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Hydronic Heating Boiler Gauge FAQs
Q&A on hot water boiler pressure/temperature gauges
- POST a QUESTION or COMMENT about gauges on hot water heating system boilers
Heating boiler gauge frequently-asked questions:
Questions and answers about how to read, interpret, or replace or repair pressure & temperature gauges found on hot water heating boilers.
This article series describes the combination pressure & temperature gauge found on most hydronic (hot water) heating systems. The boiler gauge gives helpful temperature or pressure readings that tell us if the boiler is operating normally.
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Boiler Temperature & Pressure Gauge Guide FAQs
These questions and answers are about the pressure and temperature gauge on hot water or hydronic heating boilers were posted originally at GAUGES, HYDRONIC BOILER - be sure to see that article.
[Click to enlarge any image]
On 2020-01-10 - by (mod) -
I'm puzzled too, Russ.
Usually when the gauge won't show pressure it's because the small opening on the gauge base - that admits water to the gauge's internal pressure mechanism - is debris clogged.
When you replaced the gauge did you have to drain water and pressure from the boiler? Where is the gauge mounted?
Attach a photo.
On 2020-01-10 by Russ
I have an old Edwards boiler it's full of water and is clearly functioning properly as it is heating up my registers and keeping my house warm the problem is my old gauge was reading zero pressure but still tracking temperature so I replace the old gauge with a new gauge and it's still tracks temperature but it's still reading zero pressure not sure what the problem is
On 2019-11-14 - by (mod) -
Anon
For a typical 2 story residential home the boiler pressure would beast at 12 PSI cold. You shouldn't be having to make an adjustment as I would expect your water feeder on the boiler to deliver that pressure. That's the default from the factory. For taller buildings or other types of systems or other types of buildings those pressures and heating equipment could of course be different
On 2019-11-14 by Anonymous
How much water pressure in a New Yorker boiler ?
On 2019-11-09 - by (mod) -
Phil:
The gauge just suggests the boiler pressure and temp; it has zip to do with actually making the boiler run.
Since you say the heat's not working properly: to start diagnosing you'll want to answer some basic questions given at
NO HEAT - BOILER https://inspectapedia.com/heat/Heating-Boiler-Diagnosis.php
On 2019-11-08 by Anonymous
@mike,
No
On 2019-11-08 by Phil
My pressure and temp gauge looks like it's not working and I'm having trouble with the heat not working properly
On 2019-10-04 1 by (mod) - pressure & temperature gauge it does not show pressure at all
Mike:
Watch out: 1. TURN OFF THE BOILER immediately if there is the slightest chance that it is out of water - otherwise you risk damaging or ruining the boiler or even worse, causing unsafe conditions.
2. If the boiler in fact has plenty of water and works normally then most-likely it's the pressure gauge that needs replacement.
3. If the boiler does not have water and its automagic water feeder isn't working that device could be clogged and needs cleaning or replacement.
On 2019-10-04 by mike
pressure & temperature gauge it does not show pressure at all
On 2019-01-14 by Ken
What does it mean when the temperature gauge is reading between 65 and 80 F and the PSI IS 20. The system is producing heat in the hot water radiators in a six zone house at 5 am.
Is the temperature normal and if not what could be the cause?
On 2018-11-14 by (mod) -
I don't know, Bonnie, what is the correct pressure as I don't know what kind of heat you have for sure.
But if yours is a hot water heating system (not steam radiators) then the operating pressure in a residential system will normally be between 12 psi cold and under 30 psi when the boiler is hot.
I suspect that there is air in the heating system piping that has not been found and bled out adequately.
Search this website for AIR BOUND HEATING SYSTEM to read details of how to do that.
More diagnostic procedures for your case are at COLD RADIATORS
On 2018-11-14 by Bonnie
I have a combo system and a few cold radiators that I've bled. Still no heat. The pressure gauge goes up as I add water (opening the valve) but then goes back down again when the value is closed. Which is the correct reading?
