furnace high pressure reading


  #1  
Old 12-02-09, 08:02 PM
mech1's Avatar
Member
Thread Starter
Join Date: Dec 2009
Location: usa
Posts: 29
Received 0 Votes on 0 Posts
furnace high pressure reading

i have an old american radiator oil furnace,heat and hot water.
this morning i found a puddle on the floor from the relief valve,but the valve was dry. i turned up the thermostat to run the furnace, i noticed the temp hanging at about 160 but the pressure kept increasing. i shut it down when the valve started to drip.
what is the correct readings i should see and how do i correct it.here are a couple of pictures.
100_2850 on Flickr - Photo Sharing!
100_2858 on Flickr - Photo Sharing!
 
  #2  
Old 12-02-09, 10:12 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 36 Votes on 28 Posts
Your problem is a waterlogged expansion tank. That's the tank up between the floor joists. You need to connect a short hose, no longer than to reach into a bucket on the floor, to the drain valve, the one in the middle of the tank. It looks like there is a pipe cap on a nipple from the valve, it may be necessary to get a garden hose thread adapter to fit before connecting the hose.

Close the valve from the system piping that is located at the end of the tank and then open the drain valve. There will be an initial gush of water but that will soon slow to a trickle and may completely stop. This is because the expelled water has created a partial vacuum in the tank. there are various ways to break this vacuum and just allowing the hose to drip may be all that is required. You may need to loosen the hose at the drain valve to let in some air or worst cast scenario blow into the open hose end.

Once all the water has drained from the tank (probably in excess of ten gallons) close the drain and SLOWLY open the valve from the system. The pressure in the system will drop when you open the valve and this will be indicated on the boiler pressure gauge. When the pressure drops below the fixed indicator on the gauge the "make-up water" pressure valve (also called an auto fill valve or PRV) should allow new water to enter the system until the pressure stabilizes very near to the fixed indicator hand. This should put you back in business.

If you have an air compressor with a pressure regulator there is another way but it does have a small hazard. Post back with your results.
 
  #3  
Old 12-03-09, 05:33 AM
mech1's Avatar
Member
Thread Starter
Join Date: Dec 2009
Location: usa
Posts: 29
Received 0 Votes on 0 Posts
sounds like an easy fix. just a couple of questions first.
after the furnace cooled off the pressure guage dropped back down to even with the altitude needle.
when you say "fixed indicator hand" is this the shorter altitude needle?
thanks for the help.
 
  #4  
Old 12-03-09, 11:05 AM
mech1's Avatar
Member
Thread Starter
Join Date: Dec 2009
Location: usa
Posts: 29
Received 0 Votes on 0 Posts
on the first question i meant to add is it normal after cool down to be even or should it read less?
 
  #5  
Old 12-03-09, 11:09 AM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 36 Votes on 28 Posts
Yes, the fixed hand is the altitude hand. Yes, it may very well drop back to that pressure or even lower when at room temperature. That is a classic sign of a waterlogged expansion tank.
 
  #6  
Old 12-03-09, 03:28 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
I believe this tank has a valve that allows you to vent the tank for easier draining...



See that little knob on the side of the green valve? I believe if you open that knob when you are draining the tank, you will allow air into the tank, which breaks the vacuum in the tank and it will drain very much easier.

Yes, let the boiler cool to 100F or less, and TURN OFF THE POWER while you are draining the tank. You don't want it calling for heat while you are doing this.

When you repressurize the system, it should come up to 12-15 PSI when the system is COOL, and no higher than around 25 PSI when HOT. This is the maximum, you may have less, and that would be a good thing.
 
  #7  
Old 12-03-09, 04:37 PM
M
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,339
Received 0 Votes on 0 Posts
After you get the tank charged with air, try to figure out why it lost its air cushion. A conventional expansion tank's fittings should continually remove air from the water and put it in the tank. Where is the air going?

You don't have a separate air-removal device like a Maid-O-Mist do you? They shouldn't be installed with a conventional expansion tank.

Is the line from the boiler to the expansion tank sloped upward toward the tank?

Has this problem happened before?

I'm unsure what the green/white device is connected to the bottom, midpoint of the tank - with white plastic tubing going to it. Can someone enlighten me?

