Full Answer
What is the difference between primary and secondary piping?
This is also primary/secondary (p/s) as it is connected with closely spaced tees for the boiler connection. The boiler would be considered secondary piping as it is piped out of the branch of the closely spaced tees. This piping is a good application if all the zones are looking for the same temperature water.
What is the primary pipe on a boiler?
Some people call the boiler piping the primary pipe as that is where the boiler is connected. That may or may not be true. Let's take a look at some examples of different p/s piping ideas. In this example the pipe coming from the boiler is the primary pipe as it has the closely spaced tees on it.
What is a primary loop in a boiler?
Primary Loop Piping is commonly used in boiler heating systems that run needing multiple temperatures or contstant temperature at the hydronic boiler is required. Primary Loop Piping allows non condensing boilers to maintain a heat level in the boiler high enough to allow the boiler to run at its most efficient state.
What is one pipe primary-secondary pumping?
We call the system I've been describing "one-pipe, primary-secondary pumping." The primary circulator moves the boiler water through the primary circuit. When the flow of cooler water returns from the secondary circuit, the hot primary water, which jumped the "gap" between the two tees mixes with the return water.
What is primary and secondary piping?
Primary/ secondary piping is a versatile piping method that's increasingly being used as the backbone of modern multi-load/multi-temperature hydronic systems. The concept of primary/secondary (P/S) piping has been around since the mid 1950s.
What is the purpose of primary-secondary piping?
Traditionally, Primary-Secondary piping arrangements have meant full flow in the boiler loop and variable flow in the system loop. Manufacturers tend to prefer Primary-Secondary because it ensures proper flow through the boiler.
What is primary pipe?
The primary piping elements include steel pipes, connecting elements (flanges, pipe bends, pipe elbows, tees), stop and shut-off-and-regulating valves (slide gates and valves), drain devices, expansion joints, supporting structures and parts, hangers and fastening elements, thermal insulation.
What is a primary loop on a boiler?
3:0514:26USB University: Primary Secondary Piping - YouTubeYouTubeStart of suggested clipEnd of suggested clipThis drawing shows a boiler primary loop where the flow from the boiler is through the run of theMoreThis drawing shows a boiler primary loop where the flow from the boiler is through the run of the tees. And the heating zone is through the branch of the tees.
What is a primary flow and return pipes?
The coil, or "heat exchanger" forms part of the central heating circuit, and its water heating abilities are purely a by-product of its main function, which is to heat the radiators. This heating is called the "primary" circuit, the pipes running to and from the boiler are called the primary flow and return.
What is a secondary heating system?
Secondary heating systems are those that provide space heating which is in addition to that provided by the main heating. This report considers two types of secondary heating: § Alternative heating: defined as heating that is used instead of the main heating in a room.
What is secondary support in piping?
Basically, there are two types of pipe support structures, primary and secondary supports. Primary supports are directly attached to the pipeline, whereas secondary pipe supports are attached directly to the foundation or structure supporting the pipe.
What is the primary loop?
The Primary Loop is a monthly publication created to provide an avenue for Naval Nuclear Power Training Command (NNPTC) leadership to communicate with NNPTC students and staff, as well as a means to boost morale.
What is process piping oil and gas?
Process piping moves chemicals, gases, water, and other fluids in support of an internal manufacturing or processing operation.
What is a secondary loop?
The secondary loop uses a variable speed pump to manipulate the flow of the fluid such that the cooling coil demand is satisfied. The above mentioned pumps are considered as a primary/secondary pumping pair. Therefore there are four different loops in the system. The cooling loops in the system will be modeled first.
How does a boiler loop work?
The loop works like a siphon that runs out of water. The point where the loop connects to the equalizer is higher than the boiler's crown sheet and that's what provides the safety. Since the water couldn't instantly vanish from the boiler, it bought the Dead Men some time to notice the problem and save the boiler.
How far apart are the tees on the primary loop for boiler?
It is VERY important that the closely spaced tees be no further apart than 4 times the diameter of whatever size pipe constitutes the primary/secondary loop, and it is equally important that the length of the straight pipes extending from the closely spaced tees be at least 6 times that same pipe diameter.
What is primary and secondary pipe support?
There are essentially two main types of pipe support structures, primary and secondary support. Primary supports directly attach to the pipeline. While secondary pipe supports attach to the structure that works to support the pipe.
