sitelights
10-16-2006, 08:06 PM
I wrote a review similar to this just before the lowvolt.org site was transfered to a new server; during the transfer the review disappeared along with 109 members. I write my posts directly onto the site using only rough notes; without a draft copy to work from I will have to recreate the transformer review from the notes and memory.
Ultimately bought, the 3able STB600-15 2x300w 12-15v multi-tap toroidal was sent to me at my request for evaluation in response to an email from 3able asking for my input. Rather than ship it back I purchased it for use in an upcoming expansion of my home outdoor lighting system. It meets the standard promulgated by UL1838 (which I consider important) in appearance and specifications but has no UL or ETL or any other label applied to the unit. The manufacturer produces a complete line of low voltage landscape lighting transformers: http://www.3able.com
The internals are mounted on a separate intricately stamped and folded painted steel bracket and the toroids are through-bolted to the bracket. A de-buzzing choke is bolted to the side of the bracket. The unit I purchased did not have a nut for the bracket bolt and the choke was floating free within the internal housing when I removed the separate, vented, hole-punched cover. There was also a smaller nut missing (1 of 5) that holds the bracket in place within the stainless steel case; the entire assembly had to be removed to thread on a replacement nut to secure the choke.
The de-buzzing choke eliminates or reduces the transformer hum that is sometimes a factor in dimmed low voltage systems. This feature is seldom seen on a magnetic low voltage transformer. If you don't dim the system you don't need the choke to cancel the hum.
The hum is created as a sympathetic harmonic vibration of the components of the transformer to the 60 cycle oscillations of the 120v electrical current. Potting (usually in a sand/epoxy mix) of the transformer coils reduces hum caused by vibration of loose internal/external parts and/or rigid mounting on a hard surface.
Potting is available as an option on the 3able line and making the choke optional would allow standard potting and a consequential reduction in the manufacturing cost of the units to be passed on to the user. Don't hold your breath. Landscape lighting system transformers rated for outdoor use should never be mounted on the outside wall of a bedroom, for example, if hum is detectable during operation.
In 20 years we have used dimmers on less than .01% of our (1500+) installations and only at the (misinformed) persistence of the client; light levels are designed into a system and it is better to take the control of light levels out of the client's hands.
Dimmers knock a volt off of the output of a magnetic transformer; require output level compensation via a higher tap; encourage the designer/installers to use higher output (35 or 50w) lamps to provide the client with a range of settings and are mostly "set and forget" controls.
Most systems are designed to take the burden of control out of the hands of the client by providing automated on/off times. The client does not belong in the control loop and doesn't want to be there anyway. If you will excuse my vulgarity (and even if you don't) dimmers are essentially "teats on a bull" to use a local and rural metaphor for a useless frippery.
The secondary terminal rail is configured as com com 12v 12v 13v 13v 14v 15v. The primary rail is neutral hot p/c jumper and ground; the grounded 16 ga. cord is 6' long. In addition to the internal thermal auto reset primary breakers within the toroid there are two magnetic secondary breakers with blue LED indicator lights that glow in the "on" position. These are mounted on the face plate which also contains a number of punched holes covered with metalic tape: three sets of holes for additional breakers/LEDs, one square hole for an additional receptacle and one oblong hole for another cord plug. The tape seems to me to be a "low rent" expedient as is the paint finish on the interior bracket; both are attributable to cost containment. Since the case is seldom, if ever, opened by the owner these comments are mere quibbles but why not drop the LEDs and offer face plates with only the necessary openings.
The clock receptacle is a grounding type (MDL's and similar products will accept only a plug that maintains polarity but has no ground) and the cord plugged into it has two blades and no ground. The interior cord/plug line was badly nicked most likely by getting caught between the cover and the case at some point. The nicked cord was apparent when first opening the case.
As an aside, the case contained a brand new bladed screw driver with an 8" shaft; the blue/clear handle imprinted "ML 3 x 200mm magnetic hardened". Either a gift or a tool used to connect the primaries and forgotten in the case; better here than after a surgical procedure
The grounding receptacle is a plus since newer plug-in clocks have the grounding prong which cannot be used with many of the receptacles provided in this type of configuration. The photocontrol must be wired to the primary rail replacing the jumper.
I bench tested my STB600-15 for function and output; a field test of the same unit was done by substituting the 3able unit for an existing MDL powering a 300w system. The bench test was done under no load just to insure that all the taps were working; the field test consisted of both no load and loaded output measurements.
Test system measurements had the following in common for both the MDL and the 3able: 121.3v primary input, 155' of 10/2 gauge cable (configured as two center-fed "T"s) and 15 fixtures lamped with 20w MRs or 20w bi-pin halogens. The MDL had 12, 13 and 14v secondaries so the 3able 15v tap was not used. Unloaded/loaded the original MDL measured 11.7/11.2; 12.9/12.4; 14.8/14.5 at the transformer while the 3able measured 12.5/12.5; 12.7/13.5; 14.8/14.5 under identical conditions. No lamp had more than 12v applied.
The only remarkable aspects of these measurements was the very stable output of the 3able under load at the taps. However when measurements were made at the mid-point of the cable run the MDL delivered .5v more than the 3able using the 14v tap. I was a bit surprised at this reading and asked the installation foreman to confirm the reading. The meter is identical to the newer one reviewed in this forum and was of known accuracy.
