OLD B & G COMPRESSION TANK SIZING..DO I NEED A NEW TANK?

ww

The boiler is a Delco DB4S...I'm getting mixed info from the heating museum and the old booklets as far as the BTU's...ranges in books and brochures.....121000 to 160080 boiler output..with 39.5 boiler capacity. This is a 2 family house...there are no vents in the system...the expansion tank has a drain faucet on the tank and no other gauges attached...There are 15 radiators in the house....there is one taco circulator feeding the system.

The burner is a Beckett AF with and F3 head 1.25 gph 80 degree Hollow. The burner is running fine. I just installed new vent pipes and barometric damper...brushed and cleaned the boiler...checked everything.

I drained the tank....which is an old B & G tank on ceiling....diameter is 12 inches and length is 30 inches...I figure it was just under 15 gallons. I tested it using the B & G dual valve instructions...The boiler was off for a few days...refilled the tank and the valve filled it up to 12 lbs on boiler pressure gauge.

Started the boiler and after 10 or so minutes the pressure went to 15. The book said if it's over 10% of total boiler pressure cold that the the tank is no good.

I've seen the safety valve leak some water last heating season when the pressure was in the high twenties. and figure this tank is no good anymore..unless I'm wrong...I'll change all those valves if necessary if the tank turns out to be the problem here.

I'm figuring all radiator volumes, pipes, boiler volume...etc...but it seems when I call to ask for a replacement I'm told anywhere from 4 gallons to 20 gallons..Some say the diaphragm type is smaller...none that mount on the ceiling...
Is all this math and calculation the best way to go..or is it just overkill?

Just read the below article on this site written by Dan...good and informative info here. After the responses from this post and reading this article it looks like there is hope for this tank.

https://heatinghelp.com/systems-help-center/why-compression-tanks-waterlog/

(The comment below is about a steam system I worked on and has nothing to do with this post)

I did have to measure every steam pipe in a house and figure out all the capacities to figure out the proper venting for the basement as well as all the radiators so I know how to figure out the formulas on that kind of stuff. I read about all that here on this site thanks to information leading to Gerry Gill's information...and also attended a Steam Lecture by Dan Holohan in NYC.

How should I proceed with this please?

JUGHNE

Is this steam or hot water?

How about pictures of the boiler, tank and any vents you refer to.

I see now you were referring to 2 different jobs.
If a compression tank has worked for years on a hot water system, it should continue to function unless more piping/radiators/water has been added.
If it does not leak air or water then it is not worn out.

Pressure increase went from 12? to 15?
Your pop off relief valve could be getting weak or your compression tank has lost it's air charge.
Do you have any other air removal devices on the system?

Gilmorrie

Pix might help. Your original post has some numbers and nomenclature that puzzles me.

leonz

Hello ww,

If you have a steel compression tank between the ceiling joists in the basement you do not have steam heat. do you know where the circulators are that push hot water from the boiler to the radiators???? We need pictures of them too.

What you have a steel compression tank not an expansion tank and it is a very reliable way to provide the point of no pressure change in your system.

The only time a steel compression tank goes bad is when a weld ruptures or the tank rusts out at a weld.

I have the same tank but a newer vintag with an airtrol valve, and gauge glass and an Internal Air Separator to feed any airbubbles into it.

With my coal stoker using the steel compression tank I run summer temperatures of 140 low 160 high with a 190 dump zone temperature.

If you want a reliable triple gauge you should purchase a Marsh Instruments triple gauge as it is built by them, tested and certified by marsh industries and they offer a 2 year guarantee on the gauge and they can be easily calibrated by the lay person. I have had my fill of chinese gauges and will not buy them; BUT i would not hesitate to purchase pressure gauges from Taiwan, those I would buy in a heartbeat.

When you have time would you be so kind as to provide us with many images of the near boiler plumbing as possible being the water feed valve, pressure relief valve. back flow preventer, piping leading to the steel compression tank and the pipe runs from the boiler to the ends of the basement plumbing.

