LG Heat Pump frustration
Comments
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Keep in mind that that 30 is at a 70 degree delta T. In a more clement environment — say New Jersey! — that would be more like 22 BTUh per square foot…
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
We kind of need to stay with a DT of 70 so all comparisons are valid. It's a bit disingenuous to go to NJ and claim that you "only" lose 22 with a building of similar construction.
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I’m sitting here freezing in a radiator and baseboard house! Time for a heat pump :)
But seriously guys, it’s not even fossil vs heat pump, it seems to be forced air vs forced water.
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Well, unlike with a heat pump, that should be pretty easy to fix.
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting
3 -
OK, I was just going from memory last night, here's what the 2021 IECC requires for Zone 5, which is where the OP is located (see
Windows: R3.3 (max U-Factor of 0.3)
Doors: R5
Ceilings below roofs: R60
Concrete slab: R10
Walls: Either
2x6 insulated (R20) plus 1-1/4" of continuous exterior foam (R5)
or
2x4 insulated (R13) plus 2-1/2" of continuous exterior foam (R10)
or
4" of continuous exterior foam (R15)
Putting in those numbers, and breaking out the doors and windows (now 5% doors and 10% windows) I get 35,200 BTU/hr. Slightly higher, but doesn't really change the picture.
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I would like to present a diagnosis that I think matches all of the facts that have been presented:
- The heat pump is operating normally.
- The thermostat is malfunctioning or installed in such a way that it cannot accurately read interior temperatures.
- The house is not in fact super-insulated but is more like typical late-20th-century construction.
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Along with the possibility that
4. Homeowner doesn't feel comfortable with 70 degree air being blown around the house. Which I can sympathize with, because I'm one of them.
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so true. Heat pumps blow 100+F air if they’re working.
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0
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Well, after actually reading the spec on the air handler:
https://s3.amazonaws.com/s3.supplyhouse.com/product_files/LG-LVN361HV4-Submittal.pdf
Heating: 59°-81°
@josephny
I ran and got a thermometer. Not the best, not instant, but shouldn't be too wrong.
72 at return, 80 at supply
Cannot expect better correlation than this. The system cannot have a higher supply temperature.
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I amended my earlier post, current code is max U-factor of 0.3, which is equivalent to R3.3
Looking at the spec sheet for Anderson 400 windows, the only one that doesn't seem to meet that is windows with fully-divided grills.
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Yes, understood. The new data is much easier to meet………….and the double pane windows are fine.
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I think my comment was meant, if not take, in the lines of humour, but also as a gentle warning to not assume two things about a structure: first, that just because it is old it is an energy hog and second, just because it meets all the latest codes — or that it is designed to — that it will be an energy saver.
There is another caution in this nice long and very interesting thread: designing something which ostensibly meets all the pencil and paper work and complies with code etc. doe not mean that it will be satisfactory to the ultimate authority — the consumer.
And, perhaps in addition or extension of that, it does not help us — the HVAC trade and engineers and architects — much if the consumer isn't happy, even though we can say "but it meets code" or (perhaps worse) "it's working just as intended". Both of those statements may well be true, but if the consumer isn't satisfied we're the ones holding the bag.
Not quite sure how to get around this problem: if we have code or other requirements for what we have to do, but those requirements don't meet the consumer's expectations, we've kind of got a problem, no?
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
There is another caution in this nice long and very interesting thread: designing something which ostensibly meets all the pencil and paper work and complies with code etc. doe not mean that it will be satisfactory to the ultimate authority — the consumer.
This is valid.
If you look carefully at the spec for the air handler, the maximum output temperature is 81°F. When designed properly, it has sufficient output to maintain a DT of 70°F. HOWEVER, as someone who has quite a bit of experience with a FHA system, the output is 122°F at all ambients.
I can tell you with certainty, that 122°F never gives you a truly warm feeling until the room temperature gets to 71°F or so.
I simply cannot imagine that any consumer would be pleased with a supply of 81°F (at cold ambients). The "feeling" is always "cold". Any air at a temperature of 81°F that hits the human is going to FEEL COLD!!
The sad part is that it is sold to the public without any explanation of the above.
