Simple expansion tank replacement, or MORE?

hydronical

On my hydronic heating system, the pressure relief valve (Watts 335) has started leaking, and the expansion tank (Amtrol Extrol model 30) seems to be full of water - I plan to replace both items. A pipe rises out of the boiler and is attached to a tee fitting - the pressure relief valve is attached to the top of the tee, and the expansion tank (model 30) is attached to the tee horizontally. The boiler is a 1991 Pennco (Dunkirk?) Series 9 Model 1506 HWID - 175,000 BTU per hr boiler running to finned baseboards... The linked photos show the current installation.

Overall system view
Expansion tank
Close-up

I like to follow manufacturer's guidelines and heed their warnings whenever possible... Based on Amtrol's product sizing guidelines, the system should use an Extrol EX-60, rather than the EX-30. Based on Amtrol's installation instructions, the expansion tank must be installed on the SUPPLY SIDE of the circulator, must be mounted VERTICALLY, and must not be installed on a dead-end-pipe.

Questions:
#1 - I want to do what's best, but would you simply replace the two parts with identical replacements with no other changes?
#2 - If there's a better way... What is my best course of action? In particular, is the expansion tank in an acceptable location within the system? Should I add an add an air purger / air separator? Where would it go?

Thanks! This is a great forum and I'm excited to read the replies...

Snowmelt

There are plenty of online pictures of how to do this, send a picture of what you have now. I always recommend an air seperator by taco or calaffi. Always want to pump away from the expansion tank.

hot_rod

I'm not sure how deep you want to get into re-piping? How has the system performed up to know? Any air noise when the zones are running?

Ideally you would have a central air elimination device. The vents shown are designed to be high point air elimination devices, they don't really pull air from a flowing stream so well.

Many of the older boilers had air removal chambers built into the sections of the boiler, adding a simple air vent as shown was adequate. A good separator on the supply pipe leaving the boiler speeds air removal and captures any micro bubbles that flow thru it. many installers chose a dual purpose air and dirt separator for their systems.

No harm in oversizing an expansion tank, under-sizing causes a short life often times. Is this the first replacement?

Ideally the tank is mounted vertically as the manufacturer suggests. also some support as they get heavy when they waterlog.

check the pre-charge pressure before you install the tank, also.

The key to air removal starts with the initial fill and purge. fill and flush the system.

Increase the pressure to just below the relief have setting, around 28 psi.


Purge each zone one at a time via the isolation or zone valves. You want 2 fps velocity to push air down any vertical piping, so at least 3- 5 gpm fill rate.

Next reduce pressure in system to required fill pressure, say 12 psi and circulate, this lowers the solubility, assuming you are circulating room temperature water.

Most importantly you want to next take the system to then highest operating temperature to drive out any remaining air.

Ideally the central air scrubber goes at the highest temperature, lowest pressure point in the system, the outlet of the boiler, with the pump, pumping away.

IF you want to get that deep into a 1991 vintage boiler Install a micro bubble air separator, install the expansion tank at that connection, and move the circ up to the location of the expansion tank/ air separator. The fill valve also connects there.

Now you are adding all the pump head to the system, removing air at the best possible location, for a quiet efficient system.

But a some point a heat load calc and boiler upgrade may be a consideration?

hydronical

I'd prefer not to get into re-piping if it's not really necessary. System has performed well enough so there's probably no good reason to replace it. Occasional water sloshing noise in baseboards, but I now suspect that happens when the relief valve let out water and the system was running low on water and pressure.

In the front of the overall system photo, there is an air vent with a red cap on the return line between the zone valves and the circulator. Does it make sense to install an air scoop in that location, with the air vent on top of it? Does an air scoop need an expansion tank attached to the bottom of it? Does it make sense to move the expansion tank there?

Or does the current location of the expansion tank make sense? it is installed on a tee fitting with the pressure relief valve. Is that considered supply-side or return-side?

The date code on my current Extrol Model 30 is 21225006, so I think 2006 - shortly before I bought the house.

icesailor

I doubt that the Extrol tank is full of water. If it is, it should have snapped off by now. Causing a huge leak of water.


