is this piped wrong? It's the opposite of Dan Holohan's pipe plan

PeteA

This web site just keeps giving me more work to do and it's driving my wife crazy LOL .
I was insulating the 1" iron pipe in the cellar and took a close look at the heating system piping layout in my house in Pennsylvania and the way it was plumbed seemed odd. I knew I had seen a nice simple drawing on this website for a split loop and pulled it up on my phone to compare what I was seeing to what Mr Holohan's drawing showed. Just for background it's not recent work, I've owned the house since 2018 and the previous owner had the old oil boiler replaced with a combi gas boiler.
All the near boiler piping looks very similar to many of the other combi boilers that I've seen so that part is not what caught my eye it was the direction the pump was pumping.
First mistake is that the pump is pumping towards the external expansion tank (the combi has an internal tank), the autofill does not seem to be working properly so I will leave the gate valve closed once the pressure is set, I have a new one to install and there's no back flow preventer at all fortunately I have a new one.
But even with all of that I also noticed the pump was pumping into the 1" line all the way to the back of the house and then it was split into a 1" x 3/4 x 3/4 tee which splits the left and right side of the house Burnham BaseRay cast iron baseboards. After the water courses through all of that radiation it returns through gate valves which I assume are for balancing purposes but they both see to be fully open. I do notice it takes a little longer for the left side to get as warm as the right side but I'll replace the gate valves with ball valves in order to make it easier to choke down the flow just a little bit on the right side.
Long story short should I put the circulator onto the 3/4 line and pump the system the opposite way and make the 1" the return like Dans sketch? I figure if I'm going to be fixing some stuff up I may as well do everything once I get started. Will it also make it easier to bleed any trapped air out because the flow may be higher through the 3/4 with the 1"as the return?
Attached PDF is Dan's pipe plan for a split loop and the picture attached is just a quick markup of his drawing showing my setup. All of the baseboards on each half are in series.

Jamie Hall

If it ain't broke, don't fix it. What you do want to make sure of is that the pump is pumping away from the expansion tank and the makeup water feed and air eliminator.

Robert_25

No need to replace the gate valves on the return lines unless they are leaking and you can't repair them. Tighten the left one down gradually until you have the system in balance.

If you want to pump away from the expansion tank, why not just move the circulator and/or airscoop & expansion tank?

PeteA

Jamie Hall said:

If it ain't broke, don't fix it. What you do want to make sure of is that the pump is pumping away from the expansion tank and the makeup water feed and air eliminator.

Thanks @Jamie Hall that’s what I was hoping but I wanted to be certain since whoever did the plumbing missed the pumping away from the expansion tank and basic air scoop stuff I wanted to be certain that pumping the water in reverse of the recommended drawing for that type of system  wasn’t going to create an issue that just hasn’t shown up yet.

EBEBRATT-Ed

Best practice is to pump away from the expansion tank (and the water MU should be connected at the expansion tank) if you have 2 series loops like you show it doesn't matter which way you pump.

Which end of the radiation has the air vents or bleeders (they should be on the outlet). You could do a lot of work and get 0 results if it works the way it is what will you gain?

realliveplumber

theres hundreds of thousands of boilers that are pumping toward the tank that are just fine. sure pumping away might be better, but its not the end all.

PeteA

Robert_25 said:

No need to replace the gate valves on the return lines unless they are leaking and you can't repair them. Tighten the left one down gradually until you have the system in balance. If you want to pump away from the expansion tank, why not just move the circulator and/or airscoop & expansion tank?

Thanks @Robert_25
I will definitely be rearranging those parts of the system to put them in their correct order. Just wanted to be certain that pumping into the 1” and splitting in the 3/4 pipes left and right wasn’t taking away from flow rates of going to cause me air lock issues at the end where it comes back to the boiler but I’ll make sure to put in a good set of purge valves.

PeteA

realliveplumber said:

theres hundreds of thousands of boilers that are pumping toward the tank that are just fine. sure pumping away might be better, but its not the end all.

Thanks @realliveplumber
I'm sure that you’ve seen a lot of set ups that work even though they kind of have you scratching your head.
i figure that since I’ve bought the parts for the obvious repairs that were needed it gives me a project to do when it’s quiet. I can make the piping a little neater while I’m at it.

PeteA

EBEBRATT-Ed said:

Best practice is to pump away from the expansion tank (and the water MU should be connected at the expansion tank) if you have 2 series loops like you show it doesn't matter which way you pump. Which end of the radiation has the air vents or bleeders (they should be on the outlet). You could do a lot of work and get 0 results if it works the way it is what will you gain?

@EBEBRATT-Ed that’s a great point. The bleeders are actually on the ends of the baseboard going away from the 1” pipe so I guess that using the 1” to send the hottest water to the back of the house was always the installers plan 

EBEBRATT-Ed

@PeteA

The usual method with a split loop is you come of the boiler with the HW and put a tee. One tee feeds 1 side and one the other. Then at the return end of those loops the two returns tie together and come back to the boiler with 1 pipe. Normally the balancing valves are on each return just before the returns tie together but it really doesn't matter. If you relocate the valve to the return put a tee with a drain valve between the balancing valve and the tee to purge with.