There is a another scam that is occurring with mod-cons:
I know of two manufacturers that show the boiler has an output of 199K. What goes silently unnoticed is that the primary system (P/S) has no capability of delivering 199K unless the DT is 40. This is based upon the flow rate achievable with the stock internal pump.
Now, imagine a P/S system with a 40 DT on the primary. You MUST get a DT of 40 on the secondary OR the boiler will modulate down and cannot deliver 199K anymore. Think about the difficulty of actually achieving a DT of 40 on the secondary…………..with the associated miserable performance on a series system…………….you basically cannot utilize it on a series system with baseboard. You'll end up with ONE-HALF the rated output of the boiler.
Almost no installers are understanding of this and NONE of the consumers, of course.
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@LRCCBJ thats a misreading - that’s what indoor intake temps it can handle. I still think the air handler that’s only blowing 80F is broken. It should be blowing > 100F
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In an earlier post he said he has the fan on high. If the compressor is modulating the only way it can meet the load with the fan stuck on high is by reducing the output temperature.
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Based on the spec, the output temperature is exactly at it's maximum……………so I don't see what can be reduced………….??
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Understood……………I cannot see any other spec on the output temp. It makes more sense if the output temp is > 100F. I actually cannot see how it could be otherwise. Nobody would be comfortable.
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Yup. Unless the first floor unit is blowing >100F air, I am not convinced it’s working.
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According to the spec sheet the indoor unit has four fan speeds of 1,200, 971, 883 and 794 CFM. In heating it has a maximum output of 42,100 BTUhr. At the highest fan speed that would equate to a temperature raise of 34F. At 72F room temperature, an output temperature of 106F.
The OP said he has the fan on max. He's reading a temperature delta of 8F (72F in, 80F out). At 1,200 CFM that's about 10,000 BTU/hr. He'd probably be more comfortable with the fan on its lowest setting, or ideally, just letting it modulate.
If the room temp is 72F and the unit is putting out 10K BTU/hr, I don't see what the problem is.
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If the room temp is 72F and the unit is putting out 10K BTU/hr, I don't see what the problem is.
10K/hr is about the output of a stovetop burner. I can tell you that this won't do squat to heat 1000 sq. ft. @ 0°F ambient.
You certainly know this!!!
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But it's maintaining 72F! We don't know what the outdoor temperature was when he took that measurement, for all we know it could have been 45F with the sun streaming in.
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In his original posting he said it was 7F outside, then some time later he took those measurements. We don't know how much later.
If you go back to the posting on the first page where he shows the temperature and outputs of all the units, both of the second floor units are using around 1600 Watts. At an output of 10,000 BTU/hr that would be a COP of 1.8.
In the posting where he takes the measurements, he writes: "It [the thermostat] reads 76 inside, but my frozen fingers say otherwise. More importantly, the same thermometer used at the return and supply agrees with my fingers." The thermometer is reading 72F.
If he is complaining about "frozen fingers" when the interior temperature is 72F I think we've found the real problem.
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Here's one possible explanation for the apparently contradictory facts:
- The house really is "super-well insulated" and the actual heat loss is only 35,000- 40,000 BTU/hr under current conditions.
- Installed heat pump capacity of 78,000 BTU/hr is actually oversized because of the contractor's conservative manual J.
- Unfortunately, the (possible) lack of refrigerant is making the heat pumps run very inefficiently with relatively low supply air temps.
- As a result, the heat pumps are running near 100% duty cycle at rated amperage, but outputting maybe only half their rated capacity.
- But because the installed capacity is so much larger than needed, the heat pumps are still able to maintain the house at 72 degrees, even when running inefficiently at around half their rated output, with low supply air temps as a result.
- The homeowners still feel cold because the supply air temps are low.
- But the contractor is able to claim the system is working as designed because it's maintaining the house above 70…but only because it's so oversized that it's able to maintain that inside temperature at around 50% of rated output with relatively low supply air temps.
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No doubt we understand the "real problem".
If the charge is low and the unit is running at maximum to obtain 72F, then you have identified the problem. The KWH usage would support this conclusion.
The H/O will certainly feel cold at a SWT of 80F.