Ultimately bought, the 3able STB600-15 2x300w 12-15v multi-tap toroidal was sent to me at my request for evaluation in response to an email from 3able asking for my input. Rather than ship it back I purchased it for use in an upcoming expansion of my home outdoor lighting system. It meets the standard promulgated by UL1838 (which I consider important) in appearance and specifications but has no UL or ETL or any other label applied to the unit. The manufacturer produces a complete line of low voltage landscape lighting transformers: http://www.3able.com
The internals are mounted on a separate intricately stamped and folded painted steel bracket and the toroids are through-bolted to the bracket. A de-buzzing choke is bolted to the side of the bracket. The unit I purchased did not have a nut for the bracket bolt and the choke was floating free within the internal housing when I removed the separate, vented, hole-punched cover. There was also a smaller nut missing (1 of 5) that holds the bracket in place within the stainless steel case; the entire assembly had to be removed to thread on a replacement nut to secure the choke.
The de-buzzing choke eliminates or reduces the transformer hum that is sometimes a factor in dimmed low voltage systems. This feature is seldom seen on a magnetic low voltage transformer. If you don't dim the system you don't need the choke to cancel the hum.
The hum is created as a sympathetic harmonic vibration of the components of the transformer to the 60 cycle oscillations of the 120v electrical current. Potting (usually in a sand/epoxy mix) of the transformer coils reduces hum caused by vibration of loose internal/external parts and/or rigid mounting on a hard surface.
Potting is available as an option on the 3able line and making the choke optional would allow standard potting and a consequential reduction in the manufacturing cost of the units to be passed on to the user. Don't hold your breath. Landscape lighting system transformers rated for outdoor use should never be mounted on the outside wall of a bedroom, for example, if hum is detectable during operation.
In 20 years we have used dimmers on less than .01% of our (1500+) installations and only at the (misinformed) persistence of the client; light levels are designed into a system and it is better to take the control of light levels out of the client's hands.
Dimmers knock a volt off of the output of a magnetic transformer; require output level compensation via a higher tap; encourage the designer/installers to use higher output (35 or 50w) lamps to provide the client with a range of settings and are mostly "set and forget" controls.
Most systems are designed to take the burden of control out of the hands of the client by providing automated on/off times. The client does not belong in the control loop and doesn't want to be there anyway. If you will excuse my vulgarity (and even if you don't) dimmers are essentially "teats on a bull" to use a local and rural metaphor for a useless frippery.
The secondary terminal rail is configured as com com 12v 12v 13v 13v 14v 15v. The primary rail is neutral hot p/c jumper and ground; the grounded 16 ga. cord is 6' long. In addition to the internal thermal auto reset primary breakers within the toroid there are two magnetic secondary breakers with blue LED indicator lights that glow in the "on" position. These are mounted on the face plate which also contains a number of punched holes covered with metalic tape: three sets of holes for additional breakers/LEDs, one square hole for an additional receptacle and one oblong hole for another cord plug. The tape seems to me to be a "low rent" expedient as is the paint finish on the interior bracket; both are attributable to cost containment. Since the case is seldom, if ever, opened by the owner these comments are mere quibbles but why not drop the LEDs and offer face plates with only the necessary openings.
The clock receptacle is a grounding type (MDL's and similar products will accept only a plug that maintains polarity but has no ground) and the cord plugged into it has two blades and no ground. The interior cord/plug line was badly nicked most likely by getting caught between the cover and the case at some point. The nicked cord was apparent when first opening the case.
As an aside, the case contained a brand new bladed screw driver with an 8" shaft; the blue/clear handle imprinted "ML 3 x 200mm magnetic hardened". Either a gift or a tool used to connect the primaries and forgotten in the case; better here than after a surgical procedure
The grounding receptacle is a plus since newer plug-in clocks have the grounding prong which cannot be used with many of the receptacles provided in this type of configuration. The photocontrol must be wired to the primary rail replacing the jumper.
I bench tested my STB600-15 for function and output; a field test of the same unit was done by substituting the 3able unit for an existing MDL powering a 300w system. The bench test was done under no load just to insure that all the taps were working; the field test consisted of both no load and loaded output measurements.
Test system measurements had the following in common for both the MDL and the 3able: 121.3v primary input, 155' of 10/2 gauge cable (configured as two center-fed "T"s) and 15 fixtures lamped with 20w MRs or 20w bi-pin halogens. The MDL had 12, 13 and 14v secondaries so the 3able 15v tap was not used. Unloaded/loaded the original MDL measured 11.7/11.2; 12.9/12.4; 14.8/14.5 at the transformer while the 3able measured 12.5/12.5; 12.7/13.5; 14.8/14.5 under identical conditions. No lamp had more than 12v applied.
The only remarkable aspects of these measurements was the very stable output of the 3able under load at the taps. However when measurements were made at the mid-point of the cable run the MDL delivered .5v more than the 3able using the 14v tap. I was a bit surprised at this reading and asked the installation foreman to confirm the reading. The meter is identical to the newer one reviewed in this forum and was of known accuracy.