On 2018-03-23 by (mod) -
See
https://inspectapedia.com/heat/Aquastat_Settings.php
On 2018-03-23 by Kathy
I have had the service folks here twice for my boiler - oil heat- because A. I am not consistently having hot water and B. my upstairs zone heat does not always kick in.
If we want to shower I have to crank the heat up to my the boiler turn on and run it for 5-10 min. During first repair he said it was the little box on the side (sorry not sure what it is called) was not triggering the second zone so he replaced that whole thing.
Problem still not solved so then they changed the mixing valve- it worked while he was here because I had the heat turned up. Later that day I could see the boiler temp was 99-105 and I had luke warm water. What temp is the boiler suppose to be and does that temp drive the temp of my hot water?
On 2018-03-16 by (mod) -
With the model and serial number we can find the manual for your boiler as that will tell us - that is, if there is no indicator mark on the boiler face. Meanwhile set water mid-window.
On 2018-03-14 by Terry
My crown boiler has a round window where should the water level arrow be on.
On 2018-03-14 by Gerrie casper
Psi reads zero while heater is running
On 2018-02-11 by (mod) -
Kathy
Above at the end of the article at "Continue Reading" please see the live link for AQUASTAT HI LO DIFF SETTINGS
On 2018-02-11 by Kathy
What is the correct temp of a broiler system supposed to be set at?
On 2018-02-11 by (mod) - where to find boiler temperature settings
Kathy
Above at the end of the article at "Continue Reading" please see the boiler temperature settings given
at AQUASTAT HI LO DIFF SETTINGS
and don't hesitate to ask if you have further questions.
On 2018-02-11 y Kathy
What is the correct temp of a broiler system supposed to be set at?
On 2017-11-23 by (mod) -
Claude, by remote comment like this I can only guess at the most obvious things to check. I'm on site expert will off and see things that you didn't notice to report and then I just couldn't think to ask about.
But in general I don't see that the temperature of the expansion tank what explain the problem that you have been describing. It's pretty straightforward to sort out a pressure question. Look at the pressure and look at the temperature in the system.
On 2017-11-21 by Claude
The heating cycle seems pretty normal, it always seems to cut off @ 150 degrees or less. I was told that the problem could be the cold water feed regulator. I was also curious though why the bottom of the expansion tank is never warm. I drained it last year but after reading several articles realized that it wasnt recharged. Do you still blame the fresh water feed regulator for over pressure
On 2017-11-21 by (mod) - causes of relief valve leaks?
Claude
If you search using the search box above to read our articles on RELIEF VALVE LEAKS you'll see several causes including too-high incoming cold pressure at the boiler, leaks into the boiler from a tankless coil, a control that's letting the boiler overheat etc.
When the pressure is as high as you cite, take a look at the temperature. If that's under 200F then your start pressure is too high.
On 2017-11-21 by Claude - viessmann atola series G1n boiler pressure creeps up
I have a viessmann atola series G1n. The boiler pressure rises to 30 to 32 psi during heating cycle, this causes the pressure relief to open on the combination fresh water regulator to drip.
Thanks
On 2017-11-12 by (mod) -
How,
If the room temperature is below the set temperature on the thermostat then the heat is behaving normally and the problem is that you're not able to warm the building enough to satisfy the thermostat. Of course if your baseboards are radiators aren't warm then we have another problem to solve and you'll tell me that.
If on the other hand the temperature in the room is getting above the set temperature on the thermostat then you're boiler isn't turning off when it should. You'll want to read this diagnostic article
https://inspectapedia.com/heat/Thermostat_Stuck_On.php
On 2017-11-12 by Hal
Temp is at 180 don't shut off
On 2017-10-05 by Ashley
Our gas boiler for the central heat was installed in November of 2016. Its not even a year old yet. The nights have gotten a bit cool and i turned it on to take the chill out of the air. Since then, it hasn't worked.
That was a week ago. The owners manual doesn't help. The temp and pressure gauge aren't moving. There are no lights blinking to signify an issue. The gauge is all the way down. Its a cg-e gas boiler.
Any advice would be great. Thank you.
