Need help with boiler and expansion tank pressure

bstevens33

I recently had issues with my home hot water heating system. Even with the thermostats turned up the water wouldn't seem to circulate. I have since then bled the 3 separate zones which i did end up getting some air out of all of them, and i believe the circulating pump is working. From what i have read the pressure gauge on the furnace itself should be 12-15 psi, but i am confused on the psi of the expansion tank, when i had first checked it, it was only 4.5 psi, ive read it should same as gauge on furnace but have read more that say the psi should be 40. I have a gauge to check water pressure in lines and my furthest outside cold tap was 50psi which matches what i have at my water tank. Just seems like its not working right and not sure whats wrong or what check next

PeteA

Don’t mix up the tank for a hot water heater with the tank for your home heating system. If you have a hot water tank with an expansion tank, that gets pressurized to match your incoming house water pressure typically around 50-60psi.
if you’re talking about the expansion tank for you homes hot water heating system then that tank is pressurized to 15 psi.

also the tanks are not interchangeable since one is designed for potable drinking water (hot water heater) the other is designed for non-potable water (home heating system-boiler).

Jamie Hall

Are you on a well? If so, you should have two expansion tanks -- one connected to the heating system, and one controlling the well pump.

The pressure in your domestic water system -- which you measured at the cold tap as being 50 psi -- has nothing to do with the heating system pressure.

The one connected to the heating system should read the same pressure as the heating system water pressure -- which, if this is a normal one or two story house, should be between 12 and 15 psi when the system is cold.

The proper way to set the heating system expansion tank pressure is to set the air pressure -- through the Schrader valve -- at the desired cold operating pressure with the tank empty of water and disconnected from the system. This is sometimes easy if there is an isolation valve and drain -- but most times there isn't. As a very quick check, which isn't totally reliable, you can simply measure the air pressure in the tank at the Schrader valve with the tank still connected. That will only tell you if the tank is failed or really seriously overcharged or undercharged.

Ironman

The air pressure on the tank must be measured and set with no pressure on the water side. This applies to either tank, but as Pete said, don’t confuse the two.

bstevens33

I would say im confused somewheres then, for a couple weeks it seemed like the house wasnt getting warmer or colder no matter what thermostats were set at then. My expansion tank air pressure is around 12 psi while the gauge for my furnace pressure is also right around 12 psi i have read all kinds of forums and looked at pictures but i cant find anyone with a system like mine. Water comes into basement int water tank then has a filter, i thought over time from me changing the water filter air could have gotten in and it kinda seemed like maybe the heater lines were airlocked, i believe i have them bled now and have been keeping an eye on gauges the system does seem to be performing better

bstevens33

2 levels to the house, basement and main level, one expansion tank, which the air pressure currently reads around 12 psi along with the gauge on top the furnace itself 

bstevens33

Yes i am on a well

EdTheHeaterMan

From the few pictures that you posted, it appears that all the pipes in those pictures are part of the closed heating system at 12 to 15 PSI cold fill pressure. It appears the correct expansion tank is connected to that closed system. With that tank disconnected from the system, (You have an isolation valve) and no water in the tank, the air pressure on the air side should be set at 12 PSI

The best way to be sure of the empty tank pressure is to shut off the feed valve to the boiler, then let some water out of the boiler until the boiler pressure is down to about 6 to 8 PSI. Then check the air pressure on the air side of the tank. If it is below 12 PSI, then you need to add some until you get to 12 PSI.

DO NOT GO OVER 15 PSI WITH THE AIR PRESSURE IN THAT TANK. if you get some water to leak out of the AIR side of the expansion tank, then the tanks is bad and needs to be replaced. If the tank does not hld the 12 PSI and you hear air bubbles leaving the tank going into the boiler water, the tank is bad and needs to be replaced. If the air side of the tank does not hold the 12 PSI air pressure for 1 hour after you charge the air side with 12 PSI, Then the tank is bad and needs to be replaced.

The only good tank response is to have the air side of the tank hold 12 PSI for one hour on the air side when the boiler water pressure is at 6 to 8 PSI on the boiler gauge. If that happens then you have a good expansion tank.

EdTheHeaterMan

To further understand why you need to remove the boiler pressure from the expansion tank in order to properly test the air pressure, look at the illustration in this comment https://forum.heatinghelp.com/discussion/comment/1747354#Comment_1747354
Three different pressures in the empty tank will all read the same when the water pressure from the boiler is added to the expansion tank. They will all read 20 PSI on the air side when there is 20 PSI on the boiler side. The ability to accept expanded water from the heated boiler will be different if the tank is not properly charged when there is no water in the tank.

bstevens33

So does the air pressure in the expansion tank have anything to do with the water moving through the pipes, or is that all on the circulating pump? Could the pump be getting weak, its morning now and my heat isnt working like it should be its dropped in one zone and i still have thermostat turned up , i cant see 3 thermostats all kicking the biscuit at once

EdTheHeaterMan

The Air in the tank has nothing to do with circulating the heated water thru the pipes. the only thing the air in the tank is there for is to compress ans the water expands when heat is applied. That air compresses and gives the expanding water a place to go.

