F2: Radient Systems Flashcards
What type of Pex was created using the Engel method and has a memory?
PeX A
What kind of fittings can PeX A be used with?
expansion type, crimp / compression
What is PeX A’s best quality?
ability to be kinked / repaired by just adding heat
Can PeX B and C use expansion fittings?
No and any kinks have to be cut out / replaced.
What kind of Pex has to be used when installing radiant panels?
The type that has an oxygen barrier coating for heating.
What does the oxygen barrier provide?
minimizes the rate of oxygen diffusion (decreases rusting
This type of pipe is red in colour
True or False: adding rust inhibitors additives to radiant system helps keep level of free oxygen low
True
What is a Wet system?
PeX tubing is embedded within a concrete mass
Is a wet system the best option for a radiant heat transfer in a house?
Yes
What does WWF stand for?
Wire mesh
What does the spacing between ties have to be to ensure the tube doesn’t float up in the concrete slurry?
24” between ties
Should you use an open flame to fix kinked PeX A tubing?
No
Can joints be used in embedded concrete?
No
AHJ will not allow it
What is the min of rigid polystyrene foam used between the vapour barrier and the slab bottom?
2 1/2”
True or False: most installers only use foam for the first 2 feet from the outer wall.
True - one the ground settles heat loss is min
What is the most common way to install in floor heating?
using 1 1/2” thick concrete / gypsum mixture (poured in two “lifts” over 1/2” tubing) and tubing is stapled to the plywood subfloor.
What’s the less common way of installing in floor heating?
using pre-formed plastic mats
What type of system is used outdoors as a snow melt system?
A wet system
What kind of circulating solution is used for outdoor systems?
Antifreeze or brine
How is the outdoor system separated from the building heating system?
through the use of a heat exchanger
The heat exchanger acts as what?
as a boiler –> would need it’s own expansion tank, circulator and make up water (and backflow preventer)
What is a “Dry System”?
In floor heating system used indoors
Where is the most common spot for a dry system to be installed?
Joist space - min 2 pex runs are attached to the sides of the joist placed 3” below the subfloor
What is the less common way of installing a dry system in the joists?
using hangers to support pipe
What is a major down-side of installing in floor between joists?
Air being trapped in the joist space
Is air a better insulator or a conductor?
A better insulator
What is an even better way to run in floor heating?
Using aluminum plates that are stapled to the underside of the floor.
This has a better heat transfer rate.
Are dry system temperatures higher or lower than wet systems?
Much higher
Does insulation have to be installed between joists if in floor heating is installed?
Yes
True or False: The insulation between joists has to have a higher R value than subfloor/ floor covering.
True, the heat will be driven upwards
What kind of radiant panel is used in institutions? (hospitals / schools)
Radiant ceiling panels
What type of in floor heating layout is the most common for 1 - 2 outside walls?
S-shaped serpentine pattern
What type of in floor heating layout is most common for multiple outside walls?
Spiral (counter flow) pattern
What is the main consideration in loop layouts?
That the warmest water should always be delivered to the area of greatest heat loss first
How is tube spacing determined?
tube size and the floor output in BTUH/ft2
What is the most common spacing in residential?
12” - 9” - 6” (4” is less common but usable)
What would happen if the heat output exceeds 40 BTUH/ft2?
the high temp would be uncomfortable and supplemental heat (baseboard wall fin) has to be used
how is the max length of radiant tubing determined?
on the loops delta T and size
What happens if the recommended tube lengths are exceeded?
frictional resistance increases –> causes more pressure on circulator / water flow rate is less than expected.
A total heat loss estimate will tell us what?
each room’s heat loss
Where shouldn’t tubing be installed and why?
Under cabniets - ineffective
Kitchen - ineffective/ food spoils quickly
Under stoves/ refrigerator- both generate heat
Toilet bowl - melts wax ring
Who has to approve joint or connection in concrete?
Manufacturer or AHJ
How much concrete should be maintained over tubing?
3/4”
What is the max spacing between ties on a straight run?
3m (10’)
What is the max spacing between ties on bends?
0.2m (8”)
What is the heat plant most commonly associated w/ Hydronic heating?
