HePEX - 1-1/4" through 1-1/2" hole

rossn

I have some Uponor HePEX that I am running through the mid-floor joists to radiant manifolds. The holes were drilled at 1.5" for the 1" PEX that was planned, and now there is a design change and I should consider 1-1/4" (1.375" OD).

The holes are in a good precision line, but the joists are doubled up, and invariably some of the holes drift a little before coming out the back side (most are fir with an LVL sistered on). The floor may flex a little over time, as well.

Would you run 1-1/4" or be concerned about wear or noise with heat cycling (which will be often)?

I have heard about lining a hole with hdpe (milk jug), but this is going to be pretty tight. It's about a 40' run, with an expansion joint in the center, and would be 1-1/4" on one side with the other side 1". Average water temp = 130F.

Jamie Hall

So long as the stuff will fit through the hole, should be OK. And not to worry about expansion noise (much), and the PEX outer coat is usually slippery enough. The HDPE shim is more for use with iron pipes -- and there it does make a difference.

MikeL_2

Re - drill the holes larger while things are wide open - as long as the larger diameter won't affect structural integrity. You can correct ranging by snaping a center line on the joists, and have a center mark on a template. We use plywood for our redrilliing templates.....

rossn

Thanks. I would think OK with PEX, but have nightmares of when I moved into this place, by which they had copper in the same place, and every time the hot water cycled through, it made lots of loud noises from being bound between the joists.

Any longevity/wear issues with the pex if it is rubbing a little? It is pretty tough stuff, but lots of cycles over the years.

hot_rod

Hopefully you are running straight lengths, not coiled pex? Even so it will not be perfectly straight and will rub. I would enlarge the holes and possibly add isolation bushings in the holes.

What does the tube manufacturer suggest? They usually know the best way to install their product in various applications.
Pex does grow in length as temperature changes, be sure to handle that or it will arc in the holes and cause noise.

Zman

I would be concerned with wear to the tubing as well as damage to the O2 barrier. A larger hole with slip bushing would make me sleep better...

rossn

I agree, and given I can't really expand the holes, I think I'll be relinquished to keeping to the 1". Yes, I am running straight lengths.

Even with 1" the plan was to flip the mickey-mouse ears outward, on both sides of the joists. I could probably minimize rubbing by doing this with 1-1/4", but it might be asking too much. Also, I am putting an expansion joint made of 4 elbows in the center for the projected growth (it's been a while since I calc'd it, but think expansion it was around 12" or so)

Maybe I am asking this the wrong way. The recent change would shift 12,000 BTUs to that branch, and that is increasing the load from 76,000 BTUs to 88,000 BTUs.

Everything is designed at AWT=130F, and DeltaT=20F. How many BTUs can I practically plan on getting out of the 1" PEX, which will have a little less flow than 1" copper?

Zman

If you screw or clamp a plywood jig to the joist, you can enlarge the holes with a hole saw. Not super fun but reasonably doable.

How long is the run? What other resistance in in that loop? What circ are you planning on. Unless you are going a long way, you should be able to shove an extra 1.2 GPM through the pipe.

EBEBRATT-Ed

You on the top end of the flow for 1" . You may need a slightly larger pump to get enough flow.

Larger pump could cause some noise issues

hot_rod

Lots of great calculators at the PPI site. Here is a flow example and an expansion calculator.

http://www.plasticpipecalculator.com/ExpansionArmLoop.aspx

Zman

I am generally comfortable with PEX up to 6 ft/sec as long as the run is not too long and the pump size does not get crazy. You sure are not going to wear out the pipe and I have found that noise complaints start around 8 ft/sec.

hot_rod

Zman said:

I am generally comfortable with PEX up to 6 ft/sec as long as the run is not too long and the pump size does not get crazy. You sure are not going to wear out the pipe and I have found that noise complaints start around 8 ft/sec.

Hmm, could be high velocity, high temperature, and chlorinated water causing the pex failures these days. Although they seem to be more in plumbing tube.
I think you are tempting fate with 6 fps, tube may be fine, short turn ells??
4 short turn ells in an expansion loop, excessive velocity, yikes.

rossn

Am I calculating correctly, that at DeltaT=20, we'd be talking 88,000BTUs/10000 = 8.8 GPM, or 4.7 fps? And, that is a number that could be scary to some?

Now, the other thing to note is that this 88,000 BTUs accounts for a few things, including a bonus 12,000 BTUs for future use in the garage, which would be intermittent use when working in the shop. And 15,000 BTUs in multi-use/gym area that will usually be kept cool, around 55-60 degrees in the winter (design room temp = 65F there). So, there is some extra fudge room in here, but I'd like to keep the available capacity at the end of the line, where possible. Real, living space dedicated BTUs are closer to 54,000 BTUs + some for the multi-use area running (at some interval).

