In boiler hydronic loops there are different ways to arrangement the piping depending on the budget at installation time and how efficient and balanced you want the hydronic piping system to be when the job is complete. Some piping arrangements require more pipe upon initial installation but easier to balance and provide even heat throughout all the radiators or baseboards. It is important to consult with a plumbing and heating professional before deciding which type of hydronic piping arrangement you want for your hydronic loop installation. They can show you the distinct advantages and disadvantages along with cost differences of hydronic piping arrangement for the structure where you intend on installing this system.
One Pipe Series Hydronic Loop
The One Pipe Series Loop uses less pipe than any other hydronic piping arrangement therefore it is less expensive to install the piping but you need bigger radiators or longer baseboards at the end of the loop because this part of the loop will have less heat. The radiators or baseboards at the beginning of the loop use most of the heat thus the reason for the larger radiators and baseboards at the end of the loop. There is also a larger temperature drop in this type of loop between the supply and the return versus other types of hydronic piping arrangements. The near boiler piping may need to be modified to prevent large delta T between supply and return.
Monoflow Hydronic Loop and Monoflow Tees
The monoflow hydronic loop is similar to the one pipe series except the main loop uses monoflow tees to divert the water to the radiators or baseboards. The main hydronic loop maintains a constant flow on a call for and the water temperatures for each zone are more even throughout the hydronic loop than the one pipe series hydronic loop. The monoflow tee is a special tee which needs to be installed at the supply and the return for each radiator or baseboard. This loop system is easy to zone but needs more piping and special monoflow tees for each separate circuit. Additionally, if not installed properly flow problems will occur in radiators and/or baseboards. It is really important that if you have a monoflow system and want to modify it in any way for an addition or other work that you consult a plumbing and heating HVAC specialist for this retrofit.
Two Pipe Direct Return Hydronic Loop
The Two Pipe Direct Return Loop utilizes more pipe than the one pipe series loop but all radiators and baseboards receive the same temperature of water therefore it is more even heat than in all the radiators and/or baseboards than the one pipe series loop. Another advantage of two pipe direct return loop over the one pipe series loop is that it can be zoned. Zoning gives you more control over where and when you want heat and this can save you money on the cost of heating. As with many hydronic loop systems the two pipe direct return needs balancing valves. The near boiler piping may need to be modified to prevent large delta T between supply and return.
Two Pipe Reverse Return Hydronic Loop
The Two Pipe Reverse Return Hydronic Loop uses more pipe than the two pipe direct return hydronic loop but the flow is more balanced and even than the two pipe direct return hydronic loop. All baseboards and radiators receive the same temperature of water so is the same as the two pipe direct return but an advantage over the one pipe series hydronic loop. The two pipe reverse return hydronic loop can also be zoned offering you savings on your heating bill by taking advantage of hydronic loop zoning and large pressure drop.
High Performance HVAC: Hydronic Piping Systems Information for Boiler Loops