air problem - want to pump away

bauer

Hello...



I have an increasingly prevalent air problem in one of my boilers.  Air lock keeps happening -- sometimes within a week or a day of purging.



To solve the problem (hopefully), I am planning on repiping and 'pumping away' as per page 53 of the book with the same title. 



Two pretty simple questions --

1) the boiler is fairly old, since I am moving the circulator pump anyway is it worth just swapping in a new one? (of the same size? its a Taco 007 -- feeding the 2nd and 3rd floor of a home - fin tube baseboard)



2) I would like to add the gauges suggested by Dan - but am having trouble finding a combination pressure/vacuum gauge to place on the supply side of the circulator pump...?

ChasMan

Compound guages.

These compund things are readily available. Just about everyone who makes pressure guages makes vacuum guages as well as the combination types. Here is a link to a cheapie.

http://www.statesupply.com/maintenance-supplies/boiler-room-supplies/pressure-and-temperature-gauges/ua1010

bauer

thanks

ah thanks.. I was searching for combination pressure/vacuum.... compound was the word I was looking for.



Hope dan's book saves my purging nightmares

ChasMan

Purging.

It will as long as you put that big service valve and drain valve in the right spots with the ball valves on all the returns..You don't have to pump away to get that purging benefit but since you are doing all that it makes sence to. Dan's book says to use a 1 1/4" Ball Valve or Gate Valve. A good easily serviced valve can cost 350 bucks these days. Will be worth every penny if a cheap ball valve starts leaking.

bauer

Huh?

$350 valve?

ChasMan

Just an example.

That was just an example of what one can pay to close off a pipe ranges from 2  to 1000.



I don't think you need to use a stainless 10K PSI rated valve or anything but you want one that will last a long time and if needed, you can rebuild it without removing the valve from the piping. Unless of course, in your situation you are using 1" pipe or less and a 1" sweat valve where it would be easy to replace the valve. In my situation, I have a 11/4" valve attached to 11/4" threaded black pipe. That woul'd not be easy to replace.

As for your pump question, I would replace it. You at least need new flange gaskets and probably flanges but I am not that frugal. It shouldn;t get damaged if you remove it.

icesailor

Air Problems:

I think that you have a good idea. And when you are done, make sure that you raise the pressure in the system high enough to get the water up to the top radiators or heat emitters. And make sure that the pressure tank (Extrol type) has a precharge at least equal to the pressure that you will have on the system when in operation.. Like if you have 22# on the gauge at the boiler, you have at least a 22# pre-charge. That way, you won't ever realize that the only thing that your system needed was a raise in pressure. Pumping away isn't going to solve your problem.. A raise in pressure will 

Robert_25

3 stories?

I had the same thought as ice sailor...the feed valve is probably still set at 12 psi. Bump that and the exp. tank to 18 or 20 psi and I bet the air problems go away.

Eric_32

agree with the last...

2 comments and will add, get a screw on pressure gauge which can screw on a boiler drain/hose bib to confirm the pressure in the boiler is what your existing gauge is reading is correct.



Nothing worse than a broken gauge on the boiler to mess with adjustments.

Techman

Air Bound

The "boiler" is air bound? Do you have heat on the on any of the floors? W/ your #2- Is the "supply side of the circulator" the water into the circ or the water out of the circ? And as Eric said !, w/ a temporary screw on gauge, flush out the boiler drain valve before putting on the temporary gauge or debris can block your test reading.And as icesailor said !!!!

icesailor

Compound Gauges:

Another thing about your idea and search for the perfect gauge. What you are looking for is a "compound gauge". They are nice (and expensive) and I use them on water wells or oil lines where the suction OR pressure may revert to the opposite. Destroying the gauge in an instant.

If, on the other hand, you install a compound gauge in a heating system to see the "pressure differential" between the supply and the return, you have a SERIOUS PROBLEM in your piping system. If the return ever goes negative (vacuum) you have a serious OPPS.

If you can put a vacuum gauge on the return, and while the pump is running, it shows negative/vacuum pressure, the circulator is way too big and someone may have inadvertently installed a "jet" well pump in place where a 007 would have done.

If you don't understand about "head pressure", and you want an explanation, ask. I will write a retard explanation that is how I figured it out and explain it.

