R.L. Deppmann Company

Steam Vent Operating Pressure

Norm Hall — Mon, 25 Feb 2013 13:56:21 +0000

During the past week, after 3 weeks of condensate articles, we received a couple of calls regarding steam vents. I thought the questions were universal enough that they warranted a R. L. Deppmann Monday Morning Minute.

Question 1: I have a 15 psig steam system which operates at about 7 PSIG most of the time. Is the Hoffman Main Steam Vent Model 75 appropriate for this application with its listed 15 psig maximum?

This is a great heads-up question by the engineer who asked it. Paul Prentice, sales engineer at R L Deppmann, responded correctly with a caution and another choice of Hoffman vent by Xylem.

We normally concern ourselves with maximum pressures when applying a product to a HVAC system. In the case of steam vents, that could get you in trouble. Although the Hoffman model 75 can “stand the pressure” of a low pressure steam system, with its maximum pressure of 15 PSIG, it only has an operating pressure of 3 PSIG. What does this mean?

When thinking of vents, most people think of hydronic system vents. Hydronic system air vents have a float and pin inside them. When the vent is full of water, buoyancy raises the float and the pin seats to stop water from leaking out the vent. When air arrives in the vent, the float drops and the air bleeds out. When the water re-enters the vent, the cycle continues. Steam vents use a different principle

Vent Cut-away from Hoffman TES-375 manual

Hoffman Air Vents

The vent has a thermostatic element and a float. While air is in the vent, it rises around the float and is vented. When steam enters, the hot steam expands the fluid in the vent which forces the pin to close off the vent. The steam pressure on the lower surface of the vent will keep the vent closed. It remains closed until the pressure drops enough so the weight of the float is greater than the pounds per square inch pressure holding the vent open. This steam pressure is referred to as the “drop away” or “operating pressure” of the vent.

The Xylem Hoffman 75 has a “drop away or operating pressure of 3 PSIG. That means the vent will not open until the pressure in the system drops below 3 PSIG. This is a great vent for cycling on-off loads but may be a challenge in a steam piping main. The Hoffman 75H has a drop away pressure of 10 PSIG. This could be a better choice in this application.

Hoffman makes a variety of vents for steam and hydronic applications. In Michigan and Northern Ohio, give your Deppmann sales engineer a call. In other parts of the world contact your local representative.

The Xylem TES-375 manual is available online at the Xylem Hoffman websites or through your local representative.

Disclaimer: R. L. Deppmann and it’s affiliates can not be held liable for issues caused by use of the information on this page. While the information comes from many years of experience and can be a valuable tool, it may not take into account special circumstances in your system and we therefore can not take responsibility for actions that result from this information. Please feel free to contact us if you do have any questions.

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Can I change my Vacuum Condensate Pump to a Simple condensate Pump? (Part 3)

Norm Hall — Mon, 11 Feb 2013 16:49:55 +0000

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So far, this short series of R. L. Deppmann Monday Morning Minutes briefly looked at vacuum condensate systems used to save time in night setback systems and for temperature control in older steam systems. When you use the word vacuum with most people, they think of sucking something up like a vacuum cleaner does. There are times that vacuum condensate systems were used to lift or “suck up” the condensate from a lower level. Today, we will examine the use of vacuum condensate pumps to lift condensate from a low return.

Most low pressure condensate systems have gravity returns. The water flows by gravity from a higher elevation down to the condensate receiver. There are times when a small return line is lower than the inlet to the condensate receiver and a vacuum unit is used. When attempting this, you must use what is known as a lift fitting. Figure 1 shows a typical lift fitting.

From Microsoft Office Clip art

Often I am asked why we need unusual fittings. Can’t the vacuum just suck the water up? Think of a straw? As a child I used to be quick to suck down a chocolate malt or shake. Near the bottom I just could not get that last little bit. I would suck and suck and make all kinds of noise. I’d get a lot of air and a little chocolate. I would continue until my mother would tell me to stop or worse!

OK, you know you did it too!

The return line has air and water. When we apply the vacuum to the line, we tend to suck more air than water since air is lighter. The lift fittings cause a “pool” of water in the horizontal pipe so the pipe fills with water and the vacuum pump is able to pull the water. This was so prevalent in the early 20th century that many manufacturers marketed ready-made fittings. Today if you need to replace one, you are left making one yourself.

