TXV versus VRF air source heat pumps

woobagooba

Folks. I have an insurance/storm damage situation forcing me to make a short notice decision on an 2 ton AC replacement.

I will take the opportunity to upgrade from AC to heat pump.

I am familiar with VRF having just installed Mitsubishi Hyper Heat at another location.

The contractor for this insurance job is recommending a York/Johnson TXV system.

Can someone lay out the basics of VRF versus TXV for me?

Cheers

GGross

I have never heard of it described as "VRF versus TXV" before. VRF stands for "variable refrigerant flow" TXV is a type of expansion valve "Thermal expansion valve" VRF systems I believe would use an electronic expansion valve, or EEV. But I don't think that's really what you are looking for an answer to.

To answer your question the VRF system will be able to provide cooling and heating at the same time from a single outdoor unit, A standard heat pump would provide cooling OR heating, but not both at the same time. Typically VRF systems have been reserved for commercial and more unique circumstances, but the technology has come a long way and is beginning to become popular in some residential markets.

Additionally, and maybe someone who deals with Mitsubishi can correct me if I am wrong. To the best of my knowledge the Hyper Heat is an inverter driven heat pump, not a VRF. I am pretty sure mitsubishi VRF are called "city multi"

Hot_water_fan

This is a central AC replacement? One indoor unit to one outdoor unit? The attribute I’d focus on is single speed vs > 1 speeds. 

ratio

It sounds like the choice is between mini split vs conventional split.

I'd go with what your installer is most comfortable with, as that will insure you have the best chance of getting a well-performing reliable system. It's my understanding that mini splits can be leading the way WRT efficiency (depends on the mini split—some are nothing more than a conventional split with a vertical condenser coil), but high-end (read complicated [≈ expensive]) conventional splits are catching up fast.

woobagooba

Its a residential 2 ton system with ducted air handler indoor and outdoor unit on roof. I have experience with Mits Hyper Heat (thought this was VRF) systems for residential. What is being quoted is a York/Johnson ODU with an Aspen air handler. The York is based on TXV technology.

The association has done little to technically vet the system and left this to the contractor.

I've requested full specs from the contractor, but until then I wanted to understand the VRF versus TXV issues. Right now I have no info re: turn-down ratios, cold climate capability (I'm in zone 5 coastal), etc. Soon. Thanks a bunch.

ChrisJ

woobagooba said:

Its a residential 2 ton system with ducted air handler indoor and outdoor unit on roof. I have experience with Mits Hyper Heat (though this was VRF) systems for residential. What is being quoted is a York/Johnson ODU with an Aspen air handler. The York is based on TXV technology. The association has done little to technically vet the system and left this to the contractor. I've requested full specs from the contractor, but until then I wanted to understand the VRF versus TXV issues. Right now I have no info re: turn-down ratios, cold climate capability (I'm in zone 5 coastal), etc. Soon. Thanks a bunch.

The problem is "TXV technology" isn't a thing.
You're comparing a type of expansion valve to a type of compressor.


It's like asking to compare a diesel car to one with disc brakes.   They aren't the same comparison.


For what its worth 90% of TXV issues are due to the guys installing and touching them.  I used TXVs on everything I do.

A VRF is still going to need an expansion valve I would assume either TXV or EEV.  


I wouldn't even consider a VRF for my house.  For now I think a 2 stage Copeland scroll is the best bang for the buck by far.

Hot_water_fan

I don’t think Mitsubishi Hyper heat pumps are VRF? At least the ones installed residentially. I think you’re possibly overthinking this decision. 

Ironman

This may help simplify what VRF is:

VRF stands for variable refrigerant flow, which goes a surprisingly long way toward describing how this system uses refrigerant for both air conditioning and heating. In a nutshell, VRF is a ductless, large-scale system for HVAC that performs at a high capacity.

Unlike split AC equipment, VRF allows multiple indoor units to run on the same system, which is designed differently depending on the application. VRF systems are considered either a heat pump system or a heat recovery system, which can heat and cool simultaneously

Mitsubishi City Multi 3 phase systems are Heat Recovery systems and can provide simultaneous heating and cooling.

HyperHeat (and the rest) are Heat Pump systems and cannot heat and cool simultaneously.

Both are VRF systems.

Hot_water_fan

HyperHeat (and the rest) are Heat Pump systems and cannot heat and cool simultaneously.

Both are VRF systems.

I don’t think so - the Y series is VRF but the M and P series don’t seem to be. Agree about the heat recovery bit.

ChrisJ

Hot_water_fan said:

HyperHeat (and the rest) are Heat Pump systems and cannot heat and cool simultaneously.

Both are VRF systems.

I don’t think so - the Y series is VRF but the M and P series don’t seem to be. Agree about the heat recovery bit.

Wouldn't any inverter system that can operate at a huge range of output be VRF?

ratio

From what I can see, VRF (or other variants, like VVF) systems can have the outdoor units manifolded together for increased capacity & can have a branch box (or variants like branch selector) that will allow heat recovery (simultaneous heating and cooling). Mini splits are a single outdoor unit, although they may have multiple ports on the outdoor unit & some (IIRC) can use a branch box—but do not currently support heat recovery.

I'm not sure if the VRF systems use three phase compressors or rotary compressors. Many mini splits use rotary compressors nowadays, but like I mentioned previously I've seen units sold as 'mini splits' that were nothing more than a standard condenser with a vertical slab condenser coil, no variable anything, no expansion device in the outdoor unit .