It's not what you think. As I explained to a "pro" yesterday who was looking for a high head, high volume circulator pump to get water to a third floor air handler that kept getting air bound. "It ain't what you think".

bauer

head pressure

thanks for the advice thus far...



regarding the charge pressure - shouldn't about 18# be enough? And good point about the pressure gauge on the boiler - I already know it is old and is off by a few #'s...which is why I want to add some gauges (one on the inlet side of the circulator and one on the outlet) -- but according to 'pumping away', the inlet side can create a vacuum, so a simple pressure gauge could be damaged.



with regards to the last post- let me see how much of an understanding I have --- the circulator doesn't actually create the 'pump' pressure to raise the water to the top of the building -- it simply moves the water around once the pipes are filled..it is the initial static fill pressure that fills the pipes - correct?



and finally - it is not my boiler that needs purging, I mis-spoke...I keep getting air in my top level pipes. I would like to not only fix that problem, but just set up a system that is as bullet-proof as possible, hence the pumping away, gauges, airtol fitting, IAS air separator etc.

icesailor

Pumping Vacuum:

Vacuum is when the pressure is less than 1 atmosphere. When you suck on a straw, you create a vacuum and it is atmospheric pressure that pushes the liquid in to your mouth.

A water well jet pump will create suction/negative pressure because it has the ability to move a volume of liquid at high pressure. It is an "open system". Atmospheric pressure pushes the water up the suction pipe while trying to equalize the negative pressure. In a closed system like a heating loop, it is a closed loop, and the circulator pump moves the water around. There is no vacuum anywhere in the system. If there is, and the water is hot, it will turn to steam. Cavitation is steam or water vaporizing because of localized vacuum in the impellers.

If you have a vacuum in a heating loop, you have a serious problem. A vacuum will cause water to boil at temperatures lower than 212 degrees. That's how vapor-vacuum steam systems work. You only need pressure gauges. 

icesailor

System Pressure:

Your second paragraph/question is correct.

Your third paragraph is wrong. It is the "Pressure reducing Valve (PRV) that sets the pressure in the system so that the water will be at the top of the system.

Your tridicator gauge that shows temperature in the system also shows the "pressure". Most gauges also show "Altitude". That "altitude" is the level that the water would be in a column of water, in height. equal to the pressure. 1# PSIG is equal to 2.31' in the height of the water column. If you pick a number on the gauge in PSIG, say 20#, multiply 20# times 2.31' and it will tell you how high above the gauge the water would be in a pipe, 100' in the air.

Measure carefully, the height from the gauge to the top of the radiation on the top floor in feet. Multiply that number times .434. If the numbers  in PSIG (Per Square Inch Gauge is lower, you need to raise the pressure by adjusting the PRV up and adding air pressure to the Extrol Tank.

icesailor

Head Pressure: Another explaination.

Maybe you will understand it this way.

Take two garden hoses, 50' long. El Cheapo is 3/8" ID and a good one is 5/8" ID. Connect a "rig" with a pressure gauge between the hose and the spigot. Connect another to the end of the hose woth a valve to stop the water. Take a 5 gallon plastic bucket and put it at the end. Leave the valve at the end of the hose closed/off. Turn on the water at the spigot. Read the pressure. Say it is 50#. It will be 50# at both ends of either hose. This is the "Static Pressure" Open the valve at the end. The spigot end will be 50#. the bucket end will be lower. This is the "Flow Pressure. The pressure differential is the "Head Pressure" found in a heating system. The pressure in either hose will be 50# at the spigot but at the outlet. the pressure will be higher in the 5/8" hose and lower in the 3/8". This is head loss differential. Measure the amount of water that will flow out of the end of the pipes in 1 minute. That is the flow in GPM. The larger hose will have a higher GPM. The only way to get the GPM's up in the smaller hose is to increase the pressure. This 50# pressure on the hoses can be called what a pump will be doing.

Connect a circulator pump like a Taco 007 between the two ends with the gauges in place. To be erief, there is 50# in the circuits. The loop is laid out flat on the ground. Before you start the pump, there will be 50# of pressure in the loop.  Start the pump. The outlet pressure on the pump will go yp. This is head pressure or resistance in the loop. The return gauge will be less than 50#. This is the pressure differential. The pressure differentials will ge greater on the smaller pipe than the larger pipe. Flip the horizontal circuit to the vertical position so that one end id 25' in the air. The pressure differentials don't change because there is equal pressure on both sides of the loop. What goes up, mist come down.

If you know the rating pump curve for the pump you are using, convert the PSIG to head by multiplying the pressure times 2.31 and look on the pump curve. It will give you how many GPM is flowing through the loop. The higher the head pressure, the lower the flow. Like the smaller hose.

I hope that this explains it. I'm not some sort of educated, trained engineer or something. I'm a mediocre product of the second best public school systems at the time, early 1960's, and had to figure out all this stuff on my own whensomething was broken and no one could fix it. 

 

Plumdog_2

painting a picture

with words that can be seen with the minds eye. Congradulations (sp). The concept is tough to understand. I work with Master Plumbers that still insist the pump head has to overcome gravity in a closed system. I try to explain it using the "teeter-totter" analogy. Because the weight is equal on supply and return, it only takes a gentle nudge to get the water moving.  

icesailor

Pumping in circles:

Thanks Plumdog.