Before you run off and try lifting condensate using a vacuum pump, I offer a couple warnings. Water boils at less than 212°F under vacuum so watch those leaking steam traps. Vacuum condensate pumps are expensive and not very efficient. It is always better to locate a small condensate pump at the lower level than attempting to lift condensate.

If you need a replacement condensate vacuum unit, Xylem B&G Domestic makes a great one and it comes with the R L Deppmann sales engineering team in Michigan and Northern Ohio!

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Can I change my Vacuum Condensate Pump to a Simple condensate Pump? (Part 2)

Norm Hall — Mon, 04 Feb 2013 15:41:59 +0000

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We began a series about vacuum condensate units and introduced one of their uses: the reduction of time to bring a building up to temperature after a weekend setback. Today, the R. L. Deppmann Monday Morning Minute (MMM) looks at the second use of vacuum condensate pumps, temperature control.

The modern hydronic boiler systems incorporate temperature set back controls. We understand that fin tube or coils will give out less BTUH if supplied with 140°F water instead of 200°F water. Back in the days where steam systems were common, how did you employ temperature set back controls? A boiler operating at 1 PSIG steam pressure produced steam at 215°F. The only way to supply steam below 212°F was to operate under a vacuum.

If I could create a vacuum in the steam system, I could change the BTUH output of the radiator. In fact, if I change the pressure to 20” of vacuum, I can get water to boil at 161°F. Since the BTUH output of the radiator is directly proportional to temperature difference between the steam and the room air, one could vary the output of the radiator by varying the temperature at which the steam condensed.

In today’s modern heating systems we take night or weekend setback in large office buildings for granted. In the 1930s and 1940s, not so much! Back then, on weekends, these large heating systems were just turned off for a period of time which allowed the building temperature to drop. When Monday morning came around, the office workers would want the building warm so the operator or janitor would come in early during the night to start the system.

From Xylem HOFFMAN HS-203C MANUAL

Bell and Gossett VCD vacuum condensate unit operation from manual TES-375

Many very smart people devised systems to operate under vacuum. Often, the system was named after them. I’ve seen some of these systems still in operation today.

If your system was designed for variable vacuum temperature control and is still operating, don’t assume you can replace the vacuum condensate system with a straight “condensate only” system. Ask your R. L. Deppmann sales engineer to stop by and discuss it with your installing contractor or engineer. If you are not lucky enough to be in the Deppmann territory, Call your Bell and Gossett/Domestic pump representative for their assistance.

Next week we look at a third reason you may have a vacuum condensate pumping system; condensate lift.

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Can I Change My Vacuum Condensate Pump to a Simple Condensate Pump? (Part 1)

Norm Hall — Mon, 21 Jan 2013 13:00:24 +0000

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That’s a Great Question…

Every heating season we get, at least, a half dozen calls with the question above, which is the subject of today’s R. L. Deppmann Monday Morning Minute.

Vacuum condensate transfer pumps exist in many older steam heating systems. There were many reasons contractors and engineers used these pumps but most of the systems fall into three categories: time control, temperature control, and condensate lift.

Let’s look at each category briefly.

TIME CONTROL FACT 1:

Xylem Bell and Gossett DOMESTIC VLR vacuum condensate unit

Two pipe vacuum system from manual HS-901A

TIME CONTROL FACT 2:

As the IHM nuns taught me back in science class, no two things can occupy the same space at the same time. When the operator came in to start up the system, the pipes were cold and full of air. The steam can’t get in until the air is pushed out. Vacuum units were used to help pull the air out of the systems so steam could heat the building faster.

Vacuum systems also allowed a greater differential across steam traps. This got the condensate back to the boiler room faster, again helping the system to heat faster. Sometimes this added differential of pressure to vacuum also allowed pipes to be sized smaller.

Today, there are many more controls for night setback. If your vacuum pump was installed for TIME CONTROL only, there may be areas where the vacuum portion might be unnecessary. Don’t assume and just remove it. Ask your R. L. Deppmann sales engineer to stop by and discuss it with your installing contractor or engineer. If you are not lucky enough to be in the Deppmann territory, Call your Bell and Gossett/Domestic pump representative for their assistance.

