RD-II SR compessor pulley swap

[tony2009]

G'day Guys;

Just after a confirmation on this.
I have a customer converting an RD-II SR from R134 to R404; no worries there. However, I have been asked what the difference is between the R134a compressor pulley (77-1660) and the R404 compressor pulley (77-1927). I have always assumed the difference to be the outside diameter regardless of the fact that they still retain the same belts in both applications. There is adjustment available so I can't see an issue; however, I'm now being told that both pulleys have the same outside diameter; so I'm curious as to what other difference is between the 2 pulleys to warrant having different part numbers.
If the difference is the outside diameter, would anyone have the outside diameter size of the R134a version as I suspect that maybe the original pulley may be incorrect in that it may already have an R404 pulley fitted.

Unfortunately, I don't have either pulley here, either new or second hand, so it's a little hard to do a comparison.

Best regards.... Tone

[clivemtk]

hi tony rd2sron r404a would have a tk x426 or x430 compressor the only difference was when it was a multi temp the adjustment on multi temp was a pull up type later it was changed to pulley pushing down on belt only other possibility is it used a x214 compressor 2cylinder r134a being chill only clive

[Robert Hilton]

The pulley diameter is different as will be the belts, and it should be X426 compressor.

[tony2009]

G'day Guys;

Many thanks for your reply; however; on the RD-II SR units, with the exception of the compressor pulley, the belts and pulleys remain the same, and utilizes the adjustment of the compressor and standby motor. My inquiry relates to differences between the compressor pulleys; I expected the difference to be the outside diameter and naturally expected the standby and alt/fan pulley side to reflect this. However, I'm wondering whether the difference is maybe confined to just the standby and/or alt/fan pulley?

The unit in question is interstate, so I haven't sighted it directly and can only go on what I'm told by my customer who is also a transport refrigeration engineer (not sure if that makes a difference). He tells me the the unit does not appear to have been converted from R404 previously as the txv and hpco look to be original. I also understand the id plate indicates R134 so I'm at a loss as to how a R404 compressor pulley could already be fitted to a R134 unit, hence my question.

Unfortunately, I don't have the 2 pulleys to compare, so I don't know whether we have 2 of the same pulley or if there is a minor difference that hasn't been picked up.
My last thought is that a R404 pulley may have been fitted previously, but due to the age of the unit, I can't see a reason for it to be changed.

Best regards....Tone

[Robert Hilton]

Then I can only surmise that the original pulley was defective and replaced with a pulley that happened to be available. There are gearing differences between the units. I've even converted an R502 TDII to R12 voor a specific task. That also required a new pulley and belts.

[tony2009]

G'day Robert; generally speaking the main difference is the outside diameter to increase or decrease the speed of the compressor, relative to the gas being used. The engineers have designed these parts and their differences for a reason, so it is frustrating when something that should be of a certain configuration turns out not to be so.
I appreciate your input and thank you for it, though it has probably served to confirm my thoughts of the R404 pulley already being fitted to the unit, which means that my customer and I needn't have obtained the pulley at wasted time and effort.
Best regards....Tone

[The Fox]

dont worry, just change the power eliment and hpco. we have swopped lots over to 134 and they work just fine.