It looks like the expansion tank is connected through a B&G flo control valve. I would have expected to see the tank connected from an Airtrol fitting at the boiler supply and thence to a tank Airtrol fitting connected to the tank (where that green/white thing is.) Maybe that green/white thing is like a B&G Airtrol tank fitting? If so, what are the two plastic tubes going to it?
 
  #8  
Old 12-03-09, 04:47 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 36 Votes on 28 Posts
The "white plastic tubing" is type NM electrical cable and it isn't going to the "green/white device" in the middle of the tank, it just has a loop. Actually, the green thing is the drain valve and the white part is most likely a garden hose thread cap over a garden hose thread adapter or maybe the valve has a garden hose thread outlet. Trooper noticed the valve has a side port like a stop and waste valve but maybe it goes to an internal vent line into the tank similar to a B&G airtrol fitting.
 
  #9  
Old 12-03-09, 04:52 PM
M
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,339
Received 0 Votes on 0 Posts
Originally Posted by NJ Trooper View Post
See that little knob on the side of the green valve? I believe if you open that knob when you are draining the tank, you will allow air into the tank, which breaks the vacuum in the tank and it will drain very much easier.
I see a green-handled globe valve and a green/white thing-a-ma-jig connected to the bottom of the tank. Which are you referring to?
 
  #10  
Old 12-03-09, 04:58 PM
M
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,339
Received 0 Votes on 0 Posts
Originally Posted by furd View Post
The "white plastic tubing" is type NM electrical cable and it isn't going to the "green/white device" in the middle of the tank, it just has a loop. Actually, the green thing is the drain valve and the white part is most likely a garden hose thread cap over a garden hose thread adapter or maybe the valve has a garden hose thread outlet. Trooper noticed the valve has a side port like a stop and waste valve but maybe it goes to an internal vent line into the tank similar to a B&G airtrol fitting.
OK, thanks, I see it now.

But I would have expected the Airtrol tank fitting to be connected to the bottom of the tank, where the green/white thing is. Maybe there is such an animal on the far side of the tank in the picture?

Even after I get my bearings, I still would like to know where the air went.
 
  #11  
Old 12-03-09, 06:25 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
Here's a bigger view:



I do think that 'vent' on the side of the green drain valve (not the green handle gate valve) is similar to the B&G airtrol... but I'm guessing. Being green makes me wonder if it's something Taco used to make but no longer does?

Here's what I think I see on the line to the boiler... where it comes off the port on the B&G SA, through the valve, it actually appears to be TRAPPED at that point... it looks as though it drops down into a 'trap' before going back up... that ain't right.
 
  #12  
Old 12-03-09, 06:48 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 36 Votes on 28 Posts
Thanks for the bigger pic, Trooper. I think you are correct about that drain valve. It could be a Thrush as I'm pretty sure their stuff was painted that green color.

And it may be an illusion because of the camera angle but it sure does look like that piping goes up and then down before connecting to the tank.


Mech, if we haven't completely lost you, when you try to drain the tank close the valve on the pipe connecting to the end of the tank, attach the hose to the center drain valve (remove the cap, obviously) and then open the little valve (or maybe it's just a pipe plug) on the side of the valve and the thing should drain easily unless there is a pile of mud plugging the drain.

After draining close the side valve (or replace the plug if that is what it is using Teflon tape on the threads) and slowly open the valve at the end that you previously closed.
 
  #13  
Old 12-03-09, 07:25 PM
mech1's Avatar
Member
Thread Starter
Join Date: Dec 2009
Location: usa
Posts: 29
Received 0 Votes on 0 Posts
well the good news is draining down the expansion tank worked. i drained about 12 gal from it. now it's holding at about 18 when at 200 degrees. this is when it shuts down. i wish i would have checked the posts when i got home from work, instead i went right to the basement. so i did not try opening the fitting on the side of that valve. it didn't take that long to drain. i posted a few more pictures of the tank and valve that might help with your discussion. thanks for the help.
 
  #14  
Old 12-03-09, 07:29 PM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 36 Votes on 28 Posts
The important thing is that now you have a properly functioning system.

Thanks for letting us know the outcome.
 
