Making the proper connection

pch

Disclaimer: I realize that I may have shot myself in the foot with my layout - and aiming for the other one, but my options are limited by the parts I already have and the work already done.

I have 3/8" onix tubing in my floors: four zones with two 250'(approx.) loops each; one zone has 3 loops. I have a Watts four port manifold with zone valves to supply & manage the zones.

My plan is to run 3/4" oxygen barrier PEX (rather than PEX-AL-PEX because I can use standard PEX crimp fittings) from the manifold to several locations and connect it to a multi-port tee. The onix will connect to the outlets. But, how? I am in fittings hell. I have not been able to find a 3/4" PEX tee/manifold with 3/8" onix outlets, or a 3/4" PEX tee with 1/2" swt outlets so that I can use a 1/2" swt x 3/8" onix fitting, which I have. I have found a 3/4" x 1/2" x 1/2" CxCxC reducing tee which I could make work, but any better ideas? Or general modifications to my plan?

Thanks for your thoughts.

hot_rod

The least expensive may be a pex X sweat adapter and an Onix X sweat adapter. Then a regular pex tee.

Dig around E-bay or www search for these ZT fittings that Watts Radiant had. Basically drill a 1/2" hole in 1 or 3/4" copper tube with a Unibit, and solder on this "saddle" fitting. Use 97/3 or other hard solder.
They made their tubular brass manifolds with these for years before they bought T Drill machinery.
They worked very well.

They came in several Onix tube sizes.

I'd highly recommend Fernox or Rhomar conditioner in Onix systems.

pch

Bob, "hot_rod", thanks for the suggestions! I will probably go with the pex x swt fittings - less fabrication. Also, thanks for mentioning the conditioner. Does onix tend to get gunked up quicker that other piping choices?

mattmia2

Onix doesn't have an oxygen barrier so you have to design your system to be an open system either by using nonferrous components on the part that touch water that circulates through the onix or by using and maintaining oxygen scavengers or both.

hot_rod

Actually Onix does have an o2 barrier.

The first Heatway rubber hose was Entran "energy transfer" a fairly basic EPDM hose not unlike "heater" hose No barrier of any type.

When the EVOH, then aluminum wrap was added to the tube it became Onix Oxygen nix

That being said in some Onix installations there still seems to be excessive O2 getting into the systems?

pch

Whew! Thanks for the clarification, Bob! My heart stopped momentarily; I have 2,000+ feet already in my floors. I was sure I had read somewhere (Watts PR?) that Onix does have an AL layer.

That being said in some Onix installations there still seems to be excessive O2 getting into the systems?

Any suggestions on where to keep an eye out? Overall, my piping is/will be copper, oxygen-barrier PEX, and Onix; fittings are copper or brass.

EdTheHeaterMan

@pch Do you remember when Ed McMahon used to work for you guys at (PCH) Publishers Clearing House?

Or is this a different pch?

hot_rod

Just drain small amount of water in a glass every year 
or so to see what it looks like

It will be a bit rusty colored, dark  brown or black could indicate ferrous components are breaking down

A hydronic conditioner, Rhomar or Fernox can help protect all the components 

pch

Or is this a different pch?

My initials. I had them before Pub Clearing House: them 1953*; me ...um, older.
*Wikipedia

pch

Thanks "hot rod". Will do.

pch

Another connnection question...

My radiant system is (currently) powered by a Monitor MZ 25C boiler which provides a priority DHW mode. The water is stored in an MPI 150 liter (~40 gal) tank. I have been getting 'requests' from my spouse to provide a shorter wait time for hot water - which is sometimes >30 sec + a big waste of water. So, I want to add a recirculation pump. In anticipation of this, I installed return pipling when I replaced the existing pipes during remolding of bathrooms and kitchen a few years ago. (House had been converted to 4 apartments in the 1950s, we are returning it to a single family home, so remodeling has been extensive - and on-going. 😕 )

Tank hydraulic connections :
1. Primary inlet - boiler supply
2. Domestic hot water supply outlet
3. Recycling
4. Primary outlet - boiler return
5. Domestic hot water supply inlet



All of the connections are in use as described, with the exception being #3 which currently holds a relief valve. The notation on the tank for that connection reads, "Recyl". Every piping diagram I have seen is oriented to a hot water heater and shows the recirculation pipe attached to either the cold water input or the drain down outlet. I can connect my recirc. pipe there as well, but I am confused about the #3 label. I have spent hours on 'the google' searching for some sort of instructions, but have not found any. Can anyone shed some light on the proper way to hook up the recirc. - or at least provide a believable answer so that I can move on. 😂

pch

Clarification... The MZ manual also shows the BS indirect water tank port configuration and says,

Pressure-temperature relief tap and/or DHW recycling circuit tap.

I do not understand how it can be both. The PT valve sensor is inserted into the tank, right? How are the two things combined? Am I really this dense? ... yes, unfortunately.

hot_rod

You can add a tee on that port, just make sure the probe on the relief valve reaches down into the tank a bit. Is it a metric thread however. that will complicate things.
You can but T&P valves with probes up to 12" I believe.

Are the recirculation lines insulated? If not they are a hydronic loop so the boiler will run more often to keep that loop hot.

You may want a timer or demand type control.

Controls can be from mild to wild. On/ off switch, thermostat, timer, motion sensor, switch built into bathroom door. Smart recirc pump that attempts to learn your usage pattern, or any combination of these.

pch

I have a limited, but working understanding of NPT and BSP pipe threads. So, for example, I understand that an R20 x some_size has tapered threads with a count of 20 threads per... A G20 would have straight threads. My Watts manifold seems to want T20 fittings. I have no idea, nor could I find any explanation, of that designation. I don't know if I can substitute a non-Watts fitting or not. I have found T20 3/4" x pex-al-pex comp. fittings at about $50 a pop. Seems steep, so I wonder if there is a less pricey alternative.

pch

Just found some more info... They are BSP threaded fittings. Still not sure what the T20 designation is. However, I did find them for about $25 each. I can live with that.

hot_rod

I would guess the top of the tank is a 3/4 or 1" G thread. Basically the same diameter as NPT but no taper. The seal is made with a fiber gasket typically.

Manifold connections are typically a conical connection. Tapered with an O ring as the seal.