Taco 4900 air separator service

[goosegunner]

I have a Taco 4900 air separator I am pumping away from. The 4900/expansion tank connection and 26-99 are both on the supply. I am not sure it is working properly. I hear some crackling at the pump and sometimes hear bubbles go right through the pump.

I thought maybe it was cavitation due to the valve in bypass to choke down before Danfoss valve. I removed the Danfoss and put in the New style Thermovar 823 that does not need to be throttled. The noise is still there, not quite as load but still there.

Just wondering if any of you have ever taken a 4900 apart to check or clean?

If so how difficult was it to separate the top?

Did it go back on with no issues?

 

[velvetfoot]

I can't help, but I think my Spirovent doesn't come apart, just a drain at the bottom.
I might have stabbed the stainless steel wool when reinstalling it, but that's it.
I've noticed that it tends to spit air when the coolant gets hot, like 180. Your thing is seeing some hot water, right?
You have a lot of water to deaerate, and a system that's been apart. Maybe heat up the tank good?
I get more problem pump noise in the zone circulators, which I haven't run yet, lol, than in the boiler pump, but I have 120 gallons.
Just some musings.

 

[goosegunner]

Yes, swapped out the boiler and did some piping changes. Hopefully some more run time with clear things up.

I should add, I did pull the pump apart a week ago and did not find any pitting or unusual wear on the impeller from previous use with the Danfoss.

 

[leon]

Did you close the vent on the top of the 4900 before you filled the system with water?

Did you open the flushing cock on the air separator while the system was filling?

Ideally a the 4900 should have shut off valves on both sides of the valve to allow removal and or cleaning as they do not recommend that the flushing cock be opened when the system is under pressure and the system has hot water in it before any maintenance is done as the air separator should be isolated with one shut off valve on each side of the air separator.



Is the circulator pushing water through the air separator and bladder tank??
You have a lot of trapped air you have to get rid of or it will ruin the circulator.

Do you have boiler drains on the return loops back to the boiler sump??

Ideally you need to cool the boiler down and then get rid of the trapped air either at the vents on your
baseboard or if you have boiler drains on the heating loops you can push the cold water through with
the air bubbles to remove the majority of the air bubbles from the water and then you can start the boiler and get rid of the rest of the micro air bubbles.

 

[goosegunner]

I had the screw closed on the outlet and used the flushing cock to remove initial air. I added boiler drains when I swapped boilers.

I used a utility pump and a bucket to purge air on the cold system.

Seems like the Taco isn't catching the micro bubbles.

Maybe I screwed it up because I did open flush cock to see if I could purge air when it was hot.

The circulator is pulling through the air sep and the tank connection.

I do not have valves near by to remove and clean. I have valves within 10 inches upstream and 30 inches downstream. I guess I would need to install some unions near it.

Just wondering if I re-pipe it maybe I should buy one that works better.

 

[Bob Rohr]

Can you get into the valve mechanism on the top to assure it moves freely and doesn't have a particle stuck inside.

Some brands allow very easy access to clean, others not so easy.

 

[leon]

I would find out if your model has a repair kit and if not I would just take the connection point and install a 15 gallon B&G Steel expansion tank and a B&G airtrol valve above it to remove the air from the system.

On the initial fill you fill the system and then open the drain on the airtrol valve and let the excess water drain out of the steel expansion tank until all you have is air coming out and then you shut the drain valve and then you can fire your system up and finish purging the remaining air out of it.

The steel expansion tank and airtrol valve have no moving parts it just sits there in the ceiling and pulls in hot water and microbubbles and lets out cooler water with no air bubbles as they are trapped in the air space above the water line in the expansion tank 10 gallons water/5 gallons air space and you can run with 4-8 pounds pressure at all times with no pressure spikes as you have an additional 10 gallons of water weight to help balance the system and deliver heat.

All you need to do is hang the tank with the airtrol valve already installed and you install a ball valve between it and the boiler to shut the expansion tank off if you have to replace a circulator or drain the system down for whatever reason.

 

[Bob Rohr]

Yeah, there is no way that an airtrol fitting and steel bladders tank can come close to the performance of a properly working micro bubble type eliminator.

Amtrol publishes a great Handbook, now a free download that clearly explains the mechanism involved in an air elimination system, compared to an air management type, which is what a plain steel, bladderless tank is.

With a bladders tank the air is always in contact with system water. So as water heats air is driven out, up into the tank.

BUT the opposite also applies, as the water cools that air is re-absorbed into the water, you have no mechanism to grab and remove micro bubbles, only a media can do that. Air never completely leaves a compression tank type of system, it can't as it provided the expansion space.

So all properly installed and operating brands of micro bubble removers work in the high 90% efficiencies.

One trick to get any stubborn bubbles out is to raise the fill pressure for a few days. Raising the pressure squeezes the air smaller and allows the fluid stream to push it back to the removal device. Assuming it is working.

Is it plain water? Glycol blends take a lot longer to get the last small bubbles out, maybe weeks in some cases.

 

[leon]

Hello Bob,

I have to disagree with you as my system has a B+G fifteen gallon steel expansion
tank and the B+G airtrol valve it works very well.

My boiler has a top draw off the top of the steam chest tapping with a 3/4" inch connection to the
steel expansion tank and after that the B+G NRF 25 circulator pushing water away after
the steel expansion tank. I certainly do not miss crawling around the floor to bleed my
baseboard heat which I absolutely hate.

 

[goosegunner]

Can you get into the valve mechanism on the top to assure it moves freely and doesn't have a particle stuck inside.

Some brands allow very easy access to clean, others not so easy.

Not sure about opening it up. I called Taco the other day and they said open it up to check but be careful because its brass.....really how about some actual instructions.

 

[goosegunner]

I am almost certain the 4900 is not working. Got a great tip from Jebatty, I closed the vent screw and ran it for a while today. I then opened it and did not hear any air come out.

I could hear what sounded like small bubbles running through the pump.

Might be time for surgery on either;

1. The Taco 4900 to see why it isn't working.

2. Cut the dang thing out and put in a less finicky brand that actually works...

 

[leon]

You can down load the two page owners manual to read about it if you google Taco 4900.

 

[goosegunner]

You can down load the two page owners manual to read about it if you google Taco 4900.

I had one that but have yet to find one about disassembly and repair.