  #15  
Old 12-03-09, 07:44 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
Ya know mech, you really do have an extremely well preserved antique setup there! I really like the 'EverHot Tankless' ... fun to see all that still in existence and working.

Just to double check what you did...

You closed the valve in the line from the boiler to the tank.

Opened the drain on the tank and COMPLETELY drained the tank so there was nothing but air in the tank.

You closed the drain, and reopened the valve from the boiler to the tank.

Correcto?

The thing is, when you THINK the tank is empty because the water stops flowing, it often is NOT empty at all. If that tank was waterlogged, I would think you would get more than 12 Gallons from it. What happens is like with a drinking straw, you put your finger over the end and lift it from the drink, and the drink stays in the straw. Take your finger off and it empties.

Same thing happens with those tanks... you drain some water out and the tank 'pulls a vacuum'. No more water comes out, but the tank ain't empty.

If you simply drained 12 gallons out, sure you will have better pressure when the system is hot, because you took all that water out. But then what happens is when it cools, the pressure drops like a rock, and the water feeder puts the water right back in again.

Just telling you this in case...
 
  #16  
Old 12-03-09, 07:47 PM
M
Member
Join Date: Sep 2009
Location: U.S. Midwest
Posts: 1,339
Received 0 Votes on 0 Posts
Originally Posted by NJ Trooper View Post
I do think that 'vent' on the side of the green drain valve (not the green handle gate valve) is similar to the B&G airtrol... but I'm guessing. Being green makes me wonder if it's something Taco used to make but no longer does?
A B&G Airtrol tank fitting is connected to the boiler's Airtrol fitting. I think this is just a drain valve. Whatever we're talking about must be hidden in the photo.
 
  #17  
Old 12-03-09, 07:47 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
Technically speekin'

that downward jog in the pipe before it gets to the tank should not be there. It's supposed to have a slight uphill slope all the way to the tank so that air can collect back into the tank; But who's to argue with an antique system that's been workin' like that for how many years?
 
  #18  
Old 12-03-09, 07:50 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
Originally Posted by Mike Speed 30 View Post
A B&G Airtrol tank fitting is connected to the boiler's Airtrol fitting. I think this is just a drain valve. Whatever we're talking about must be hidden in the photo.


Mike, talkin' about that 'plug' on the side of the drain valve. That's most likely an 'air letter inner' to make draining the tank easier.
 
  #19  
Old 12-03-09, 08:12 PM
mech1's Avatar
Member
Thread Starter
Join Date: Dec 2009
Location: usa
Posts: 29
Received 0 Votes on 0 Posts
nj trooper you are correct, i stopped short of completly emptying the tank.(i tapped on the side until the hollow sound was right near the bottom) guess i wanted to finish so i could eat dinner. when i open the valve to the tank, the feeder stopped at about 12-14. furnace was cold didn't run since yesterday. as for my tankless hot water i stopped using it this past spring. i installed a propane fired bosch instant hot water heater.as for the age this house was moved to this spot in the late fifties i think.
 
  #20  
Old 12-04-09, 05:59 PM
mech1's Avatar
Member
Thread Starter
Join Date: Dec 2009
Location: usa
Posts: 29
Received 0 Votes on 0 Posts
Originally Posted by NJ Trooper
If you simply drained 12 gallons out, sure you will have better pressure when the system is hot, because you took all that water out. But then what happens is when it cools, the pressure drops like a rock, and the water feeder puts the water right back in again.

Just telling you this in case
...
today the pressure is @ 20 ,is this a sign i should listen to what you said and drain it again this time completely so the tank is filled with air when i reopen the fill valve. or should i just keep an eye on it for now?
 
  #21  
Old 12-04-09, 06:05 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
20 ain't bad really... as long as that's at the highest temp you can expect... like 180-190... if that's at some lower temp, it will of course go higher as the boiler gets hotter.

I would do it again... make sure the tank is completely empty, and at atmospheric pressure.
 
