Replies

1. 
   aunsafe2015 | Jul 28, 2020 05:38am | #1

   I can't really comment on a VRF, but I have a Trane XV18 (which is basically a slightly cheaper version of the XV20) and think it's great. Good turn down ratio, good dehumidification even at its lower operating capacities, extremely quiet, decent heat output down to about 20F, etc. I've got my system split into 3 zones, and it easily keeps each zone at exactly the temperature I set (and sometimes it's a pretty big spread. For example, 73 in bedrooms and 78 in a bonus room).

   If I were building a new house I would consider having a single zoned XV18 system for the entire house. Though in your case, at 5000 sq feet, it might be difficult to cover the whole area with 1 system.

1. 
   smac355 | Jul 28, 2020 02:54pm | #3

   Thanks, yes plan to have at least 2 zones upstairs/downstairs. May zone the master separately as well

2. GBA Editor
   Brian Pontolilo | Jul 28, 2020 09:11am | #2

   Hi Sean,

   I looked into VRF systems a bit and found, very broadly that they are not necessary in homes, but are better suited for institutional buildings and commercial buildings that could possibly need heating in one are and cooling in another at the same time. As Aun points out, in a house of your size, you may need a zoned system, I don't think you need a VRF system. Have you had HVAC design work done yet? If not, you may want to read this: A Beginner’s Guide to HVAC Design.

1. 
   smac355 | Jul 28, 2020 02:56pm | #4

   Appreciate it. Yes going through design phase now with builder on what type of system we want to utilize. We don’t have house fully spec'ed out yet, so a bit too early to have manual J done.

   From VRF standpoint unlikely we would be heating /cooling separate parts of house given simple residential use so maybe the more traditional heat pump setup is the way to go.

3. 
   joshdurston | Jul 28, 2020 03:18pm | #5

   I think there is confusion on terminology. I would consider both to be in the VRF family.
   VRF can refer to any modulating heat pump system. But people often associate it with the traditional Asian vendors.
   Generally they have variable speed inverter compressors, with advanced refrigeration circuits for extended operational range and modulation range. You may or may not have multiple zones per outdoor unit.
   Simultaneously heat cool VRF systems are often labelled as heat recovery. This allows you to re-purpose heat captured during a cooling cycle rather than just reject it outside, and allow simultaneous heat/cool (on multi zone).

   If you are in a cold heating dominated climate you need to pay attention to the HSPF, and the capacity and efficiency at lower temperatures. Keep in mind when it's really really cold you care more about capacity than efficiency since you don't spend many hours per year at the extremes (near the heating design temp).

   You also need something that is compatible with how you intend to duct the house, or vice versa.

   Anecdotally, the Trane and Carrier (and other traditional NA brand) cold climate air source heat pumps seem to be fine pieces of equipment for the right applications with lots of happy customers.

   If you have a high latent to sensible cooling ratio you should consider that as well. There is some variance on how high humidity with low loads are handled.

4. 
   walta100 | Jul 28, 2020 05:29pm | #6

   I my mind VRF equal Variable Refrigerant Flow and any system that changes the speed of the compressor can fairly claim the title VRF.

   I am not comfortable with the way you drew your line VRF vs. American. Many of the familiar American brand names are putting their brand labels on equipment on the same equipment you have Labeled VRF.

   How much each a system varies the flow is an important question.

   The Asian brands are offering ducted mini splits and the US brands are offering conventional variable speed systems. I think this would be a better line to draw for your discussion.

   The turndown ratio is what percentage of full speed is its lows speed is able to operate at.
   I am guessing the Asian equipment will have a higher turn down ratio when you have one indoor unit and one outdoor unit, than the more conventional systems.

   I think you should consider separate systems for upstairs and down.

   I found every contractor would quote a mini split system priced much higher than the conventional system they were offering.

   I have been very happy with my RHEEM conventional system with a variable speed compressor, electronic valves, variable speed blower and commutating thermostat.

   Walta

1. 
   smac355 | Jul 28, 2020 10:06pm | #7

   Thank you! I am in climate zone 4, eastern PA.

   I think the confusion from my POV there is lots of discussions around the mini-split or now ducted mini-split systems from green/high performance building science, but I haven’t seen much on a traditional variable speed inverter type heat pump.

   I am still not quite sure what the real difference is from a ducted mini-split be traditional variable speed system is. To me as of this point they seem to accomplish the same thing.