What are these pipes?

Question

This might not be the best place to ask, but here I go.  I am looking at a house that has old radiators (the cast iron type).  Can someone answer the following regarding the photo below:

1. Is the large white pipe the supply/return for the radiators?

2. Am I correct in assuming this is a hot water system not a steam system (maybe this picture is not enough to answer that question)

3. What is the knob looking thing that looks to be attached to an electrical junction box (right in front of the connection between the white and silver pipe)

Thanks.

Jeremiah O'Neill · Answer

Makes sense.   Thanks for the help.

Kyle Gregg · Answer

The building's sensible heat load will be unchanged so the existing boiler will be sufficient. The individual room's sensible heat load is whats changing. So if you're making one room bigger and another smaller, you'll have to increase the size of the radiator in the large room and decrease the size in the smaller room.

You can add radiators into the water loop but keep in mind if you add radiators to the system, yes those rooms will have additional heat, but it will be taking that heat from the rest of the system.

Hope that makes some sort of sense....

Jeremiah O'Neill · Answer

Great,  thanks.   Since you seem to have knowledge of these systems,  can I ask another couple questions:

1. I will be relocating and maybe adding a couple radiators to reconfigure some rooms, no added square footage.   Is it as simple as splicing into the existing water loop?

2. Seeing that I am not adding any square footage (in same total btu demand) ,  is it a safe assumption that the existing boiler will be sufficient even with 1 or 2 additional radiators?

Thanks.

Kyle Gregg · Answer

In my experience of designing boiler systems, the expansion tank is always on the supply line. So in your case, the large white pipe is the hot water return. Your system is a hot water system typically supplying water at 140 degrees. A steam system will not require an expansion tank.

I'm a mechanical guy and couldn't tell you what is sticking out that junction box.