Search with Wattson

Notifications

Clear all

Joining the Renewable Heating Hub forums is completely free and only takes a minute. By registering you’ll be able to ask questions, join discussions, follow topics you’re interested in, bookmark useful threads and receive notifications when someone replies. Non-registered members also do not have access to our AI features. When choosing your username, please note that it cannot be changed later, so we recommend avoiding brand or product names. Before registering, please take a moment to read the Forum Rules & Terms of Use so we can keep the community helpful, respectful and informative for everyone. Thanks for joining!

Performance in the current cold snap…

HughF · 2024-01-18T07:27:39Z

How is everyone’s system performing in this current cold snap? Just curious to see if everyone is happy with their comfort and running costs, given that we are now well into ‘design conditions’ for the heat loss calcs.

Page 8 / 8 Prev

Air Source Heat Pumps (ASHPs)

Last Post by HughF 3 years ago

85 Posts

17 Users

28 Reactions

30.4 K Views

RSS

HughF

(@hughf)

Honorable Member Member

Joined: 5 years ago

Posts: 489

Topic starter 23/01/2024 10:29 am

Posted by: @derek-m

↑

Posted by: @hughf

↑

@derek-m single heat pump, just run on weather comp, no stats, no setback.

The Carel platform that my heat pump is built on allows full tuning of the PID settings, along with full control of the compressor ramp speeds. It’s close to maintaining setpoint, but I’ve still got some work to do. I’d like to deal with the initial overshoot next, I think I’ve got the oscillation damped quite well.

When it’s around freezing outside, it runs happily for a long period of time, it’s dealing with the overshoot when it’s cycling that’s the next area of tuning that needs my attention.

I suspect that it will not be possible to accurately control the LWT during milder weather conditions, simply due to the fact that the heat pump will be starting to operate outside its control envelope. i.e. it cannot turn-down any further.

As far as controlling IAT is concerned this should not be a major issue, though it could take some time to optimise for maximum efficiency.

Out of interest what are your PID settings?

It is my suspicion too, that in milder weather, we are simply oversized. I didn't take into consideration the possibility that the ACH value used in the heat loss spreadsheet (and by heating engineer) could be considerably higher than we actually achieve.

The fact that it was tracking the requested setpoint to within 0.1 degree during the last 2 weeks of freezing weather leads me to think my PID settings aren't a million miles off.

At the moment they are: P = 5 deg. C, I = 50 secs, D = 0 secs.

The controller also allows me to open up the overshoot window, which gives headroom for compressor rampdown - currently set to 5 degrees. I can't remember the rampdown settings though, it's specified in Hz/sec inside the Power+ inverter settings.

To comment on the original question in the thread title - I was away for a lot of the 2 week freeze, but the residents reported stable internal temperatures (21-22) 24/7 and there were no issues with defrosting, even with our limited system volume.

Whole house electric consumption was running around 50kWh/day - all electric house now.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.

👍

ReplyQuote

Page 8 / 8 Prev