Boilers
What is the determining factor when sizing heat loss?
The heat plants OUTPUT
If the boiler’s output is greater than the heat load, this ensures what?
That there is enough of a buffer to deliver the heat needed even of the coldest days of the year.
What does the choice of piping dictate when sizing a circulator?
How many circulators are needed
Where they are to be located
Where should pumps be installed?
Downstream of the “point of no pressure change”
What is the point of no pressure change?
The point in the piping system where the expansion tank attaches to the supply main
What is the pumps job?
To move water when zones call for heat
produce pressure needed to overcome frictional losses
Head loss that a pump has to overcome, comes from where?
It only has to overcome the single circuit w/ the most frictional resistance which includes head loss through the longest loop that it supplies.
How is Circuit length measured?
Start from pumps outlet –> most remote manifold or heat emitter / back to the pump’s inlet
Add 50% - accounts for extra frictional resistance caused by fittings
True or False: Having multiple small, high head, low flow rate pumps is that way to go with todays hydronic systems.
True
How are pumps picked?
Flow rate required (USGPM)
Resistance to flow that the pump must overcome (in feet of head)
How are flow rate (GPM) and resistance to flow (head) calculated?
Through pump curve
How is high head described?
High pressure, Low flow
How would Low Head be discribed?
High flow, Low pressure
What are key points to remember when selecting a pump?
1) Choose the pump with the flattest curve –> avoiding excessive pressures = noise
2) Pump curve has to be above the max requirements when plotted => overcoming head loss/ still move water
3) use middle third of graph = most effective
True or False: the height of a closed system has no effect on a pump’s operation.
True
The pump only has to overcome what?
Frictional resistance
What language does a pump speak?
GPM
Frictional losses will increase if the what increases?
The flow rate
Hot water systems want what kind of flow rates?
Low (1-4 feet/sec)
What happens if water moves too quickly through the system?
- There would be an increase noise / erosion
- Less time for heat to be heated up
In domestic potable water systems, How is friction loss expressed?
PSI / foot
feet of head/foot
In hydronic heating systems, how is frictional resistance expressed?
millinches / foot
What is the designers norm for frictional losses?
400 millinches / foot
1 psi = how many feet of head?
2.31
1 foot of head = how many psi?
.433
Who supplies head losses for various types / sizes of tube at diff flow rates / temps / different glycol mixtures?
Manufactures
What temp of water has more frictional resistance?
cold water
True or False: When using glycol in in floor heating systems a backflow preventer is needed
True
Where would a backflow preventer be installed?
On the cold water makeup to the system
What is the normal backflow preventer to use on a residential system?
Dual check w/ atmospheric port (DCAP)
What is the most common type of Glycol
Polypropylene glycol
Why is Polypropylene glycol popular?
Known as the food grade antifreeze.
non- toxic but expensive
What type of glycol is popular in the automotive industry?
Ethylene glycol
(extremely toxic)
Does glycol have an effect on pumps and expansion tanks?
Yes
a 50% glycol / water mixture will make water how much harder to move? (% wise)
14 - 22%
in turn also creates more head pressure
What does glycol have a detrimental effect on?
Rubber –> the rubber ball inside a zone valve.
Why are balancing valves used?
To create an accurate flow rate through a circuit
What type of valve is a balancing valve?
low - loss type of globe valve
Balancing valves will also have what type of plug on them?
Pete’s plugs –> on the upstream / downstream side of the valve seat
When does water have to be tempered?
When a system requires water temps that differ greatly
How many ports does a mixing valve have?
2 - 4
Where are mixing valve located?
at the Mixing point : where high temp and low temp water merge
What is a thermostatic mixing valve?
a valve that is manually set to supply a constant temp
What is a Reset control mixing valve?
a motorized actuator / controller that is capable of modulating temps as thermal conditions change
what type of valve has the same entering / leaving temps and is located on the return piping?
Diverting valves
What is Injection Mixing?
It’s when a pump is used to ‘inject’ an amount of hot water into the supply side of a manifold
What type of system commonly uses Injection mixing?