  #22  
Old 12-04-09, 06:17 PM
mech1's Avatar
Member
Thread Starter
Join Date: Dec 2009
Location: usa
Posts: 29
Received 0 Votes on 0 Posts
i will drain it again. this time i will try removing that plug on the side of valve and we will find out if it is a vent. it really did not take that long to do. best to make sure before the snow starts to fly.
also since i don't use the tankless hot water anymore should i change the setting on the aquastat? it set to 160 now. when i installed the new water heater i just closed the hot & cold water valves to the tank.
 
  #23  
Old 12-05-09, 01:30 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
since i don't use the tankless hot water anymore should i change the setting on the aquastat? it set to 160 now. when i installed the new water heater i just closed the hot & cold water valves to the tank.
Not real sure about that... the age of your system makes me somewhat unfamiliar with your controls.

I see another aquastat, a strap-on, on the pipe just above the boiler. What is that other aquastat set to, and how is it wired?

Photo 2855 looks like part of your 'primary control' for the oil burner, is that the 'stack switch' on the flue pipe?

What I don't know is if the control on the tankless is somehow tied in to the high limit circuit for the heating.

Is the green wire in the tankless control the same green wire on the B terminal in 2855?

I guess what I'm saying is that without tracing all the control wiring out, and understanding what it's doing, can't really say.

One thing I might be a little concerned about... closing the valves to the tankless. Depending on how it's piped, I might be a bit concerned about a pressure build up in the valved off piping... can you show us more of how that is piped?
 
  #24  
Old 12-05-09, 04:01 PM
mech1's Avatar
Member
Thread Starter
Join Date: Dec 2009
Location: usa
Posts: 29
Received 0 Votes on 0 Posts
i have posted a few more pictures that may help.
not sure but it looks like that aquastat on top is wired to house voltage. the bx goes to a box that has house wiring. i could pop the cover off and trace the wiring.

i was thinking after writing that i closed off the water valves to the HWH if it is full of water it may build up pressure when hot. maybe i should drain some (or all) of the water out of it.

as for the operation, after i got the new water heater up and running, i shut the valves and disconnected the thermostat wires on the water heater. thinking that the furnace would only come on for heat. when i turned on the heat this season, the circulator pump came on, but the furnace wouldn't fire up. after following the thermostat wires i saw that the ones i disconnected are the only ones that go to the control box. i reconnected the ones at HWH since this is the only thing that changed. furnace fired right up.

i think the way this operates is: when the furnace is on it maintains min of 160 degrees adn shuts down at 200 degrees to give you hot water. when the house thermostat calls for heat, the circulator comes on first drops the water temp below 160 degrees to fire the furnace(if your lucky you'll be in the shower and the water goes cold,you get to enjoy that for 3-4 mins)

i don't see anything that would shut it down at 200 degrees, but that's what it does.

i am ok with it running to maintaining a min temp without calling for heat if thats how it has to work. i think i have to do something about the HWH being full of water.

i didn't use a drop of oil this summer and never ran out of hot water.
 
  #25  
Old 12-05-09, 05:54 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
I think you are on the right track as to how it's operating.

The R845 relay on the back is most likely the circulator relay. The red and white wires to that are from the house thermostat. Is this right so far?

I'm betting that the 6006 aquastat on the pipe has the 120 coming in, with the hot wires on the R-B terminals, and nothing on the W terminal. This is probably an 'auxiliary' high limit. The 120 going OUT of this aquastat is probably feeding power to the 'stack switch'. Does that sound right?

The aquastat on the Everhot seems to be your boiler temp operating control... and I think what you are saying about how it controls the temp is true.

The 200 limit could be coming from either of the two aquastats.

They both have a built-in 'differential', where the 'open' and 'close' temp are different. ON at 160, OFF at 200...

The 6006 aquastat should have a differential adjustment below the block that the wires are on. There should be a 'wheel' peeking out from under that block.

I think that screw in the everhot aquastat with the copper washer on it with the 'pointer' is your differential control. Are there markings on that washer? Is there any manufacturer/model info on that aquastat?

I'm 99% certain that the everhot tank is full of boiler water, and the domestic connections are to a copper coil inside that tank. It appears there is a drain on the domestic coil at the base of the everhot. You can probably just open that to relieve the pressure, and leave it open. It shouldn't leak anything after it's drained, as long as the ball valves on the in and out are closed.

Are there plans to replace this boiler any time soon?
 