ChrisJ

ratio said:

From what I can see, VRF (or other variants, like VVF) systems can have the outdoor units manifolded together for increased capacity & can have a branch box (or variants like branch selector) that will allow heat recovery (simultaneous heating and cooling). Mini splits are a single outdoor unit, although they may have multiple ports on the outdoor unit & some (IIRC) can use a branch box—but do not currently support heat recovery.

I'm not sure if the VRF systems use three phase compressors or rotary compressors. Many mini splits use rotary compressors nowadays, but like I mentioned previously I've seen units sold as 'mini splits' that were nothing more than a standard condenser with a vertical slab condenser coil, no variable anything, no expansion device in the outdoor unit .

But if VRF stands for variable refrigerant flow then how isn't an inverter minisplit VRF?

ratio

VRF systems predate mini splits with variable compressors. In Ye Olden Days, mini splits had two distinguishing characteristic: the form (vertical slab condenser coil) & the expansion device was located in the outdoor unit. Over the centuries they've gained other technologies, but the naming stayed the same to avoid confusion.

Hot_water_fan

Wouldn't any inverter system that can operate at a huge range of output be VRF?

No? Variable refrigerant flow is different than a variable speed inverters. Otherwise Mitsubishi would be making exclusively VRFs but only marketing some as VRFs. 

woobagooba

OK so I am clearly clueless here. Let me try a reset.

I have this system installed at another location.

https://ashp.neep.org/#!/product/31992/7/25000///0

Is it VRF and do I care, damned if I know (I've been matching too much Risinger).

What I think I should be caring about when comparing with the the York/Johnson unit...

- the SEER rating.
- the turn-down ratio.
- its cold climate capabilities.
- variable capacity. Is it slamming on/off or able to vary output to match conditions?
- warranty
- installer reputation.

Cheers

Ironman

I don’t see where you gave us any info on the York system. To make a comparison between that and a HyperHeat system, we’d need model numbers and size. Just saying it has a TXV doesn’t provide any specifics as most units now have one. It’s like saying the car is fuel injected but not giving a make or model.

If the York system that you’re being quoted is just a standard heat pump, then there’s no comparison between that and a HyperHeat system.

Ironman

All the things that you just listed above are things you should be asking the contractor who quoted you the York system.

Matching a York heat pump with an Aspen AHU sounds like a basic 14 seer system and begs the question “why not a York AHU?” Is the Aspen even an AHRI listed match? There’s nothing wrong with Aspen, but it’s more typically used as a replacement where the primary manufacturer’s indoor unit won’t fit.

woobagooba

Thanks Ironman. I have pretty thin info re: the heat pump ODU and air handler and are pressing for more.

The Aspen/York combo did catch my attention.

mattmia2

Didn't at least some of the 3rd party evaporator manufacturers claim to be making higher quality coils?

The other question is do they have the right tools to properly braze, evacuate, and charge it.

Ironman

woobagooba said:

Thanks Ironman. I have pretty thin info re: the heat pump ODU and air handler and are pressing for more. The Aspen/York combo did catch my attention.

It sounds like that guy is quoting you the easiest and cheapest thing he can cobble together while trying to lead you to believe that it’s the equivalent of a HyperHeat system. It is not.

A HyperHeat system produces full heat output at 5* outdoor without the aid of backup electric elements. A standard heat pump looses capacity as it gets colder outside and usually requires the backup elements to kick in around 25-35* outside. When the backup elements kick in, your electric meter spins about three times faster.

woobagooba

Finally received more detailed info. The proposal is a York YHE24B21S 2 ton single stage heat pump paired with the Aspen AHU.

https://www.york.com/residential-equipment/heating-and-cooling/split-system-heat-pumps/yhe_ds/yhe-14-seer-single-stage-heat-pump

https://resource.carrierenterprise.com/is/content/Watscocom/ce_hom_home_20210812_aspen-matchups_documentpdf

Single stage scroll compressor. Budget end of the York line.
@47 degrees OD 24K Net MBH Heat
@17 degrees OD 15K Net MBH heat
@10 degrees OD 13.5 Net MBH heat.

Ironman

I thought so.

woobagooba

After a quick technical refresh re: heat pumps, my OP is indeed cringe-worthy

GGross

@woobagooba

Good news then. You came seeking knowledge, and your realization is a sign that you have started down the correct path toward that knowledge. Feel free to continue asking questions here, most are happy to help.

mattmia2

If the damage is physical damage to the condenser and it is an older r410a system from before we forgot how to manufacture copper tubing I'd be inclined to just replace the condenser(possibly with a heat pump changing out the refrigerant control to something that can deal with a heat pump).

woobagooba

A wind storm peeled up the membrane roof with the result looking like a bulldozer piled all the condensers into one corner of the roof. It was impressive. Most all of these are older systems so both the condensers and air handlers will need replacing. Several of us will pay the difference to upgrade from the "like" replacements allowed by insurance company. I intend to go back in with a heat pump (existing heat is baseboard electric).

Ecoer has come up several times as an option. I'll start another thread for that.

ChrisJ

mattmia2 said:

If the damage is physical damage to the condenser and it is an older r410a system from before we forgot how to manufacture copper tubing I'd be inclined to just replace the condenser(possibly with a heat pump changing out the refrigerant control to something that can deal with a heat pump).

Mainly claim all aluminum condensers get rid of a lot of issues copper ones had.
I personally have no idea, because I've seen both materials last 30+ years.

I even have steel condensers that are pushing 100 years old.