Symptoms of a partially-clogged Hartford loop?

Precaud

Title says it all. What are some of the telltale signs of a partially-clogged Hartford loop, which IIUC is synonymous with a wet return? Especially after a burn cycle ends and condensate returns.

EBEBRATT-Ed

The only two symptoms I can think of is condensate backing up in the returns=water not getting back to the boiler...sluggish and possible hammering if it backs up into the steam main

Jamie Hall

Well... it would be really odd, for one thing. I'm not quite sure I see how it would get clogged, However, assuming it did get clogged, it would be much the same in some ways as a partially clogged wet return.

Precaud

EBEBRATT-Ed said:

The only two symptoms I can think of is condensate backing up in the returns=water not getting back to the boiler...sluggish and possible hammering if it backs up into the steam main

This sorta fits with what I'm seeing (without the backing up / hammering). Very slow and irregular condensate return.

A couple days ago I closed off the water valves on either side of the auto-feeder (M&M 47-2) in order to monitor system water use. Last night I watched the gauge glass for 20+ minutes (exciting, eh?) after the evening's last burn cycle before setback. I saw two things that bothered me: 1) after 20 minutes, the gauge glass water level had only recovered maybe 1/3 of the loss during the burn cycle, and 2) it was highly irregular, with occasional "burps", where suddenly the level would momentarily rise then drop say 1/2", and slowly recover from there. The only things I could imagine are that a) air was being trapped and then released, or b) the condensate returning was encountering resistance and having to seep or push through sludge or something to get to the boiler return, and did so in surges sometimes.

In the morning, water level had returned fairly close to the starting level noted the day before. But it took a very long time to do so.

I know for fact that it has been at least 30 years since the Hartford loop / wet return was last cleaned/flushed. Probably longer. It is #1 on the to-do list when the heating season ends.

Jamie Hall said:

... it would be much the same in some ways as a partially clogged wet return.

I thought Hartford loop = wet return? Aren't they synonymous terms?

Jamie Hall

"I thought Hartford loop = wet return? Aren't they synonymous terms? "

Not at all. The Hartford loop is the assemblage of pipe which starts (going backwards here) at the condensate return fitting on the boiler, then turns up 90 degrees to a point an inch or two below the normal water line, then turns horizontal an inch or two, then turns down to the wet return(s). The boiler equalizer comes down to it. It is part of the near boiler piping.

A wet return is any return line which is below the normal water line of the boiler. Some systems have very extensive wet returns. Some have almost none.

Precaud

Jamie Hall said:

A wet return is any return line which is below the normal water line of the boiler. Some systems have very extensive wet returns. Some have almost none.

OK, thanks. It appears my system is of the latter type. It's that pipe along the floor that I'm concerned about.

clammy

Loosen that cap and drain and hook a hose to the boilers boiler drain and flush some water through the boiler to that lower return pipe . Put a reducer coupling and ball valve w a hose adapter on where that cap is . Is a good thing to flush the crap out of not only wet returns but also the boiler block to ensure it not full of mud . Usually the wiser installer would have put a tee leaving access to return passage in the boiler so it can be properly flushed , I can’t tell from your pics if there s a tee there or not . Peace and good luck clammy

Precaud

Thanks @clammy , yes, at the end of the heating season I will flush it and add a ball valve there. For now I'm just trying to see if I'm understanding the symptoms correctly.

EBEBRATT-Ed

@Precaud
What do you have for air vents? Are you sure the vents are letting air back into the system? If the system is in a vacuum condensate will be slow to return.

If you have a tapping on the boiler above the water line you can get into you might stick a vacuum breaker or a swing check valve on it just for fun. anything 1/4" or larger just to see what happens

The fact the water line was burping makes me think it could be vacuum

Precaud

Hi @EBEBRATT-Ed , thanks for your thoughts. Yes, I can hear air getting sucked back into the vent of the radiator near me when a burn cycle ends, so it being in a vacuum condition didn't cross my mind. Lifting the pressure safety valve would break a vacuum, and it has no impact.

The weather is about to turn nasty here, the system will be running more, so I'll watch it more often for the "burps".

nicholas bonham-carter

Relieving the vacuum in the returns is the second duty of the main vents, as the recommended radiator vents are very undersized for that task.
Maybe you can unscrew the main vent, while the vacuum is strong after shutdown, and see if the water returns more quickly.—NBC

Precaud

OK, will do.

Precaud

Well I've been able to watch the gauge glass at the end of 4 burn cycles this morning, and I'm not seeing the "burping" again. Not sure what else to say...