The circulator does not have a lot of force either. That is because it is not pumping anything, it is just circulating the water in a loop (or number of loops) around the pipes, radiators, and the boiler in the system. But that only works if the system has no air in the rest of the pipes and radiators. If you have air in the radiators at the top of the loop(s) then the pump is not strong enough to push that water to the top of the system. You will need to get the air out.

Q. What if there is no air? What if the system IS full of water?
A. Then there may be a problem with the zone valves not opening.

Q. But All three at once?
A. Yes if the transformer that powers the zone valves has failed.

Q. And if the transformer is fine and the zone valves are actually working? I did say a little heat is getting in but not like it used to.
A. Then perhaps there is no electric power going to the circulator motor or the circulator has just failed. Then you would need a new circulator. Heated water can move by Thermosiphoning, or Gravity. The hotter water is lighter so it goes to the top of the system. The colder water in the radiators is heavier so it will drop to the bottom of the system. That is gravity flow and that happens slowly, So you don't get as much heat from Gravity flow.

A professional familiar with Hydronics can determine the problem quickly. If you can not find the reason yourself, then maybe you need to consider getting a pro.

PeteA

@bstevens33 can we get some info from you regarding the boiler operating or not. If you go upstairs and turn down the thermostat and then go back down stairs does the boiler start? If the boiler doesn't start did you check to make sure the power is on (sometimes theres a switch on the wall with a red plate and then theres also a switch sometimes located on the side of the boiler itself. They should be ON.
If the boiler does start does it stay running for a little while? What does the temp gauge say when it stops?
If the boiler is getting hot then look at the zone valves and see if any of the 3 zone valves have moved over to the open position if not then your power supply could be bad and like @EdTheHeaterMan says above some of the things your describing doesn't really get impacted by air and may be more of an electric/controls issue where you may need a pro if you're not comfortable enough to work on or troubleshoot further. Folks like @EdTheHeaterMan and many other here can help get you to where you need to go but a little more detail is needed.

PeteA

also I might add @bstevens33 if the zone valve or valves are open, feel the 3 pipes on the opposite side of the boiler (return side) if they are much cooler than the line rising above the zone valve or valves then you may just have air locked zones and they just need to be purged to get the heat circulating right.
Sorry for the double posts but these are the easiest things a homeowner can check to get these folks pointed in the right direction to guide you.

bstevens33

The return lines are much cooler then the feed lines, i can hear the circulator pumping almost like a humm sounds like it is spinning doing what it should, the boiler kicks on when water temp reachs 160 is and kicks off just before 180, the boiler itself is functioning properly ive had a chance to ask around to a few more people today and i believe i did not get all the air out of system and im thinking when i did bleed the air i may not have had something exactly right

bstevens33

I believe the zone valves on at least the feed side are working they were cool and after i bled the lines the once boiler kicked in and started making hot water again then you could slowly feel the lines heating up and the copper pipes them selves were to hot too hold your hand on

bstevens33

That seems to be the only hose tap i have to bleed air outta my zones the 3 copper pipes on right hand side are my 3 retrun lines by my hose tap is down below, everyone else seems to have one for each zone is mine plumbed oddly? 

PeteA

@bstevens33
yes sound like everything is working correctly and you just have trapped air in the zones.
That is the only drain you need to purge but you have 3 zones to purge so you have to do it in a pretty specific way in order to not allow the water to take the easiest path and go back into the lines you think you flushed. The water at this point will be pretty hot so you need to be careful. I would spend a few minutes googling some videos of folks purging multiple zones on youtube. Once you're comfortable comparing what they do and see the same components on your system you can go for it. I think you'll get this done relatively quickly once you get started.
You'll need to look at your zone valves and see where the manual lever is to open and close those and then you'll also need to operate the gate valves on the return side to do the purging but I think if you've gotten this far you can get those bubbles out.

bstevens33

One thing i cant really find is how to isolate the boiler completely and if you all this with power off how is any water coming back into system ? The only real way i can find to put water back into my system is through the boiler its self with the auto feed, mine has the manual override leaver on top and i would almost be willing to bet without using it probably isnt working right, on assumption nothing has been serviced in roughly 5 years if not longer

bstevens33

I appreciate all the help, you guys are defiantely helping me understand things a little better 

PeteA

@bstevens33

you have plenty of valves on your setup to properly isolate where needed. The only thing I could not see clearly in your photo is where the auto feed valve is connected but it seems to be working well so far since it is pressurizing your system to the proper PSI.
But bottom line is you would shut the power to the boiler off, open the manual levers on the feed side of the boiler connect your garden hose to the drain spigot use that lever to pump the pressure up. Close the valve just above your boiler on the return side (its right below the spigot) and the valve below your expansion tank. Close 2 of the 3 valves on the return side raise the autofill lever and open the garden hose spigot and let the water rush through the 1st circuit until no air bubbles leave the garden hose, close the return valve and then open the second valve, flush until no air bubbles close that valve and open the 3rd valve run until no air bubbles. Close the garden hose spigot and drop the lever on the autofill right away. look at your pressure gauge. If your over 12to 15 pounds don't worry about it yet. open all your valves back up on your zones, open the valve above the boiler you closed and the valve above your compression tank.
check the pressure again, if its above 20 bleed a little out right at the garden hose valve, just a little open at a time. set your zone valves back to their normal position and test the boiler out and see how it heats. This should get 99% of your air out. Make sure the cap on top of your autovent on your air scoop is not tight it needs to be loose to burp out air.

