please help- System is overpressuring

[eriesigtau]

Guys, I am still having this problem with my system overpressuring when the storage is hot. I know my design isnt the best but it would be very difficult to change at this point. I have posted about this problem before but and I thought I had it under sontrol but it returned. This time I decided to post a diagram of the design.
I think the problem is that there are too many circs thus producing to much pressure but I wanted to see what you thought.
I have about 600 gal in the system. I have a Extrol SX-90 and a Extrol #90 expansion tanks. With everthing off, my pressure ranges from 12-15lbs. When storage is charged and circs are running, I can get pressures of 25-30. I have 2 relief valves. One on the boiler and one on the tank. The tank one weaps when I get around 30lbs. Never seem to have a problem with the boiler one.
What is your thought here. Is there any way to keep the pressure under control? I'm starting to think there may be a problem with the SX-90 even though its new.

 

[stee6043]

Is the leaking relief valve an old one? And why do you need two? I know pressure relief valves fail. I had one give it up on my hot water heater a couple years back for no reason. Quick fix if that's the problem.

My system very regularly runs up to 27-28psi when my tanks are 180+ top to bottom. This is exactly where I want it to be at peak temps. I'm 14psi +/- when everything is room temp.

 

[eriesigtau]

Here are some pics to help

 

[eriesigtau]

The releif that leaks is a few years old. It was used on a boiler I had at my previous home. Never leaked there nor does this one when less than 28 or so psi. It has leaked quite a bit since this new system was installed last year. I wasnt aware that 28psi was acceptable. I thought the expansion should keep everything at its normal operating pressure of 12-15psi? Thats why I got larger sized tanks. Maybe I'm wrong.

 

[Clarkbug]

What is the flow direction of the circ pump right next to the SX-90? Are you pushing towards it or away from it?

EDIT: You posted before I replied. In order to keep your pressure at 12-15, you would need a LOT more expansion tank. Its pretty common to take the pressure in your system from the fill pressure of 12 PSI up to near the limit of 30. If your relief is leaking at 28, you may want to think about replacing it. Also, is it just for pressure, or also pressure and temperature? If it has a temp relief also, could that be whats tripping it?

 

[timberr]

Erie,

I am running a primary/secondary setup with a Pressure relief on the boiler and storage. And my pressures are consistent with yours (and stee's when @ 180*) and I have no leaking. You may have a PR that has a weak spring?

 

[Pat53]

have you checked your expansion tanks to make sure they are set properly? I have only 1 extrol 90 plus a small exp tank on my system and it runs from 15 psi at 120F up to about 25 psi when the 500 gallon tank is charged with 195F water.

 

[eriesigtau]

I will replace the relief valve. This has been driving me nuts for a year now haha. I'm glad to hear that the climbing pressure is normal.

 

[maple1]

Might be just me, but I think I would try to get my pressures lower - maybe even if I had to add more expansion. I start to get squirmy when mine head for 20.

Likely just a personal comfy factor on my part...

 

[eriesigtau]

Next question. Anyone have an idea on how to prevent the blackflow im getting from the manafold to the tank? ie..When the boiler is heating the house, 180 water is pumped into the manafold and jumps into the return to the tank instead of flowing through the manfold. The only way I can remedy the situation is to have the valve on the return to the tank on about 1/4 instead of full open.

 

[bpirger]

I guess I don't understand the primary loop not being "free" to flow, i.e. you show a closed valve in the primary loop. When water is coming from the boiler to the manifold, and assuming a load is on, water flows to the load. If more water comes into the manifold than the load requires, then water will flow out of the manifold as well....and apparently back to the tank is the lowest resistance pathway for it. I assume the idea is to feed the primary loop by a secondary loop, i.e. the boiler or the storage? So those are plumbed in with closely spaced tees? But the primary loop doesn't provide a "loop", that closed valve kinda changes everything...that's my first question anyways!

I had a pressure reflief valve on my buderus discharge every now and then and then it seemed to weep. I lifted it out and let the water flow a bit, maybe a quart, and then closed it. Never has done it again. I guess crud can sit in the seats, etc. so who knows.....hopefully you just have the leaky seal!

 

[eriesigtau]

It is a primary sec system. If I leave the ball valve open (as designed), the manafold gets starved of hot water. You can see this valve in the pic. its right in front of the SX-90 expansion tank). I do have close proximity tees as you can see in the pic of the manfold. (the bottom 2 are the supply and return for the tank and the top 2 are the supply return for the boiler). Basically the hot water get pushed back into the tank return when tank is not being charged/house is calling from the boiler). Hopefully that makes sense. I guess the only other way to explain it is that when the house is calling for heat from the boiler, it is actually heating tank from the bottom through the return pipe of the manafold.

