Hydronic help please

Unknown

it's acting as if it has no expansion. I'm fairly certain the tank is right, it could be stuck all the way in. Maybe I should let some air out and see if it pops loose.?

Thanks!

Unknown

What do you think?

Set up, infamous new Robur HP system 100 gallons of 50/50 gycol min temp 48* max temp 120*. #30 expansion tank . I'm finding the system pressure varies quite a bit between temps. So much that at 120* pressure is 30psi and at 54* pressure drops to zero psi and may be sucking in air through auto vent. Tank pressurized to 25 psi. Any thoughts. I've got a similar system with 125 Gal, #30 tank and 25psi static pressure. It does not have this issue. What am I missing? There's still air in the system maybe? Not an issue right now but when I shoot for 48* chilled water temp it will be. Any thoughts?

Mark Eatherton

Stuck diaphragm??

I've seen the expansion tank bladder get stuck to the inside face of the expansion tank, thereby giving you ZERO compensation, which it sounds like you have going on. Raising the tank pressure will actually not be beneficial at lower operating temperatures. Try lowering it the pressure, and adjust your fluid fill pressure at mid temperature range (say 12 PSI at 87 degrees F.) this way, you are starting in the middle of your highest and lowest temperature/pressure potentials.

Also remember that glycnoids reduce your expansion tanks capacity due to increased fluid volumes.

ME

Mark Eatherton

Do this...

Keep the fluid pressure high, say 29 PSI, then bleed ALL of the air off the diaphragm side of the tank and see what happens on the fluid side. If no drop in pressure, you have a stuck diaphragm. If it drops, then it is free.

To reset, lower system pressure to zero PSI, then air the tank up to 10 PSI, then charge the fluid to 15 PSI. This will put your tank into a mid range condition, with fluid in the reservoir to compensate for contracting fluids, and still have room on the air side to allow for expanding fluids. you will NEVER have a completely stable pressure, but you should be able to keep the system minimally pressurized, and less than 27 PSI (90% of 30 PSI).

As an alternative, re-run the calculations on how big the expansion tank should be. I can do it, but would need minimum fill pressure, maximum operating pressure, minimum fluid temp (you already gave that), maximum fluid temp (that too), fluid content in system, and percentage and type of glycol in the system, and lastly, what size of expansion tank you currently have in place. I have a Siggy program around here I can run it on.

ME

Unknown

Thanks ME

I'll try the suggested method. Makes sense. if I'm understanding you correctly the answers are mimimum fill pressure, 12.5# Max pressure? There is a 50# relief on there per Robur. Max I'd like to see ever is 45ish, no? 100 gallons of 50/50 using No Burst Noble, 3 gallons of NB to 2 Gallons of water ratio. Minimum temp we'll say is 45* max temp 120*. BTUH output of unit 123,500.

According to a chart I have a #30 tank should handle 177 gallons of water @120*. My system is only ~100 gallons, maybe 103 tops. I'm going out there tomorrow, I'll see if the diaphragm is stuck or not. I'll let you know what I find.

I'll tell you why I raised staic pressure to 25/30 too. If the system was running 13 psi as soon as a floor came on and dumped a bunch of cold water in there the pressure would drop right off to 0 and the secondary pumps would start to cavitate. So to alleviate that I raised it up but today I found someone had shut the unit down at the breaker and the water went all the way down to 54* which resulted in 0 pressure and pumps cavitating. First I thought it was air had gotten in but as soon as the water warmed back up it went right back up to 30 psi and the pumps settled out so they had to be cavitating.

Unknown

Well,

I let air out until 20 psi at 103* and it did drop system pressure, however, it seems to have stabilized. I turned on the floor and pressure stayed up. It did creep up a bit once it warmed to 110/115. Maybe to 23 psi but did not seem to react as much. I let it go. I'll wait till we shut it down to switch over and see what it does. Maybe it was stuck and let go, maybe not. We'll see.

[Deleted User]

According to Siggys Software

See attachement.

You still need to reduce the pressure in the diaphragm. By airing UP the diaphargm, you excluded the tank from accepting any fluid, and when the fluid got cold and contracted, there was no compensation for this shrinkage.

Also, I may have overkilled on the amount of glycnoids in the system (3/5's of 50/50 = 30%, but in one spot you said 50/50, so I assumed the higher value), but if it is truly less glycol, then you are OK. Better safe than sorry.

ME

Unknown

Thanks, makes sense.

What I have in there is 50/50 glycol vs water. To achieve that mix you must use 3 gallons of No Burst to 2 gallons of water. Per No Burst guy on the phone. So actually, I think you got it right. So, by rights now, I need to remove the tank, set it to 10.4 PSI, reinstall it and then set system pressure to 10.4 cold as well. Yes? At least we know the bladder isn't stuck. Guess what, I installed a valve so I can shut off the tank.

Unknown

How do I get this Siggy program?

Mark Eatherton

Go to Siggy's web site at www.hydronicpros.com

http://store.hydronicpros.com/category.php?qcc=1003&qpg=1

It's $285.00 for this particular version, but IMPO, if you're going to be in the hydronics biz,it's a MUST have piece of software.

ME

Unknown

Thanks

I'll check it out.

m

Drew_2

Noburst mix

MPF
If you are using Noburst -100 or Noburst AL at that ratio, you are at 37% propylene glycol.
I you are using Super Noburst at that ratio, you are at 70% propylene glycol.

Unknown

Hmmm,

maybe I'm "mixed up". Do you happen to know what 37% gives me for flow limit? No burst rep and I talked about needing flow protection to -20 and he told me 3/2 NB -100 to H2O.

Drew_2

Flow

At 37% propylene glycol you have 0 degrees freeze and about -7 flow.

Unknown

Sigh,,,

Why oh why did I not get the right info from the factory rep? I'll look into it.

Drew_2

Information

MPF
I'd like to talk with you about the information you've received. Give me a call 800-678-6625, Ext. 108

Unknown

I will,

later today maybe, I've got to roll right now.

m

Mark Eatherton

Drew...

Please explain the difference between freeze and flow. Looking at your numbers, I'd think they are flip flopped. My intuition tells me that if its at FREEZE, it won't FLOW. Your numbers indicate otherwise.

Thanks for sharing.

ME

scrook_3

mixture/alloy freezing

mixtures of two (or more) materials (e.g. water+glycol or tin+lead or other solders) usually do not have a single freeze point but a "liquidius" temperature below which they become slushy -- but can still be pumped with enough effort -- the colder they get, the thicker the slush becomes, and a lower "solidius" temperature where they become fully frozen/solid.

Unknown

Yea,

the more I thought about those numbers the more I realized something wasn't adding up. The bucket says 75% of No Burst to 25% H20 will protect flow down to -40*. I'm at 60/40 which I believe, without going back downstairs to look at the bucket again, puts me conservatively at -15*.

hot_rod

3 temperatures to know

the first is where the fluid starts to form ice crystals, but is still pump-able.

the second is where it is no longer pump-able with a centrifical pump.

The third is the burst point.

hr

Drew_2

Freeze/Flow/Burst

Scrook & Hot Rod
Thanks for covering for me and answering the Freeze/Flow/Burst question.
I'll add one thing about the definition of "Freeze".

With chemicals, Freeze is defend as; the temperature at which the chemical first forms crystals.
Example; Pure glycerine crystallizes at around +56 degrees F.

So, in the case of Noburst 'Freeze Point", that's where ice crystal first forms.