Who ever did that is a pathetic hack. You need to get that fixed ASAP. If that breaks off, you have one big issue on your hands. Extend the tank away from the boiler with a nipple and 90' ell so as to miss the boiler. A #60 or equal is not a bad idea. The tank needs to be installed in a vertical position.

Its wrong. Just because it has been working since 2006, won't make it right.

hot_rod

hydronical said:

I'd prefer not to get into re-piping if it's not really necessary. System has performed well enough so there's probably no good reason to replace it. Occasional water sloshing noise in baseboards, but I now suspect that happens when the relief valve let out water and the system was running low on water and pressure.

In the front of the overall system photo, there is an air vent with a red cap on the return line between the zone valves and the circulator. Does it make sense to install an air scoop in that location, with the air vent on top of it? Does an air scoop need an expansion tank attached to the bottom of it? Does it make sense to move the expansion tank there?

Or does the current location of the expansion tank make sense? it is installed on a tee fitting with the pressure relief valve. Is that considered supply-side or return-side?

The date code on my current Extrol Model 30 is 21225006, so I think 2006 - shortly before I bought the house.

The air vent above the pump is doing little if any good, other than leaking and causing a puddle

Only if you have had ongoing air and noise issues would I bother adding another air purger.

The best location to add one would be above the gray control box on the outlet, supply side of the boiler. Either a vertical or horizontal micro bubble type would work there. Shown below.

It will require a drain down, addition of the vent, refill and purge, of course.

If the relief valve just recently started weeping, I

would suspect a failed tank, push in the tire stem, water or air?

A couple fittings and nipples would re-position it vertically.

Actually I'd like to see the air vent directly above the connection to the boiler, tank armed over and supported. Use a vent with a service valve should it ever need cleaning or replacement.

My point is, if you are considering draining the system and upgrading, adding a separator, and moving the circ location along with the fill and expansion would be a nice upgrade, buy of course more $$.

If just replacing a failed tank, simple enough to rearrange that piping at the vent tank location, as shown in the sketch.

Snowmelt

Hot rod I do have a question on that drawing, would you want to put the expansion tank behind the pump.
Then keep dirt mag or just an air seperator where you have it.

hot_rod

Correct, I suggested that a few post up , IF he wants to get that deep into the system. This drawing was showing a "clean up" for the vent and expansion tank at then top of the boiler, mainly.

I'm not sure a complete piping upgrade on a 24 year old boiler, possibly oversized, is a wise investment.

Snowmelt

Hot rod I have a silly question, why don't they make residential expansion tanks so you can stand them on the ground, with these wall hung boilers sometimes I wish I could just install on ground in the corner.

hot_rod

Good question and idea. I think one of the expansion tank manufacturers already build freon tanks, they already have then base on them. Probably about the same shell? Like most things it's a very price sensitive products, they look to say pennies everywhere.

I did see a clever expansion tank from Canada recently, connections at both ends, fluid in a bladder not the steel tank. as flow thru design.

It was for DHW the key being no stagnant fluid to be potential legionella hiding place, which is possible in a typical top port DHW tank.

I think it could be used for hydronic also, easy to pipe right thru and suspend with then piping.

Snowmelt

Know that you say that I think I saw that toooo

icesailor

Snowmelt said:

Hot rod I have a silly question, why don't they make residential expansion tanks so you can stand them on the ground, with these wall hung boilers sometimes I wish I could just install on ground in the corner.

They do. They cost big buckaroos. More Buckaroos that the genetically cheap are willing to pay for.

SWEI

Not much difference for equivalent capacities:
Amtrol EX-90 list $209
Amtrol SX-30V list $242

hydronical

Do I have the right idea in this labeled photo? (I drew the dirt separator horizontally by accident, but I will install it correctly)

Should I remove the float air vent from the return side?

I would like to move the expansion tank from the tee with the pressure relief valve to the new air separator location, but there is no space - it would touch the boiler and hot water heater. What is the downside of replacing it in the same location (but in vertical orientation) where it is now?

bmwpowere36m3

Orientation doesn't matter... However you want the x-tank on the suction side of the pump.

bmwpowere36m3

Getting a proper air separator and re-plumbing the x-tank would be enough. Dirt separation... while it won't hurt, is probably overkill for an older CI boiler. Are you seeing rust in the water? (pieces, not rusty color water)

hot_rod

The expansion tank does not need to be physically mounted to the new air purger, take a piece of 1/2 pex or copper from the air purger to wherever you can mount the tank. It could mount on the wall, on a floor stand, really anywhere near by.

