VRF with DOAS

Question 1

What are the two main options for a VRF System?

Answer 1

Heat Pump VRF and Heat Recovery VRF

Question 2

What is Heat Pump VRF?

Answer 2

All zones are in heating or cooling at once (majority rule)

Question 3

Where is Heat Pump VRF applicable?

Answer 3

Large single zones, electrical rooms, etc.

Question 4

What is Heat Recovery VRF?

Answer 4

Heating or cooling is determined at zone level. (energy RECOVERED between zones)

Question 5

Where is Heat Recovery applicable?

Answer 5

Hotels, offices, condos, etc.

Question 6

What are 3 key components for a VRF system?

Answer 6

Condensing unit, ducted fan coil and branch selector(HR VRF)

Question 7

How does the FC modulate?

Answer 7

It looks at RA temp vs zone set point and uses an electronic expansion valve to regulate refrigerant flow

Question 8

How does the CU modulate?

Answer 8

With variable speed compressors

Question 9

What are branch selectors and when are they used?

Answer 9

They separate hot gas, cold gas, and liquid phases and direct flow of refrigerant to FCs. They are only used in Heat Recovery systems?

Question 10

Thermal Expansion temperature difference in cooling and heating?

Answer 10

Roughly 40-50 in cooling and 170-190 in heating

Question 11

What are the two pipes in a 2-pipe sytem?

Answer 11

High pressure liquid, low pressure gas

Question 12

What is the added pipe in a 3 pipe system?

Answer 12

A high pressure gas

Question 13

What are 3 expansion compensation strategies?

Answer 13

L bend, Z bend or pipe loop

Question 14

2 things to remember about expansion loops

Answer 14

They should lay flat and be constructed with pipe and elbows, not flex joints

Question 15

Hard pipe between ___ and ____

Answer 15

CU to BC

Question 16

Line sets between ___ and ___

Answer 16

BC to FC

Question 17

Single CUs generally don’t exceed ___ T

Answer 17

18

Question 18

______ is the process of connecting more than one CU in a single system

Answer 18

Twinning

Question 19

Common to see up to ___ CUs twinned together

Answer 19

3

Question 20

Total system tonnage varies by manufacturer, but is typically

Answer 20

50

Question 21

Where are isolation valve(s) located if branch selector is multiport?

Answer 21

Downstream of BC to allow system to stay operational if one zone has a leak, or if construction is phased.

Question 22

Where are isolation valve(s) located if it is 1:1?

Answer 22

Upstream of branch selector to allow for service of BC or FC in this arrangement.

Question 23

_____ ceiling units can have filter

installed at rear of unit

Answer 23

Unducted

Question 24

_____ ceiling units should add the

optional factory filter box

Answer 24

Ducted

Question 25

Pipe junctions should always use factory “_____” or Headers

Answer 25

Y Splitters

Question 26

CUs become ____ in heating mode. If installed indoors they will need _____.

Answer 26

Evaporators, drip pan and condensate pipe to drain

Question 27

Some branch controllers require condensate. _____ requires this. Check IOM

Answer 27

Mitsubishi