How are pipes classified?
The classification of pipes are schedule and nominal diameter. Pipe is typically ordered using the Nominal Pipe Size (NPS) standard and by specifying a nominal diameter (pipe size) and schedule number (wall thickness).
Why are pipes called nipples?
0:162:52What Is A Pipe Nipple? - YouTubeYouTubeStart of suggested clipEnd of suggested clipOr barrel nipples which lack this feature some pipe nipples lack any unthreaded area connecting maleMoreOr barrel nipples which lack this feature some pipe nipples lack any unthreaded area connecting male thread right to male thread.
How many types of pipe joints are there?
Different Types of Pipe Joints and Where Are Use?Sr.No.Types of Pipe Joints1Threaded Joint.2Brazed Joint.3Spigot and Socket joint.4Socket Welded Joint.7 more rows
Why do we use primary secondary piping?
Manufacturers tend to prefer Primary-Secondary because it ensures proper flow through the boiler.
Why is variable primary piping better?
A Variable Primary piping arrangement can result in lower initial costs due to the installation of fewer pumps, less piping, less electrical, etc. Variable Primary systems are generally considered to be more energy efficient. This is based solely on the concept that fewer pumps use less energy.
Is there more piping in a variable primary?
Yes, there is slightly more piping associated with a Variable Primary-Variable Secondary piping arrangement, however, the installation cost is not significantly more. Variable primary systems require a two-way control valve on each boiler to prohibit flow through an unfired boiler.
Does a Nuro boiler have a VFD motor?
The NURO® can vary the speed of your boiler pump, equipped with either a VFD or EC motor. As the boiler firing rate varies, the pump speed and flow adjust accordingly. It’s the best of both worlds; flow rate ensured through the boiler, and energy savings associated with variable flow.
Why is it important to protect a boiler?
There is one reason… protecting the boiler! Condensing boilers have very low water content, which makes flow through the exchanger highly important. Stainless steel and aluminum boilers are designed to handle low boiler return temperatures. Cast iron, on the other hand, is not well equipped to handle the same cold return water.
Why is my flue pipe rotten?
The root cause is condensation. The cast iron boiler is sitting in condensation mode for far too long. This type of boiler will take some time to show you an issue inside the heat exchanger, but the flue pipe deterioration is an early indication you have a problem. This needs to be addressed before the boiler gets compromised and turns into a very expensive replacement.
Drawing 1
In this example the pipe coming from the boiler is the primary pipe as it has the closely spaced tees on it. The water will leave the boiler and go back to the boiler through the connected loop. As the secondary circuits (piped off the closely spaced tees) are running, the water temperature in the primary pipe will drop.
Drawing 2
This is the same as the above drawing where the boiler loop is the primary pipe. The only difference here is I am showing how to pipe two secondary zones of the same water temperature. The first two zones on the right will supply the same water temperature to the baseboard zones. The zones to the left will receive lower supply temperature.
Drawing 3
In this drawing the primary pipe, again being the one with the closely spaced tees would be the primary loop. There are four secondary heating zones on the top and of course the boiler is a secondary zone on the bottom.
Drawing 4
This is also primary/secondary (p/s) as it is connected with closely spaced tees for the boiler connection. The boiler would be considered secondary piping as it is piped out of the branch of the closely spaced tees. This piping is a good application if all the zones are looking for the same temperature water.
Drawing 5
This drawing shows a device called a hydraulic separator. It will take the place of closely spaced tees. The advantage of the hydraulic separator is it will offer an air vent on top and possible dirt drain on the bottom (not shown).
Drawing 6
If using close spaced tees on a primary loop, it is important to follow these measurements. The boiler or heating zones can be piped as secondary piping and would follow the distance between the closely spaced tees as per drawing #3 or #4 above. The most confusing is the distance between the closely spaced tees.
Flow in the Tees
Now with all the above explained, let's look at what is happening in the system. We will look first at the primary loop drawings 1 - 3 above. There are two rules we must remember when piping p/s. The first is "What enters a tee exits a tee". It has nowhere else to go and cannot stay in the tee. If 10 gpm enters a tee it must exit at 10 gpm.
What is primary secondary piping?
Primary/ secondary piping is a versatile piping method that's increasingly being used as the backbone of modern multi-load/multi-temperature hydronic systems.
