You Can't Commission A Heat Pump In Heating Mode - Here's Why
HTML-код
- Опубликовано: 5 июн 2024
- Heating season is here, and everyone is talking about heat pumps. Unfortunately, heat pumps can't be commissioned in heating mode - at least, not properly.
Jim Bergmann dives into the reasons why heat pumps can't be commissioned in the winter, and how to be successful when servicing or installing heat pumps in cold weather using measureQuick.
00:00 Introductions
00:20 Heating Season Is Here
01:00 AC & Heat Pump Commissioning Similarities
02:07 Weigh It In, But Always Measure Your Linesets
03:25 Package Units = Easy, Split Units = Challenging
04:42 You Can't Rush A Heat Pump
05:21 The Tricks To Testing Heat Pumps In Heating Mode
06:34 Heat Pumps vs AC: The Terminology Differences
09:21 The Importance Of The Outdoor Air Probes
11:00 It's All About The Charge
12:57 Why It's So Difficult To Get A Perfect Heat Pump Installation
15:37 Heat Pumps Don't Have Targets Like ACs
16:28 Watch For Dirty Coils In The Winter
17:32 You Get A Sanity Check In Heating Mode, But No Commissioning
19:46 24 Hour Warm Up Period On Cold Starts
21:28 The Limitations of Physics
23:38 measureQuick Overcomes Cold Weather Challenges
25:40 Remember To Map Your Probes & Go Slow
27:33 Let's Talk Ductless Mini Split Heat Pumps 
Наука
![Best Practices for System Evacuation [2024 Version]](http://i.ytimg.com/vi/QJTFESe2VhM/mqdefault.jpg)
![Best Practices for System Evacuation [2024 Version]](/img/tr.png)
We are a Lennox dealer. Lennox provides a charging chart for both heating and cooling with changes depending on what evaporator is installed. These cold weather heatpumps have been interesting because they just take so long to stabilize and read the heating subcooling. For the most part we try and commission during cooling season l, but up here in Canada we have really long winters which makes that tough
Even with the chart, most if not all manufacturers still require the system charge to be final checked in cooling. I have yet to see a chart the compensates for both the coil and the indoor airflow. As well the ranges are fairly wide.
Many challenges with heat pumps in Pacific Northwest. Most all of my career was in the Southeast, so a big learning curve for me after I re located. Not all makes include pressure curves. Also, I know the importance of a crankcase heater, but in the residential market doing same day replacements it can be difficult to tell the customer we took out your heat and we can't turn it on till tomorrow. It's hard enough to train people to work on unitary equipment never mind all the inverter driven systems that are flooding onto the market, each type seems to have their own peculiar quirks. Oh well-we call it job security!
Listened to this while on calls today. Great episode
Great video, thank you. Do you have any videos that shows real world usage of placing the probes and using MeasureQuick on a live demonstration?
Some good info here thanks Jim
Thank you Jim.
Having been ramping up our HP winter commissioning, we are finding a few interesting things: 1. Have half a day for testing while you're learning early lessons. You will learn a lot. 2. If a system is well matched and installed and accurately probed and True Flow is employed, you have an excellent chance at a good outcome. 3. There will be no perfect outcome, meaning, we were able to get slightly better COP and HSPF but at slightly diminished output, then conversely 99.9% normalized capacity but at very slightly reduced COP and HSPF. We're thinking the highest capacity is the right target but you can correct me. On point number 2 of well matched systems: to us it means that we can fire off, get good numbers sooner, and then look at what other value added items we can give to a home owner before we leave. Maybe that's just very good documentation, or a recommendation on better registers if they decide to paint the house next summer, etc. So far we are thrilled with True Flow and Measure Quick. Thanks for this video, and the continued fight for quality.
You pretty well nailed it. Every system is unique and requires some “tuning” meaning adjustment of charge and airflow to meet the design requirements. The highest capacity is the right metric. Don’t forget also there is some uncertainty in every measurement and calculation so the numbers may not always be perfect. You would also have to know the design fan speed and design static that was used when the system was AHRI rated. You are doing better then 99% of the industry.
Great Content!
I have watched many of Jim's videos and learned from them. Measure Quick's system doesn't solve the heating season charging is mostly what he is saying. He didn't suggest a real method to get close to the right charge without spending hours charging.
Many systems aren't matched- the indoor and outside units aren't the same brand or the the same series so there isn't a magic amount of refrigerant to make them perform best summer and winter. So any charge in a heat pump is usually a compromise.
Turning the t-stat up 10° will turn on the heat strips so after 30 minutes of adjusting the charge the conditioned space is too hot and this affects the refrigerant heat transfer and the customer will be ready for you to leave.
Estimating the line set length may be the best charging method for in new installs or replacements. I think you can figure this to within 10ft. or 6 ounces of refrigerant.
For service calls I still always weigh the additional charge so I don't get way too much charge. Note if the outdoor metering device a TXV or a piston. Either way it should still have some subcooling I would think.
