cycle), but it’s not costing a fortune and the rads are always warm.

 

A combination of a couple of fan coils being out of circuit, and the ufh not hooked up yet.

[HughF]

[DanDee]

24 minutes ago, HughF said:

Delta-t 5, pump pwm set to auto.

 

I don’t get a delta-t on heating as my connected emitter volume is small compared to the size of the heat pump, it’s short cycling the compressor quite a lot (probably 20% duty cycle), but it’s not costing a fortune and the rads are always warm.

 

A combination of a couple of fan coils being out of circuit, and the ufh not hooked up yet.

 

You should tweak your pipes such that at low house load(or for the reason you have now) to divert some of the return from the heating through the cold(when it's colder than the return from heating) bottom of the cylinder(coil). No more cycling/reduces cycling. Forget about how much this would benefit, just do it for the guys.

[HughF]

45 minutes ago, DanDee said:

 

You should tweak your pipes such that at low house load(or for the reason you have now) to divert some of the return from the heating through the cold(when it's colder than the return from heating) bottom of the cylinder(coil). No more cycling/reduces cycling. Forget about how much this would benefit, just do it for the guys.

That makes sense, but also sounds like a complicated plumbing mess that I don't have time for at the moment. Struggling to keep on top of the rest of this renovation project, day job, and clearing a 10 acre site of scrap...

[HughF]

And just done its first defrost cycle. Which I was a bit paranoid about given that I don’t have a buffer or a volumiser in circuit.

 

Defrosted in under 5 mins, thermal switch in the fan coils shut them down when the flow dropped below 35 and fired them back up again after the defrost was complete.

 

Result….

[JohnMo]

9 hours ago, HughF said:

And just done its first defrost cycle. Which I was a bit paranoid about given that I don’t have a buffer or a volumiser in circuit.

 

Defrosted in under 5 mins, thermal switch in the fan coils shut them down when the flow dropped below 35 and fired them back up again after the defrost was complete.

 

Result….

I was also curious how it did it, but has done loads now - in the colder north.

Edited November 25, 2023 by JohnMo

[HughF]

I’m still none the wiser about the time clock and temperature settings for that. I emailed Chris about it but not heard back yet.

 

Still also struggling with it short cycling, it seems to want to run hard up to the setpoint, overshoot, then wait for the compressor restart delay timer to expire. Which at -2 and pushing 45 degrees, into a bunch of wide open rads, the ufh slab and two fan coils, surprises me…

[HughF]

1 hour ago, JohnMo said:

I was also curious how it did it, but has done loads now - in the colder north.

Does a very good job of the defrost too, very quick. I just watched it do a other one and it was sub 2 mins.

[JohnMo]

25 minutes ago, HughF said:

Still also struggling with it short cycling, it seems to want to run hard up to the setpoint, overshoot

There should be a "PI regulator integral time" setting you can adjust, it affects the temperature control, and how rapid or slow it is. I had to bring mine down a fair amount. The setting from the factory was 255 and I am currently running at 60. The lower the system volume the lower the number required.

[HughF]

1 hour ago, JohnMo said:

There should be a "PI regulator integral time" setting you can adjust, it affects the temperature control, and how rapid or slow it is. I had to bring mine down a fair amount. The setting from the factory was 255 and I am currently running at 60. The lower the system volume the lower the number required.

Interesting, I’ll investigate.

[HughF]

Found it, it was at 200secs… dropped it to 30, let’s see what happens.

 

its not helped by the ambient air temperature sensor being attached to the evaporator. Unit fires up, fan starts, temperature sensor drops due to air movement, setpoint increases, unit ramps up, unit turns off.

[dpmiller]

you can easily shift the ambient probe clear of the evap.

[HughF]

5 hours ago, HughF said:

Found it, it was at 200secs… dropped it to 30, let’s see what happens.

 

its not helped by the ambient air temperature sensor being attached to the evaporator. Unit fires up, fan starts, temperature sensor drops due to air movement, setpoint increases, unit ramps up, unit turns off.

It's better, but not perfect. Watched it shoot strait past the setpoint and end up 2 degrees above, then the compressor stopped. Dropped it to 15 secs, will keep an eye on it.

 

Any idea what the other settings in here do? I know it's a PID controller, but tuning these isn't my strongest subject...

 

 

At least the house is warm, but It would be nice if it would modulate down better.

Edited November 25, 2023 by HughF

[HughF]

5 hours ago, dpmiller said:

you can easily shift the ambient probe clear of the evap.

Yep, job for tomorrow.

[HughF]

Taken from the attached:

 

"On the other hand it is possible to save energy by controlling the minimum inverter frequency in order to avoid the compressor working with very low COP. For this reason the minimum inverter frequency has been calculated by the control algorithm on a case-by-case basis. It generally depends on the outside temperature and has been set between 30 and 35 Hz. We experienced that working with an on/off modulating frequency stopped at the minimum value is sometimes more efficient than working at constant low frequency values."

 

Interesting...

+402200110.pdf

[HughF]

Bingo, PID tuning basics:

 

Tuning Methods of a PID Controller - CTRL ALT FTC

[HughF]

Can I get this to modulate, can I heck…..

 

It starts off all fine and dandy running at about 1800w, then after a minute or so it decides it isn’t hitting the setpoint fast enough so ramps to full power, overshoots, then won’t start to modulate before it’s too late.

 

I’ve upped the stop-temp to 5 degrees to give it some more modulation overhead, that’s doesn’t seem to make much difference. Still looking at these PID controller values and wondering what a good set of numbers would be.

Edited November 26, 2023 by HughF

[JohnMo]

43 minutes ago, HughF said:

starts off all fine and dandy running at about 1800w, then after a minute or so it decides it isn’t hitting the setpoint fast enough so ramps to full power, overshoots, then won’t start to modulate before it’s too late.

Mine did exactly the same when I first started commissioning, eventually messed with PID, but before I did that I had to do quite a few other changes. But the PID hasn't let me run as cool as I really want, just slowed everything down a little at startup.

 

Your mixer on the UFH reduces the system size quite a bit, because the heat pump supply is only drip feeding the mixer as required, some of the flow is recycling. So although there's lots of system flow, the only real flow all the time is the radiator/fan coils circuit.

 

In theory/practice I should be able to supply the floor 27 deg flow temp, but couldn't get the heat pump to do that temp without doing exactly the same thing yours is doing. Just don't think there was enough system to absorb the heat quickly enough, I have set my min flow temp at 29.7 degs. When it's not too cold (4 to 10 degs) the heating is on for about 5 to 6 hours only. I then set up a quite flat WC curve, so it runs for longer as it gets colder. Even today and currently -1 (09:30) the heat pump will be off for the day at 10:00.

 

One of the other things I encountered at lower flow temps, was the control hysterisis when I eventually got low temp flow started, it did a cycle, heat cut down and return temp from the floor would not reduce enough to give a start permission to heat pump. That was another reason I started running higher temps.

 

The fun we have. And people wonder why their heat pump isn't optimised by the installer. They set it high and run to the hills, never to be seen again.