Do compressors, specifically the Tecumseh AVA model, need a motor starter or can they simple use contactors?
Printable View
Do compressors, specifically the Tecumseh AVA model, need a motor starter or can they simple use contactors?
Hi, It would help if you could include more info when you post. (Refrigerant, Voltage and no. of Phases ... less assumptions have to be made!)
I found some info about the Tecumseh AVA model compressor on their US website (as you are based in US), and this is not a UK model that I recognise.
They appear to be a 2 to 3 HP unit but are available as both 3 phase and CSR (all 208-230v).
If the unit you are talking about is a 3 phase unit then you should be OK to start it 'DOL' (direct on line). For this you will need a 3 pole contactor as a minimum.....probably better to use a 4 pole contactor (3 NO, 1 NC) which will allow the wiring of a crankcase heater.
If you are using a CSR (Capacitor Start Run) you will have to use the correct starting relay device as specified by the compressor manufacturers, as well as the two capacitors (one Start and one Run). See the following http://www.tcc-nacg.com/pro_comp.html
However as you are in the US and you get your 208/230 v supply from across TWO phases, you will STILL NEED TO USE A CONTACTOR for switching the supply to the compressor (for safety)....in this case it will need to have a minimum of 2 NO poles....however as above, I would recommend using a 4 pole contactor (3 NO, 1 NC) (probably easier to get hold of than a 2 NO, 1 NC) in order to allow for a crankcase heater.
The compressor ident plate should give you the correct info ( 3 phase or not) and model# to get further info.
Hope this helps.
Hi Bluewheeler
A starter is a contactor with start and stop push buttons mechanism with overload in a separate encloser and normally used for motors where a manual operation is required, for R.A.C compressors you have to use a contactor with overload if required because it has to operate automatically with its system controls.
malik55
Does anyone have practical diagrams rather than circuit diags on how to wire up single and three phase contactors which may or not include heaters and how we set overload ratings
I dont really want the theory sites as l have seen plenty but none explain where the wires are connected ie A1 A2 95 96 etc:confused:
Firstly, you should really start a new thread rather than posting onto an existing thread!Quote:
Originally Posted by Panikmkanic
What exactly are you expecting from a PRACTICAL diagram? These do not normally exist....and if you are working on equipment especially at 240/415v and you are not competent THEN LEAVE IT ALONE. As a technician your skills should be such that you can interpret and follow a wiring diagram.
A proper wiring diagram might seem complex, but will have cable numbers and what terminals the wires connect to. Note that in practical terms, the routing of the wires will not always follow the flow of the wiring diagram, hence the need for cable numbers.
You might find that all the contacts of a contactor are spread over the diagram, but that is for clarity and understanding. You also ought to become familiar with a LADDER diagram.
As for contact numbers.....firstly you need to understand that not all contacts and contactors are the same....some are power contacts, others control contacts and more like a relay. There are NO and NC contacts, and changeover contacts. The numbers indicate what type of contact it is.
A1 and A2 are the coil or control supply.
1,3,5, are the Main high current NO contacts and pair with 2,4,6 (the output contacts)....so odd numbers are input, even are output.
Auxiliary contact blocks, switch contacts and relays are double digit numbers with the first digit the pole number ie. 1X,2X,3X,4X the second digit indicates the type of contact ie a 1,2 is NC and 3,4 is NO. Thus 13-14 would be pole 1 and NO, 21-22 is pole 2 and NC
15,16,18 are C/O contacts (15 is normally the Common)
95,96 and 97,98 are associated with an overload.
This should hopefully give you something to start with.
As for Single phase....the only thing to remember with single phase and overloads is that ALL 3 poles need to pass the same current, so you will often see the phase looped through 2 poles and the neutral on the 3rd pole. This keeps the overload 'balanced'.
Hi, bluewheeler. which range of your AVA model? AC or Commercia L/H application? If you got a AVA4XXXX, you need a start capacitor and a current relay. beacause it's a high torque compressor, it needs higher current to strat. And the circuit diagram can be found in the box with compressor's accerssories. Otherwise, Contactors should be installed in the electrical box of units for the security. Hope it's useful.Quote:
Originally Posted by bluewheeler
From past experience with 2 & 3 phase equipment it all depends whether or not the equipment will single phase on you without a motor starter. Fuse protection does not do this and a winding can sit there and burn. My opinion, a motor starter supplies the best protection cause if it senses an overload condition all power leads to the load are disconnected thus saving the compressor or motor.Quote:
Originally Posted by bluewheeler
Hi panikmkanic,
Electocoolman says it perhaps a little bit rude but somehow he has a point.
I follow him if you only wire contactors just by the numbers you see on the connections without knowing exactly what you're doing.
His comment about a 2 phase motor connected to an overload is very important I often see this fault.
Just like I often see on a multiple heater (more then 3 heaters) for defrosting where the neutral isn't connected to the starpoint.