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circulator vacuum reading

leonz Member Posts: 1,050
Good afternoon fellow board members,

Thankfully I followed Dans suggestion about adding
a vacuum gauge to my system circulator on the
suction side when it was installed in 2015.

I am drawing 3 Hg currently and the circulator is not
making any noise.

The B+G NRF 3 speed circulator is 6 years old and only used
seasonally for pushing hot water through my 225 foot
single loop fin tube baseboard on speed one which is 12
gallons per minute-I KNOW its too much flow but I needed
circulators and that is all they had since the TACO circulators
failed after 24 years of seasonal use.

The steel compression tank is properly filled with the
1/3 air 2/3 water ratio for system pressure balance to
maintain the point of no pressure change.
The pressure in my system is zero PSIG on average and no
more than 2 PSIG normally with 54 gallons of water in
my system; counting the boiler water volume, baseboard
water volume and the 10 gallons in the steel compression
tank(thank you Dan for convincing me to use the steel
compression tank- I wish I still had the open to air saddle
tank I had here when we moved here in 1978.

SO, my question is should I change the circulator now or wait
until the end of the heating season? there is a bit more vibration
in the near boiler piping BUT the vacuum reading goes back to zero
when the circulator shuts off when a heating call is satisfied.

I have an identical NRF25 that was used on the old system and it has
not been used in 6 years and I do not know whether I should use it if
the other circulator starts screaming from air bubbles

Thanks much, I have to do chores.

PS, I cancelled the window contract the same weekend and I pissed
off a few people but I did not like the guy or the lack of a warm fuzzy
feeling I got from him especially when he said the wife's dog tried to bite him.


  • Jamie Hall
    Jamie Hall Member Posts: 22,894
    You still have the ;plain compression tank? That's good! Any air which might be drawn in by the vacuum at your pump inlet will wind up there, and that's as it should be. If you're concerned about the circulator and know you are going to replace it, there'd be no harm to getting it now and putting it on a shelf somewhere (just don't forget it) until you need it -- or this summer.

    Glad you cancelled the windows contract. Those salesmen always give me the creeps...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • leonz
    leonz Member Posts: 1,050
    edited February 2021
    Thanks Jamie,

    I explained in great detail to two friends how simple life is with a steel compression tank(thank you Dan).

    They have coal stokers they will be installing soon; one of which is an new AHS260(260000 BTU) with the traveling fire grate and the other which is a used VanWert VA600 underfed tuyere Pot stoker(150-200,000 BTU) to heat their homes.

    2 homes will use the AHS 260 and the other with the VA600 where it is a large ranch home with a walk out basement-easy install.

    I explained how easy they are to manage-no work haha and how easy it is to take care of them and avoid crawling around on ones knees to bleed baseboard-no maintenance haha.
  • leonz
    leonz Member Posts: 1,050
    I have to get the almost all the near boiler copper replaced with black iron pipe as their solder joints are really starting to corrode on me and I do want to hook the Domestic Hot Water Coil back up to preheat the water entering the propane hot water heater during the heating season. Their propress fittings blew apart twice and I do not want to live through that again as we lost our well water that night.
  • hot_rod
    hot_rod Member Posts: 21,826
    Why is your system pressure 0- 2 psi? I assume that is a static fill pressure, no circulators running?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • PC7060
    PC7060 Member Posts: 1,135
    edited February 2021
    Glad you cancelled the windows contract. Those salesmen always give me the creeps...
    Me too.  
    “Best deal ever”
    “Offer expires this Friday”

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,518
    edited February 2021
    hot_rod said:

    Why is your system pressure 0- 2 psi? I assume that is a static fill pressure, no circulators running?

    Same query here? As water goes into Vacuum the boiling point will also become lower. Any water up near 200° is in the area of flashing into steam and causing cavitation at say 4"Hg on the pump inlet gauge

    Why not operate at 5 PSI or so?
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • leonz
    leonz Member Posts: 1,050
    edited February 2021
    Hello hot rod/Bob, Ed, Jamie, PC7060,

    My coal stoker boiler has been running at 150 low-170 high for several years now and my system is all on one level in this old house with 225 feet of 3/4" fin tube baseboard all on one level in one loop.
    I wish I had cast iron radiators. I could turn the high limit up I guess.

    I believe the pressure is always low simply because of the lower temperature and the steel compression tanks volume with 5 gallons of air and 10 gallons of water to manage the system and keep my circulator flooded.

    I believe my circulator is beginning to fail(worn volute/increased space between the volute and the cast housing) hence the vacuum 2"-3" Hg. reading as the vacuum reading disappears when the heating call is satisfied(I believe the volute is probably worn from seven plus winters of continuous use at 12 gallons per minute.

    Hot Rod and Ed, my system is sealed with 54 gallons of water+- (water fill valve shut off etc.) and the only pressure that is created is from the heating of the water by the coal stoker.

    My coal stoker is pushing coal very slowly across the flat fire grates and burning the coal very well with nice fluffy ashes proving it is working well. The combustion air is blown up through the three fire grates
    burning about 80 pounds of coal a day.

    I will turn up the high and low limit 10 degrees tonight to 150 low-170 high and see how it goes tonight as it is supposed to get near zero again tonight.
  • leonz
    leonz Member Posts: 1,050
    After raising the low limit and high limit 10 degrees the vacuum went back to zero Hg. :)