Boiler pressure/New Question same problem


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Old 02-04-11, 01:02 PM
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Boiler pressure/New Question same problem

This question is directed to NJTropper only because we have conversed in the past about this particular problem. I gratefully accept anyone that has information that can help me out as well.

NJ Trooper explained this issue I am having with my boiler pressure, which make sense to me. My problem…or question is why the pressure would ‘drop’ off once a zone valve was commanded open, followed by a pressure rise and stabilization some time later.

Due to the fact that the circulator pump is downstream of the pressure sensor, it will initially ‘drop’ then ‘rise’ as pressure comes around in the system. (These are my words not his….NJTrooper was a lot more technical, but I got the idea).

OK…so obviously I am still not satisfied, or better yet, need some confidence that the system, or a portion of the system has not faulted. (I say this because I do not remember pressure fluctuations of this magnitude in previous year(s)).

Here is the situation:

As the boiler cools, the pressure decreases to almost zero. Once the boiler lights, the pressure will increase as the temperature increases to a maximum of 12 to 14 psi.

I do not hear any cavitations in the circulator pump, The expansion tank is around 2 years old…it is hot on the top and cool on the bottom…I can tap it above and below the diaphragm and hear different echo patterns so I am assuming it is still operational.

Even though the pressure falls off to …what seems like zero…(I can not get a good reading at that level so it could be 2 or 4 psi)….I can still go upstairs and feel the baseboard heaters to find them very hot to the touch..so that tells me that there IS enough pressure to raise the water to the second floor for heating, even though the pressure gauge reads well below the 5 psi mark.

During operation at low temperature levels with some zones demanding heat…if I close off the valve(s)…(water shutoff valves) to the appropriate operating zone. The pressure does NOT jump up to 12 psi…it just continues to rise as the temperature increases.

Having said that, all zones can be OFF/CLOSED and the pressure displays the same scenario…low when temperature low…and high (normal) when temperature is high.

You can actually sit there and watch the pressure fall as the temperature bleeds off….then as the furnace lights off to increase temperature…you can watch the pressure rise…sometimes stabilizing @ 10 psi…or occasionally 14 psi is there is a zone demanding heat.

Any thoughts?

Here are some pictures:

Furnace pictures by Mach73 - Photobucket
 
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Old 02-04-11, 02:54 PM
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Hi Mach, of course I remember ya, but details and what not escape me... good to 'see' ya again though!

The fact that you see a pressure drop is 'OK' for the way your system is piped, but the magnitude of it is not, because there seems to be other 'problems'.

As the boiler cools, the pressure decreases to almost zero.
This should definitely NOT happen. When the boiler is idle and cools off, the MINIMUM pressure you should see on the gauge should be 12 PSI.

As always, the FIRST thing to do is to verify that the gauge is accurate. If you can't find any of the posts wherein I describe a way to verify the gauge by using an external one, let me know and I'll repost... (use the 'search forum' in the tool bar above the message list)

In spite of the 'tap test' seeming to indicate that the tank is doing what it should be, I would like you to drop the system pressure and CHECK WITH AN ACCURATE TIRE GAUGE that the tank actually does have the correct precharge in it.

Here's a way to do so fairly easily:

==================================

Please note that in the following procedure I am instructing to use 15 PSI in the tank. Technically the correct air pressure is that which MATCHES exactly the COLD BOILER idle pressure. A few extra PSI won't 'hurt' anything really, and will slightly extend the service interval by adding some 'windage'. If you intend to service the tank yearly, go ahead and use 12 PSI if that is your fill pressure setting.

1. Shut off boiler and allow to cool to under 100°F.

2. Shut off water supply line to boiler.

3. Drain only enough water from the boiler drain to drop the system pressure to ZERO. REPEAT: DO NOT COMPLETELY DRAIN THE BOILER! ONLY ENOUGH TO DROP THE PRESSURE TO ZERO!