The more pictures you can upload the faster one of us can help you.

Do not lose hope, you can keep the tank in the ceiling you just need to do some work.

ww

Seems to be some confusion...i was referring to another job when i was talking about the steam. I do hope this tank is good..will save me problems of getting the right one....I referred to the pressure valve releasing water in the past...not when it went up to 15 lbs.....all radiators have been bled as well.

What are you thinking it could be besides the tank?...I'll take some photos when I can and attach them. It just seems the amount of water I drained from the tank was about 2/3 the volume of the tank.

there is one taco circulator which I installed. What work do you think I need to do on this...?

leonz

If you have an automatic air vent in that plumbing set up get rid of it and plug the tapping its in.

Please take pictures-lots of them even if you spend the time to pan and take pictures that way with adequate lighting it will help everyone to help you

If you do not have an airtrol valve installed in the bottom of the tank and you leave the automatic fill valve open(you should not)
you will flood the tank and lose your point of pressure change.

Take a big wad of pictures that way we can identify everything for you.

You should also wander over to Dans bookstore page and purchase PUMPING AWAY and CLASSIC HYDRONICS so you know what you are looking at and you can talk to a plumber you trust if you need one to fix what ever is wrong.

ww

there is no air vent in the setup...no airtrol valve in bottom of tank..just a faucet...the boiler fills to 12 lbs when low pressure due to draining tank....auto fill is not on...the boiler and system would be overfilled...is that what you are talking about?

I know all the parts on the boiler. Is there a procedure to do this draining of the tank that I'm not doing properly...thought i was doing it correctly ..but if not ..please let me know....it's getting cold over the weekend and will have to use as is until I figure out the problem. I'm told the maximum pressure should be 20 lbs at full heat and saw it close to 30 at 150 to 180 setting of aquastat.

the pressure relief valve is set at factory for 30 lbs...maybe these gauges are inaccurate. Will post photos soon.

ww

you mention if auto fill valve is on....i interpret as lifting the lever and the valve fills to boiler until you push it down...is that what you mean?

leonz

You have a boiler drain valve in the tank chances are it has the tiny drain line that sticks up into the steel compression tank to drain excess water from the tank to correctly create the 1/3 air 2/3 water ratio in the steel compression tank.

If the tank is refilling in the event of low pressure without intervention you need to shut the feed water off.

The lever in the regulator lets you bypass the regulator for a quick boiler filling.

Shut the water feed valve off(the one in front of the pressure regulator" and then drain any excess water off from the steel compression tank and when it spits only air shut the valve off.

My coal stoker boiler can operate with water pressures from 1-2 PSI to 10 PSI depending on the demand for heat in the home.

You should no longer have any issues with the steel compression tank after you shut the fill valve off and drain the steel compression tank of excess water as any air in the system will vent into the steel compression tank.

ww

1/2" ATF-12 Airtrol Fitting (For 12"-14" Compression Tank Dia)

this is the valve mentioned here as well as in the article attached written by Dan. Enclosed are the photos.

It looks like that the valve on the tank is just a valve and not the above...?

leonz

No photos,

The ATF 12 airtrol valve (which I have) has the copper tube and a simple drain that lets you drain the excess water out like I described.

I wish I could be more help.

I take it the steel compression tank does not have a gauge glass in one end?

ww

I took a look at airtrol directions and it said that you can't have a valve between the tank and boiler..and i see a valve in front of the inlet to the tank and it restricts flow of air into tank...don't see an airtrol there so don't know if this applies in the absence of one..but it would make sense that it does. see photo

leonz

The system needs some work.

I have no idea why they plumbed in two automatic water feed valves and left one wide open. If the globe vale is shut off and the tank is full of water it has some dirt stuck in it apparently.

The tank appears to have a boiler drain valve in that tapping rather than a water venting type of drain valve that would have the long tube in it.