The radiant guy that has been helping me out is unreachable this week, and I'm trying to get some work done on the project. He did mention the possibility of a hydraulic separator at the far end if more capacity is needed. To me, it seems like more cost, maintenance, and heat loss, if avoidable. At some point he mentioned up to 120,000 BTUs on 1", and I think he must have meant 1-1/4"; he's also suggested seeing if we can drop the DeltaT, which of course doesn't work in our favor for this issue.

Now, the discussion above on the expansion 'U' with 4 ells and velocity, got me thinking. I originally thought to have that in the middle of the run, though maybe I am better pinning the PEX at the middle of the run, and allowing the movement at the ends (one end mechanical room, other end where it makes a 90 before going through a chase. Could reduce to 2 ells. I know Uponor makes a pre-made u-shaped expansion joint for 2", but don't think they make it for 1" or 1-1/4".

What type of velocity would most be comfortable with, going through the expansion joint made of 4 ells? I didn't find a spec on the Uponor site, though they mention for AquaPex, something crazy high like 13GPM.

Other ideas?

In terms of other resistance, below is a rough depiction of the distribution in question. Except, the first manifold goes up by 12,000 BTUs. This isn't quite literal... the 1" run actually sits a few more feet to the north. There are a few turns and drop as it makes the angled turn at the right side.

Circulator is a Grundfos Alpha 2 15-55F. FWIW, everything will be on TRVs.

Zman

I stand by my 6 ft./sec comfort level. That little company that makes some tubing does as well. Their charts go to 8 ft./sec https://assets.supply.com/ul_pdfs/712593_ownersmanual.pdf
You also need to keep in mind that all the zones rarely call at the same time.

rossn

Thanks, Zman. I think between the fact we'd be talking 4.7fps (versus the 6 you suggest), and that practically (between TRVs, room use, variable speed pump, and outdoor reset - though maybe that drives up average velocity), I'm unlikely to frequently use design condition flow. I am probably fine as-is (if we ever flow full flow rate and there is some noise, it is probably only a few days per year)... and if I do have issues, I guess that's when I start looking at a separator or other reservoir. 1-1/4 would be better, for sure.

rossn

Anyone have other ideas on managing expansion and turbulence over that 40', beyond pinning at the center of the run or the 4 ell make-up?

psb75

I am currently working with 1-1/4" pex run as twinned underground (supply and return) heating pipe. I measured the i.d. as 1". The o.d. was 1-7/16" or 1.437". Just letting you know.
If you find yourself drilling holes for it--err towards LARGER holes i.e. 1-1/2" or even 2" ...if you can stand it--structurally.

hot_rod

It would be interesting to know how they make this 2" U loop, certainly it could be done in smaller sizes?

If you have enough space in the bay, just make a circle loop.
Here is a piece of 1" Viega FostaPex that I bent on the REMS Curvo

rossn

psb - good to know the OD is bigger than then 1.375 it is spec'd at.

hot_rod - thanks for the ideas, including the drawing showing the change of direction loop. Uponor advertises a bend radius of 6x OD, which would put us at 8.25 x 2 if I want to say in-bounds, and my joists are 16" OC, with extra sistering. Technically the 1" would also be too tight, but it seems it should be OK, and that 2" U they make certainly isn't 25" wide! Let me chew on the options.

Zman

40' of pipe should only expand about 5" with 100 degree delta.
Can you put a swing 90 at either end of the run?

hot_rod

would the tube be always turning in a swing ell?
I think with a loop it moves laterally to accept the expansion?
Looks like Viega Fosta has a tighter bend radius, if you use a bender.

rossn

there will be a turn at the far end of the run, of some sort. Initially it was slated to be a 90 degree drop into an 2x8 bay, so it would be end-to-end constrained. I have some other options to first 45 horizontally in the joist bay and then 90 down, though I'm not sure that would benefit us. I could do 3 90's to give that needed flex, but am not sure that helps much on the flow sie.

On the other end, it comes into the utility room... that end is probably less flexible in terms of movement, given it will turn roughly a 90 to the north 18", then 90 down. Alternatively, may be able to do a 45 on each one of those joints, but many not be as good for movement.

In both cases, is it if an issue if the expansion is inducing rotation of the 90 (versus an expansion joint pushing/pulling laterally on a 90)?

hot_rod

There is plenty of documentation and approvals on expansion loops. I have not seen any with swing ells? I'd check with the tube manufacturer if you are consider trying it. Get the approval in writing

https://up.codes/s/thermal-expansion-and-contraction

Zman

I was referring to something like this on either end.