There are some nice wall mount brackets for tanks out there, then important detail is the piping connection at or close to the suction side of the circ.
Hydro Claw makes a great tank bracket, find them at suppliers or online sources, Sioux Chief, HoldRite, Watts are some of the other bracket manufacturers.

I see tanks mounted on their side all the time, ideally they mount with the nipple connection straight up, either from a bracket, or the bottom of the purger.

hydronical

I like the idea of a floor stand, rather than tapping into the concrete block wall, or hanging several feet down from the ceiling. The Amtrol Extrol EX-60 is 11" in diameter x 23" high. The tee fitting to which the current expansion tank is installed is about 34" off the ground. I have a metal bucket 10 3/4" in diameter x 9" high, and its rim would nicely support the expansion tank. A small nipple can make up the height difference, so 23" tank + 9" bucket + nipple = 34". Is this a good idea, or too atypical to merit consideration?

Mark Eatherton

You need to maintain access to the Schrader air charging valve on the bottom of the expansion tank. Ideally, the expansion tank should be isolatable, and drainable so you can check the gas charge with ZERO pressure on the water side of the diaphragm.

hydronical

Would it make sense to just install a floor standing expansion tank such as the Amtrol Extrol SX-30V? It only costs about $40 more than the EX-60, and has almost double the capacity. Also, consider that some good support brackets, such as the Storm King HydroClaw recommended by hot rod, can cost about $40.

Is there a downside to an oversized floor standing expansion tank when one is not required?

SWEI

These work well for small systems. Most of the time, we just use a Union Ball Drain.

icesailor

hydronical said:

Would it make sense to just install a floor standing expansion tank such as the Amtrol Extrol SX-30V? It only costs about $40 more than the EX-60, and has almost double the capacity. Also, consider that some good support brackets, such as the Storm King HydroClaw recommended by hot rod, can cost about $40.

Is there a downside to an oversized floor standing expansion tank when one is not required?

Personally, I've never seen one that was too big, cause a problem that I was aware of. The same can not be said with tanks that are too small.

hydronical

Here is a diagram of my system, which is also pictured above... My biggest question is still whether to leave the expansion tank in its current location, or add an Air Separator and move the expansion tank.



Amtrol's expansion tank must be (1) installed on the SUCTION SIDE of the circulator, (2) must be mounted VERTICALLY, and (3) must not be installed on a dead-end-pipe.

Caleffi recommends that its Air Separator be (1) installed after the boiler and (2) on the pump suction side.

Given that I cannot move the circulator pump or do any major repiping for this project, I don't think there is an ideal location. The current expansion tank fails to meet any of these requirements. If I install an Air Separator, I must choose after boiler OR pump suction side - but not both. What is the best approach?

There are a few other considerations:
-- Is it possible the boiler manufacturer's original instructions specified the current location for the expansion tank?
-- The current location is the most convenient. Any other location may require a floor-standing expansion tank, and a few feet of extra piping
-- The system works well enough, but I may not know any better.
-- The current expansion tank failed, and needs to be replaced. I figure it can't hurt to do some minor upgrades while the system is drained.

hydronical

I think my inexperience is showing, and the only reasonable location for the air separator and expansion tank is on the supply main just after the 90 from vertical to horizontal. Hot rod's simple diagram above already answer this question.

Thanks to all!

bmwpowere36m3

If your set on making changes... put the x-tank near the fill valve on the return side and mount the air separator on the supply side.

Shane_2

I would agree with the poster above. Install expansion tank where the cold supply is before the pump. (We use the watts RBFF fitting a lot of the time)- has a built in gauge, 3 way ball valve.(http://www.watts.com/pages/whatsnew/RBFF.asp)

Then install an air separator at the highest point you can on the supply side. I would replace the can vents with key vents (quick and easy) which would still give you a way to clear the boiler of air if it has the built-in scoop.

hydronical

I would like to replace this tapped tee fitting. Any ideas what it is called, or alternate ideas? The new expansion tank will be mounted vertically. I thought about using an air scoop and plugging the other end, but there is no 3/4" version for some reason. My system will also have a Caleffi 551 Discal Air Separator on the supply main, but I cannot mount the expansion tank in that location.

