R.L. Deppmann Co.

Heat Added to Chilled Water Systems Due to Pump Efficiency

Norm Hall — Mon, 09 Aug 2010 04:00:47 +0000

We received an interesting question this week from a consultant engineer: “How much temperature increase will I get in the chilled water from the pump? My secondary chilled water pump has a capacity of 1400 GPM at 100 feet” Let’s look at the answer.

ANSWER: Centrifugal pumps in hydronic systems do the work of moving gallons per minute of fluid against a differential head in feet. This work is defined as Brake Horsepower (BHP) also expressed in equation 1.

The maximum amount of horsepower available to heat the water is 1 minus the pump efficiency multiplied by the motor horsepower. Bell and Gossett refers to this as the Heating Horsepower (HHP) expressed in equation 2. 1 HP equals 42.44 BTU/Minute (equation 3) and BTU/minute is GPM times ∆T times 8.33 times specific gravity times specific heat (equation 4). The later two items are equal to 1 for water. Using all of this we arrive at a formula for ∆T shown as equation 5.

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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Norm Hall — Mon, 19 Jul 2010 04:00:45 +0000

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Motor Specifications for HVAC & Plumbing Building Trades

Norm Hall — Mon, 05 Jul 2010 04:00:54 +0000

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The most frequently asked question is “How do I specify the right motor for variable speed applications”? Let’s start by referring to NEMA, which is the National Electrical Manufacturers Association standards. NEMA does not use terms such as Inverter Duty, Inverter Rated, or Inverter Ready. These are marketing terms used by motor manufacturers. These are marketing terms used by motor manufacturers.

Before discussing the standards, let’s examine the motors used in our industry. Motors used in applications, such as elevators or conveyer belts, experience constant torque loads. Some of these constant torque devices require motors that experience much more severe duty than our HVAC and Plumbing applications. Fans, blowers, and (my favorite) pumps are variable torque loads. As the speed drops, so does the load, so there is less strain on the motor due to work. When you go on the internet and find complicated motor specifications for drives, make sure you match the specification to the duty.

“Note that these protective devices must be specified and are not automatically included just because a motor is used with an inverter”

Here are the important points for use in our Industry.

1. Motor should be NEMA Design B with Class F insulation

2. Motor should be able to operate with a 10:1 speed reduction.

3. NEMA standard MG-1 2006 – Part 31.4.4.2 specifies voltage spikes over a time constant. The motors used on variable speed drives, for HVAC applications, should meet this section. 460/60/3 motors shall have an insulation system designed to operate at 1 1426 Volt spike for 0.1μS

4. NEMA standard MG-1 2006 – Part 31.4.4.3 has recently included suggestions to protect the motor from EDM (Electronic discharge machining), commonly called bearing fluting or wash boarding. Motor damage may be caused by the shaft currents created by the use of PWM inverters. Shaft grounding brushes or rings are suggested in this specification. Note that these protective devices must be specified and are not automatically included just because a motor is used with an inverter.

If you are in the R. L. Deppmann territory of Michigan and Northern Ohio and would like us to review you motor and pump specifications CLICK HERE.

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Motor Specifications for HVAC & Plumbing Building Trades

Norm Hall — Mon, 21 Jun 2010 04:00:03 +0000

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Thought I’d take break from the Sump and Sewage pump subject of the last few weeks and spend a little time talking about motor specifications for Plumbing and HVAC applications. R. L. Deppmann does not represent any motor manufacturers, but we obviously sell a lot of motors, since almost every pump has a motor on it. So let’s start.

Motor efficiency specifications have changed. In 2007, the Energy Independence and Security Act (EISA) set new standards for motors built after December 19, 2010. Let’s take a look at the new specifications.

Most of us are familiar with the terms High Efficiency from the NEMA (National Electrical Manufacturers Association) standard MG1 table 12.11 and Premium Efficiency motors from MG1 table 12.12. These tables may be found at: http://www.nema.org/stds/complimentary-docs/upload/MG1premium.pdf

The specifications are broken down by frame and horsepower. T frame motors are used in most base mounted pump and AHU applications. Pumps, such as the B&G 1510 and VSX, use T frame motors. C, JM, and JP frame motors are used on inline pumps and close coupled pumps, such as the B&G series 60, 80, and 1531 style.

