Pex Expansion Damper?

Jim R.

Is there a PEX springy-thing accordion-type damper that will accommodate the linear change in length? I don't have space to make a U-bend which I've seen elsewhere.

My baseboard to panel radiator project has gone well except for one major thing: PEX expansion. I have a reverse-return system with the lines boxed in along the wall. Tee's go up to the radiators which leaves very little room for linear movement. About 60' of 3/4 pex total secured with clips about every 24".

Most of the pex is covered at this point except for connection points and the ends where it ties into copper. Is there anything I can do? I'm worried the expansion/contraction will wear on the fittings. I wanted it quiet so I used clips to keep tlines from touching each other or the wall. Should I have left it loose to allow for movement? I used black 3/4" straight lengths from Viega I believe.

In this pic, I planned to put two more clips but I don't know if forcing it to NOT move is the right thing. To the left is copper pipe going into the floor (no movement) and to the right is a tee into the radiator. Pipe gets water up to 180 degrees. Ugh.

Jamie Hall

You don't have to worry about wear on the fittings. They won't. The movement will be in between fittings. If you have as much flex opportunity as you show in your picture pretty much everywhere, you should have enough flex to take up most of the expansion and contraction, if not all of it.

hot_rod

If you can limit the temperature swing, and supply the lowest possible temperature that will help greatly with temperature induced expansion noise.

Ideally, with a properly dialed in outdoor reset control you could get ideal comfort and virtually no noise.

Do you have TRVs on the radiators?

Insulating the pex can help, easier to suspend and prevent ticking, expansion noise.

Jim R.

There isn’t that much room to expand because with the baseboard on, the pipe can’t push out like that. Should I put two clips on as planned and see if it still buckles out? If it doesn’t, where is the expansion force going?

Have TRVs on the rads but no outdoor reset. I have a Buderus and wanted to do a logmatic but it’s $1000 just for the control. Not sure it will ever pay for itself. Ultimate plan is to get solar panels and an air-to-water heat pump but that’s years off budget wise. Every year I talk myself out of ODR because of the different types of zones (DHW, radiant w/ mixing, baseboard, panel rads). So not sure.

Jamie Hall

If the PE is restrained at the ends, it will buckle out to the sides (or up or down --whatever is easiest). I would use the minimum number of clips possible, at the maximum distance between. The longer the distance is, the less it will deflect to one side -- so I'd keep it to what is needed to keep it sort of tidy and sort of out of sight.

ODR or more constant temperature circulation would minimize any noise, that's true -- but not minimize the expansion between what it's running at on a cold day and what it is running at when it's warm out.

mattmia2

There are copper expansion joints if you can't figure out a way to snake the tubing to be able to move.

GroundUp

No, there is no such thing as a pex expansion joint. You can restrain pex as often as you like to keep it straight, just make sure it's anchored near any fittings. Think of a radiant slab, for example. Everything is embedded in concrete and has no way of expanding- it lasts decades like that. Nothing to worry about

ChrisJ

From Uponor's documentation.

Their expansion compensating devices are in how a system is engineered rather than being an actual device.

Retired_guy

Mattmia2 is right. A copper expansion joint fitted with PEX connections. A boiler reset such as Tekmar will help reduce the expansion until you need warmer water on peak days. The above Uponour example doesn't discuss the water temperature of a heating system with radiators vs. domestic water temp.

Paul Pollets

All controls are expensive. If you've sized the radiators larger to run at lower temps, OR and TRV's will give you the lowest operating temps and lowest fuel costs. The boiler also lasts longer when run at lower temperatures. I'd worry less about PEX expansion in this case, and try and put a control on the system.

ChrisJ

Retired_guy said:

Mattmia2 is right. A copper expansion joint fitted with PEX connections. A boiler reset such as Tekmar will help reduce the expansion until you need warmer water on peak days. The above Uponour example doesn't discuss the water temperature of a heating system with radiators vs. domestic water temp.

No,
It says to use a loop to allow movement. I do not think it needs to discuss water temperatures.

Steam piping is run similar, with one end allowed to float to an extent and it's very important when designing either system.

I'd love to know what actually happens with pex buried in concrete tho.

mattmia2

ChrisJ said:

I'd love to know what actually happens with pex buried in concrete tho.

I would assume the id gets slightly smaller since that is the only direction it can move in.