It is our intension to bring the Automatic motor base into the HVAC industry as a OEM standard and retrofit the equipment presently in use. After extensive research and field maintenance experience, it is obvious that, as in the automotive industry, the ability of the equipment to self-adjust the belt is an absolute necessity in the HVAC environment. When the v-belt retains proper tension, belt and pulley wear are greatly diminished and machine reliability and energy efficiency can be maintained at a higher level with less maintenance.
With many years of mechanical experience, we have strived to simplify the installation of the automatic motor base in the HVAC and commercial/industrial environment. The first 601 base’s (56 frame) we used for HVAC packaged units were quite difficult to install. We started out welding or marking and drilling the Automatic base to the factory motor mount. This requires precision placement to make a satisfactory installation. This has proven to be acceptable but not the ideal situation for a field installation.
We have made modifications to the Automatic motor bases and supply the hardware that enable the service man to install them on most equipment using only hand tools with no drilling or fabricating required. The Kits were designed to be installed with minimal effort. Most direct replacement capable machines can be installed in under an hour. Some machines require factory motor base modifications to utilize the automatic motor base. If the factory motor base is vertical or more than 30 degrees off on belt angle to the plane of the base it must be converted to horizontal or to within limits.
We have made many of these field modifications and can still modify the unit and install the automatic base in under an hour. On larger air handlers with manual adjust NEMA base motor mounts we had a very difficult time installing the Automatic base. In many machines, the standard NEMA base is mounted to channel or angle irons and the stock Automatic base attach holes will not align without hitting the channel/angle flanges.
Once again, we made modifications so the Automatic motor base will bolt to where the NEMA base was. The automatic motor base with the NEMA modification is a direct bolt on conversion. We find that if the pulleys were aligned in the first place they will align perfectly after the automatic motor base installation.
PermaTORQ is ready to supply all your manufacturing needs with a full line of automatic motor bases from ¼ hp to 500 hp with a wide range of service duty requirements.
Effects of Belt Stretch on HVAC Equipment
President, PermaTORQ LLC
I have been in the HVAC service industry for over 25 years and have been in the machinery repair field my entire life. I would like to discuss my thoughts on belt maintenance, or lack thereof, and the effects on commercial HVAC equipment. I have had bi-annual service contracts on rooftop equipment and it still seems to be insufficient to keep up with belt driven system condition. Most of the equipment we service will make the 15 to 20 year life span and we have very rarely ever had issues with blower or motor bearings. We have tried every possible way to install belts, too tight to try to compensate for belt stretch, too loose to see if we’re over tensioning. A major V belt manufacturer recommends re-tensioning after 8 ,24, and 100 hours and then periodically thereafter. This is not going to happen in the real world as it would be too cost prohibitive to keep sending a technician out to re-tension belts. Some equipment seems to hold belt tension sufficiently, but most equipment does not. The fractional horsepower motors have less starting torque and don’t stretch the belts out as quickly, however the larger horsepower motors have a tremendous starting torque. My observations are as follows: the belts are punished on every startup by the abrupt starting torque of the motor. Every time the machine cycles the belt is stretched. Soon after the drive pully has an abrupt slip on startup, then more and longer each time. As the pulley slips, heat is generated and it begins removing rubber from the belt and the pulley also begins to wear. Eventually the drive pulley is slipping continuously while heating up the belt, grinding the rubber off the belt and destroying the pulley. At this point the belt drive system has lost the ability to deliver the energy from the motor to the blower to move air.
What’s happening with the machine? I consider the filter condition, belt tension and evaporator coil fouling all the same thing, airflow. As the belt gets loose the blower speed reduces, air volume reduces and the suction pressure/temperature drops from lack of heat to pick up. As the belt tension deteriorates the airflow decreases and the suction pressure gets lower yet. The lower the suction pressure, the lower the corresponding temperature & frost may begin to form on the evaporator coil. Now, add the effect of the filter being a little dirty and the machine’s efficiency has greatly diminished. I have experienced evaporator coil freeze ups from poor blower performance alone. The colder supply air through your ductwork and ceiling diffusers cause condensation dripping and possible mold issues. Less volume of air being delivered means longer and more frequent cycle times to satisfy the thermostat (this is where a great deal of efficiency is lost). The compressor is running and the evaporator isn’t picking up the heat it should. Now you have the possibility of a totally frozen evaporator coil, along with a substantial to a total loss in cooling efficiency. The colder evaporator may also allow liquid refrigerant to make its way back to the compressor to cause damage.
What do you get in heating mode? Reduced airflow over the heat exchanger will increase its temperature. Combustion exhaust temperature increases reducing the efficiency of the unit. Along with less volume and less pressure, supply air temperature increases. When it leaves the ceiling diffuser it is so hot it doesn’t want to mix with the surrounding air which results in heat stratification. This in turn causes longer inefficient cycle times and uncomfortable office conditions. If the airflow is reduced enough the machine may cycle on and off on the high limit switch.
The smaller packaged units have direct driven blowers and do not experience these problems. Three tons of cooling seems to be the general cutoff to where a belt driven system is installed. Belt slippage is an undesirable condition on any piece of equipment and must be avoided by whatever means are available.