The new standards have defined two subtypes for motors; subtype I and subtype II. Subtype I motors are T frame style from 1 HP to 200 HP. These motors must meet Table 12.12, which is referred to as Premium Efficiency. Subtype II include T frame from 200 HP to 500 HP. Subtype II also include U-frame (Old automotive specs), Design C (small inline pumps), Close-coupled pump motors, Footless motors and Vertical turbine hollow shaft motors, and fire pumps up to 200 HP.

It is important to understand that the standard excludes submersible pumps. Submersible pump motors are normally built by the pump people and are not available in higher efficiencies.

You may specify higher efficiencies than the standards, but make sure the product exists before doing so.

If you are in the R. L. Deppmann territory of Michigan and Northern Ohio and would like us to review you motor and pump specifications CLICK HERE.

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Sump and Sewage Lag Pump & Alarm Float Settings

Norm Hall — Mon, 14 Jun 2010 04:00:27 +0000

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We presented suggestions for the pumps off float level and the lead pump on float level in the last few articles. You may review those by clicking on the “Past Articles” area of the website.
We know the minimum submergence or float off setting by contacting R L Deppmann for the pump selection or by using the rules of thumb identified in our May 3rd article. We can determine the lead pump on setting from using the basin diameter and the information shared in our May 31st article. Sometimes it is acceptable and possibly required to allow effluent to back up into the piping system but in general if the sump depth is not causing a problem with water tables or other obstructions then the maximum water level would be the bottom of the lowest inlet connection to the sump.

Today we look at the lag or standby pump float setting and alarm setting. These floats must fit between the lead pump on and the bottom of the inlet. The less space between these settings, the less depth required on the sump.

The recommendation is a 6” or more between the floats. We also recommend the use of 3 floats with the lag pump and alarm at the same level. (See MMM of May 10 2010)

Next week we will begin a discussion about motor specifications.

Thank you for using products sold by R. L. Deppmann Company in Michigan and Ohio!

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Sump and Sewage Pump Flow Rate & Minimum Run Time

Norm Hall — Mon, 31 May 2010 04:00:48 +0000

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The last few articles focused on the sump diameter and float levels. The flow rate is also used in the sump sizing. Obviously, the pump flow rate must be greater than, or equal to, the maximum expected effluent flow into the sump. In addition, the sump storage from the lead pump on, float to the off float, must be large enough so we do not cycle the pumps too often.

Let’s look at an example: Assume you are designing a storm water sump pump system and you have determined you need to pump 50 GPM against 20 feet of head. You select a B&G 2DES series effluent pump with a ½ HP motor, since you only expect ¾” solids and want the advantage of dual seals, with moisture sensing, between the two seals. Your head selection is based on 3” pipe size, which is just above the minimum velocity of 2 FPS (see MMM of 4-26-10). You could have also chosen 2” pipe with a 4.5 FPS velocity.

You want pump guide rails, and based on the MMM article from 5-17-10, you select the recommended 60” diameter sump for 3” pipe. Today’s article advises you have 500 gallons of storage between pump on and off. Based on the chart above, you will require about 42” of storage level.

Next week we will examine the float levels for the lag pump and alarm conditions.

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Pump Guide Rail Assemblies and Sump Diameter

Norm Hall — Mon, 17 May 2010 16:32:53 +0000

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One universal fact about sump and sewage pumping systems is that no one wants to go into the sump to pull out a pump for maintenance! Today we will discuss pump guide rails or lift out assemblies which allow the service person to disengage the pump from the discharge piping and lift the pump out of the sump.

These lift out products go under a number of different names such as; guide rail assembly, base assembly, lift out assembly, or slide rail assembly. They all work through a sliding coupling at the pump discharge and they all require the sump to be a minimum diameter so all the hardware can fit in the sump.

When specifying ITT Bell and Gossett guide rail assemblies, make sure you include the stainless steel chain and shackle for lifting the pump out. The assembly should match both the pump size and the selected pipe size.

There is a great deal of hardware to install in the sump basin. There must be room for the elbow, pump, slide rail, floats, brackets, and room for clearance when removing the pumps. For this reason, B&G recommends the following minimum sump diameters when using guide rail systems.

Next week the article will address pump minimum run time and sump sizing.

Thank you for using products sold by R. L. Deppmann Company in Michigan and Ohio!