4. With an ACCURATE tire pressure gauge, check the air charge in the tank on the air valve opposite the end of the tank that's connected to the system. If ANY water comes out of the air valve, the bladder inside the tank is shot and the tank needs replaced. If no water comes out the air valve, and the pressure is less than 12-15 PSI, continue to step 5. If the pressure is OK, turn the water supply to the boiler back on and repressurize the system, turn the power back on to the boiler, no service is necessary.

5. Using a bicycle pump, or a small air compressor, add air to the tank until you have 15 PSI air charge.

6. Check the boiler pressure gauge again, and if it has risen off ZERO, drain some more water from the boiler drain until it is again at ZERO.

7. Check the air charge on the tank again. If it is below 15 PSI, add air to the tank until it is at 15 PSI.

8. Repeat steps 6 and 7 until the boiler stays at ZERO and the tank stays at 15 PSI. At this point, the tank is properly recharged and the water supply can be turned on to re-pressurize the system, turn the power on to boiler and return to service.

9. Perform this procedure at LEAST every 2 years! These tanks lose 1-2 PSI per year. Even brand new ones! This should be routine preventative maintenance!

===========================================

more...
 
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Old 02-04-11, 03:18 PM
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A bit about the expansion tank:

When the boiler is COLD and the pressure is at 12 PSI, there should be NO WATER AT ALL in the expansion tank. The air pressure behind the bladder will push it all out.

As soon as the water begins to heat, the water begins expanding and the excess water will enter the top of the tank. Depending on the volume of water in your system, when the boiler is fully HOT, you may have 1-2 gallons (more or less) in that tank.
 
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Old 02-04-11, 03:21 PM
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Bottom line is that we can't truly conclude anything unless we know that the gauge is accurate, so as mentioned, that is the first thing you need to do.

It does sound as if the pressure reducing valve isn't feeding water, and that the air charge in your expansion tank may be low...
 
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Old 02-04-11, 04:33 PM
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OK...just waiting for the boiler to cool below 100 degrees...I have the water to the regulator valve 'off'.

Now...if I DO check the expansion tank pressure and it is below normal...will it hurt to repressurize the system and run the furnace until I can get my hands on a tire pump...(Little late up here and all the stores are closed).

Also could not find you post on checking boiler pressure

-Jim
 
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Old 02-04-11, 05:03 PM
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Jim, no problem running if the air charge is low in the tank... it's probably not THAT low... but as long as the pressure isn't soaring to 30 PSI and opening the relief valve you should be OK...

I was just thinking though... if your feed valve is not feeding, before you drain the boiler it might be a good idea to see if you CAN feed water into it first!

There's a 'fast fill' lever on the valve... lift that lever and listen for water to flow, and watch the gauge... you should see the pressure increase... don't add any more water at this time than necessary to be sure that the valve will at least work to put water back in.
 
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Old 02-04-11, 05:08 PM
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I think you should be able to pick one of these up at whatever home improvement stores you have up there... it can usually be found in the section for lawn sprinkler stuff... package might be a little dusty this time of year!



They are about $10 USD ... the 300 PSI gauge is USELESS for boiler work, but the fitting is what you need. Try a regular plumbing supply, or swimming pool supply (won't be busy this time of year!) and pick up a gauge with 0-30 (preferred) or 0-50 PSI and the same threads as the one that came with the gadget. Replace the gauge on the fitting. Screw onto boiler drain (any one) and open the drain. Read pressure, compare with boiler gauge.
 
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Old 02-04-11, 05:35 PM
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Hello NJTropper...totally confused now....

I let the temp drop...as it did the pressure came up to around 12 psi then fell slightly as the boiler temp approached 100 degrees. (The water valve to the feed valve was off).

I continued with the appropriate steps and found that the expansion tank was at adequete pressure...around 13 psi or so...maybe 14. My tire pressure gauge is analog.

OK...so I re-opened the water valve to the feed valve...

Turned the furnace on and let it warm up...then operated some zones on and off. To my surprise the pressure is around 16 psi with all zones off, and around 12 psi with zones open.

Now....so far as I can tell...the pressure is remaining stable at low and high boiler temperatures....

any thoughts??
 
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Old 02-04-11, 05:49 PM
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any thoughts??
hmmmmmmmm... magic?