On 2017-08-19 by (mod) -
Ken:
It would be unusual to see a boiler heat to above the boiling point of water (212 F) since you'd be making steam, and more-important, the pressure in a hot water heating boiler at sea level at 200 degF will be just under 30 psi, but up at 220F you'd expect the pressure/temperature relief valve to open.
So I speculate (picture your remote InspectApedia.com consultant sitting at her desk waving her arms in the air) that the pressure gauge is inaccurate, probably due to debris clogging with rust and sediment. I would replace the gauge. The convenient time to do that is at annual service in the spring when you are not in the heating season, thus when it is convenient to let the boiler cool down and to drain water and pressure from it to permit gauge replacement.
Send us a photo of the boiler and a close-up of the gauge using the page bottom CONTACT link and we can comment further.
DF
On 2017-08-19 by Ken
The temp.guage and aquastat setting are far apart. The aquastat is on around 180---my boiler is going to 220. I tried a new aquastat---same thing. Ihave a Dunkirrk boiler. We have used it like this for several years. It works fine like this. The pressure guage reaches the low 20,s.I was thinking of installing a temp. guage, but maybe this is not the answer.Thank you---Ken
On 2017-03-10 by (mod) -
Mike:
It's possible that the gauge itself is what's failed.
Before feeding water, I suggest obtaining or making an independent pressure measuring gauge - see https://inspectapedia.com/water/Water_Pressure_Measure.php for an inexpensive solution;
I attach the gauge to the boiler drain, then open the drain valve just a bit - enough to put pressure on the gauge to get an independent reading.
If your boiler is at below 12 psi cold or even hot, then yes pressure is probably too low and it's appropriate to call for a repair. The trouble could be a bad water pressure regulator/water feeder valve.
There's a risk making the measurement I describe that the boiler drain itself is stuck or doesn't close again completely, leaving a drip.
1. Do not "force" the drain valve it it doesn't open
2. Have a garden hose cap on hand so it can be screwed over the drain valve opening in an emergency
On 2017-03-10 by Mike
I have a Burnham oil fired boiler for baseboard heat, and the gauge(tradicator) the pressure is at 0 not 10 or 12 where is usually is, although we have heat coming through all baseboards up on top level (singe level home) there is no heat in one baseboard in basement. question, is it ok for me to slowly add a little water from the house water supply feeder valve, to bring up pressure, while the system is running, I have read several posts, and now worry I might cause a crack or some damage.
On 2016-10-27 by (mod) -
Scott,
Replacement temperature/pressure gauges for heating boilers are sold at plumbing suppliers, heating suppliers, building supply stores like Lowes and Home Depot, and even online. I just installed a replacement gauge on a heating boiler for a total cost of $10. as the gauge was used - salvaged from a boiler that was being removed. A new gauge is about $45. U.S.
On 2016-10-27 by Scott
where can I buy a gauge like the one above ?
On 2016-02-20 by (mod) - defective boiler gauge - unsafe
Dave, I suspect that the boiler pressure gauge is defective, perhaps rust/debris-clogged. I'd have it replaced.
Separately, if the pressure/temperature relief valve is spilling THE SYSTEM IS UNSAFE and should be TURNED OFF. Call your heating company to diagnose and repair that problem.
Watch out: over-pressure at a heating boiler or water heater risks dangerous BLEVE explosion. (Search InspectApedia.com for BLEVE EXPLOSION to read details). That's why the relief valve is a critical safety device. Yours is doing its job.
Search InspectAPedia.com for RELIEF VALVE LEAKS to read the causes and repairs for spillage at that valve.
On 2016-02-20 by Dave
I have a Peerless oil burner. The PSI on the gauge is at zero. The water temp at 180 degrees.
A pressure relief valve on the back side of the boiler is escaping steam and releasing some water. Hot water is fine in the house. Thermostat set at 70, temp has dropped to 64. Boiler runs. Seems like no pressure on gauge yet pressure relief valve going off???
On 2016-02-16 by (mod) -
See https://www.vaillant.com/home/
On 2016-02-16 by Anonymous
Where can I purchases a valiant gas furnace
On 2015-12-21 by (mod) -
Anon it means the gauge is shot and needs replacement -which will require shutting off the boiler and removing some water and pressure. Ask for this repair before the leak becomes a catastrophe.
