Shouldn't I need a low pressure switch made for R-134a? mine is the original, made for R12, you brought up quite an interesting point I didn't consider before.

 

R134a and R12 run similar pressures with R12 being a few psi lower. When you do a retrofit it does not require changing the switch. So what ever switch is called for will be o.k.

The problem with putting a bigger capacity compressor into a system without changing to the corresponding condenser and evaporator is the condenser will not have enough cooling capacity, increasing discharge pressure and possibly sending vapor o the expansion device(orifice tube) which in turn increases evaporator pressure(suction pressure) If anything you want to oversize your condenser so you will have increased sub cooling on those hot days. This is why the high efficiency house units have such large outdoor condensing units, the extra subcooling.

Matt

 

Mine is a stacked plate, and slightly larger in surface than the original tube/fin condenser, but mine is also about 1/2in thinner. I will also add a 12" electric fan soon, not a very powerful one, but I'm sure it will help.

 

Are you adding the electric fan as a pusher just for the a/c condenser? If you are removing your mechanical fan that one little electric will not be enough. You would have to find out the capacities of your replacement condenser and compare that to the original condenser to know if you have a large enough condenser for your compressor application

matt

 

I'm not removing the stock fan, it's an aditional pusher fan. I have been told the SD7H15 (the 15 regards the compressor's capacity) is actually a little weaker than the stock one (AR-15 I think).

 

Probably the same pumping capacity, but being made for R134a it will have a slightly lower tonnage rating than the R12 compressor

Matt