What about this idea- use the temp of the liquid line while temporarily insulating the liquid line between the building and the heat pump and look for some (maybe 6°F to 10°) subcooling after it stabilizes for 15 to 20 minutes. This way you are measuring the liquid line just before the metering device and the outdoor "evaporator" coil. This seems like it should work.
Note that on standard ICP brand heat pumps the liquid service port on the heat pump is after the metering piston so using the hot vapor port on the "cooling-suction pipe" is the only "liquid" side port. On most other brands I use the same liquid service port that I use for cooling mode.
Another thing is that mini splits don't have a metering device on the indoor coil just a electronic TXV in the outdoor unit- those are always recover and weigh in new charge with a warm bottle of 410A.
I don't mind being wrong about some of this I just want to hear what other people are thinking that aren't using a $1000.00 worth of extra equipment to charge with.
Just get some probes and do things better. If your installing or servicing you can afford to do it right for the customer! The probes are so much better and make things 100% easier and much less chance of doing things wrong. Plus a new guy can learn so much faster with probes. Companys are hurting them self cause they make everything much more controlled and faster.
The problem cannot be solved due to the design of the equipment and charging limitations that are bound by physics. What measureQuick does is provide you with a tool that can get it really close in the heating mode and a tool to give you better expectations of what you should expect to see when in the heating mode. I disconnect the electric heat so it does not come on and the inverter ramps all the way up if there is no test mode. Weight it still the best in heating, but 1-2 ounces can really mess with the system, especially if it has microchannel.
I did a start up today in heat mode the daikin didn’t work untill I turned it in ac mode and then turned it to heating is this normal ?
Would it be possible to measure the lineset with a time-domain reflection? It would need to be disconnected from the ends of but I would think you could determine the length using RF just like you would with a cable.
Maybe if it was not already connected and or you the characteristics of the material. Wall thickness varies.
@@measureQuick Very true regarding not being connected but isn't the velocity factor mostly a function of the "dielectric" as open air metals have a VF of 0.95. Since the dielectric would be the potential outer foam and is it highly inconsistent (removed or compressed) and not melded to the copper (gaps of air between the copper and the foam) it might be pretty unreliable.
Now thinking about it, I wonder if there might be better ways to determine the area of the lineset using internal acoustic reflections and/or pressurizing the lineset then connecting it to a known volume of vacuum (or pressure) and looking for the change in pressure of the combined lineset and previously vacuum chamber. This new pressure would then be able to be put into a cross multiplication operation resulting in the area of the lineset. This would still require disconnecting and temporally terminating the end of the lineset but it should give you the area so additional change could be properly added to the system. Another nice thing about pressurizing or a vacuum is that you could use nitrogen and improve the drying of the lineset at the same time. Pressurizing or vacuum could also include the dryer, something that an RF test or acoustic test would have issues with. The known volume of vacuum (or pressure) would need to be within a sweet spot for the length of a lineset and temperature variations would need to be compensated but it might be enough to get the charge accurate enough.
Maybe a 16oz CO2 cartridge could be used along with a Push-to-connect (rectorseal) cap, a T fitting, a thermal probe, a vacuum pump, a gauge, and some fittings would work to be able to vacuum the lineset then pressurize with a known quantity of gas and look at the final pressures.
Are HVAC techs adequately trained in heat pumps? The technical requirements to set up or diagnose a heat pump seems very complex and sensitive.
No all by a long shot. On average on air conditioners studies have shown as little as 23% have correct charge. Heat pumps are much more charge critical and will be installed by the same technicians.
They are not.
I am having a really hard time with the title of this video unless you mean you can't commission a heat pump with a rule-of-thumb air conditioner education and a fist full of cheat sheets from the manufacturer. I work on dairy farm bulk milk tanks near the Iowa/Minnesota boarder where the milk I am cooling might be 98 degrees or 35 degrees and the condenser might be in a 115 degree environment or a -35 degree environment. It is exceptionally rare to have ANY charging instructions from the manufacturer. Often there is a desuperheater based water preheater which might contain 42 degree water or 170 degree water. With a good refrigeration education, formal or self-guided, and some experience, you can commission a system like this under nearly any set of conditions. You have to if you want to get paid. If you are called out to a new customer, after a leak, you have to figure out the correct charge and control settings from scratch. You have to understand what each component does and how a refrigeration system responds to a wide variety of ambient and load conditions, and then measure, monitor, and adjust until it is right. I understand that there is far more work than there is experienced refrigeration tech talent available but that is not the same thing as saying you CAN'T do something.
This type of system is like trying to charge a system with a flooded condenser in mild ambient weather. The only way to do it right is by weight. Weigh out the residual and calculate the entire capacity. You cannot charge by superheat or subcooling and or rules of thumb. You cannot simulate the conditions that you could check it and you cannot use a sight glass as an indicator. You simply cannot see what is in the receiver and what is in the condenser.