Obstruction?

brazensol

I have a radiant floor heat system. One of the zones has 10 loops (covering the master bedroom, master bathroom, and master closet as well as an office and a guest bathroom). The two zones on the left of the manifold have no or very, very little flow. These two undoubtedly run to the bedroom as the floor farthest away from the manifold is cold and with the current cold snap (-20*F), needless to say the bedroom is cold. The valves on the return have checked good (swapped with zones that were working and verified the valves were good). My best guess is a kink or obstruction (air?) in the loops and was wondering if I could try purging them with compressed air and, if yes, what psi should I use? Any other ideas? I do not have access to the loops without removing the ceiling in my basement workshop and of course want to avoid this if possible. Thanks for any help offered!

Jamie Hall

If you can get access to both ends of the recalcitrant loop, I'd suggest trying to purge it with water under real pressure, like a hose, first -- see if you can get flow that way. Trouble with air is it is just as likely to blow past an obstruction as to move it.

DZoro

Like @Jamie Hall said, not only that but air maybe your issue of no flow. Hopefully not frozen.
D

brazensol

DZoro said:

Like @Jamie Hall said, not only that but air maybe your issue of no flow. Hopefully not frozen.
D

My workshop is below and the temp in there is 50* so shouldn't be frozen.

brazensol

Jamie Hall said:

If you can get access to both ends of the recalcitrant loop, I'd suggest trying to purge it with water under real pressure, like a hose, first -- see if you can get flow that way. Trouble with air is it is just as likely to blow past an obstruction as to move it.

I have access so just hook up a garden hose and use house pressure?

DZoro

Yes you can use house pressure. If you can flush the water into 5 gallon pails to see what the blockage is.
D

EBEBRATT-Ed

Or temporally try shutting down the other loops coming off this manifold and see if the cold loop gets more flow/starts to heat.

Possibly the run is too long for the pump you have

brazensol

EBEBRATT-Ed said:

Or temporally try shutting down the other loops coming off this manifold and see if the cold loop gets more flow/starts to heat.

Possibly the run is too long for the pump you have

I estimate the farthest run to be 200-225 feet. The next one would of course be even less. I shut down the other loops and still no flow from either of the two problem loops. Tried isolating both problem loops and seeing if there would be any flow but got none so if it's an airlock then the system pressure is unable to clear it. I have had problem with air in the system before so I think an airlock is the most likely problem (vs debris or kinked lines) and am now just trying to figure a way to clear it.

JUGHNE

Being frozen is still not out of the picture.
If you have had -20F and your room below is only 50F, is it possible the end loops near an outside wall are frozen.

The water pressure flow will let you know.

JUGHNE

Has this worked well in the past or just the -20F cold snap stop the operation?

brazensol

JUGHNE said:

Has this worked well in the past or just the -20F cold snap stop the operation?

It has been a problem since we moved in three years ago. Unfortunately we did not discover it before I put in the ceiling below in my workshop. I am hoping to avoid pulling the ceiling down by trying to clear the lines from the manifold. I am hoping it is just an air block (the two non-working loops are the first in line from the supply) and that the system pressure is not able to clear and just needs some additional oomph! to get them flowing again. This is why I was asking about using compressed air (I know it sounds counter-intuitive) but at least it would help to determine if the line is clear or if I have a kink or blockage from debris.

Jamie Hall

If those lines are anything close to horizontal, an air lock is not the problem. Sorry. It may reduce the flow. In fact, it may reduce it to the point where virtually all of the flow goes somewhere else -- if there is somewhere else to go. But if it is the only path, and your pump has a shutoff head greater than the elevation of the highest point on the pipe, and the only place the pump's flow can go is into that pipe, it will flow. Maybe slowly, but it will flow.

Hit it with household pressure water from a hose. If it's crud blocking it, it will flow. If it's frozen or, if it's never worked if it's kinked at some bend or other, game over.

brazensol

Jamie Hall said:

If those lines are anything close to horizontal, an air lock is not the problem. Sorry. It may reduce the flow. In fact, it may reduce it to the point where virtually all of the flow goes somewhere else -- if there is somewhere else to go. But if it is the only path, and your pump has a shutoff head greater than the elevation of the highest point on the pipe, and the only place the pump's flow can go is into that pipe, it will flow. Maybe slowly, but it will flow.

Hit it with household pressure water from a hose. If it's crud blocking it, it will flow. If it's frozen or, if it's never worked if it's kinked at some bend or other, game over.

I'll give the household pressure a shot as soon as this cold snap is over. Supposed to be back in the 30's on Sunday. Thanks!

JUGHNE

If your shop had some source of heat and you put a ceiling up that may have denied the tubing some heat to prevent freezing.

If that is the case, you could add grills to the ceiling to allow some air circulation from below. It is possible the outside sill plate is not insulated as well as it could be.

EBEBRATT-Ed

What @jughne mentioned in the above post is what I was also thinking. It doesn't take much cold air through the sill plate to freeze something