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B&G Triple Duty® valves or Metraflex check valves on your variable speed hydronic pumps (Revisited)

Norm Hall — Mon, 14 Jan 2013 14:20:01 +0000

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Our Monday Morning Minute (MMM) in October outlined the value and need of using Bell and Gossett triple duty valves in variable speed pumping applications. The use of the triple duty valve ports will make it easier to determine the maximum speed to set in the drive. This will assure your client will enjoy maximum energy savings in a properly designed hydronic system. See Triple Duty® valves on your variable speed hydronic pumps to review the MMM on this subject.

We’ve received many calls from contractors about the application of triple duty valves in variable speed systems with concern about costs.

The Bell and Gossett triple duty valve is a combination non slam check device, balance, and shut off. Let’s assume we are not using the valve for shutoff because there will be an additional butterfly valve on the outlet. The triple duty valve will only be used for determining the excess pressure drop, by measuring across the convenient pressure ports, and as a non-slam check valve.


Metraflex Globe Style Non-Slam Check Valve	Installed Metraflex Check Valve	B&G triple duty valve

You will find there are times when the installed cost of the B&G triple duty valve is less than the non-slam check with the required pipe diameters. There are other times when the installed cost of the Metraflex non-slam check valve wins out over the B&G triple duty valve.

Suggestion on variable speed pumps: If you require a butterfly shut off on the discharge of the triple duty valve, detail the check and shut off but allow the triple duty valve with butterfly valve as a voluntary alternate. The mechanical contractor along with the balancing contractor will determine which method will provide the most cost effective solution.

Disclaimer: R. L. Deppmann and it’s affiliates can not be held liable for issues caused by use of the information on this page. While the- information comes from many years of experience and can be a valuable tool, it may not take into account special circumstances in your system and we therefore can not take responsibility for actions that result from this information. Please feel free to contact us if you do have any questions.

Archives – Click here for Past Articles

Using the New Bell and Gossett System Syzer Programs PART 3

Norm Hall — Mon, 03 Dec 2012 04:11:30 +0000

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Xylem Bell and Gossett recently announced the new System Syzer programs for your computer. You may download these through links on our website at the www.deppmann.com/resources/ page.

Last week we discussed the new ASHRAE 90.1 2010 pipe sizing standards and how the Bell and Gossett system syzer tool can be used for the pipe sizing. The tab labeled “Length/Pressure Drop” can now calculate the pressure drop of the circuit. The representation below is an AHU coil with a flow rate of 450 GPM.

When we open the Length/Pressure Drop tab and click on the “help with total equivalent length” box, a screen opens where you can enter the components to calculate the total friction loss.

Entering each component in the B&G System Syzer gives us a sub circuit requirement of 450 GPM at 19.47 feet.

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Using the New Bell and Gossett System Syzer Programs PART 2

Norm Hall — Mon, 19 Nov 2012 14:28:04 +0000

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Xylem Bell and Gossett recently announced the new System Syzer programs for your computer. You may download these through links on our website at the www.deppmann.com/resources/ page.

The flow/pressure drop tab can be an extremely important tool. ASHRAE 90.1-2010 standards Table 6.5.4.5, introduces new sizing data for hydronic systems. The maximum recommended flow rate depends on three factors: velocity, number of expected operating hours of the system, and whether the system is variable flow/variable speed or other.

Let’s look at an example. Assume you have 1500 GPM. What is the minimum pipe size should you use? The answer is: it depends! Check the screenshots below.

8” pipe is too small if you are operating over 4400 Hours per year Variable speed.

10” pipe is correct if you are operating over 4400 Hours per year Variable speed.

12” pipe is correct if you are operating over 4400 Hours per year and not Variable speed.

8” pipe is correct if you are operating less than 2000 Hours per year and Variable speed.

Download the program and experience the power of this new tool from Bell and Gossett.

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Using the New Bell and Gossett System Syzer Programs

Norm Hall — Mon, 05 Nov 2012 14:31:32 +0000

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Xylem Bell and Gossett recently announced the new System Syzer programs for your computer. You may download these through links on our website at the www.deppmann.com/resources/ page.

This new tool has a powerful lineup of useful features. Let’s look at a couple of them.

The first tab is marked TEMP/LOAD and in this example I entered temperatures of 40°F to 60°F as well as 100 GPM. Calculating the load for water is normally simple on a calculator. but in this case I changed the fluid to 30% propylene glycol/water.

Look, everything is at your fingertips! We have the correct load in MBH or BTUH or Tons. We have metric conversions! We have the viscosity and specific gravity needed for pump calculations. All this and a “PRINT” button so you can save to a file.