The tank looks fine from what I can see of it you just need to have work done to bring it back to the correct way to plumb it with the right fitting a back flow preventer, low water cut off, new relief valve and what ever else you need to bring it up to code.

ww

one is a feeder valve and the other is the pressure valve. i agree with the valve in the tank....i listed the valve i saw above...thanks for your help!

ww

The two members who asked for the pictures never responded back again after I posted them.

I attached a photo of a pressure relief valve. This boiler doesn't have one like this...the b & g on is next to the fill valve in the photo...is there a difference in the both?

ww

Just attached two more photos just taken...the aquastat set 150 to 180....set thermostat to 65....started at 54....radiators hot...and now boiler off.. ...you can see the pressure is 28 lbs on the gauge and the water is coming out of the relief valve.

I guess next week will look into the airtrol valve for the compression tank and make some inquiries.....

other than spilling some water out seems like all running fine.
I might lower the aquastat numbers and keep them 30 degrees between them...who knows what the temperature is and if the gauge is right...and the hotter the water the more it expands.

ww

I was looking at PDF instructions for airtrol and it looks like if i put an airtrol in and replace the faucet drain there won't be a way to drain tank unless you can do it from the airtrol Also the water feed to the tank is in the back of the tank. I would have to re pipe into the tank to put in airtrol with 3/4 pipe.

It seems that parts places i call just say to replace with an expansion tank but don't want to do that at this point. I was wondering that this must have been installed incorrectly from the beginning.

mattmia2

I suspect everything you have is in working order, you just need the maintenance instructions from 60 years ago to keep the right air level in the tank. There may not be an automatic control, the old timers here and Dan's books should explain how it works.

Note that it looks like they edited the original post and added pictures that were not there originally.

ww

i put those pictures in there. let me know if you need more...so far i find directions on the airtrol but haven't found anything in the old library yet..still looking. thanks

Jamie Hall

These tanks work just fine. Maintenance is minimal -- but what I don't see on yours is any sort of gauge glass to check the air/water level in the tank. In principle, the Airtrol is supposed to do that. The only thing that can really go wrong with them is they can get waterlogged -- lose the air cushion -- and the solution is simple enough: close the valve to the rest of the system, open a tank drain, close the drain, and open it to the system.

In theory the Airtrol has a little valve on the bottom which you can open. If water comes out, let it drain (patience) and close it right away when air starts to come out. That should set the proper level in the tank. It's a good check.

One caution: do not put an air separator such as you would have with a modern expansion tank on the system. The compression tank depends on trapping the air in the system to work.

ww

ok thanks....it seems no one knows much about these tanks at all when you call for parts....is the DT-2 Drain-O-Tank Air Charger able to be used in place of the airtrol?...have to find out about the site glass too....i have the airtrol instructions and it seems when you call no one ever calls you back when they hear about this. I guess this is another of those Dead Men issues that few and far in between know about other than yourself and a handful of others.

EdTheHeaterMan

In all the posts that I read herein, i don't see anyone explaining that "Draining the tank" actually means "Adding Air" to the tank. if you let 5 or 10 gallons of water out of the tank, but no air goes into the tank, then you did not solve the problem.

I have found this method successful: #1. Connect a garden hose to the boiler drain valve (usually near the bottom of the boiler). #2 Shut off feed to the boiler with a manual valve. (you don't want to auto feed any water during this procedure) #3 open the boiler drain and let the water out of the boiler until the gauge drops to zero PSI. (assuming the gauge works) #4 once the water stops flowing from the from the drain hose, place the end of the hose in an empty 5 gallon bucket. #5 open the boiler drain valve on the tank in the rafters. you will hear getting sucked into the tank in the rafters. #6 once the bucket is full of water, you have added the equivalent of 5 gallons of air into the tank.
#7 close the tank valve first, then close the boiler drain valve, then open the water feed valve and watch the pressure return to 12 PSI.

