LG Heat Pump frustration

LRCCBJ

His response:

"The supply temp coming out will be about 110 yes. 

Your response:

Then I suggest you fix the system so that we can both measure 110° at the supply registers. I will not accept the system until you do.

KarlW

I feel for you - it's time to get another installer as it seems like the diagnosis here regarding too small ductwork does appear to be the case - perhaps you have a 5-year warranty and can go after them? (although good luck with that)

My recommendation is to hire a company that does commercial and residential - they'll have someone who can do the calculations you need to determine what if any duct improvements can be done. Many residential guys (in theory all) can do this, but some can't and you don't want to roll the dice again.

KarlW

@LRCCBJ unfortunately, it appears he had it installed 4 years ago so that argument isn't so simple…

jesmed1

I feel your pain. In the case of our church furnace, it took months of my own data collection to convince the installer that the furnace was overheating because the return plenum he installed was too small, choking the airflow.

There was no easy fix, because space constraints made it impossible to install a larger return plenum. We ended up locking the furnace in "low fire" mode to permanently reduce the heat output and prevent overheating.

I agree with @KarlW that you may need to give up on this guy and pay someone else to fix his mistakes, whether it turns out to be insufficient refrigerant or a duct problem or both.

pecmsg

heat pumps are actually fairly simple to troubleshoot. Measure air in air out. Each manufacturer has charts. If not in range pull and weigh the charge. If short there’s issues, if not this is where it gets difficult.
the tech on site MUST contact tech support. That can be a long frustrating process!

Jamie Hall

If the system was designed for a 67 degree delta T, and you accepted the design (which, since it looks like you may have been dealing with some sort of State mandate, you had to), and it managed that delta T in the space, you got what you paid for.

Note what I said above about unrealistic expectations.

If you can find another company and engineer to go over the operation of the equipment, and the design, and find where something isn't right or wasn't designed correctly, you may be able to get somewhere.

bburd

@josephny this comment about your HVAC tech's visit got my attention:

"We then opened the unit and (shockingly) there is no electric coil installed."

Heat pump installations in cold climates have always required a backup heat source. Maybe this industry practice has changed now that we have hyperheat units, but these are relatively new to the market; if I had one, I would want backup heat. If nothing else, without it the house will be uncomfortable during defrost cycles.

It may not be installed at the air handler, but there should be some other way of heating the house when the heat pump isn't working or cannot keep up in extreme weather.

If your system has no back up, you will probably want to add something. Electric resistance heat strips are the typical default; as others observed you already have a propane boiler for domestic hot water that can probably supply a couple of hot water coils in the ductwork.

Also as others have said, the heat pump performance should be checked against the factory specs. Your delta T between supply air and return seems awfully low. You might need to get a manufacturer's representative involved, or pay someone qualified to assess the system.

Kaos

Folks, lets not confuse the issue here.

The OP does not have a design or ducting issue. He has a simple equipment not putting out hot enough air. This is easy to deal with except you need to work with the installer.

@bburd There is nowhere in code that requires a heat pump to have backup heat. This is one of those myths that is very hard to squash. The equipment needs to be sized to supply 99% design temp, as long as it does that, you don't need anything else.

Some insurance companies do require backup heat in areas with intermittent electric supply. The backup is required no matter your heat source, a boiler would need one the same as a furnace or a heat pump. In that case, it can't be powered anyways, so both heat strip and hydro coil are out.

GW

ok yes probably better if you don't tell the hvac guy you "set it to 82 and it never got there". 99% of the hvac people will give you a polite yet head-tilting look "of course it won't get to 82".

Did he check the superheat and sub-cooling? (did he hook up gauges)? I wouldn't blame the dude if he didn't, because it was 70, after all

If your home is staying at 70 when it's that cold, you're doing pretty good.

I re read your initial post, what temps are you hoping for?

pecmsg

A good example of why Back up heat is need!

lkstdl

I think I agree with Kaos here.

If it was the problem was undersized ducts, wouldn't we see supply air temperatures that were too high rather than too low?

Unless the units were automatically modulating down due to insufficient airflow — but based on the reported 11 kW power usage, they are running fairly close to their rated capacity. @josephny, can you get modulation data with the API?

A competent tech should be able to determine if the refrigerant charge is correct. (NYSERDA may be able to recommend one, and may even be willing to send one out on their dime.)

It is also possible that the system is working as designed, and the house just isn't comfortable for you at 73 degrees when its 5 or 10 degrees outside.

Our thermal comfort isn't determined by air temperature alone — it is also affected by the humidity, air movement (air leakage, or intentional air movement from fans), and the "mean radiant temperature" (think about walking in front of a large window).

If this is the case, you can work to reduce the leakage, turn off extra fans, increase humidity, or raise the mean radiant temperature.

If your whole basement is as accessible as what's shown in the photograph, a radiant floor might not be too difficult to retrofit. You could run it off your existing IBC boiler.

neilc

@josephny

did you say above that the units are determining room temp at the units, and not at the wall controllers?

Can that be changed to read at the wall ?

DCContrarian

"BTW, keeping the tstat well above the temp setting that the system can provide uses about 11kw/h (which costs me about $2.20/hr or $53/day). This is maddening."

11 kW is 37,000 BTU/hr. At 5F the unit has a rated capacity of 40,000 BTU/hr and at -4 it's 35,970 BTU/hr. So it looks like we're seeing COP of under 1.0.

Looking at the NEEP page (I think the right one is:) https://ashp.neep.org/#!/product/33645/7/25000/95/7500/0///0

At 5F and max output it should have a COP of 1.8.

The unit is not performing properly.

DCContrarian

"If the system was designed for a 67 degree delta T, and you accepted the design (which, since it looks like you may have been dealing with some sort of State mandate, you had to), and it managed that delta T in the space, you got what you paid for."

I took the tech's comment to mean that the design temp was 3F and the equipment was sized according to Manual J.

DCContrarian

https://forum.heatinghelp.com/discussion/comment/1829018#Comment_1829018

It depends on the noise! If it's air whistling and rushing in the ducts, sure. If it's the compressor outside rattling and moaning that has nothing to do with the ductwork.

DCContrarian

"I've been fighting with this failed, $50k heat pump for going on 4 years now."

So has it been like this for the entire four years? Or did it suddenly (or gradually) get worse?

DCContrarian

https://forum.heatinghelp.com/discussion/comment/1829209#Comment_1829209

On second thought, 11kW would mean a draw of 46 Amps. According to the spec sheet the maximum overcurrent protection is 40A so if that were happening it should be blowing the circuit breaker. On the other hand, if it were really drawing only 6kW or so it would be achieving the rated COP of 1.8 and the only thing that wouldn't be working as expected would be that the thermostat is way off. That would be about 25A draw.

Where is the 11kW number coming from?