On 2015-12-20 by Anonymous
Water is leaking into temp/pressure gauge. What does it mean?
On 2015-03-13 by (mod) -
Kat
If there is a leak at what is really the boiler drain that valve needs replacement and meanwhile can be closed with a screw cap.
If the leak is at a temperature/pressure relief valve that is an unsafe condition that needs proper diagnosis and repair.
And yes 12 psi hot is a bit low unless you're in a one story house - but then the gauge may be inaccurate.
On 2015-03-13 by Kat
Also I noticed it seem to leak water from the boiler drain when it is not running and not when it is running???
Thank you for your reply, but I just wanted to add that I checked the pressure and temp when the boiler was not running and when it was running and tried to see where the pointers were on the gauge(through the condensation). When not running it was about 10psi and 70 degrees, and when running it was about 12 psi and 190 degrees. If it is working right, the pressure seems too low. yet it is heating most of the baseboards? Also, I am only setting the temp at 64 degrees because the daytime temp has been warm outside. I set it at 60 degrees at night.
Kat
I have a Vaillant boiler installed in 1989. It is heating the house ok, except 2 short baseboards seem to lose heat and we have let out air manually on them and then they work for awhile. Also two bathroom corner baseboards are also not working. One has a frozen valve and the other is not easily accessable behind a toilet. But it has not caused a problem and the rooms always have the doors open.
We have also drained the water tank twice near the boiler, but in the last few days, I have noticed a puddle of water under the boiler dripping from the boiler drain.
When the door to the boiler is opened the pressure gauge has alot of condensation in it and is hard to read. I am planning on calling our furnace repairman but need to know more about this problem?
If you have any ideas on this let me know.
Thanks,
Kat
On 2015-01-25 by (mod) - how does water get delivered to my hydronic heating system,
Tom
In a companion article at
PRESSURE REDUCING VALVES
we discuss hot water heating boiler water feed valves. Check that out and let me know if questions remain
On 2015-01-25 by Tom
how does water get delivered to my hydronic heating system, and how can I supply the water myself if needed?
...
Continue reading at GAUGES, HYDRONIC BOILER - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.
Or see these
Heating System Gauge Articles
- BOILER CONTROLS & SWITCHES
- BOILERS, HEATING - home
- EXPANSION TANKS
- GAUGES ON HEATING EQUIPMENT
- PRESSURE & TEMPERATURE SETTINGS, CONTROLS
- STEAM BOILER PRESSURE
- STEAM BOILER TEMPERATURE
- STEAM BOILER SIGHT GLASS
- STEAM HEATING SYSTEMS & CONTROLS
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Citations & References
In addition to any citations in the article above, a full list is available on request.
- [1] Power Technology and Engineering (formerly Hydrotechnical Construction), Volume 43, Number 4, 247-250, DOI: 10.1007/s10749-010-0105-4 - Thermal Power Stations, Temperature regime for damaged steam superheater coils, V. A. Bogachev (this is a PDF file - if you can't find contact SpringerLeak)
- [2] "Deaerator", Wikipedia, web search 12/18/11. Quoting:
The deaerators in the steam generating systems of most thermal power plants use low pressure steam obtained from an extraction point in their steam turbine system. However, the steam generators in many large industrial facilities such as petroleum refineries may use whatever low-pressure steam is available. - [3] Babcock & Wilcox Co. (2005). Steam: Its Generation and Use (41st ed.).
- [4] Thomas C. Elliott, Kao Chen, Robert Swanekamp (coauthors) (1997). Standard Handbook of Powerplant Engineering (2nd edition ed.). McGraw-Hill Professional. ISBN: 0-07-019435-1.
- Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
- Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
- National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
- The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
- Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
- The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
- Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
- "Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
- "Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
- "Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
- Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
- Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
- Installation Guide for Residential Hydronic Heating Systems
- Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
- The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
- In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested
CONTINUE READING or RECOMMENDED ARTICLES.
- Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: info@carsondunlop.com. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
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