(if you want to add the equivalent of 10 gallons of air to the basement ceiling tank, then use two 5 gallons pails in step #4. Just be sure that you don't make the tank totally empty so the air from the empty tank enters the near boiler piping and then into the radiators or baseboard loops. If that happens you will need to vent the radiators or purge the baseboard loops.)

nicholas bonham-carter

Excellent advice Ed, thanks.--NBC

EdTheHeaterMan

follow up:


I believe from your photos that this is your setup. No special fittings and the water feed valve has a tee near the expansion tank that connects to the flow control valve (Red). This is a classic "el cheepo" installation that has worked for years. The air in the expansion tank is migrating from the tank to the closed system radiators over time, just as indicated in the article by Dan H.

You don't have to reinvent the wheel. Just know that the air cushion tank needs to be drained (which means add air to the tank) every season. If the tank gets waterlogged faster and needs to be "Drained" more than once a year, then you can reinvent the system. but by the age of the boiler, You might want to think about new equipment before spending $$$ on reinventing the system with air-trol and expansion tank fittings.

save that money for when you get the new boiler in a few years.

ww

Thanks alot Ed...I'll be going through this method you have outlined....and the way you outlined the procedures is great. I'll report what happened!

EdTheHeaterMan

FOLLOW-UP:
Im reviewing service tickets for today and thought of you! We had a relief valve problem like yours and I diagnosed the DHW coil was passing, so I isolated it so water could not enter the boiler thru the pin hole leak in the coil (By-passing the water feed pressure reducer). This did not solve the problem. We then replaced the feed valve... and the problem is resolved. It was cheeper to close a couple of valves than it was to replace the relief valve or water feed or expansion tank. When I eliminated the leaking coil theory from the equation and the problem continued then we tried the next lowest cost repair.. customer is thrilled...

With you problem, after you get the air cushion tank right. and the pressure back to 12 PSI... Close the feed valve and leave it closed. If the problem goes away, wait a week or so, then open the feed valve. If the problem returns, the feed valve is passing!

ww

UPDATE...
Ed, Followed all the instructions you sent...and it worked out great. I put the heat on and set it to 70 degrees...the maximum pressure was 19 lbs and that's great compared to 26 plus!

That worked really neat how the air filled into the tank and how the the air replaced the water taken out.

I put the fill valve on already before I saw your post....but I checked it for quite awhile and it wasn't leaking...I can turn it off like you said and see what happens if necessary.

I did notice though that at not too much pressure...like 15 lbs the PRV dripped when I tapped the valve......I spit out some water fast to clear possible dirt and it still had a slight drip when I tapped it...

So maybe I can clean it or change the gaskets if they have a kit for that...it's a B and G dual valve and looks like the F3...wonder if I can't get the drip to stop if I can replace just the PRV since the fill valve is good...but will see on that one...

A long time ago I took a similar unit apart and made my own gaskets and it worked great.

also found that the thermostat is what looks like 2 degrees off on the high side...I set the temp to 66 and boiler went off at 63....then moved it to 67 and it went off at 67. It's a honeywell ct3200 and can't be adjusted for temperature. Any suggestions on a thermostat or what I should do with this?

I checked the radiators and the one closest to the boiler had air in it and bled it so water ran out..I expected that...Will check that as I go along..this procedure worked out and was on point to what you said.

I'll say thanks again Ed for your help and analysis...and I'll also thank the other people who helped out with this problem...I believe that gathering information and taking bits and pieces of what works can yield great results...as you've seen here.

I feel that the system will be more efficient now and after I get the rest of the bugs worked out... it can only get better!

EdTheHeaterMan

The weeping relief valve is most likely debris on the sealing face of the relief valve. Popping the handle to flush clean water thru the valve should work. You may need to do that several times. Since the valve is fairly new I believe that you can get it to stop weeping. If not ... you can certainly replace the relief valve only. sometimes it just takes a little time to reseat and stop weeping. give it a couple of days. Just hang a bucket under it for now.

