Why am I putting pressure reducing valves on 160psi boilers?

JohnNY

Here in NYC our street pressure is about 45-55 psi.
I'm using lots of 160 psi Lochinvar boilers with 75 psi relief valves. Can anyone think of a reason I'd need a pressure reducing valve? I'm trying to explain to my helpers the roles and reasons for all our controls and stuff.

Harvey Ramer

Hydraulic shock. If you have imbeciles working on the mains.

Danny Scully

Can the system handle that much pressure (radiators, piping, etc) ?

JStar

To match expansion tank pressure and keep them safe.

ProblemSolver

What is the operating and cold pressures on that system?

nicholas bonham-carter

There could be spikes in pressure from the tall buildings around you, especially if there were an open connection by accident with a water tank 1000 feet in the air and a sudden closing of valves , such as would happen at halftime on a televised game with 20,000 thousand people all flushing toilets at the same time.the inertia of the water, with the high water tank connection could cause a spike of high pressure. Is that a possibility?--NBC

Gordy

Never know what that city pressure will be in 5 ,10 or 15 years. Or tomorrow.

JohnNY

Well all those are decent answers, but the reality is that every water heater has a 150# relief valve. So there's some fixed vulnerability there.

nicholas bonham-carter

If I have figured right, the pressure at the bottom of a column of water 1000 feet high is close to 450 psi, and the relief valve is only protecting the roof mounted tank's internal pressure, by limiting it to 150 psi incoming, but not the pressure at the bottom of the piping of the building. If that check valve fails, and The Kansas city Royals are at a particular point in the game tomorrow, there could be some hydraulic activity which sends the pressure of the water mains up to the maximum, and is hopefully controlled by the pressure reducing valve, unless it is old and tired like the rest of the system in many buildings in NYC.
Does this seem like I am on the right track with this?--NBC

JohnNY

I'm not going to pretend to be an authority on roof tanks but I can say I get the general principle and I've never heard of a single incidence that produced a high-pressure condition in the water mains, or even within the building. You could be right. I just don't know.

nicholas bonham-carter

It's not me who must be right, it's some chief inspector who woke up in the middle of the night to take a leak, and that made him think of this requirement.--nbc

Gordy

Darn it, never thought about the WH relief valve psi. Run away WH all that psi has no where to go before she corks, but with in the domestic piping.

icesailor

Are we talking "Boilers" or Water heaters? Most water heaters are supposed to run at a maximum working or operating pressure of 75#. The 150# is the test pressure. Which is a percentage higher than the operating pressure. Most plumbing appliances are rated to have no more than 75# and if they fail, , the Warranty is void.

Its always been my understanding that water pressure in tall buildings is pushed/pumped UP in stages, and sent back down in stages. Something like 10 floor intervals. Are the water towers there more for fire protection? Do you want to be drinking water out of a rooftop cistern tank that dead animals and insects have died in? Not me.

JohnNY

So, your first question is to clarify whether or not I know the difference between a boiler and a water heater.
Awesome. So glad my posts here so accurately convey my level of expertise.

Your second paragraph is...well...I don't know where it came from.

Cheers!

icesailor

JohnNY said:

So, your first question is to clarify whether or not I know the difference between a boiler and a water heater.
Awesome. So glad my posts here so accurately convey my level of expertise.

Your second paragraph is...well...I don't know where it came from.

Cheers!

Don't be ridiculous.

People interchange the two all the time.

I was asking about what the "Working Pressure" on whatever you were talking about because the "Test Pressure and the rated pressure of the relief valve are part of the equation.

Temperature/Pressure Relief Valves are rated with a 210 Degree blow off pressure. Pressure relief is supposed to be determined by the working or operating pressure.

Pressures in tall buildings are handled in strange ways that most don't understand unless you have studied them.

A steam boiler in the sub basement of the Empire State building (as I understand it) will send 10# steam to the whole system. From the basement to the top floor. A hydronic/water only system would be well over 400# (As NBC pointed out above. Potable water pressure in buildings over 100# can be absolutely dangerous. Like deadly dangerous.

Gordy

I think protecting his equipment, and system from "fixed vulnerability", or what some people take for granted as constants which can quickly turn into variables is insightful. One does not have control of every system that can have adverse effects to your system when they are linked. So you protect it with any means possible.

icesailor

Gordy,

What I was asking is this: On the rating/manufacturers rating plate with all the information, what is the maximum working pressure and what is the maximum test pressure. Both are required on any working tank or boiler. Here is the relevant section on the subject as Massachusetts deals with it. The National Codes follow suit. Massachusetts was the first jurisdiction in the USA to set up requirements for hot water tanks and relief valves (Watts Regulator Co.) Notice the part about working pressure and maximum pressure. When it comes to tanks, they drilled into our heads the things that all hot water storage tanks require:

Manufacturers name and registered trade mark on a tag permanently affixed to the tank.

Date of manufacturer.

Maximum working pressure

Maximum test pressure.
The Maximum test pressure is a percentage above the maximum working pressure. I can't remember what the percentage is and I left all my plumbing courses information behind from over 40 years ago.

You don't size pressure relief valves on the test pressure but the maximum working pressure. As far as I know, potable water in a building is not supposed to be over 80#, and if it is, it is supposed to be reduced down to 80# or lower. I've never seen a residential or commercial potable water heater that had a working pressure over 150#. High pressure steam boilers, but they are a different animal. They are different animals and covered by ASME boiler codes.

My only question in asking was, is there confusion between the working pressure and the maximum test pressure.

https://malegislature.gov/Laws/GeneralLaws/PartI/TitleXX/Chapter142/Section19