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# Pressure question - MJStraw

Member Posts: 57
Open ended, static or dynamic, the pressure of a system is always lower as you get to a higher elevation because the 'head' or weight of the water is less as you travel up the column.
Example -

100' column of water would have 43.3 psi at its base, only 4.3 psi 90' above base.

100' column of water pressurized to 143.3 psi at base (100 psi increase)would have 104.3 psi 90' above base.

100' column of water with return line and pump installed at base (10 psi head increase at pump discharge) and system pressurized (while pump is off) to 143.3 psi at base would have 153.3 psi at base with the pump on and 104.3++ psi(head increase at point) 90' above base.

The only way this would change is if you introduced a pump somewhere midstream on return, which would add head pressure to the return side of things.

## Comments

• Member Posts: 625
static fill

Typical 2-story system with fill valve in basement static pressure is 12psi. With the system quiescent (circ not running) what is the pressure in a 2nd floor radiator?

Is it 12psi or something less (under the assumption that some of that 12 in the basement is from weight of water
above).

Sorry for such a basic question.
• Member Posts: 427
Measure from the gauge center to the the top of the

of the radiator. Devide this by 2.31 feet. that will give you the pressuer of that space. subtract that from 12 and the result will be the pressuer in the radiator. hope this helps bigugh
• Member Posts: 427
Measure from the gauge center to the the top of the

of the radiator. Devide this by 2.31 feet. that will give you the pressuer of that space. subtract that from 12 and the result will be the pressuer in the radiator. hope this helps bigugh
• Member Posts: 625
as I suspected

OK - so the pressure is going to be lower at the 2nd fl rad than in the basement (where the circ, fill and expansion tank are located).

Consider a circ with 6psi head pumping away. If upstairs rad is half way thru a loop, the pump will only be adding 3psi to the static there. If it's 20ft up, the static is about 3 so total pressure in that rad is 6psi.

So we have 12+6=18psi at the pump discharge, 6psi at the rad, and back up to 12psi at the pump suction.

Would that not cause air to come out of solution in said radiator?
• Member Posts: 1
boiler pressure

THE PRESSURE IS THE SAME DUE TO THE FACT THAT YOU ARE DEAlING WITH A CLOSED LOOP SYSTEM. IF YOU HAD AN OPEN COLUMN OF WATER YOU TAKE EVERY FOOT TIME .433 PSI PER FOOT.
• Member Posts: 410
Yep, but..

If the air separator is scrubing the air out of the system water before it is sent up to the rad, the water will gradually absorb this air and carry it down to the air separator.

Boilerpro
• Member Posts: 625
it's a tie

1 vote each for same pressure and reduced pressure at the 2nd floor rad.

Vote early and often :-)
• Member Posts: 4,909

Maybe you should try "Find a Contractor".

There are a lot of questions that can be answered here, but there are more questions that will go unasked.

It's your system and your comfort so do with it as you will.

Please be careful, CO is a tricky gas.

Mark H

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"
• Member Posts: 625
did you post this to the right thread?

If so - what does my original question have to do with CO?
• Member Posts: 4,909

Hi Mark,

Yes I meant it to go here and I know it doesn't answer your question. Although I believe Archimedes principal comes into play here.

I read your post below about pipe sizing and now a post about pressure. It sounds like you are planning on doing this replacement on your own. OK. This is America and you are free to do that.

My concern is that, even if all of your piping and control questions are answered here, will you know if the system is venting properly? What effect will your new system have on the remaining appliances in the combustion appliance zone?
Will the new system be fired correctly?

I know you've seen Timmie's posts here and you know what he does for a living. He teaches pros how to set up combustion appliances.

I do too many tests each month Mark, where the systems are either vented wrong or where the new system is vented correctly but the effect on the rest of the house is ignored. I was in a house on Thursday where the homeowners brother in law installed a 40 gallon gas water heater. He did a great job piping it and venting it. What he did not know to test was what happened when the blower on the furnace ran. It caused enough of a negative pressure that the water heater back drafted, spilling CO into the basement and subsequently into the return ducts. The next stop from there was the house.

This forum is a great way for a homeowner to educate themselves so they can ask the right questions of the contractors they will consider for a job.

I have read many of your posts and you definately have a better than average knowledge base. But I am compelled to warn you of dangers that you may not be aware of.

Of course if you have access to the testing equipment and are familiar with their operation, I apologize for insulting your ability. It's hard to know just how informed someone is over the internet.

One last point, have you considered who will service your system if you install it yourself?
It may be harder than you think to get someone out of bed at 3 am to fix something they had nothing to do with.

Again, you may have the ability to do that yourself as well and if you do, I mean no offense.

Just playing devil's advocate.

Good luck with your project.

