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snap/banging sound from PEX, doesn't keep up on cold nights upstairs (16 Posts)
snap/banging sound from PEX, doesn't keep up on cold nights upstairsI've got two issues with my in-floor heat. First, a quick
Boiler = Slant Fin Concept 21 cast iron
Tubing = In concrete PEX in basement (3 zones), PEX stapled to two zones on 1st
floor (mix of carpet, tile, and hardwoods), PEX stapled to single zone on 2nd
floor (all carpet)
One zone for hot water storage tank, another zone for 2nd floor baseboard
heater in play room, another zone for outdoor driveway melt system (that I
Plumber has told me that the mixing valve to my PEX / lower water temp zones
appears clogged/broken because unless we open a bypass valve, the lower
temp/PEX zones don't heat up good enough. Temporary workaround has been to open
that bypass valve bringing the ~185 degree water into PEX. I wonder if this is
damaging my PEX?
Now my two (possibly interrelated) problems:
(1) Snapping and banging sound
All above grade zones with PEX stapled to the floor do it. The upstairs zone
where our bedrooms are is the most annoying, as it wakes my wife and I up when
the heat comes on. It starts about 3.5 minutes after the thermostat calls for
heat and gets even louder around 4.5 minutes until quieting down a few minutes
later. I'm assuming there is a manifold feeding multiple PEX loops on the
upstairs bedrooms zone since the square footage would certainly exceed 300' in
PEX tubing and there is a copper pipe running up from the boiler room in
basement (whereas the bedrooms are up two flights of stairs from the basement
on the second floor). The noise is louder on the side of the rooms where this
manifold should be - not sure if that
helps point to a certain diagnosis or not
I pulled a can light out from the ceiling below to try and look at the PEX
install and found NONE! This was a bit concerning to me, but there is ducting
between those two joists for an air exchanger and a local plumber told me that
run might have been skipped for that reason. I then cut a hole in some drywall
and found the PEX stapled fairly tight to the floor and then run through the
steele joists with some foam material wrapped around it at that bend through
the joist hole. The PEX seems pretty tight, meaning there isn't much play on
that loop through the joist.
(2) Heat doesn't always keep up
I live in Northwest Colorado. When the temperature drops below about 4 F, my
bedroom zone heat won't maintain the 71 degree set point on thermostat. It will
drop to between 66 and 69. I have foam core insulation in the house but the
bedrooms do have high ceilings (vaulted from about 8' to ~12' with only
insulation between the interior ceiling and roof...no attic space). The other
zones seem to keep up ok, so I'm not sure if I should expect to maintain a 71
degree inside temperature when it's below 0 out or need to lower my
expectations. One plumbing company's owner suggested there might be air in the
lines, causing the upstairs zone to perform poorly, and suggested bleeding it
all out. However, when his actual plumber arrived to do the work, he didn't
want to waste my money because he said if there was air in the system, he could
hear it in the boiler room and the return pipes would likely be colder due to a
blockage (whereas they currently feel pretty much the same temp as
supply...although no exact temperature measurements have been taken). He also
didn't replace that bad mixing valve because it is directly connected to the
piping without a turnoff valve or anything and would require bleeding the
entire system. He thought I might want to think about outdoor reset and
variable temp/injection system etc. instead of just replacing the mixing valve.
The third bedroom upstairs furthest away from the main line
up from boiler also runs about 2-4 degrees cooler than the room with
thermostat. The room is about 25-35 feet away from where the main line comes up
from the boiler...so not sure if this is normal heat loss on the end of the
line or not.
I've read several forum threads about snapping and banging sound. I'm assuming my staples are too tight, like so
many others. However, I don't have much of an appetite for replacing $3-6k
worth of ceiling sheetrock and am looking for alternatives like the outdoor
reset and variable temp system. I have a home warranty that approved
replacement of the mixing valve, but I'm wondering if I should replace it with
the outdoor reset and injection pump instead (since my boiler is cast iron) for
a few more bucks. The plumber tells me that the outdoor reset system would require significant re-piping based on
how my system is currently setup (see pictures below).
I've seen several recommendations on this forum to try an
outdoor reset instead of tearing down sheetrock - with the idea being to try
and have constant, variable temperature water flow through the PEX to lower the
noise impact. This makes sense to me in that the expansion of PEX would happen
very slowly instead of such a sharp temperature increase, but the plumbing
company I've been working with doesn't think this system will lessen the noise
much. They claim the outdoor reset varies the temperature throughout the season,
but that on a cold day the system would still either be on at full blast (ie.
