Piping Questions

J.C.A._3

Where's the pressure reducing valve? Chris

Unknown

Piping Questions

Hi there, I'm a contractor in the Northeast. I recently installed a primary secondary system and placed the expansion tank and air separator just before the pump in my primary loop. The loop run is actually quite long so I had to use a fairly hefty pump to meet the requirements of the system. Now I find that although my static pressure is 12.5 psi, the pressure at the expansion tank goes to around 3 psi with the pump running. I know my air pressure in the tank is 12.5 so I'm wondering what effect this might have on the life of the bladder. Seems like I'm flexing it quite a bit. Any thoughts out there?

Thanks

m

Noel

Yes, your system isn't full of water.

If it was, there would be no air anyplace else in the system, and the pressure at the expansion tank would not change when the pump starts.

Noel

ALH_4

head loss

Sounds like you have quite a bit of head loss in your primary loop. What was the air pressure in the expansion tank before you filled the system? It may have been higher than 12.5 or it may have been zero from the factory. It doesn't sound like your expansion tank is working right to me.

Ed_26

pressures

I think we need some numbers/diagram etc.
pump size
primary loop length & size
boiler sizing
emitters/heat loss

Unknown

Thank you all. I'll have to get the numbers together but yes, it is a very long run. 12 gpm through 140 ft of 1" HePEX plus another 15 feet worth of head from other stuff. If I recall correctly it was 38 feet of head and the pump(s) are Taco 1100s. I'd have to look at the pumps to confirm that though. They draw 4 amps and are rated for 5. It contains 40% glycol. We sized it for 50%. I DO believe there is still air in the system because it keeps losing pressure over time. I haven't found any fluid leaks. It was completely tested with air to 60 psi for days prior to charging.

It is a pretty big system ~135 gallons all pumped away from the manifold. You wet heads would love it. 5 zones of floors including basement and garage slabs and 6 zones of hydro air. It's using chilled water for A/C. Mostly HePEX, very little copper. I'm heating close to 10,000 sq ft with 107* water at this point.

I'll have to draw and post a diagram. It is a little different. I used the pumps from the chiller/heaters to circulate the loop through the manifold and back. I did this to eliminate the primary loop pump. A drawing was submitted to the mfg of the units and approved. I find, however, that the secondary pumps add their pressure changes to the circuit which causes excessive pressures on the discharge side as well as causing the off cycle loop to circulate slightly. (Which I see as a benefit because these chiller heaters sit outside and it keeps the off circuit at temp instead of it reaching outdoor ambient.) There is virtually no heat loss in the off loop. A couple tenths of a degree. None of this is a problem except I'm worried about stress on the bladder. I did check and adjust the pressure to 12.5 before installation.

The units are Robur GAHPs. Do a search on them. I installed the first two in pretty much the Western Hemisphere, they were released in Europe two years prior to being released here so they have some field testing under their belt. They work pretty darn good too. I think they are the perfect type of unit to heat a radiant house. Drawback, they shut down below -4*F and above 120*F. so in either extreme they would need to be supplemented.

Unknown

Pressure reducing valve?

Unknown

Pump picture...

Here is a pic of the pump room. You can see the primary pumps in the back and the manifold to the right. There are check valves after the primary pumps and the secondary pumps are IFC.

Unknown

Diagram...

All valves are in place although not indicated. Fill is at expansion tank and kept closed. Check valves after primary pumps all secondary are IFC. Primary runs are 1" PEX / 1" copper. Manifolds are 2" and connector is 1 1/2".

Rumor has it Robur is going to allow the -4* parameter to be lowered to as much as -20*. They are testing right now. These gas fired units will pull heat out of the air down to at least -4 and give you a 100% efficiency rate at that outdoor ambient. They exceed 100% as the ODT goes up. These are NOT your grandpa's old R-22 heat pump.