ALSO... you should add a safety tube to the outlet of the relief valve. according to code the discharge should terminate within 6" of the floor, or into a floor drain. minimum amount of elbows.

ww

ok...I popped it open and will try again...the valve looks new but has been on there a long time...also will work on that discharge tube...there was one on there going to the sink..but that is more than six inches off the floor...so maybe a bucket or something...will see. thanks

ww

Checked system this morning and all fine. heat not needed last night and gauge pressure 12 lbs. i turned off the feed valve anyway and will monitor it this week like you said.

i see the thermostat temperature is a degree or so high...so still looking into that and if i should get another one...don't know how these digital thermostats work and if at certain temps they are more accurate than other temps.

mattmia2

What do you mean by the thermostat is high? Is it reading different than another thermometer or is it getting hotter than the setting when/after it shuts off?

ww

yes..the thermostat is reading higher than a thermometer..it gets hotter than setting if temp set to mid sixties.....usually rises a couple of degrees due to radiation.

I'll give you this example ...

the temperature in the house this morning was 56 degrees on a thermometer near the thermostat.

the hold temperature I set on thermostat was 58 degrees and the boiler was off. I then moved the hold temperature to 59..60..then 61...the boiler went on....boiler shut off when thermostat said 61....temp on the thermometer was 58.
....
then set thermostat hold temp to 63..boiler goes on and shuts off when thermostat says 63...the thermometer said 60.

set hold temp on thermostat to 65...boiler goes on and shuts off when thermostat reaches 65...thermometer reads 62 as room temperature.

after awhile the temp on thermostat reads 67 and the thermometer reads 64. I understand the rise in temperature is due to the radiation from the radiators.

Is this normal and the temperature variance acceptable?..seems that the difference is greater the lower the temperature....I don't go that high as far as temperature so 64 is too hot for me. this termostat can't be adjusted.

ww

According to installation instructions of B and G dual valves the water supply line valve before the fill valve has to be shut off at all times unless filling water to the system...just like you said Ed. Water must not be added when the system is hot.

ww

That's great...will try and open it after a week...and see if pressure increases when cold so not to add water to system when hot....if pressure doesn't move then I'll figure fill valve is good and close the fill valve and leave it closed.

ww

I've followed above instructions and heating system is working fine as far as draining and refilling expansion tank...the other day i had to turn off the system for 24 hours...i looked at the boiler pressure gauge ...it was 6 lbs...when i set this up...from a total cold start...it was set to 12 lbs...i am on bottom floor...looked around for leaks and didn't find any yet....I added water and now at 12 lbs cold..put heat on..fine...any ideas on this one?...where am i losing this water...i think the gauge is fine.

JUGHNE

You may not have a problem, cold water and cold air could be dropping the pressure. As long as you have enough pressure to get water up to the highest radiator.

But if it continues, IMO, you are losing air not water.
It could be at any high point in the system.
For example, those compression tanks that have sight glasses, would lose air out of the top sight glass valve.

You may not have that, but any tank fitting above the water line could lose air.

ww

the only thing that happens sometimes is the radiator closest to the boiler on the first floor gets air in it. i bleed it and it stays good for awhile and then have to do again.

upon checking other radiators they were all bled...will continue to recheck again...and will check again if top floor is getting enough heat...i did that a couple of weeks ago and it was fine.

i only had to turn off the system for a day to check something out leading me to finding out about the lower pressure. thanks

JUGHNE

Your auto pressure fill valve must be off or not working. It should have put 12 psi back into the system.

You may be losing your air cushion by bleeding the rad out.
The air is what is producing the pressure if the fill is off.
All the air should end up in your compression tank.

If you can be certain all rads are bled of air AND can isolate the tank you could drain the tank empty and then fill it up to 12 psi.

ww

the autofill valve works...the water valve leading to the autofill valve is closed. it would put 12 lbs into the system if the valve leading to it was on...when i turn on the valve it will fill up the system to 12.

JUGHNE

The main concern is what the pressure rises to when the boiler heats up.

ww

that's been solved after the tank was drained properly...water no longer comes out of prv and that works great..so will monitor it and see how it goes. thanks