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under 10 psi in hot water boiler?

JBW_2 Member Posts: 67
hey john,

very nicely detailed explanation.

How many floors do you have above grade? 8 psi will only get water up 16 feet above the pressure reducing valve on a house that has 2 stories might not be getting the water up to the top rads...

Have you tried bleeding one of the radiators on the top floor? If you get air and then notice that neither or air or water is coming out, you do not have enough pressure in the system.

Also, the issue with boiler never going above 140 deg- do you have a aquastat on the boiler that is set to that temp?? Most of the old warden kings have an old honeywell stat right on the supply pipe coming out the top of the boiler.

Ultimately, I agree with the other guys. You are best served calling a licensed heating professional. Moreover, you are due for an upgrade to a more efficient boiler.

I do like the warden kings, though. Especially since they were manufactured in Montreal!!!!! Those were the good old days, when residential boilers weighed half a ton. Back when my father and grandfather were installing boilers.



  • S Ben
    S Ben Member Posts: 1
    under 10 PSI in hot water boiler?

    I have a 4 y/o New Yorker and a leak free system (i think) however I bled my radiators and quite a lot of air came out of them and now the system has less than 10psi in it. The taco boiler feed valve is making hissing sounds but the water shut off valve above it (on the inlet) is closed so I dont think the inlet valve can work correctly. My expansion tank also sounds very hollow. Is it possible this is a low water condition? what should I do?
  • Brad White
    Brad White Member Posts: 2,398
    How tall is your system?

    10 PSI should be plenty for a single-story house (12 is a good default and is the factory charge for most expansion tanks and would be suitable for a two-story house). If a three story house, 18 PSI.

    Your 10 PSI should lift your water about 23 feet and if you have the appropriate 4 PSI at the top of the system, you should be fine if your system height is under 14 feet.

    The hissing sound? No idea. If the hand valve is closed there should be no flow even if the fill valve is open a bit.

    The expansion tank should be hollow or at least not full of water.

    It is the emptiness, Grasshoppa, which does the work.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • chapchap70_2
    chapchap70_2 Member Posts: 147
    Find out why

    If I understand correctly, the valve that allows water to get to the boiler via the pressure reducing valve (commonly called feed valve) is off? Normally, this valve is open so if you have someone that services your boiler, call and find out why it is closed before you do anything.
  • Timco
    Timco Member Posts: 3,040

    typically the fill valve is left on so the prv can fill the boiler to the set pressure as you bleed out air. the more air-free the system is, the better. Good installs have an isolation valve on the ex tank so it can be isolated & removed easily to check or replace it without draining the entire system, or the near-boiler piping. some systems have valves on the supply & return so the zones can be isolated and only the near boiler piping needs to be drained down for ex tank service...

    Just a guy running some pipes.
  • Brad White
    Brad White Member Posts: 2,398
    On the other hand

    leaving the fill valve off and isolated once filling, purging and venting is done, can be beneficial.

    You could have a small leak for years with constant make-up (maybe what is going on now with the subject system come to think of it). Lots of fresh water over time in a trickle and you would never know...

    LWCO protection a must, of course.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • coalcracker
    coalcracker Member Posts: 51

    In my area, LWCO are only recently being used and few at that, and I don't think they are required. So, having a boiler with the water make-up system turned off and a leak, equal danger.
  • Brad White
    Brad White Member Posts: 2,398
    No question!

    You would do better with a fill valve if no LWCO in your situation.

    Of course in your area, a thermostat looks like a shovel?

    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"

    -Ernie White, my Dad
  • John_185
    John_185 Member Posts: 6
    analysing an old system and its ailments

    I have a 56 year old, 2 storey house, and it has its original boiler. That's a "Viking Junior" made by Warden King Ltd, and it has model "# W-350" stamped on the middle access door at the front, with "4101" stamped on the lower door. It measures about 3 feet tall and 2 x 2 feet wide. The burner unit is made by "Roberts Gordon"; showing as model 400RA, minimum input of 50,000 BTU/hr, with max. of 210,000BTU/hr. It's a standing pilot.

    From the look of the front of it, I am guessing that this unit has been converted from coal fired to oil fired to gas fired over its career. Recent tests by the municipality have shown a CO output reading of 4PPM cold and 4PPM hot, taken at the first vertical section of pipe from the exhaust flange rear of the boiler.