Snowmelt

There's no 3/4 version of what? I would get a tee then a close nipple, then get a shut off with a bleeder on it.

bmwpowere36m3

If you aren't planning on keep the x-tank and air bleeder in that location… you can just remove the tee and thread the T&P right into the boiler nipple.

Or replace that tee with a regular tee and nipple, thread in the T&P on top. Then tie the air vent into the side (branch) with some form of a elbow and/or bushing. Or you could just remove the x-tank and put in a plug and be done.

Since the recommendation was to put the x-tank on the return side by the fill valve. Tie it in with a tee over there and use whatever fittings you need to mount the tank vertically if you desire.

There are so many ways to do it as far as placement and fittings to use. Hard to give a concrete answer, because there isn't always a right or wrong way.

hydronical

Thanks! I think I can use a 3/4" tee with 1/2" bushing for the x-tank and 1/8" bushing for the air vent. Sounds reasonable?

bmwpowere36m3

Sure, but why are you stuck on putting it on the supply side? That's pretty much what you have now… so I see no benefit in doing that.

hydronical

Based on space constraints, this is the best location for my expansion tank. And the tee with the bushings will simply allow me to mount the x-tank vertically with the float air vent on top.

I also want to install a service valve. Should I install a 3/4 ball valve on the horizontal pipe, or something like the Caleffi 1/2" service check valve on the bottom of the tee? (How does that Caleffi valve work, by the way?)

hot_rod

not my first choice of a rebuild, but if you want to keep all the components there
A 3/4 cross fitting, a couple 3/4 X 1/2 bushings a 1/2 x 6" threaded nipple and a 1/2 ell

Use service checks under the vent and at the exp tank.

The vent "likes to be straight above the spot it's venting air from.

And I think relief valves are preferred on their side, some manufacturers suggest that. A vent tube from the relief to the floor, also.

Snowmelt

That air vent isn't doing anything, why don't you repipe the boiler the way it's soppose to be done.

hydronical

Is it possible the boiler manufacturer supplied the tapped tee fitting in order for the expansion tank to be mounted in this location? Keep in mind, this is a 1991 Pennco (Dunkirk?) boiler.

hot_rod

Often those older cast boilers had air purger capability built into the end section, they did a fair job of air removal, as long as the air vent was function

Complicated piping or zone piping with a lot of fittings and ups and downs really benefit from an additional purger.

Micro bubble types will quiet and possibly improve efficiency. Moving the pump would add some air removal benefit,if itches been a noisy or problematic system.

hydronical

So many great replies in this thread - I appreciate that I'm being pushed in the right direction. The only conflicting information seems to be installation of the x-tank on supply or return, but I am leaning toward supply.

Below is another view of my system. Maybe I can raise the horizontal supply main pipe a few feet, and install the air separator and x-tank below it, close to the water heater. Also, I can reroute the water feed supply line to the same location (it is currently feeding into the return main). Does this all sound reasonable? What can I use to support the x-tank several feet down from the ceiling joists?

hot_rod

A number 30 tanks sits inside a 5 gallon bucket nicely. If you connect it to the system with pex, it can be lifted out if service is needed.

I've seen them strapped to the side of the boiler with perforated plumbers tape also.

bmwpowere36m3

hot rod said:

And I think relief valves are preferred on their side, some manufacturers suggest that. A vent tube from the relief to the floor, also.

I've read conflicting statements wrt relief valve position. Seems the argument for installing them vertically is to reduce the chances of sediment build up on the valve. I don't whether is a requirement or not.

hydronical

Never considered (or used) pex before, but I like the idea of flexible tubing so I can connect the x-tank to the air separator and place it on a 5-gallon bucket. Are there other acceptable flexible connectors, such as corrugated copper or braided stainless steel, like you see with water heater connectors? Or is pex the best choice?

hydronical

Below, I added an air separator on the supply main, and attached the cold water feed and expansion tank to it, using a flexible connector (due to space constraints). How can I improve this system overhaul (given that the circulator pump cannot be moved)?

@bmwpowere36m3 and @Shane had suggested to keep the cold water feed on the return main, and mount the expansion tank near it, before the pump.