Question about my heating system

Hi all, can someone explain to me what is the purpose of the pipe highlighted below between the supply and return? I was told that it shouldn't be there by a friend who is a plumber. The boiler is a Weil McLain Ultra model if that matters. Any ideas?

1st thing I did was try to grab and drag your picture to look at what's next the heater. I see a T&P to the left, so is there a hot water storage tank next to the heater? I see a grundfros recirc pump at the top and another black pump on the left pipe on top of heater.
That black pump I will presume is the main drive pump. It keeps the water flowing through the heaters heat exchanger while the burner is on. If there is a tank then that normally moves the water through the tank and the heater while heating. I'm familiar with Raypac and Teledyne Larrs.


Is this space heating?? Just noticed what looks like make up water supply in the back. I would have to look up some piping diagrams first before I could give a better answer

I'm back
This link for a manual looks like your Gas fired boiler. I was looking at an oil fired boiler but the connections looked wrong.

ultraboilermanual.pdf

#9 in my snapshot looks like your pipe in question.
I did not read into it much, maybe later.

Mr_David said:

I'm back
This link for a manual looks like your Gas fired boiler. I was looking at an oil fired boiler but the connections looked wrong.

ultraboilermanual.pdf

#9 in my snapshot looks like your pipe in question.
I did not read into it much, maybe later.

Click to expand...

Thank you for taking the time. To answer your previous question, yes there is a hot water heater next to the boiler. Let me know if you look into it some more.

Yardley said:

Let me know if you look into it some more.

Click to expand...

This I believe answers your question.