We’ll look at other tabs next week in the R. L. Deppmann Monday Morning Minutes.

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Air Separator Location in Hydronic Systems

Norm Hall — Mon, 29 Oct 2012 14:06:30 +0000

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R. L. Deppmann is offering another series of seminars, this fall, which are centered on “Energy Savings and ASHRAE 90.1 and 189.1 standards”. During a couple of the first 7 seminars, the question of the air separation location sparked a short discussion. Let’s review the response in this Monday Morning Minute.

Entrained air is released from the water or Dow glycol heat transfer fluid as the temperature increases. (See chart below). Entrained air is also released at the lowest pressure in the system. So as a general rule, the air separator performs best in the warmest water and at the lowest pressure point in the system.

From B&G Rolairtrol manual A-307A page 8

COMMERCIAL & PROCESS:
Whether you are using a Bell and Gossett CRS coalescing air and dirt separator, a Bell and Gossett Rolairtrol air separator, or a low velocity buffer tank; the placement of the air separator in a chilled water system is on the secondary return. The air separator in a heating system is on the secondary supply.

RESIDENTIAL:
Whether you are using a Bell and Gossett EAS coalescing air separator, a Bell and Gossett IAS inline air separator, or a low velocity buffer tank; the placement of the air separator in a chilled water system is on the secondary return. The air separator in a heating system is on the secondary supply.

B&G CRS air/dirt separator

B&G Rolairtrol air separator

Cemline Buffer Tank

B&G EAS air separator

B&G IAS air separator

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Minimum Flow in Variable Speed Pumps for HVAC and Building Plumbing Systems

Norm Hall — Mon, 22 Oct 2012 13:20:10 +0000

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Every week a question comes in to R. L. Deppmann
about the minimum flow rate through pumps.

In hydronic heating and cooling systems, it is normal to have 2-way valves in the system at the terminal units. As the system temperature is satisfied, the valves close and the flow rate drops from design toward zero flow. If all of the valves were closed, we would be at “dead-head” pump operation or zero flow rate. In plumbing systems, there are times when there is little or no usage in the building which, again, results in possible zero flow rates through pressure booster pumps. Operating the pump near zero flow may be a disaster waiting to happen for several possible reasons: heat, vibration, discharge recirculation, and suction recirculation. For these reasons, Xylem Bell and Gossett publishes minimum flow rates for pumps.

What happens when we operate at variable speed?

The example shown is a multistage eSV pump captured from the Bell and Gossett website. The minimum flow is shown as 21 GPM at 3500 RPM. What would the minimum flow be in a vaiable speed system? Flow varies as the speed varies. If this pump runs at 1750 RPM, the minimum flow is 10.5 GPM since:

Flow=21 X (1750/3500)

If we are operating at 1150 RPM, the minimum drops to 6.9 GPM.

Example: The pump shown is selected for 100 GPM at 100 feet in a variable speed secondary chilled water application. The set point, at the end of the system, is 23 feet or 10 PSIG. What is the minimum flow?

Solution: We know that speed varies proportionally with flow and head varies as the square of the flow. So we use the second affinity law to the variable head:

(RPM1/RPM2)2 = Head1/Head2 OR (3500/ RPM2)2 = 100/23

SO

RPM2 = 1678 RPM & Minimum flow = 21 X (1678/3500) = 10 GPM.

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R.L. Deppmann Company

Steam Vent Operating Pressure

Can I change my Vacuum Condensate Pump to a Simple condensate Pump? (Part 3)

Can I change my Vacuum Condensate Pump to a Simple condensate Pump? (Part 2)

Can I Change My Vacuum Condensate Pump to a Simple Condensate Pump? (Part 1)

That’s a Great Question…

Let’s look at each category briefly.

B&G Triple Duty® valves or Metraflex check valves on your variable speed hydronic pumps (Revisited)

Using the New Bell and Gossett System Syzer Programs PART 3

Using the New Bell and Gossett System Syzer Programs PART 2

Using the New Bell and Gossett System Syzer Programs

Air Separator Location in Hydronic Systems

Minimum Flow in Variable Speed Pumps for HVAC and Building Plumbing Systems

Every week a question comes in to R. L. Deppmann about the minimum flow rate through pumps.

What happens when we operate at variable speed?

Every week a question comes in to R. L. Deppmann
about the minimum flow rate through pumps.