~160-190 degrees) or off, still causing a loud noise when the room temperature
pipes get heated up. I thought the variable temp / outdoor reset would slowly
ramp up to ~160 degrees instead of going from room temp to that high temp. I'd
like some clarification on this.
If I can fix the noise with an outdoor reset, that still leaves the heat not
keeping up on cold days. I'm assuming that if I did pull down all my sheetrock
to loosen the staples, I could solve two problems by using heat transfer plates
for lessened noise and better heat transfer. Short of doing that, I'm wondering
if there are any other options to look into or if I just need to lower my
Many thanks for any insight. If I can provide any additional
pictures or other information, just let me know. I'm happy to upload a video or
sound bite of the noise, but in another thread I noticed that got deleted by a
moderator, so didn't want to break any rules.
wow... long post.Is there insulation? how much? Was there a heatloss done? How long are the loops? What do you have for tubing? O2 barrier pex? What do you have for a boiler?
I'll take a crack at it....Am I correct to assume this is a new install? 2nd problem first.
Heat not keeping up could be a result of many thing:
1. You say you have a manifold upstairs. Are there flow meters on them? This would help diagnose flow problems.
2. Do you have any diagrams of the design, loop lengths, heat load/loss, btu requirement, etc? Was carpet considered in the design?
3. On the staple up zones, any aluminum transfer plates? This could be the bulk of your problem, necessitating ta need for a higher water temp, but not185 degrees.
4. Bleeding needs to done properly, loop by loop, zone by zone.
5. We're the joist bays w/staple up insulated properly?
Although constant circulation could help, there's most likely an installation problem. Something is too tight. Installer should have got system up and running before drywall finished, if possible, to check for this problem.
But overall, you paid a lot of money for your system, and rather then have the original installer trying to fix it with ideas that won't work, I would get a radiant consultant in there to go over everything, and make recommendations the original installer should correct.steve
this is an existing installI bought the house from a bank (foreclosure)...so it's not a new install and I can't talk to the owner nor do I have any diagrams of install etc. The house is about 9 years old. I have inspected several places (by taking out a can light from the ceiling and looking around between the joists) and don't see any aluminum transfer plates...so I can only assume it's purely staple. There is insulation above the ceiling sheetrock and below the PEX. Not
sure of it's exact R-value but it looks to be the typical yellow
insulation...not extremely thick, not too thin either. I'm not exactly sure of the PEX type but could look into that more if it's important. I'm not sure if there are flow meters on the manifold as everything is
covered in sheetrock. I'm not even sure there is a manifold except that
two heating co/plumbers have told me there has to be a manifold
otherwise the loop would be so long it would never heat up enough.
I'm not aware of any heat loss calculations done and so far none of the three plumbers/heat guys I've had come look at it even mention that...which concerns me. I'm assuming the three basic options for remedying an underperforming system are the transfer plates, more insulation, and/or a larger boiler (with the first two all requiring a large drywall bill)?
description of picturesQuick description of what you see in the pictures in case that helps...
Far Left (#1): Rotate this 90 degrees counter clockwise and it will be the view looking in on boiler room. Upper manifold is return, lower supply. To the right (bottom of pic) is the outdoor snowmelt system which I'll never use (afford).
Far Right (#3): Rotate this 90 degrees and you see the three pumps. Top (far right of pic) and mostly cut off is the main Taco circulating pump. The other two (in middle) are for the med temp and hot temp zones. In the bottom left third of this pic is the mixing valve which I'm assuming is clogged because the heat won't work well unless I have the bypass valve (just above and to the right of mixing valve in this pic) open.
and what about an outdoor reset?Is the plumber correct in telling me that he'd have to re-pipe a bunch of the stuff toward the boiler side of these pictures in order to do an outdoor reset? I don't quite understand why, as it seems like a different mixing valve could be used that is controlled by outdoor temp...and the mixing valve could simply let in more hot water in the cold winter days and less in the warmer spring/fall nights.
The main issue...Is the lack of heat transfer plates.
Adding outdoor reset can be accomplished by adding motorized or electronic valves and should not require major re-piping. This would probably reduce the majority of the noise, but would not increase the heat output in the areas that are lacking. However, your comfort may possibly be increased by the longer run times with a more balanced water temp. Maybe. No guaranty.
Putting a larger boiler in will not do any good unless the present one is under-sized. Putting more logs on the wagon isn't gonna do any good if the mule (piping) can't carry the load now. You need to do a heat loss calc.
I would recommend that you look elsewhere for professional help. The three "heat guys' that you've had are not.
