IFC vs. Flow Control Valve

mowgs

Last summer I re-piped my boiler to be pumping away just like the book Pumping Away suggest. It works great and I've been doing it that way now whenever I get to do a boiler install. I especially love that I don't have to spend the evening waiting for all the air to purge on the initial fill now too. Great book! Anyways, when I did my boiler I got a new circulator with the IFC installed, and got rid of the old Thrush No. 114 flow control that was originally on. My boiler also has a domestic coil. You probably see where this is going. Basically my question is has anyone else had problems with gravity flow and IFC's? I plan on putting a flow control valve back on and taking the IFC (just an unnecessary restriction then right?) out.

mattmia2

Unless there is some debris in it there shouldn't be flow in that application. There can be another circulator creating pressure that opens it, but in a single circulator and a tankless coil you shouldn't get gravity flow if it is sealing.

hot_rod

Damaged or something stuck in it.
They have a conical face and a rubber seal, .35 psi spring holding them closed. It is what is know as a bubble free seal.

EdTheHeaterMan

mowgs said:

Basically my question is has anyone else had problems with gravity flow and IFC's? I plan on putting a flow control valve back on and taking the IFC (just an unnecessary restriction then right?) out.

Im not sure if this information is in the pumping away book, but there is a situation called ghost flow that you may be experiencing. You will find the explanation in this book. https://documentlibrary.xylemappliedwater.com/wp-content/blogs.dir/22/files/2020/01/FH-Z100B-BG-Zoning-Made-Easy-2.pdf

Starting on page 10

HVACNUT

Water quality is a concern with an IFC. If everything wasn't flushed well after you did the work, there could be residue built up in the IFC. It doesn't take much. Looking at them, I'm surprised they allow the GPM.
It's still easier replacing an IFC with isolation valves on the circulator, than dropping the pressure and getting pipe wrenches to open the top of a flow valve. 

hot_rod

It’s possible to have ghost or buoyancy induced flow in the return piping,a two direction flow. As @EdTheHeaterMan mentioned, a check in both supply and return is sometimes needed.

mowgs

I realized that I had a spare check valve for the circulator so I put that in and it seems to be working for now. I will say when I took off the circulator it was pretty black inside (see pic) and left a silvery black residue on my fingers. The check valve was also stuck in there pretty good and I ended up breaking it with pliers trying to pull it out, so that was a good time.

Thanks for all the insights, it definitely does not hurt to ask questions here!

mattmia2

What kind of system is it? If it is a converted gravity system or even if it is just cast iron radiators a dirtmag magnetic dirt separator would be a great idea to keep that stuff out of the magnet in the circulator. If it is mostly copper just some chemical cleaner and some flushing might do it.

mowgs

@mattmia2 it’s just a single zone series loop hwbb. The boiler is a non-con w/ a domestic coil.

After seeing the inside of the circulator I am a bit concerned as to what exactly causes it. You don’t think it’s just a result of not having to add water since I filled it last year? I know the oxygen in fresh water will react with any iron or steel initially but stabilizes after it forms iron oxide. Thanks!

HVACNUT

Cast iron? There are inhibitors you can add. 

mowgs

@HVACNUT Oh yeah sorry, it’s Slant Fin copper baseboard. The boiler is made of steel, and I believe the only other iron involved is the circulator.