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Discussion Starter · #1 ·
I am looking to select a 1.5T heat pump for my newly constructed 1200 sq foot house. My feeling about most things electro mechanical is keep it simple. This house is 1200 sq feet not 3000 so big saving there, insulate to R35 in walls and R 50 ceiling so more savings. I would be happy with 15 seer heat pump with a 5KW heat strip. My question is it advisable to have TXV valves on both indoor and outdoor coil. I am thinking only on indoor and piston valve on outdoor. My duct work is all 24 gauge spiral inside heated space, visible with ten foot ceilings.
Another saving on efficiency. Here is a photo of my closet for airhandler with the compressor directly thru the back wall on a outside slab.

Thanks
JM
 

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No tech here, but I would select the heatpump based on heating performance data vs whether there's an outdoor txv or not.

The indoor txv is likely optional especially on 13 or 14 seer depending on the unit. Some air handlers may come with the txv, especially the higher end brands.

You may get slightly worse cooling performance without the txv, but it's a moving part that can fail and these days with manufacturers doing everything to cut costs, it's going to come from a third world country built to the minimum standard needed to last through the warranty period.
 

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Discussion Starter · #4 ·
Another option I am unsure of is the variable speed air handler fans. Any above 14 seer seem to require them. Are the variable speed air handlers prone to expensive failures? From what I have seen in specs a indoor only TXV with a variable speed fan falls in the 15 seer range while a multi speed fan preset by tap is about 14 max.
 

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ECM for the indoor blower can save enough to compensate for the more expensive parts. Especially true for heat/cool demanding climate or where electricity is expensive.

TXV will allow for higher efficiency outside the 95/80*F testing environment. While they can fail prematurely, most last a significant time, if not the lifetime of the unit. 14seer is the line that most manufacturers decide to go exclusive txv. (when working correctly, it'll protect the compressor, allowing for longer service life. When they fail, they can cause compressor failure if the unit continues to run.)

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(when working correctly, it'll protect the compressor, allowing for longer service life. When they fail, they can cause compressor failure if the unit continues to run.)
Get a unit with high and low pressure switches to prevent this.

In fact don't get a heatpump without them.

Many of the cheapie builders models won't have them.

Get a quality machine, ideally with easy access to the reversing valve, outdoor txv if applicable. Getting harder and harder to find - most of the better makes used to offer the compressor and other components requiring service in an easy to access compartment - now it's all under the fan.

Cheaper to make? yup. but bad for the technician and bad for you because it increases labour costs. must be hard to change a reversing valve with only access from the top.
 

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Get a unit with high and low pressure switches to prevent this.

In fact don't get a heatpump without them.

Many of the cheapie builders models won't have them.

Get a quality machine, ideally with easy access to the reversing valve, outdoor txv if applicable. Getting harder and harder to find - most of the better makes used to offer the compressor and other components requiring service in an easy to access compartment - now it's all under the fan.

Cheaper to make? yup. but bad for the technician and bad for you because it increases labour costs. must be hard to change a reversing valve with only access from the top.
They are easy to add on after, and usually cheaper. I've been experimenting with icm head pressure controls. A really great add-on that improves performance and efficiency. It's easy to turn a builder special into an almost premium unit.

Yes, removing the top sucks, but you do what you have to. Roof top package units seam to be going the other way though, and getting easier to repair stuff. I guess consumer stuff is just disposable now.

Cheers!
 

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I think I understand a TXN at the indoor evaperator coil . However , I had not heard of a TXV in the outdoor unit ? Please help me out here .

Thanks ,
Wyr
God bless
This would be for a heat pump. The outdoor coil becomes the evaporator when in heat mode. While it's possible to get away with only one txv, they've found it more favorable to have a txv for each coil.

(A cool note: mini-splits only use one, even when they have txvs or exvs. They always put them in the outdoor unit. This is why both lines have to be insulated for those.)

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Discussion Starter · #10 ·
I think I understand a TXN at the indoor evaperator coil . However , I had not heard of a TXV in the outdoor unit ? Please help me out here .

Thanks ,
Wyr
God bless
I think the higher seer heat pumps have a TXV valve on both indoor and outdoor coil. Maybe someone can confirm for both of us. When I read the specs on many outdoor compressor units of heat pump systems they list a TXV valve as one the the upgrade options.
 

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The txv will make the coil more efficient across the entire operating temperature range.

Fixed orifices work perfect only at the designed temperature region. Outside of that they start to starve or flood the coil. They do work OK, for most applications, but trade-offs are made when sizing/engineering to ensure that it works, impacting efficiency.

Cheers!
 
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