Mark H

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"
• Member Posts: 625
you might be extrapolating too far

> Yes I meant it to go here and I know

> it doesn't answer your question. Although I

> believe Archimedes principal comes into play

> here.

I purposely asked the question open-ended, even though I believed the answer to be the one that's gotten more votes so far. I was attempting to reconcile it with what Dan's Pumping Away book claims. It now appears that the book assumes eveything is at the same altitude.

> I read your post below about pipe sizing

> and now a post about pressure. It sounds like you

> are planning on doing this replacement on your

> own. OK. This is America and you are free to do

> that.

Who said anything about a replacement? I sure didn't.

My question about sizing was again an attempt to reconcile differing pieces of information written by Dan. Good thing I did since Pumping Away never mentions that it doesn't apply to gravity systems being converted to forced circulation.

I've got a gravity system that was converted to forced circulation. Pumping into boiler, reduced (but not enough)
near boiler piping, no bypass.

Having trouble finding a qualified wet-head around here.

I'm considering several modifications - TRVs on some/all rads, bypass piping, pumping away etc. I'll either do it myself or write a set of specs and see if any of the locals
can understand them.

My ultimate goal is to someday replace the boiler with something along the lines of a Munchkin, Monitor MZ or Viessmann Vitodens200. I'll either hire someone to do it or get myself certified and do it.

> My concern is that, even if all of your

> piping and control questions are answered here,

> will you know if the system is venting properly?

> What effect will your new system have on the

> remaining appliances in the combustion appliance

> zone? Will the new system be fired

> correctly?

>

> I know you've seen Timmie's posts

> here and you know what he does for a living. He

> teaches pros how to set up combustion appliances.

> I do too many tests each month Mark, where the

> systems are either vented wrong or where the new

> system is vented correctly but the effect on the

> rest of the house is ignored. I was in a house on

> Thursday where the homeowners brother in law

> installed a 40 gallon gas water heater. He did a

> great job piping it and venting it. What he did

> not know to test was what happened when the

> blower on the furnace ran. It caused enough of a

> negative pressure that the water heater back

> drafted, spilling CO into the basement and

> subsequently into the return ducts. The next stop

> from there was the house.

>

> This forum is a

> great way for a homeowner to educate themselves

> so they can ask the right questions of the

> contractors they will consider for a job.

>

> I

> have read many of your posts and you definately

> have a better than average knowledge base. But I

> am compelled to warn you of dangers that you may

> not be aware of.

I appriciate your concern - as expressed in this message.
But not in your previous one.

> Of course if you have access

> to the testing equipment and are familiar with

> their operation, I apologize for insulting your

> ability. It's hard to know just how informed

> someone is over the internet.

Requirement for specialized tools will be one factor in deciding if I want to ever replace a boiler myself.

Just to give another perspective on this particular point,
recall an earlier posting I made about the "fall service" I received from a long-time local company where the "tech" adjusted the manifold pressure "until the flame just touched the sections" and claimed he never used a manometer.

Call me gun-shy...

> One last point,

> have you considered who will service your system

> if you install it yourself? It may be harder

> than you think to get someone out of bed at 3 am

> to fix something they had nothing to do

> with.

If I eventually decide to install a new boiler myself I'll be certified to both install and repair it.

> Again, you may have the ability to do

> that yourself as well and if you do, I mean no

> offense.

>

> Just playing devil's

> advocate.

>

> Good luck with your project.

thanks - I do appriciate the generally cordial attitude here on the wall. Even if I never do any of this myself, I still enjoy learning about things for the sake of learning.

Call me crazy :-)

• Member Posts: 4,909

Knowledge is a good thing!!

Missed your post about the fall sevice, but that is what I face every day.

"Gee.... my heating company was just here, how come they didn't measure the CO?"

I just heard that a couple in Mississippi(?) is suing the Depot and a pressure treatment facility. Seems they installed some pressure treated lumber in their kitchen and now they claim to have arsenic poisoning from it?!?!?!?

There are many dangerous things out there. If you put your circulator in the wrong spot or forget to solder a joint I don't think you will be killed.

Venting of flue gasses is a whole other thing.

Mark, I wish you the very best of luck.

Mark H

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"
• Member Posts: 625
Did that long ago

and retry periodically.

Closest one is Dave Yates - 132.9 miles :-)
• Member Posts: 140
Mark S, sounds like...

you and I are similar in that we are a bit nutty about our systems, and are not contractors.

I went through a similar experience as you when doing my house. Without going into detail, I didn't have The Wall to help me ('98), and I did not touch anything as far as testing or firing-up my boiler...left that stuff to the experts and still do to this day.

Do you work @ IUP? Two of my sisters went there, and have fond memories.

This is the best place to be for guys like us. You seem to truly seek only the best information, and it's here. If I can be of any help otherwise, e-mail me.

Take Care, PJO
This discussion has been closed.