Transcript
Introduction to Heat Pumps and the Winter Peak
Hello, everybody. My name is Vincent Lazzara, and today I’m going to be talking about my white paper, Heat Pumps and the Winter Peak. Part of the reason that I wrote about this is because heat pumps have been outselling gas furnaces in the US, about thirty-two percent in twenty twenty-four, which is the widest margin on record, and shipments are running at about three to four million units a year.
The load that used to burn gas now shows up at the residential transformer in winter at the coldest hours on every house at once. While everyone has talked about demand, this paper is really about what lands on the power quality engineer’s desk. Specifically, we talk about four signatures that are showing up in more recordings every season and what that looks like on PQ Canvass, our power quality software.
Four Signatures
The first one is the starting current sag. The voltage dips at every compressor start, which is usually the worst on weak services. Then the cold build pickup, which is post-outage, everything restarts simultaneously. Once there’s any outage, all the heaters will then come back up at once, and they all have the same cold load, so they’re all restarting. That can obviously put more strain, and if there’s an outage, it’s probably already strained.
The other thing that you can see is flicker, like repetitive cycling and defrost making light visibly pulse, which can lead to an increase in customer complaints. And then we have harmonics, which are inverter-driven compressors and electronic loads that inject distortion.
Examining a Recording
What we’ll look at is one recording from one house, and I’ll show what they look like. This recording is a one twenty, two hundred and forty volt single phase residential service that has a heating pump in operation. There are two events that dominate the record, starting at twelve twelve to about twelve fourteen. A companion capture shows a clean restoration.
The first and most reliable attribution test here is to look at the current channels during the voltage event. Current sits at the measurement floor, milliamps. Nothing inside the house can pull the service to zero without drawing current. A customer side fault announces itself on the ammeter.
Power View and Reactive Current
The whole day PQ Canvass power view, which is in figure four, shows why the compressor depresses voltage out of proportion to its real power draw. Each start spikes the real power about five kilowatts before settling near two kilowatts. The reactive dominated current, not the two kilowatt of heating, is what pulls the voltage down.
Attribution Test: Do the Legs Mirror
One rule out of the imposter is attribution test three, which is do the legs mirror. On the service, a loose or open neutral mimics load and regulation problems, but usually with one tail, the leg moves in opposition, one rising as the other one falls. It’s worth checking on every residential recording because overvoltage on the light leg destroys equipment.
Harmonics and Flicker
Finally, you have harmonics and flicker being able to split them by the same test. On this recording, voltage THD runs clean at about one and a half to one point nine percent all day with one brief spike at around seven percent. The distortion spike lives and dies with the star transient order and it persists through zero load. The four is identical at about zero amps, twelve amps. The background belongs upstream and is benign.
Flicker splits along the same seam. The late night block shows the PST rising towards about the one point o compatibility, but at mid-afternoon it’s about zero point four to zero point nine. Coincidence with the current again is the discriminator.
Five Findings
What this really tells us is it closes in on five findings:
- Two severe utility side interruptions
- One genuine ride through risk
- Well-behaved but visible heat pump
- A slightly high but compliant baseline
- Sound neutral and clean harmonics
Every attribution rests on three checks:
- Does the current move with the voltage?
- Do the legs move together or in opposition?
- Does the disturbance persist beyond the transient?
That’s really the deliverable, and it’s several hours of an engineer’s time per recording to try to find that.
What Merlin Can Do
What we’re going to look at too here is what Merlin can do, which is our automated PQ assistant. We’re going to see what Merlin can do off of that same investigation and what it finds. For any recording, we can go in, go to our assistant, go to our overview, and see what it can find. Right away it says deep utility interruptions plus heat pump voltage steps.
Off of the Merlin dashboard, we can see that it has a severe sag immunity, which is out of compliance. If we click on it, it gives us a detailed analysis of how our two sub-cycle de-voltage tags on the heat pump circuit are out of IEEE sixteen sixty-eight compliance. It can even cite, and you can get a full PDF report off of it.
Power Quality Report and Snapshots
If you want to dig into this a little bit more, we can go over to the power quality report. What’s cool is we can see specific snapshots that it’s referring to. Based off of our power quality report, we can see any of the snapshots. For example, right here, it’s saying that it’s good steady state voltage overlaid by two very deep brief supply interruptions around midday, which is what we saw, and waveform captures. We can go over here to snapshot and see exactly what it’s looking at.
This is a high severity event. The legs drop with zero minimal current, indicating that it’s an upstream interruption.
Asking Merlin Questions and Generating Letters
Based off of this, we can also ask it any questions. If we had any further questions about the analysis that it ran, or if we would like to then take our analysis and let’s say there is a heat pump that’s bad that’s causing a lot of issues for a customer and around them, then we can have it generate a customer letter telling them, “Hey, you need to replace your heat pump,” and we can cite anything that we found specifically into it.
We can tell it to avoid certain things, certain sayings if we don’t want to get into plain language. If we have to prove why they have to replace it, we can then give it a technical letter, and it can go into a little bit more of the low-level technical findings of the report.
Wrap-Up
This is a really good way to save yourself a good amount of time and to be able to find things without having to really trudge through a lot of the normal graphs you would have to.
With that said, if you guys have any questions, you can always email us at any time. One thing that we added too is you can email Merlin, ask it any power quality question. That is askmerlin@powermonitors.com, or you can email us at support@powermonitors.com, and we will get back to you. Thank you guys for joining us in our webinar today. Hope to see you again soon.