What is the opening pressure of a secondary circuit?
The opening pressure of these valves is about 1/4 psi. Sufficient to prevent buoyancy forces from sneaking any hot water into the secondary circuit when the pump is off. A spring-loaded check valve is an acceptable alternative to a flow-check in these locations.
Why is it important that a secondary circulator pump into the circuit?
This allows the pressure in the secondary circuit to increase when its circulator operates.
What is P/S piping?
The fundamental concept of a P/S system is to "uncouple" the pressure differential established by any given circulator, from those established by other circulators in the same system. P/S piping allows any pump in the system to operate with virtually no tendency to induce flow, or even disturb flow, in circuits other than it's own. It's about as forgiving as hydronics can get.
What is the function of a circulator in a P/S system?
Every circulator in a P/S system functions as if it were installed in an isolated circuit. The primary circulator does not assist in moving flow through any of the secondary circuits, or vice versa. The function of the primary loop is simply to convey the output of the heat source to the secondary circuits while operating at a selected temperature drop.
What is the purpose of the closely spaced tees connecting a secondary circuit to the primary circuit?
The closely-spaced tees connecting a secondary circuit to the primary circuit are counter-productive to the desired effect when the system is being purged of air. A strong purging flow in the primary circuit will not induce a similar flow in a secondary circuit. The solution is to install a means of independently purging each secondary circuit. One approach is to install ball valve and hose bib near the end of each secondary return riser (Fig. 3).
What is secondary riser?
The secondary risers can be treated as headers from which two or more independently controlled zone circuits can begin and end, or the secondary circuit could form a two pipe direct- or reverse-return subcircuit. Another possibility is to install a pumped manifold station as the secondary circuit connected to circuits of flexible PEX or PEX-AL-PEX tubing which run out to individual heat emitters. The latter is known as a "homerun" distribution system.
What is primary loop piping?
Primary Loop Piping is commonly used in boiler heating systems that run needing multiple temperatures or contstant temperature at the hydronic boiler is required. Primary Loop Piping allows non condensing boilers to maintain a heat level in the boiler high enough to allow the boiler to run at its most efficient state.
Does primary loop piping work with condensing boilers?
Primary Loop Piping also works well with condensing boilers allowing proper flow through the boiler for the highest rate of heat delivery.
Can a boiler be reset indoors?
Many modern boilers (Either Condensing or Non-Condending Types) have an indoor outdoor reset capability and using thus piping layout will allow the most cost effective use of your boiler. Effective use of a single indoor outdoor reset acress the entire heating load.
What happens if you add a pump to a secondary loop?
So what happens if we add pump to the secondary loop? A secondary pump will establish flow in the secondary loop whether a balancing valve is present in the common pipe or not. In this case, we’ve installed a secondary pump that is generating 150 GPM of flow in the secondary circuit. Meanwhile, we still have just 100 GPM in the primary loop. Going back to the Tee Law, we know that you can’t have 100 GPM going in the Tee and 150 GPM coming out. So where is the other 50 GPM coming from?
What is the law of piping tees?
The Tee Law simply states that what goes in the opening (s) of the tee must come out the remaining opening (s). In other words, if you’ve got 150 GPM going into the tee, you’re going to have 150 GPM exiting the tee.
Is the Tee Law true in common pipe?
(Figure 4) Intuitively you may know this is not an ideal scenario in many situations and we’ll get into why that’s the case later in this series. For now, it is important for you to understand that the Tee Law holds true, even if it means creating a reverse flow situation.
What is a secondary circuit?
The secondary circuit is “hydraulically separated” from the primary circuit by the closely spaced tees. This concept can be extended to multiple secondary circuits served by a common primary loop: high temperature secondary circuit medium temperature secondary circuit low temperature secondary circuit.
What is hydraulic separation?
Hydraulic separation is a new term to hydronic system designers in North America. Primary / secondary piping, using closely spaced tees, is the best known form of hydraulic separation now used in North America. The secondary circuit is “hydraulically separated” from the primary circuit by the closely spaced tees.
Does a hydraulic separator prevent flue gas condensation?
Heat output is temporarily higher than current system load. Heat is being injected faster than the load is removing heat. Use of a hydraulic separator alone does not prevent flue gas condensation under all circumstances.