Primary - Secondary piping systems
What does a variable - speed pump do?
sets itself to the speed required in order to maintain a desired temp
Why must multiple pumps that share pipe be hydraulically separated?
So that the operation of one pump does not affect the operation of the other
How is hydraulically separation achieved?
by using a hydraulic separator
or
tees located very close to one another
Do pumps have to work harder or easier to pump water through brazed plate heat exchangers?
Harder
What is a CV value?
it is the flow rate in GPM through the valve that would result in a 1 psi pressure drop across it
What is the System Operating Point?
The intersecting lines on a pump graph that indicate the max needs of the system in head loss / flow rate
What has to happen for a pump to be effective?
the pump curve has to fall above the system operating point
What happens if the pump curve falls below the system operating point?
pump won’t put out enough pressure at the required flow rate to offset frictional losses
a noisy system is due to?
excessive pressures
Where on the pump curve is the circ’s efficiency high?
within the middle third of their pump curve.
An expansion tank is located where to a circ pump?
as near to the inlet side of the circ as possible
Why is a differential pressure valve installed on systems using a single pump / multiple zone valves?
to avoid over - pressurizing the system
What will a differential pressure valve (DPV) do when excessive pressure is sensed?
It will open to bypass water from the supply main to the return main
What kind of circulator is used on larger hydronic systems?
Variable - speed circulators
(regulates differential pressure)
What are Electronically commutated motors (ECM) ideal for?
systems using valve-based zoning
(eliminates need for differential pressure bypass valve)
What happens to pressure output when two pumps are in a series?
Pressure output doubles
Flow rate = remains unchanged
What happens the there are two circulators in parallel?
Flow rate = doubles
Output pressure = stays the same
What job does an expansion tank have?
Keeps the system pressure from fluctuating widely when system heats up and cools off
What other names are given to an Expansion tank?
Cushion tank
Compression tank
What happens if there was no expansion tank?
- pressure builds up, trips pressure relief valve -> discharges system water to max level.
- When boiler shuts off / water cools –> pressure drops below fill valve’s set point
water is added to desired set point.
This continuously happens when boiler turns on / off
What happens with the constant addition of water to a boiler?
rust
To correctly size an expansion tank, what must we know?
1) min / max operating pressures
2) system vol in gallons
3) min / max operating temp
4) Glycol % mixture (if used)
A properly sized expansion tank should have a max pressure of?
5 psi lower than the relief valve setting (prevents relief valve from leaking)
Should the pressure on the air-side of the diaphragm be adjusted before or after adding fluid?
Before
What happens if a tank is underpressurized?
it can cause the relief valve to open each time the system heats up
True or False: Glycol has an effect on the rate of expansion depending on the % of glycol in the system.
True
What are the 2 locations where there’s a choice of pipe size?
Radiant tubing - on either a wet or dry system
Piping in the mains / branches bn boiler / manifold.
In a primary / secondary system, boiler / primary loops are sized according to what?
Output of the boile
piping in secondary loops are sized according to what?
Heat load of that particular loop
What is the temperature differential between the supply and return radiant flooring?
20F
What is the max length of a 1/2” loop using a temp diff of 20F?
300’
What kind of spacing is 1:1?
12” (12/12 = 1)
What kind of spacing is 1.3:1
9” (12/9 = 1.3)
What kind of spacing is 2:1
6” (12/6 =2)
What kind of spacing is 3:1
4” (12/4 = 3)
a 20F temp differential produces how many GPM?
10,000
A 15F temp differential produces how many GPM?
7500
A 10F temp differential produces how many GPM?
5000
Once concrete is finished pouring, what should be done with the water pressure in the pipe?
Water pressure can be released from tubing (blow out with dry air - prevents freezing)
Until concrete is at max pressure what shouldn’t be done?
Do not re-pressurize tubing
True or False: The pump that has the flattest curve should be chosen
True
True or False: The height of a closed system has no effect on a pump’s operation
True
How do heat exchangers have enormous heat exchanging capacities?
The stainless steel plates inside have a huge surface area
What is waterlogged?
When air is reabsorbed into the water –> this reduces air vol until tank has little air