bstevens33

The autofeed is on the backside of the boiler

bstevens33

So i think maybe my biggest mistake was i never did anything with the valve on the feed line before exspansion tank

neilc

I'm having a problem with the copper behind the boiler,
is the copper headers against the wall with the pex above your domestic? or a radiant zone?
and is your auto feeder to the boiler coming off the bottom of that mix valve and into the boiler?

then there's the backflow, which looks to be protecting into the domestic, or should I say from the domestic,
the backflow and reducing feed valve to the boiler should be together, stopping boiler water from backing into the domestic,

but maybe I'm not seeing that correct,
can we see a low angle shot showing the backflow, reducing feed valve, mix valve, and boiler connection, all in one inclusive shot

bstevens33

bstevens33

Water on floor is from me im currently trying to bled the system if i close the valve under exspansion tank i cannot put water in and make it circulate if i try and close the valve on the return at boiler below the spigot to bled from nothing happens except my furnace pressure spiking and the pressure relief valve goes off and spits water at 30 psi

neilc

wow, those other pictures were deceiving,
I can see clearly now,

I think someone said to shut the ball valve right at the compression tank, I really not sure why though, don't bother,

as for purging,
shut the boiler off at the service switch,
shut the ball valve under the purge bib,
open all the zone valves manually, swing the little levers and engage them in their notches to hold,
close 2 of the 3 ball valves above the purge bib,
hose on the purge bib and open the bib,
maintain 20~25 psi with the fast fill lever on the feed valve,
let that zone run till bubbles and air stop,
now briefly open the ball valve under the purge bib to burp anything there, briefly open and close, open and close a couple times, leave lower ball valve closed and release fast fill while closing purge bib,
that zone is done, close it's ball valve above the purge bib, and open the next,
rinse and repeat as above,
when you're done purging the 3 zones, reopen all 4 ball valves at purge bib(3 above and 1 below), and release the manual levers at the zone valves,
set the boiler pressure back down, or up to your 12~15 psi,
and that should do it,
restart the boiler at the service switch.

EdTheHeaterMan

We can disregard these PEX pipes/tubes with regards to getting the heat to work.

Now we need to start somewhere if we want to get the air out of the baseboard loops. Let's start where the water goes into the boiler. You want to see if the automatic feed valve has a bypass lever of some type in prder to get the pressure in the boiler up to about 25 PSI


If you look closely at the auto feed valve (pressure reducing valve or PRV) there is a metal tab at the top of the PRV. If you lift that tab, you will add water pressure to the boiler greater than the automatic setting. Be careful to watch the gauge on the boiler. You will want to turn off the feed water when the pressure gets to 25 PSI. If it goes over 30 PSI the relief valve will open, as it should, and you will get water all over the place. If that does happen, don't worry, it's only water.

Now that you have the boiler filled with higher pressure, let's look at how that higher pressure might leave the boiler

As you can see there are 2 exits, the supply and the return. There is a valve on the return. If you close that valve then the water pressure can only leave by way of the supply.

There is a boiler drain for purging on the return just above the ball valve you just closed. If you open that valve, then the water pressure in the boiler MUST take the long way around the radiators to get to that purge valve in order to exit the boiler. With that extra water pressure the air will get pushed out of the radiator loops, and you will have an air free system.

There is one last thing to consider. The zone valves. If the electric to the boiler is off, those valves will be closed. In order to purge, you will need to manually open them. Then take a look just above the zone valves.

There are isolation valves that you will close to make sure the water from the boiler goes where you need it to go. Open one of those valves to get the purge started. When you are sure that zone is air free, then close that valve and open the valve in the middle zone. Repeat the procedure. When you are sure the middle zone is air free then close the middle valve and move to the last valve. repeat the procedure for that zone loop.

After you are finished purging, put the PRV tab back the the automatic setting (flipped down). close the boiler drain purge valve as needed to get the boiler pressure set to 12 PSI.
Then open all the other valves that you closed to do the purge. The large one on the return and the 3 smaller ones above the zone valves. Reset the zone valves from manual open to automatic operation.

Now you should be ready to start to heat your home

PeteA

@EdTheHeaterMan great visuals as always.

bstevens33

So i caved and had someone come look at, he bled the system while the furnace was running and let the furnace move all the air around he did all the different zones and leaving all feed valves open and closing 2 out of 3 returns and closed valve right above furnace on return line, system was still acting up he said circulator pump had power and appeared to be working but wanted to change it. So with a new pump and another bled its hotter in house now then has been in couple weeks

SuperTech

He should know that it's not good to purge a boiler with it running. You need to close a valve to purge water through the zone, why would want the circulator running? It can't do anything with the valve on the purge station closed. If anything was actually wrong with the circulator it might have been a result of him doing that.  But I doubt it actually needed replacement.