Hot water heat piping layout

RonABC_2

I am in the process of moving and replacing hot water heating pipes in a small property I own that has 3 apartments, each with its own gas boiler and separate hot water radiator heat.  Each apartment has 4 radiators.

My access to the pipes is in the basement where the gas boilers are located and where the piping is up toward the ceiling.  The main reason that I am doing this is so I can raise all of the pipes in the basement up higher to create more ceiling height.  Most of the existing pipes are iron, but I will be replacing all of them with copper piping.

What I noticed is that the piping system layout for the 3 systems are all different.  I found a website with examples of the different piping arrangements at:

<a href="http://highperformancehvac.com/hot-water-boiler-loops#two_pipe_reverse_return">http://highperformancehvac.com/hot-water-boiler-loops#two_pipe_reverse_return</a> 

One of the existing systems is set up as a one-pipe series loop with all  baseboard heating unit fed in one continuous series.  The second existing system is set up as  monoflow hydronic system with each radiator teeing off of the same pipe.  And the third existing system is set up as a two-pipe direct return system where each radiator gets a supply form the supply side pipe and then returns to a return side pipe.

When I do the new connections, I would like to do them in whatever way would be best.  I'm sthinking either the two-pipe direct return or two-pipe reverse return setup (as shown on the above link) would be the best.

I can easily do the two-pipe direct return setup for all three systems.  I am not sure I understand how I would do the two-pipe reverse return system since I can't quite visualize how I would do that in real life as compared to the schematic diagram. 

Am I correct in assuming that either of the "two-pipe" systems shown on theabove website link would be better than either the one-pipe series or monoflow hydronic system?

Als, is there much of a difference between the two options for the "two-pipe" system in terms of performance and efficiency?  

Charlie from wmass

Reverse return is best

then mono flow then direct return is last choice. I would if it was easy enough to do leave the reverse return, raise the monoflow system and repipe the direct return to one of the other two. probably revers return when the cost of mono flow tees are what they are today. Or for a third thought do a pex home run system to a manifold at each boiler and install trvs on the radiators.

TonyS

The problem with

Loop systems  and monoflows is that each consecutive radiator receives cooler and cooler water which is no problem if the radiation was sized for the lower water temps.

If the systems were originally gravity, they were not sized this way. They were sized to receive equal temperature water. If you pipe with a 2 pipe direct return you will have uneven flow, because water like electricity is lazy and will look for the path of least resistance, this can be corrected using TRV,s. If you use a 2 pipe reverse return the water must flow through equal lengths of pipe no matter which radiator gets water first, this usually sets up a balance with no further attention even if the radiators are different sizes.

To visualize a two pipe reverse return put your hand on your return at the boiler, now follow the return backward away from the boiler until you get to the first T. Remove the piping between the T and the boiler and plug the T where you removed the piping. Now continue following the return all the way to the end, usually there is a 90 that comes from the last radiator but sometimes you get lucky and there will be a plugged T. If there is a plugged T remove the plug install your adapter and head back to the boiler return where you removed the piping. If you have 2 sets of mains...do it twice. The piping arrangement is easy but the problems are usually with the stubborn 100 year old pipe and fittings. Since you are going to replace the piping anyway this is probably the best way and you can still use some well placed TRV,s anytime you want.

RonABC_2

Hot water heat piping layout

Thanks.  All of the piping for the 3 systems has been removed, so I can do the new piping however is best.  I think I'll skip trying the PEX option, but I'm working on getting all 3 to a two-pipe reverse retrun setup.

RonABC_2

Hot water heat piping layout

Thanks.  I really appreciate you taking the time to explain all of this.  I think I "almost" get how to do the two-pipe reverse return system, so I'm going to try that.



The supply and return pipes coming from the boiler are 1-inch copper.  I am assuming that I can run the supply loop with 1-inch copper pipe, and then use 1/2-inch copper pipe to tap off of the supply to each radiator.  The same is with the return pipe -- my plan is to use 1-inch copper pipe for the return loop, and then use 1/2-inch copper pipe from the return side of each radiator down to the 1-inch main return pipe.



The way that I am thinking of it is to run the 1-inch supply loop in one direction going from the boiler to the first radiator, then the second radiator, then the third radiator, then the last (4th) radiator.  Then run the return loop in the reverse direction -- meaning from the return side of the boiler to the return side of the 4th radiator, then to the 3rd radiator, then to the 2nd radiator then to the first radiator -- and stop there.



Dose that seem to make sense?

 

Am I correct in assuming that the supply and return loops should be all 1-inch pipe, and the taps/tie-ins from each radiator to the 1-inch supply and return loops can be 1/2-inch pipe?

Charlie from wmass

pipe size increases and

decreases as the heat load is shed. the main supply pipe at the last radiator may be 1/2" and this is off a 3/4 x 1/2"x 1/2" tee at the second to last radiator which is fed by a 1"x 3/4" x 1/2" tee fed by a 1 1/4" x 1" x 1/2" tee at the first radiator. The tees are in the opposite order for the return piping. depending on load you may be able to stop at 1" but without knowing the exact numbers this is a basic layout.

RonABC_2

Hot water heat piping layout

Thanks.  I mostly wanted to be sure that it is okay to have the pipes going to and from each individual radiator be 1/2", and have those 1/2" pipes tie into the main supply and return loops.  In my case, the main supply and return loops will all be 1", although I see from what you wrote that I could have the supply loop step down in size and the return loop step up in size.  The supply and return pipes at each boiler are already 1", so I am asuming that nothing could be gained by using anything larger than 1" anywhere in the piping system.

Charlie from wmass

Not quite true on pipe size

Pipe size needs to be determined by BTU load at each radiator. You need to do a heat loss and determine if 1/2" will work. Also system size is not dictated by the boiler piping size but by the system requirements. Why pay for 1" for the whole loop when smaller could work?

RonABC_2

Hot water heat piping layout

Thanks again.  I am sure what you are saying is correct, and I do know that the way that I am going about doing this is not exactly the best approach.  But, I think it will be close enough.  The 3 exisiting systems were working okay the way they were originally set up (one was a 1-pipe series loop, one was a monoflow hydronic loop system, and one was a 2-pipe direct return system).  I think that by converting all 3 to a 2-pipe reverse return system will be an improvement over what was already there, and since it is a small area (about a 25' by 30' basement), the amount that I could save in the cost of pipe by trying to be more exact in the sizing along the loops would not be that significant -- maybe $200 +/-.   So, I'm going to go with that and hope for the best.  I already have all the pipe and fittings and started the reconnecting of the new system yesterday and should probably be done by today or tomorrow morning.  I chose the 1/2" pipes to each individual radiator off the loops because each radiator now already has 1/2" pipe going in and out of them.