I incorrectly identified the temperatures in the manual as the supply air temps. So, forget about that.
It really is time to get a true professional to weigh the charge and search for any leak.
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The OP keeps referring to what he has as "a system" but it's really three separate systems.
In his second post he posted this chart:
Now, it's confusing as hell. It's showing four sets of data even though he said he only has three heat pumps. And it's hard to tell the lines apart. But what I get from it is:
- The third floor is set for 76F, and in the timespan represented in this graph it stays within about a degree of that.
- The second floor west is also set for 76F, and also stays close to that.
- Second floor east is set for 72F, and is almost a perfectly horizontal line at 72F.
- The first floor is set for 70F, and it is all over the place. Sometimes it climbs a bit above 70, and sometimes it dips as low as 45F. Although in a later post he said that the measured interior temperature didn't fall as far as the chart indicated.
A few times he has alluded to the interior thermostat not being accurate, and not agreeing with a thermometer placed beside it. But there are three or possibly four thermostats in this system, we don't know if this behavior is happening with one, some or all of them. And if one, which one.
Looking at the power consumption lines:
- The third floor seems to be loafing along, it's often close to zero and it looks like it only turned on 2-3 times during the measured period. Even when it's on it's only pulling at most 1500 Watts, or less than 10K BTU/hr
- Since the two second floor lines are so close I'm going to assume they're measuring the same unit. It seems to be spending a lot of time around 1500W and occasionally bumping up to 2000W or so, which is at the low end of output for the unit.
- The first floor spends most of its time around 4000W, and only occasionally dropping below 2000W. When it does drop below 2000W, the temperature inside drops pretty quickly.
So I'd focus on the first floor unit. At 240V, 4000W is 16.7 Amps, the rated heating Amps from the spec sheet is 14.2. So it's going all-out while the other two units are loafing. It also seems to be the only unit that is having trouble at all maintaining the setpoint (subject of course to the inaccuracies of the measurements).
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Wow! You guys are so knowledeable and so generous — thank you!
I'm struggling to digest everything, but here is what I can address now.
The house is about 30x50 per floor, 3 floors.
It was spray foamed completely (not a retrofit) with closed cell, including the basement walls and all exterior walls and roof.
First floor is 11' ceilings; 2nd floor 10'; 3rd floor 9'.
It has lots of glass (not the best, but very good quality Anderson windows (I don't remember the exact model). Probably 1st floor has total glass of 60 linear feet of windows that are 5 ot 6' tall.
The tech did not find an offset to the temp readings and confirm that the temp displayed on the tstat is being measured at the tstat.
I confirmed that the delta-t is about 10-12F
I am not sure of how tight the house is. I did not have a blower test done.
I installed 3, 4500 watt electric heaters in the basement a couple of days ago, connected to a line-voltage mechanical tstat (also in the basement) set to 70F. The heaters come on for 12 minutes, then go off for 10 (24/7).
No static pressure measurements have been done. But, the noise is not at all coming from the ducts or air handler. The noise is coming from the condensors outside. I complained initially, the tech came back 4 times, then LG replaced the condensors. Still very noisy.
Tech says the "condensors are going to be loud. It's 0 degrees out. They are running at 90 hertz. You are going to hear them." when I tell him they are crazy loud, he restates.
No ceiling cassettes. All ducts from air handlers.
Below is a graph of the electric usage by hour this morning. Each zone is a different color. There are 4 zones: 1st floor, 2nd floor East, 2nd floor West, 3rd floor.
However, the electric usage is measure a little differently. Ignore "Balance 6" — that is the basically the basement heaters. "1st fl 3 6" and "1st fl 4 6" together is the 1st floor electric. "2nd fl 5 6" and "2nd fl 6 6" is the combined 2nd floor East and 2nd floor West zones. "3rd fl 1 6" and "3rd fl 2 6" together is the 3rd floor zone.
This is a graph of when the different zones are running/active/calling-for-heat this morning:
HVAC company owner is on his way there this morning. He keeps repeating that my house will never be 82 degrees. I keep repeating that the supply air temp should be about 110 but is far far lower. Might as well be talking to each other with hearing protection in place.