Seriously, not really... only thing I can think is that maybe for some strange reason the feed valve wasn't feeding... maybe a piece of crud in the valve... and when you refilled it, it washed the crud out?

That's my best shot...
 
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Old 02-04-11, 06:00 PM
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Ok. thanks NJTropper. I was able to bring the pressure up in the past with that lever on top the fill valve...but like you said, maybe the release of backpressure cleared something loose.

Boiler temperature is still low and pressurre is still stable @ 12 psi...here is hoping
 
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Old 02-05-11, 05:21 AM
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Hello NJTrooper. Just to follow up on previous snag...when the boiler is at low temperature with zone zone valve(s) open or closed, it will maintain an honest 10 psi. at the High temperature...just before the furnace cuts out, the pressure will be around 14 to 16 psi.

I think I am at least getting close to 'normal' here ? Anyway the pressure is 100 times better than before, and the needle has not dipped below 10 psi in any temperature/ zone valve regime.

Once again NJTrooper I thank you for your help.

-Jim
 
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Old 02-09-11, 11:48 PM
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Superhot Boiler No Change in Psi

Hello NJTrooper,
I recently had a superhot boiler installed. I have read in your post that the psi on boilers should be 12-15psi when the boiler is turned off and increase to under 20 psi when the boiler is turned back on. The gauge on my boiler remains the same 20 psi when it is off AND when it is on. Could you advise on how I can get this fixed? What sort of problems arise from having no changes in the psi?
I would appreciate your advice on this. Thank you.
 
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Old 02-10-11, 08:02 AM
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hi quest2 –

I am not one of the experts here on the forum. But I believe you are going to hear from the experts that gauges do frequently lie. And I’ll bet you’ll hear that you should replace your gauge and then see how things look. If the gauge just doesn’t move off 20- that sounds suspicious! (My gauge on my well pressure tank would never drop below 40, and that really misled me for a while).

Maybe the guys would give you a test to see if your gauge is functional – or maybe that fact that it never moves off 20 would be enough. Maybe I’m wrong but I hope it is just the gauge, since I don’t think the replacement job is too difficult or expensive!

Good luck!
 
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Old 02-10-11, 09:18 AM
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I recently had a superhot boiler installed.
How recently? Brand new gauge on a brand new boiler?

Dad knows the drill pretty well! It could be a case of a defective gauge.

Before pronouncing though, let's get a little more info.

What model of EverHot boiler do you have?

Does your boiler also heat the domestic hot water to the home?

More important than just a pressure reading is information at what TEMPERATURE you are seeing this pressure.

When the boiler is COLD, generally the pressure will drop to say 12-15, and when it is HOT (say 180F) you may see up around 20-ish...
 
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Old 02-10-11, 10:07 AM
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Thanks for responding to my question.
I had an Allied Mini Star Superhot Boiler 125 installed 3 months ago. It also heats the hot water tank. Even when the boiler is cold for 2 hours, it dropped only to 18 psi. The temperature really dropped but cannot remember the temperature.
Thanks again for your help.
 
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Old 02-10-11, 10:30 AM
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Originally Posted by quest2 View Post
I have read in your post that the psi on boilers should be 12-15psi when the boiler is turned off and increase to under 20 psi when the boiler is turned back on.
If I may. Pressure is not really dependent on if your boiler is on or off like you state. It is dependent on the temperature of your water. If a boiler turns on at 100f it will have a lower pressure then if it turns on at 160f. So stop thinking on/off cycles and just think about temp vs pressure.
 
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Old 02-10-11, 02:40 PM
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Yeah, what bid said... with boilers, when mentioning a pressure, there should be a temperature associated with that. i.e. 17 PSI AT 180F ... otherwise the term is relatively meaningless.

I'm leaning toward 'no problem'... the reality is that as long as the pressure relief isn't blowing off, and there's no air gurgling around the system, and the home is heating properly... well, everything is probably OK.

If you wanted to know for sure, shut off the boiler for a few hours and let it get cold, to under 100F ... then read the gauge and let us know.
 
 

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