Mark Eatherton is in the Denver area and you won't find any better. Maybe he can help or direct you to someone who can. His foot prints are all over this site.Bob Boan
You can choose to do what you want, but you cannot choose the consequences.This post was edited by an admin on January 31, 2012 12:28 AM.
more concise questionsI tried to provide as much detail as possible about my current system but realized my questions are not really questions as much as they are run-on sentences :) Here's a better attempt:
QUESTION 1: Is a "too tight" staple up system with PEX running any risk of damage to the system, like the PEX rubbing so much it starts to leak, or is it purely going to cause the annoying noise? This would change my interest level on spending the money to rip out the sheet rock and correct this issue.
QUESTION 2: Based on the pictures provided (I can post more if needed)...does it appear that my mixing valve could simply be replaced with one that connects to an outdoor reset? I'm calling more heat specialists today...but I'd really like to confirm or deny the other company's claim that major repiping would be required to add this option (and another plumber stating that it isn't even possible since my boiler is cast iron).
QUESTION 3: Would and outdoor reset and new mixing valve connected to that run variable temperature even on the colder days? In other words, anytime my heater isn't running all night at full blast (because it's so cold out)...would it slowly ramp up to ~160 degrees anytime it came on, or would there still be times when it goes from ambient room temperature to ~160 all of the sudden. If it's the former (slow run-up), I can see how this would drastically decrease my noise problem.
QUESTION 4: Are my expectations realistic about keeping my house at a comfortable 71 degrees, or will any house dip a bit on the ultra-cold days? One heat contractor says the later. The house is in Northwestern Colorado with 2,400 square feet above grade (and ~800 in basement that never calls for heat because it stays above 62, my set point down there, by just the heat coming out of boiler room), vaulted ceilings throughout the top floor but with foam core insulation, steel frame, and stucco exterior in Northwestern Colorado. I know a heat loss calculation is desired, which I'm going to demand from my next contractor, but I'm just curious if 71 is "too warm" of an expecation.
MANY THANKS again to everyone! I realize the Internet is not a substitute for a good local contractor/expert, but so far my small town hasn't produced someone who can give me consistent advice, so I really appreciate validating things off the larger community here.
answers1. yes, staple up systems can chew through pex over time. one of the many reasons this install method has fallen out of favor.
2. it would be good to know why that valve is not working. can't tell from your pics what the issue might be. IF the valve really is clogged and not piped incorrectly then you could replace with a motorized valve, yes, but it would only serve the same areas that valve serves, which I would guess is slab only? at the very least you'll want 2 temps if you are doing slab radiant and naked staple up pipe, so you won't do this from one valve, most likely.
3. if the reset curve is set properly you'll have close to constant circulation in the "lead zone" for each water temp nearly all the time.
4. it's highly doubtful you're going to maintain 71 with plateless system. but it's possible.NRT.Rob
my two zonesMy two water temp zones are:
(1) HOT water directly from boiler: feeds the hot water storage tank, driveway snow melt system (that I never use), and a baseboard heater in a play room.
(2) less hot water that is supposed to go through the mixing valves serves all other zones, including basement and all the staple up floor areas.
I'm not worried about the basement, as it stays very comfortable purely from being below grade and getting the heat coming out of boiler room.
a little bit more info...I've gotten a lot of advice from people so far as well as a few more questions. Attached is an attempted panoramic stitch of multiple images from my very tight boiler room, including some labels on what is where.
One contractor that came by today though it was weird that the mixing valve is 3'4" pipe whereas the three pipes connecting to it are ~1"-1.25" piping. He thought that might have just been a cut corner to save cost but I'm curious if there would ever be a reason to do that.
He also mentioned zone valves that open up gradually and could possibly help alleviate the noise to just my bedroom zone (allowing the PEX in that zone to heat up slower, making the PEX expand gradually and hopefully lessening the noise). I'm curious if anyone has had success with that approach.
Another suggestion was to replace that mixing valve with a 4-way unit
connected to outdoor reset to get variable water temperature running
through what I call "Group 2" (PEX zones).
mixing valve sizeIn inches does not have to match the size of piping connected to it. When properly sized for full authority (Cv) it can sometimes be a smaller nominal size.
large tempering valvesare very, very expensive. small ones like you have are very restrictive. lots of tradeoffs.
slow acting zone valves will not help expansion noises appreciably. might make some difference.
I have to admit I still can't follow your piping to tell if the 3 way valve is piped in properly. bit of a nest in there...NRT.Rob
heat is now keeping upProblem was simple - one of my pumps was going out and wasn't circulating good enough. Now the heat keeps up!
InterestingThis should have been apparent from the return temperature on that zone. Flow issues always show up as too high temperature drop through the branch. But you have to measure the branch return temp, not the system return temp, in order to detect this.