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Wanting 82°F inside is unachievable and unrealistic! 68 - 72° is more realistic.
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Thank you for putting this in simple terms (for us non-experts).
The thermostat reading has been verified by putting a thermometer right on top of it. Matches the reading exactly. And, I have confirmed that the reading shown is taking from the location of the tstat. And, it sure seems like raising or lower the set point on the tstats has the expected results on the heating system.
The house has a lot of foam, done very well (no walls were up, many inches of closed cell use, every bit of exterior wall with the possible exception of an area on the North and South walls as they meet the basement wall. But, I have not done a blower test. And, there is a lot (a lot) of windows on the 1st floor (which is where I'm having the hardest time keeping warm). So, #3 very well could be the case.
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Yes, I apologize for the confusion, contractory info.
There are 3 condensors and 4 air handlers (that correspond to 4 zones).
But, the electric usage monitor reads the power drawn on each leg of each of the 3 condensor's electric lines.
But, it gets even more convoluted: LG provides the energy usage directly but only for floors 1 and 3, I think because 2nd floor has 2 air handlers and LG's system is not capable of that. Therefore, I use Emporia Vue electric usage monitor for that.
Yes again, the 2nd and 3rd floors have a much easier time maintaining temp.
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This morning's graph, in case that is helpful.
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People get stuck on the 82F sometimes.
With modulating equipment you need some easy way to make sure it is running at full tilt. The easiest way to do that is by cranking the thermostat setpoint well above room temperature. There is no expectation of the room getting up to 82F, this is simply to make sure the heat pump is running at max when doing the temperature measurements.
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"HVAC company owner is on his way there this morning. He keeps repeating that my house will never be 82 degrees. I keep repeating that the supply air temp should be about 110 but is far far lower. Might as well be talking to each other with hearing protection in place."
Do you want the house to be 82? If not, maybe a better response would be to tell him you don't want it to be 82.
My recollection is the thermostats are set for 76 and 72, but you had moved one of the thermostats to 82 because that was the only way you could get it to hold 72. He's not a psychic and he's not a mindreader, you need to be explicit with him about what you feel the issues are.
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"I confirmed that the delta-t is about 10-12F."
You have four air handlers. Is the delta-t the same on all of them?
Did you see my earlier post about how if the fan is on high the delta-t is going to be reduced when the heating load is low? With 1200 CFM your heat output is going to be 12-14K BTU/hr.
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So I'd focus on the first floor unit. At 240V, 4000W is 16.7 Amps, the rated heating Amps from the spec sheet is 14.2. So it's going all-out while the other two units are loafing. It also seems to be the only unit that is having trouble at all maintaining the setpoint (subject of course to the inaccuracies of the measurements).
Agreed.
4000W is 13640 BTU/H. Assume a COP of 2.5 = 34,100 BTU/HR
First floor glass (R3) loses 8400 BTU/HR @DT of 70
First floor walls (R15) lose 6500 BTU/HR @ DT of 70
Infiltration……………assume another 30%: 4470 BTU/HR
So, 20,000 BTU/HR Total Heatloss for the first floor at 0° Ambient
Assumption is that first floor loses nothing to the second floor or the basement.
The unit should effortlessly hold 70°F at nowhere near 4000W!
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"This morning's graph, in case that is helpful."
What's the outdoor temperature?
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"This morning's graph, in case that is helpful."
And what are the four thermostats set for?
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Well, owner of the company came, brought thermometer meant for supply air measuring and read 110F.
Looks like my thermometer was the wrong type.
I wasn't there, so it's all by pictures and text messages.
I'm sorry I took everyone here down a wrong path.
When I asked about why the 1st floor unit has to be running continuously and making loud noise to maintain 72F, he again said it was cold outside and that is normal.
I just don't know any more.
I don't know what the outdoor temp was when the owner came.
The thermostats were set as shown in the images above, copied here — on the right side, bracketed by a "-" and a "+" sign.
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@josephny , the burning question is- are you comfortable?
All Steamed Up, Inc.
Towson, MD, USA
Steam, Vapor & Hot-Water Heating Specialists
Oil & Gas Burner Service
Consulting1
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