On a residential A/C or heat pump

TonyS

what is the advantage of using a TXV with no bleed port? It seems to me that being able to start the compressor under no load would be a better choice.

Techman

TXV

The bleed port takes time to equalize the pressurers,so, no short cycling is allowed.Unless there is a hard start assembly.Some mfrg's do ,some don't. How many AC units  are  out there w/  a TXV and no start assist.? Most need that  compressor starting helper.

TonyS

You bring up a good point

I recently found out not all hard starts are the same after trying to use a SUPCO ptc on a reciprocating compressor with a TXV. Of course after it wouldnt start I went to their website and read their booklet. What a great primer on start kits http://www.supco.com/images/pdfs/AC%20Hardstarts%20Booklet.pdf

I just dont see the reason why they dont use a bleed port TXV, most of the stats and control boards have a 5 minute restart wait and even if that wasnt enough time to fully equalize it would be a lot closer that a positive stop type valve. Is a positive stop TXV more efficient?

Ironman

Non Bleed TXV

A non bleed is somewhat more efficient. If you'll recall, about 15 - 20 years ago, several manufacturers were recommending the addition of a liquid line solenoid, not for pump down, but to stop liquid from being fed into the evap after the compressor shut off. That, coupled with a TDR on the blower, raised he efficiency about .05 S.E.E.R.



A non bleed TXV also helps prevent refrigerant migration and liquid in the crankcase (or the accumulator) upon start up.

Techman

Supco

In the begining Supco and others pushed their products as "one size fits all" . NOT!!!!!!!!!!!!!!!.  The packages that the Supco Start Assist  and others ,came in DID NOT have microfared ratings on the paper work . So ,which one of these  [7 ] " fits all " do I need? Now adays,the package has the m/fd rating printed on them. You still have to look up the compressors proper size start capacitor and then match the "specific" Start Assist to the comp.But ,what do you do @ 5:01 when no one can tell you the needed m/fd rating?And you are lucky enough to have all 7 start assists on board! Which way do I go ?

Techman

TonyS

Hi Tony,the 3-5 minute time delay is  usually in the t'stat.So, on cond units w/ hi/lo press safetys there is [usually ] no time delay  safety when cycling on  the hi/lo  press switch. And another junky compressor bites the dust!

TonyS

Thanks for the help

here is a utube clip I think you guys will like.

http://www.youtube.com/watch?v=jFFRpxFkpcM

JStar

Soooo...

...you can take the PTC out of a SuperBoost and wire it to its own potential relay to make it work better?