AA130 - Circ Pump Question...

When I isolated last evening to add the gauges, the pressure at the coal boiler dropped from 30 psi to 15 psi. I vented after adding the gauges to be sure that the air trapped was out of the system. I did get a little but not much.

I bought cheep gauges at Home Depot... went against my better judgement and bought Chinese junk. So, the gauges 12" apart with the circ pump off were reading about 4psi differential. I will be installing better gauges this evening so I don't leaad myself down a rabbit trail without the rabbit.

Pressure at the pump was around 18 psi with the pump off. Pump suction dropped to 15 when turned on.

Is it possible for the pex-al-pex to delaminate? I'm grasping at straws here but I cannot think of anything that would cause this amount of resistance in the system. I have only four valves in the system and they are all in the photo previously posted... full flow ball valves.

I have the list of piping and fittings along with the equivilant lengths at home and will post later this evening. I tried running a claculation but there's a couple things I don't know how to deal with in the calc.

Thanks for the input guys.

Tom

Oh and the safeties I just replaced and are set at 30 psi. The one at the coal boiler dripples occasionally due to running just below the seat pressure.

Safety valves per ASME standards start to lift at 10% below setting. This is why you are getting weeping at the valves. Re-adjust the fill valve to 10 to 12 psi which is more typical for your installation. Otherwise, you will run out of expansion tank capacity when the system gets hot. With the additional volume the new piping and boiler added to the system, you may still need to check your tank size.

A tip on the gauges may be to install small gauge valves and use one gauge and move it between the taps. If you want, pipe the two valves to a tee with the gauge in it and open one valve at a time to read pressures. "A man with one watch knows what time it is. A man with two watches is never really sure."
The point being your pressure readings only need to be based on differential, and if your gauge calibration is off, using one gauge will compensate for the error.

I am concerned about how much force it took you to pull the pex into the pipe and the radius of your bends. I have pulled regular pex though conduit with considerable effort. Pex-AL-Pex is resistant to bending and running it around two bends had to be difficult. The aluminum keeps the pex in the last shape it was bent to. I don't know about delamination but I think it may be possible you kinked or flattened the pex in one or more spots. I know this is a really, really bad thought.

I'm trying to stay positive... but the bad thoughts are crossing my mind..

When I layed out the underground run I tried to think through these aspects of pulling the tubing in. I dug the ditch as straight as possible and where I had to turn it I dug very large sweeping turns. If I had a borescope that was long enough I could actually look at the tubing from inside to see if there is a problem.

I'm not saying (yet) that this is a likely cause of the added resistance in the system, but the ugly thought has crossed my mind.

I saw the gauge set-up in the TACO paper and should've used that configuration. It's an easy change to make.

Get an accurate differential pressure reading at the pump, then we will look at the numbers and options.

I have a meeting tonight but will check the forum tomorrow.

Assuming you have a diaphragm tank (or compression tank) and air scoop, where do you have your fill valve. These should be located before the pump at the point of no pressure. The Pump should pump into the system after the boilers, rather than before.

Check out this link for some info on p-s pumping:

**Broken Link(s) Removed**HeatingHelp.com is a good resource.

I've been out of pocket for a couple of days due to extended work hours.

A curious thing happened two evenings ago. I haven't had the chance to re-configure the gauges around the pump but I thought I'd try a quick change to the system. I flipped the pump and pumped in the reverse direction. I know this is not the right way to do this... pumping into the expansion tank, but I wanted to see if I had the same amount of restriction pumping the other way. Immediately, I could hear and see a difference in the pump. I checked the coal boiler and the pressure was running about 8 psi. The coal boiler is firing it's little heart out because now it seems to be taking on the load of the house.

I payed very close attention to the ditch when I burried the lines and the yard is sloped up to the shop but maybe something settled and there was an air pocket somewhere that I had not yet removed.

The pump suction/discharge did not change much... suction is about 8 and discharge is about 20... which reads the same way on pump flow.

I'm not sure if I can explain all this in technical terms but the oil boiler hasn't kicked on in two days. That's purely anecdotal evidence, but it works.

This weekend, I need to flip the pump around again and see if the proper installation will work ok.

Can anyone tell me in technical terms how an air pocket would affect pump flow?

An air pocket would create a restriction just like any other physical blockage. The buoyancy effect of air is very powerful. Try pushing a beach ball to the bottom of a pool.

You would only have to be off the diameter of the pipe to create an air bubble. The under pressure the bubble could have collasped enough to permit partial flow but there was not enough pressure to force it out of a high spot. This is why intial purge with a garden hose and high flow is good. However, even with a good purge, air is entrained in solution with the water and will come out of solution when heated. Air pockets can reform and cause problems.

Not a highly technical explaination, but I hope it helps.