Reverse return

Metrotown

Could someone clarify something for me? I have a simple baseboard heating system in my house with one circulator and four zone valves. All supply lines originate from a manifold and return to another manifold. The first supply take-off is connected to the last return on the manifold. My question is: Can we call this a reserve return system?

My answer is no. The reason being, the loops may have different lengths of piping which can affect the flow balance. Just because the supply and return pipes are connected first and last on the manifold doesn't guarantee an equal flow rate through the loops if their piping lengths vary. What are your thoughts on this? Thank you for your help!"

Jamie Hall

Reverse return has nothing to do with the order in which the supply and return pipes to loops or circulators are connected to the primary manifolds. Nor can it be applied to home run systems, where each radiator (or sometimes room) has its own supply and return brought back to central manifolds.

Rather reverse return refers to a method of piping a group of radiators in such a way as make the total resistance to flow the same for each radiator, thus making balancing a lot easier. This is done by having a supply line and a separate return line. The first radiator in the group has the first takeoff from the supply — but the last connection to the return. The next radiator the next takeoff, and the second to last connection to the return. The last radiator in the group will have the last takeoff from the supply, but the return connection is closest in piping distance to the boiler. Thus the total length of pipe starting at the boiler and going all the way back is the same fir each radiator.

Intplm.

@Metrotown

From your description, it sounds like you are describing a series loop system.

hot_rod

Got a pic? Does every heat emitter or a few have its own feed and return. Or are there a "series" of heat emitters on one loop.

PRR

https://www.pumpsandsystems.com/what-reverse-return-system

My answer is no.

Agree. Unless the manifold is long and tortured, taking tap "1" vs tap "3" makes about no difference.

It is different when running pipes or wires in streets, where there is a "long way" to go around. But 2 feet of 2 inch pipe won't be any "drag" on domestic heating.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1806723#Comment_1806723

Missing from that drawing is how the 450 gpm circ responds when only one zone opens?

Seems a delta P circ or pressure activated bypass should be in the discussion.

mattmia2

https://forum.heatinghelp.com/discussion/comment/1806723#Comment_1806723

If there were just pipe that would be the case but since there is a tee with a section of pipe it does make a difference. The water wants to take the first branch a lot more than it wants to pass the other 3 branches and take the 4th branch and the same is true of the return so it does have a moderate effect. The zone valves will balance everything out bu adjusting the length and frequency of the heat calls even if the manifolds didn't.