 

[Clarkbug]

Can you just add a swing check in that line to prevent the reverse flow?

 

[eriesigtau]

Check valve wont work because that is the direction the water is supposed to flow when the storage is heating. A solonoid valve might work though.

 

[Singed Eyebrows]

Might be just me, but I think I would try to get my pressures lower - maybe even if I had to add more expansion. I start to get squirmy when mine head for 20.

Likely just a personal comfy factor on my part...

Me too, I have a 500 liter & 5 gallon expansion tanks. Cold pressure is 7 to 8 psi & fully expanded is 13.5. The 500 liter is the minimum capacity for my boiler per Atmos, Randy

 

[woodsmaster]

When I first filled my systym I went with the pre-set 13 psi on my feed valve. When storage was fully hot it would get up to around 28 - 29 psi. When I added the house to the load I adjusted the feed valve. Now it don't go over 20 psi and at 10 psi I have to build a fire. Don't Know what It would be at room temp.

 

[Clarkbug]

Check valve wont work because that is the direction the water is supposed to flow when the storage is heating. A solonoid valve might work though.

What about using a flo-check instead? Also known as a weighted check valve. That would provide resistance to the flow when you dont want it, but when a pump pushes hard on it, it will open.

 

[taxidermist]

I dropped my pressure down to 10psi when cold. I too was getting a weeping valve when i hit the 190* around 30psi now i might get to 25psi when 190*


Rob

 

[James Ascherl]

My EKO is between the storage tanks and the load, so I predicted that when the eko is running some of the water would run back towards the storage so I installed a 2way valve (Taco 573-2) between the tee and the top of the storage that will close to prevent the water from going the wrong way into the storage. When the house demands heat from the storage, it will open. The only thing I don't understand is why there is a directional arrow on the housing. How does it make a difference which way water flows against an elec valve? In theory, water will flow both directions depending on whether it's charging or drawing. Anyone? My system is almost up and running so I have yet to prove or disprove my theory.

 

[Clarkbug]

My EKO is between the storage tanks and the load, so I predicted that when the eko is running some of the water would run back towards the storage so I installed a 2way valve (Taco 573-2) between the tee and the top of the storage that will close to prevent the water from going the wrong way into the storage. When the house demands heat from the storage, it will open. The only thing I don't understand is why there is a directional arrow on the housing. How does it make a difference which way water flows against an elec valve? In theory, water will flow both directions depending on whether it's charging or drawing. Anyone? My system is almost up and running so I have yet to prove or disprove my theory.

The only thing I can think of is that the Taco 570 series uses a globe valve, and flow against the arrow will be attempting to force the valve to close when the wax motor is driving it open.

No idea the long term effects or impacts, but you can see the cut-away of the valve here:

http://www.taco-hvac.com/uploads/FileLibrary/100-3.pdf

 

[Hunderliggur]

Old news, but you only need the pressure relief at the unit that can create the dangerous pressure (the boiler). I would plug the storage one. I just replaced by boiler pressure relief with a boiler relief valve from a good plumbing supply house (don't recall where I got the first one). The replacement unit is much beefier than the leaking/early tripping one it replaced. And, I pipe my pressure relief in an unrestricted, down slope run to the outside just in case.

 

[EffectaBoilerUser (USA)]

I would remove some air from the expansion tank when the storage tank water temp is 180/190F.

From the factory most expansion tanks are set at 12.7 psi. However, when the tank is conencted to water storage the pressure will build to 20-25 psi in the expansion tank.

Thus, I would remove some pressure from the expansion tank when the water tanks are up to their high limit temperature. I would get the pressure in the expansion tank down to 15 psi in the expansion tank.

I did this to my effecta lambda 35 boiler with 1,000 gallon system and my pressure relief stopped weeping because the max. pressure in the system never gets above 18-20 psi now (before it would get close to 30 psi).

Brian

 

[huffdawg]

I would remove some air from the expansion tank when the storage tank water temp is 180/190F.

From the factory most expansion tanks are set at 12.7 psi. However, when the tank is conencted to water storage the pressure will build to 20-25 psi in the expansion tank.

Thus, I would remove some pressure from the expansion tank when the water tanks are up to their high limit temperature. I would get the pressure in the expansion tank down to 15 psi in the expansion tank.

I did this to my effecta lambda 35 boiler with 1,000 gallon system and my pressure relief stopped weeping because the max. pressure in the system never gets above 18-20 psi now (before it would get close to 30 psi).

Brian

How much expansion do have Brian

 

[EffectaBoilerUser (USA)]

My system has 2 x 52 gallon bladder type expansion tanks.

 

[eriesigtau]

thanks for the advice guys... ill give some of these things a try.