- Joined
- Feb 24, 2018
- Messages
- 1,044
I’ve basically spent the last 5-6 weeks, dealing with VFDs. We have a series of boilers running blower motors ranging from 5 hp to 75 hp, input voltages running from 208 vac to 600 vac. So far its taken 14 VFDs, to get 9 boilers running.
75 hp (600 vac) - severe programming issues, first complicated by a defective HMI module, then the faulty set of parameters sent by the manufacturer, numerous phone calls and multiple parameter changes, the units is running fine.
25 hp (480 vac) - 3 units, one VFD, completely dead right out of the box, one VFD with a faulty 4-20 ma (analog) output section and one VFD that worked as expected, programmed perfectly and worked perfectly as well. The dead VFD was replaced, the replacement was bulky to program, but finally worked as expected. I had to replace the VFD with the bad analog section, replacement unit worked as expected with no issues.
7.5 hp (480 vac) - 3 units, first VFD was programmed and rand perfectly for about 2 weeks, before it failed completely, no drive output, it had to be replaced with no further issue. The second and third VFDs were again bulky to get the parameters correct, but since then, they have worked as expected.
5 hp (208 vac) - 2 units, one dead out of the box and the other with a dead output section, both had to be replaced, identical boilers, but the operating parameters that work on unit #1, would fault out in the #2 unit, roughly 2 days of phone calls and trial and error setting of the parameters, we finally got a viable working issue. We loaded the parameters of the second unit into the first unit and had faults almost instantly. So while both units seem to function perfectly (identically), the actual operating parameters, are vastly different.
Knock on wood, its been about 2 weeks since the last start up and all seems to be going okay.
Most of the major boiler manufacturers, will tell you that, except for the soft start feature, you gain absolutely nothing my the use of a VFD on the blower motor, on the boiler. But it is almost alway a feature in the new digital control systems on the market and the young engineers, have seemed to blindly all ganged together requesting this feature on new boilers and control upgrades. All it really does is complicate an already over complicated control systems. But its a feature that, when operating correctly has a huge wow factor, which seems to make the bean counters have that warm and fuzzy feeling.
So my luck with VFDs has been roughly 75/25. We had an issue with the small (fractional hp) VFDs, on a series of boilers (direct from the manufacturer), where we had some units, have the VFD replaced 6-7 times, before they got a viable one. I once took 5 new VFDs to a job, walked out with 5 bad VFDs, the original bad one and the 4 bad ones I brought with me. On the other side, I installed 5 VFDs in a steam plant, on 50 hp motors, about 8 yrs ago and have absolutely zero issues.
When I started this job about 45 yrs ago, you needed a VOM, a couple of screwdrivers, some sockets and wrenches and a few pipe wrenches, those days are gone, while I still need those tools on occasion, I now also need 3 laptops. About 6 months ago, I had a laptop running the boiler control system, a second laptop running the VFD and the third laptop searching for the updated software fixes for the VFD program. Probably not in my life time, but sometime soon, they will have a scanner available, similar to McCoy’s on Star Trek, that will diagnose the faults and operational issues of the boiler.
75 hp (600 vac) - severe programming issues, first complicated by a defective HMI module, then the faulty set of parameters sent by the manufacturer, numerous phone calls and multiple parameter changes, the units is running fine.
25 hp (480 vac) - 3 units, one VFD, completely dead right out of the box, one VFD with a faulty 4-20 ma (analog) output section and one VFD that worked as expected, programmed perfectly and worked perfectly as well. The dead VFD was replaced, the replacement was bulky to program, but finally worked as expected. I had to replace the VFD with the bad analog section, replacement unit worked as expected with no issues.
7.5 hp (480 vac) - 3 units, first VFD was programmed and rand perfectly for about 2 weeks, before it failed completely, no drive output, it had to be replaced with no further issue. The second and third VFDs were again bulky to get the parameters correct, but since then, they have worked as expected.
5 hp (208 vac) - 2 units, one dead out of the box and the other with a dead output section, both had to be replaced, identical boilers, but the operating parameters that work on unit #1, would fault out in the #2 unit, roughly 2 days of phone calls and trial and error setting of the parameters, we finally got a viable working issue. We loaded the parameters of the second unit into the first unit and had faults almost instantly. So while both units seem to function perfectly (identically), the actual operating parameters, are vastly different.
Knock on wood, its been about 2 weeks since the last start up and all seems to be going okay.
Most of the major boiler manufacturers, will tell you that, except for the soft start feature, you gain absolutely nothing my the use of a VFD on the blower motor, on the boiler. But it is almost alway a feature in the new digital control systems on the market and the young engineers, have seemed to blindly all ganged together requesting this feature on new boilers and control upgrades. All it really does is complicate an already over complicated control systems. But its a feature that, when operating correctly has a huge wow factor, which seems to make the bean counters have that warm and fuzzy feeling.
So my luck with VFDs has been roughly 75/25. We had an issue with the small (fractional hp) VFDs, on a series of boilers (direct from the manufacturer), where we had some units, have the VFD replaced 6-7 times, before they got a viable one. I once took 5 new VFDs to a job, walked out with 5 bad VFDs, the original bad one and the 4 bad ones I brought with me. On the other side, I installed 5 VFDs in a steam plant, on 50 hp motors, about 8 yrs ago and have absolutely zero issues.
When I started this job about 45 yrs ago, you needed a VOM, a couple of screwdrivers, some sockets and wrenches and a few pipe wrenches, those days are gone, while I still need those tools on occasion, I now also need 3 laptops. About 6 months ago, I had a laptop running the boiler control system, a second laptop running the VFD and the third laptop searching for the updated software fixes for the VFD program. Probably not in my life time, but sometime soon, they will have a scanner available, similar to McCoy’s on Star Trek, that will diagnose the faults and operational issues of the boiler.