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Sump and Sewage Pump Float Settings

Norm Hall — Mon, 10 May 2010 04:00:33 +0000

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There are basically four float control schemes used in sump and sewage pump applications. Simple one pump sumps normally have a single float attached to the pump, which is off when the float is down and turns the pump on when the level raises to a level of 7” to 10”. When the amp draw of the motor is less than 15 amps and the pump is single phase, you could use a “piggyback” switch available in various lengths. ITT Bell and Gossett Centripro series A2E float switch can be used on pumps up to ¾ HP at 115 volt and 2HP at 230 volt.

Simplex, single phase applications, with very little storage of the effluent, can be handled with a two float system. One float operates the pump, as above, and a second float operates the alarm. B&G offers weatherproof alarm panels, with and without battery backup, for these applications. The elevator sump we discussed in the MMM a few weeks back is an example of this control.

Most commercial duplex applications use three or four of the B&G Centripro A2D switches with bare leads to be wired to a control panel. In the four float system, the low level float turns the pumps off, the next float up turns on the lead pump, the next float turns on the lag or standby pump, and the highest float turns on the alarm. In a three float system, the third float turns on the lag or standby pump AND the alarm.

Many representatives recommend the four float system, but R. L. Deppmann Company recommends using a three float system. In a four float system, the lead pump could fail. The system would continue to operate off the lag pump. You would not know about the failure until the lag or standby pump also failed, allowing the level to rise to the alarm condition. Call the R.L. Deppmann Company to discuss the best float system for your application.

…R. L. Deppmann Company recommends the use of a three float system…

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Sump and Sewage Pump Minimum Submergence

Norm Hall — Mon, 03 May 2010 04:00:13 +0000

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We now begin a Monday Morning discussion about pumps, controls, and sumps. This article addresses a basic, but important question, which comes up often when setting the level controls in a sump, “How low should the pump-off float switch be set?”

The safest way to know the minimum water level is to read the installation, operation, and maintenance manual (IOM). The IOM also provides important safety considerations to keep the installer and operator safe from harm.

When the engineer is designing the project he or she may not know what brand they will end up with, after bids. The minimum water level is required to assist in the sump sizing. Many of the ITT Bell and Gossett sump and sewage pumps can operate with the low level about 6” below the top of the pump motor. Explosion proof pumps must have the motor fully submerged. In fact, any time the pump may be called to operate continuously; it is recommended that the motor be completely submerged. Based on these comments, we assembled the following selection guidelines. Once the pump model is selected, it is best to call us and ask what the factory recommends for minimum submergence. Contractors should ALWAYS check the IOM and follow the manufacturer’s recommendations.

Rule of thumb table for minimum level in sumps (Not explosion proof).

Always check exact manufacturer requirements before setting the minimum level.
Next week we will examine float systems.

Thank you for using products sold by R. L. Deppmann Company in Michigan and Ohio!

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Sump and Sewage Pumps – Discharge Line Size

Norm Hall — Mon, 26 Apr 2010 04:00:20 +0000

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There are several considerations when selecting the discharge line size from a sump or sewage pump. The discharge line must be large enough to handle the EXPECTED SOLIDS. Sump pumps normally have very little solid content in the discharge. Residential sump pumps in general handle 3/8” solids. Small commercial sump pumps may be similar to residential, however, we normally use effluent pumps for commercial applications. These pumps handle solids up to ¾”.

Sewage pumps, and their discharge pipes, are selected to handle a maximum spherical solid. Residential pumps handle a minimum of 1-1/2” up to 3”. Any of us with small children would naturally opt for the larger sizes, based on what gets flushed down the toilet. Commercial applications demand the ability to handle 2-1/2” to 3” solids or more.

In general, the discharge line size is equal to or larger than the pump connection size. In sewage pumps, the discharge size should also be selected so the minimum velocity is 2 feet per second or more. This is referred to as the scouring velocity to avoid clogged pipes.

The liquid in the discharge pipe must be turned a minimum of once every pump cycle. This means the run time, at the selected gallons per minute (GPM) flow rate, should move enough total gallons of liquid to completely replace all of the liquid in the discharge pipe. If we oversize the pipe or have long runs, we may have to increase the flow rate to achieve the turn rate, as well as maintain the scouring velocity. Here is a chart to help you determine volume.

Thank you for using products sold by R. L. Deppmann Company in Michigan and Ohio!

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