  #26  
Old 12-05-09, 07:42 PM
mech1's Avatar
Member
Thread Starter
Join Date: Dec 2009
Location: usa
Posts: 29
Received 0 Votes on 0 Posts
i looked over the wiring and drew up a diagram, then tool a picture of it. here is the link again.
Flickr: mech12's Photostream
the aquastat on the everhot says minneapolis honeywell, later i will take a close look at the wheel.
that drain valve used to drip and the valve is frozen shut. i had a cap on it. took that off and it started to drip. tried to loosen the valve, it turned a little bit and a small amount of water came out. i left the cap off thinking if it drips and it won't build pressure.
no plans to replace the furnace unless some major thing happens to it. we have been here 15 years and other than regular maintenance, a leaking relief valve once, it works fine, cast iron radiators are the best.
 
  #27  
Old 12-05-09, 09:08 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
I think the dripping will stop once the water drains out of the coil, then yeah, just leave that valve open.

I think there's some pretty easy changes you can make if you are comfortable doing electrical wiring that will convert your boiler to 'cold start' and save you some $$$ on fuel.

Myself, I would actually replace most of that old BX cable with the fabric/rubber insulation with modern MC cable as part of the change.

There is a spare set of contacts on your R845 circulator relay.

If you move the feed for Aquastat 2 from it's current connection to the HOT wire in the junction box, and instead feed it from the spare relay contact in the circ relay, the boiler won't have to stay at 160 all winter long... BUT... and this is a big BUTT!...

The system will be MUCH less responsive to heat calls.

With the system warm all the time, when the thermostat calls for heat, you instantly have at LEAST 160 water on it's way to the radiators.

If the system is allowed to go cold between heat calls, given the volume of water in your system, it might take some time before you start getting heat because of the warm up time. It might end up not being worth the change if it makes the house less constant in temp, and uncomfortable.

ALSO, because of that large water volume, you might could open your system up to problems with the flue gases condensing... you definitely don't want that... it's not as much a problem with older systems, but it's still real.

So, instead, I am going to recommend turning the aquastat on the everhot down to say 150... you will still get heat quickly, not have to worry about condensing, and save a few $$$ on fuel. You could probably go even a bit lower, maybe down to 140...

Did you say that you have the burner serviced and chambers vacuumed every year?
 
  #28  
Old 12-06-09, 07:39 AM
mech1's Avatar
Member
Thread Starter
Join Date: Dec 2009
Location: usa
Posts: 29
Received 0 Votes on 0 Posts
i was thinking of trying 140 degrees. i watched how long it took when i fired it up from cold (55-60 degrees) it took a good 20-30 min to get up to temp with the circ pump running.
i keep an eye on the soot in the chamber and have it serviced about every 2 yrs unless it looks like it needs to sooner. this one seems to work fairly well.
the slow drip on the frozen drain valve is working, got half a gallon between yesterday and today.
thanks for the help
if you have a car question let me know maybe i can help, thats my real trade.
 
  #29  
Old 12-06-09, 08:09 AM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 23,538
Received 7 Votes on 5 Posts
Large water volume systems can be problematic with cold starting the boiler. The home usually ends up swinging around in temperature by more than a few degrees. There are ways to mitigate the problem but any of them would mean significant repiping, and quite a few $$$.

140 will most likely be fine, I don't think I would go much lower than that though... when you do this, keep an eye on the flue pipe. If you start to see white streaks of dried condensate coming out of the seams, turn it back up. Ditto if you open the combustion or heat exchangers and see white or red 'flakes' laying around inside. Since you will be maintaining temp, I don't expect 140 will be a problem though.

got half a gallon between yesterday and today.
It should stop though... or has it? ...if it doesn't, it means that either of the ball valves isn't closing all the way, or there is an internal leak of boiler water into the internal coil.

It's generally recommended that oil burners be serviced yearly, but I guess if yer doing OK at two year intervals, there's no arguing with success! One thing I would recommend is filter changes yearly. There is also a screen in the fuel pump that should probably be changed if it has never been done.

I've been known to turn a few wrenches myownself... but those days are pretty much over. Sure wish I still had some of them cars, I could retire nicely with what they are worth today!
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: