3rd Period Hydronic Heating Review

Question 1

What are the 2 types of heat exchangers?

Answer 1

High Mass and Low Mass

Question 2

What are the 2 types of high mass heat exchangers?

Answer 2

Cast iron and fire tube

Question 3

What are the 2 types of low mass boilers?

Answer 3

Copper tube and steel tube

Question 4

What are 3 advantages of high mass boilers?

Answer 4

1. Stable water temp
2. Sections are expandable (cast iron)
3. Gravity system, low mass needs flow so can’t be gravity (cast iron)

Question 5

What are 3 advantages of low mass boilers?

Answer 5

1. Quick response time
2. Lighter, easier install
3. Heat domestic directly (copper tube) tankless

Question 6

What are 2 precautions regarding high mass boilers?

Answer 6

1. High explosive potential

2. 30 psi max (cast iron)

Question 7

What are 2 precautions regarding low mass boilers?

Answer 7

1. Flow is critical

2. Susceptible to thermal shock

Question 8

What component is required on all

High mass boilers over 400,000 BTU?

Answer 8

Low water cut off

Question 9

What component is required on all

Low mass boilers over 400,000 BTU?

Answer 9

Flow switch

Question 10

What is input rating and how do you find it?

Answer 10

Amount of heat energy in the fuel burned by the burner

Located on the rating plate of the appliance

Question 11

What is output or gross output rating and how do you find it?

Answer 11

Amount of heat energy available at the boiler outlet

Located on the rating plate or manufacturers instructions

Input 100 MBH 95% eff. Output is 95 MBH

Question 12

What is net rating and how do you find it?

Answer 12

Amount of heat energy available at the heat emission units (rooms)

Gross output x 0.75 = net rating
(75% of gross rating)

Question 13

Calculate output rating of a 250MBH boiler that is 85% efficient

Answer 13

250,000 BTU x 0.85 = 212,500 BTU/hr

Net rating

212,500 x 0.75 = 159,375 BTU/hr

Question 14

What is the function of the operating switch on a boiler?

Answer 14

Controls operation of the boiler (controls the burner)

Question 15

What is the function of a high limit switch?

Answer 15

Set at a higher temperature than the preferred operating temperature and acts as a safety if temp is too high (shuts off the burner)

Question 16

Where must a low water cut off be located on a high mass boiler?

Answer 16

Above the heat exchanger of the boiler

Question 17

Series Loop

Answer 17

One pipe system

Temperature reduces after each unit

Flow rate stays the same (balanced)

Limited to one thermostat

Question 18

Split series loop

Answer 18

One pipe system

Temp. reduced at each unit after split

Flow rate depends on balancing valves

2 thermostats possible

Question 19

Mono flow system

Answer 19

One pipe system

Temperature reduced at each unit

Flow rate variable at each unit (balancing valve on each)

Multiple zoning possible (can service individual units)

Question 20

Direct Return

First Supply First Return

Answer 20

Two Pipe System

Supply temp. same at each unit

Flowrate: variable at each unit, short circuit potential (balancing valves required)

Multiple zoning, can service individual units

Question 21

Reverse Return

First supplied Last returned

Answer 21

Two pipe system

Supply temp. same at each unit

Flowrate: variable at each unit, balanced flow

Multiple zoning, can service individual units

Question 22

If flowrate or boiler temp increases, what happens to the length of baseboard required?

Answer 22

Less baseboard

Question 23

If the entering air temp decreases, what happens to the amount of BTU output?

Answer 23

Increase (has to work harder)

Question 24

BTU = ___ x ___ x ___

Answer 24

500 x 🔺T x gpm

or

gpm = BTU / (500 x 🔺T)

Question 25

What is flow rate measured in?

Answer 25

GPM

Question 26

What is the recommended fluid velocity when selecting pipe for a boiler system?

Answer 26

2 to 4 feet/sec