    The circulation pump, oddly mounted in the return pipe just before entry back into the boiler itself, is a "Leland", 2.7 amp, one sixth HP, 1725 RPM pump. It has some noises associated with the bearing, and it appears to be leaking slightly at the flange where the main housing joins the impeller housing. (I count one drop every 10 seconds currently leaking into a large can below it...). Makeup from municipal supply comes through two filters, (down to 1 micron) as well as a water softener.

    In the interest of economy and without fully understanding the effects, I think I may have been achieving the opposite effect from my goal.

    For the last several years I have run the system with a low programmed thermostat setting, using 18C as a nightly setting, cycling up to 19C during mornings for an hour or so, then setting back to 18C until around 5:30pm, then running at 19C until about 10:30 pm, when it settles back to 18C for the night. It gave me a false sense of economy, I think.

    The chimney is tall, about 30 feet, and is brick with tile liner of about 8 inch square size. Now I find a lot of damage to the chimney, and there was some sign of water penetration into the inside wall in one of the bedrooms adjacent to the chimney recently. The system was completely turned off from April until mid October this year. All I did to restart was oil the pump, turn on the gas, light the pilot and switch on power.

    The house is about 1500 square feet in total. It has inch and a quarter main pipes, all copper, feeding 12 baseboard and wall located aluminium finned, half inch copper pipe radiators. Only one rad is below grade. It is a one main loop system, without any split runs, and all rads are fed by a diverter tee setup.

    I have a relatively new Amitrol 30 expansion tank, which I find out may have been mounted incorrectly by the installer, it being mounted horizontally.

    So, what is the problem I am observing?

    There doesn't seem to be very good heat production or distribution anymore, even in relatively mild weather(today is only hovering around freezing). Boiler temperatures only reach up to 140F when I set the thermostat up as high as 21 C on my wall unit. Today I am running it at 21C, as a test to see what happens.

    The pump then runs for quite a while and the house warms up to between 19 and 21 depending upon where one sits, but there seems to be a lot of moisture in the house. Boiler pressure only gets up to 12 or so, whereas it has run a little higher in years past, getting up as high as 19 or 20 on the guage with extended use. I see a fair amount of condensation excaping up the chimney today, compared to other houses around me, and compared to what I would expect for the temperatures outside. There is high humidity outside recently.

    The second floor on some pipe runs is not getting much heat at all...especially where I sleep...

    Inside the heat exchanger when the flames are at their highest, it sounds like there is water dripping onto the flames. There is a more uneven sound to the burn than before.

    Once the unit shuts off and sits dormant for a while I have seen the pressure dropping significantly...in the time it has taken for me to write this, it has gone from 12 to less than 10 psi, yet the pump is not seeming to show a lot of leakage at the moment. I have turned the power off, opened the front door, and inspected with a flashlight. There is some dark staining of the cast iton heat exchanger in places, but most of it seems to be an even colour of rusted iron. There is a light dusting of what seems to be sulphur crystals here and there inside it, too.

    The dark stains are in the higher reaches of the unit, and they tend to be vertically oriented. There isn't any sign of water actually leaking out of the heat exchanger at this point.

    Yet, the pressure indicator has shown pressure has now further dropped to 8 psi, within about 20 minutes.

    Boiler temperature has dropped to around 100 F currently.

    What's happening, and what is my best option to get this system back up again?

    All suggestions are appreciated.

    I am located in Kitchener Ontario, Canada.
  • Timco
    Timco Member Posts: 3,040

    You just need a new boiler. Sounds like a leak. Go outside at night and look for steam coming out of your chimney when the boiler runs. Call a pro and have this looked at very soon.

    Just a guy running some pipes.
  • Weezbo
    Weezbo Member Posts: 6,232
    my best guess ...

    you have air in the system the pressure changes with temp.... you have no outside combustion air make up,or 1/2 of what you should have.

    the stack temp is not high enough.

    the boiler is under fired.

    corrosion has encrusted within the plumbing and unless you have a strainer then you need to flush the system.

    the stack is likely corroded with less heat actually making it into the heat exchanger than you think...your efficiencies are likely way outta whack with what you could have.

    get someone who can just look at it check a few basic parameters roll up their sleeves and get the best out of the system and or ask the same person if they would have a better more economical boiler available that they would install and service for you. as a guess... not being there .. I am certain that you like the existing boiler and really would like it to last forever buh, like me, sometimes you have to spend a dollar to save a dollar....
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