enough expansion?

Did you check the precharge pressure on them? What was your storage pressure before you started heating? 20 is too high for 130 water - that's almost up to the blow off point for my boiler.

Can you isolate them and let the water pressure off their wet side to check it?

I put a new one on this summer and it had about 4 psi too much air in it out of the box. Although I'm not 100% confident in my air guage.

You could likely let some water out to lower pressure a bit but it would climb again with more heat if air pressure is too much. Where are the expansion tanks with respect to low system point, vertically speaking? And how high is your system and where are your pumps with respect to your expansion tanks vertically speaking? And where is your pressure gauge with respect to the other things again up & down wise? Have more than one guage?

How high is your system? My pumps & tank are also low, just off the basement floor of a 2 storey house. I think when I started heating the water up this fall my system was showing around 8 psi at top of boiler. Cold pressure would depend on your system height. I suspect you had high precharge, two of those tanks should do you I think. Or at least do better than what you're seeing.

wtrass said:

The tanks are on the floor and the pump is also low to the floor on the return side. I have a gauge on the boiler and one on storage- they are both reading about the same and they are also within a foot of each other.

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I doubt this is your issue but I had the same kind of problem last year. I had some Elbi expansion tanks. I let of some pressure so my relieve valve would not blow but I saw pretty big pressure swings (before, during, after a fire). I didn't know any better so I assumed it was normal. The next thing i noticed is that I would often get air trapped in 1 of my zones requiring that I bleed it. Eventually the blatters completely blew (turns out a lot of folks with Elbi ended up with blown bladders). Not suggesting this is your problem, just sharing my experience in case it might help. Replacement tanks work fine and I don't even notice any changes in pressure. Good luck!

System height is height from bottom to top. Mine, bottom of system is about a foot off basement floor. Top is upstairs rads. There is about 18ft vertical between them = system height. You shouldn't go to zero pressure at the top when cold, and there is about 0.4psi for every vertical foot. So extrapolating a bit with quick rough numbers, 2psi at top when full cold plus 18' down x0.4 = 9psi at bottom. Most system guages aren't at the bottom. If it's at the top of the boiler, that might be 4 ft off the bottom or 1.6psi. So around 7.5 or 8 psi at the boiler guage. When cold. There should actually be more than 2psi at the top when heating, but my assumption is the system won't be doing anything until it gets heated up some, by which point pressure should be well beyond 4psi at the top. Couple of key things is to keep pressure on your circs (think they like 4psi on their suction side), and if there is no pressure then air vents can actually suck air into the system. So, long story short, the less tall your system is, the less pressure you need to see at the bottom on startup.

I think you need to verify/check/adjust your precharges before you go much further. If you can't isolate & then drain the pressure off the wet side of them, you should likely cut in whatever you need to do that (usually a ball valve to isolate & boiler drain to drain). You should have that ability anyway for future checks & possible maintenance. Also - try to find a good low pressure air guage to check with. Most don't read accurate that low.

Do you have a fresh feed setup connected? All the time? That may also create an issue on startup, as they maintain a minumum pressure usually of 12 psi. My feed is valved off. I kept it on, when cold, until I got 8psi or so of water in my system, then turned it off before I started heating. I keep mine turned off, but if you want to keep it turned on all the time for peace of mind & extra protection should something go pop, don't turn it back on until your system is up to temp and pressures build above 12psi. You will have to keep in mind though that if your system cools completely off again, it will let more water in if pressures go below 12. I figure with around 700 gallons of reserve in my system, the need for constantly connected fresh feed is diminished - and if something does start leaking it could make a heck of a mess even if there is no fire going or danger. Not sure that's 'proper' or not though.

Something else I did this summer after swapping in my bladder tank, was add yet another expansion tank. A small 15 gallon non-bladder one. My pressure was swinging a bit more than I wanted after getting the bladder setup in place, could have used a bigger one or second one. My problem is no good places to put proper sized expansion tanks. But I could tuck the 15 gallon one up high under the top of my upstairs stairwell, only a foot or two below the top of my system, and fish a piece of O2 barrier pex to it. So now my pressures are where I like to see them, they usually stay between 10-15 psi during the cold/hot heat swings at the top of the boiler.

maple is on point. And you are going to have a mess if you continue to heat storage right now. It is remarkable how much 1000g will expand going from ambient to operating temp.
I have two of your same tanks with 1000gals storage. I had large pressure swings until i correctly set my precharge. You need to disconnect your expansion tanks. The water side NEEDS to be open to atmosphere. Hopefully it is plumbed so this is easy for you to do. There should be valves and unions at that location. Connected to system with zero pressure will not cut it. Valving them off will not work either. Then set your precharge (air side) to 10 psi (if your tanks are even with first floor of second story building). You need an accurate gauge to do this. I borrowed a motorcycle tire pressure dial gauge. Now you can hook the water side back into you system. Add water to bring your water side pressure up to match the precharge when cold. You will have some air to work out but this should set you really close to where you need to be. My pressure now climbs to about 16psi at full charge. Hope this helps.

If your system height is really only 6.5', from the very bottom to the very top, you would only need maybe 6-7 psi cold when you start heating, depending on where the gauges & pumps are all at with respect to each other. If it is going to be a seriously sticky job to cut a ball valve in, that you would really rather do in the off-season, you might be able to get away with letting a bit of pressure off each side (air & water), carefully, in stages, as you get things warmed up. But you don't want to let too much air out & go too low there.

Good luck with it, anyway.

Wtrass, I had a SX160 and a SX30 plumbed in with 1000 gallons storage and was getting pressure readings very similar to yours. I ended up adding a second SX160 in order to get the readings down to the 16 psi range with storage fully charged. This was after properly setting the precharge as Coal Reaper described.

I had initially judged the amount of expansion needed by acceptance value only. After looking again at different expansion calculators, I found that although the acceptance I had calculated for 1000 gallons plus pipe volume was sufficient, the full volume of the expansion tanks wasn't. I still don't know why that might make a difference, but when added, the extra expansion tank solved the problem.

AFSupply had the best price I could find on an SX160 by the way; $418.00 including shipping. Hope you don't have to buy another. A picture previously posted by a site member showed two Extrol SX160's side by side next to a thousand gallon storage tank. That picture had me worried before my fist burn I hadn't enough expansion, which turned out to be the case.

Mike

wtrass said:

Well, finally got to the point where I can fire up the vigas 40- what a long road. Still bringing things up to temp on 1000 gallons storage, fixing leaks, etc. I have two sx90v expansion tanks and I am getting pressure readings on the storage tank of 20 pounds with 130 degree water. That seems high to me. Thoughts?

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I have 2 sx110v expansion tanks with 1175 gals of total system volume I get around 30 psi @ 190