sizing txv and need for hard start kit

[resolutetech]

when sizing a txv for air handler would it be sized for odu tonnage or airhandler tonnage.

another question if i might. i read york's install instructions for txv installation and they recomend a hard start kit with a recipicating compressor and say its not needed for scroll compressor. several mechanics on this sight call for hard start kit period with txv. what is best?

[ultratec]

Are you building a system? LOL J/K. Evap size, BTU's, cfm all come into play when sizing a TXV. Scroll compressors do not reqiure the aid of a start cap or kit.

[Mr Bill]

Originally posted by ultratec
Scroll compressors do not reqiure the aid of a start cap or kit.

ultratec, I have read lots of your posts here and you have become an asset to this forum you can tell you have a clue on lots of stuff, but this is the first thing I would have to disagree with you on,they may not require one but my advise would be to install one when used with a TXV, but it's ok as long as we agree to disagree and move on I can personally live
with that.

[ultratec]

Well Mrbill, Its nice to disagree, it really is, thats how we all learn. But, lol. I have never seen a scroll hard start, unless! The internal discharge check was defective, and thats very very rare. Thats why the manufuactures of the compressors dont feel the need for them.. IE Copland. The start assist doesnt even reduce the starting draw. Many feel, including me and the manufactures that build them is that it does nothing. P.S.. Thank you for your kind words. I have read alot of your posts, learned and enjoyed reading them..

[Mr Bill]

If you buy a 12 seer or 14 seer Ruud I think 3-ton up could be all of them at those seer ratings with Copeland Scroll why do they come from the factory with a start assist? Just wondering.

[beenthere]

REs:

Get the factory txv from york.

On the 4 and 5 ton units they use the same size txv.

Also they are balance port txv's, on all sizes.

And it is sized for the outdoor unit.

York uses kickstarts for their stast kits, they have potencial relays.

Not required for scroll compressor. But no harm if you use one.

[j-bill]

the trane co. uses a hard start on some high end products with their copeland alliance scrolls & also to solve or reduce light flicker caused by starting amp draw on other scroll units that don't come with one.

[docholiday]

To be frank, the scroll compressors rarely if ever need the start kit. However, on some systems it is included as a result of one or more other mfg's including it as a "Spec Buster". This is nothing more that a case of "well, brand x has one, why should I buy yours". Many specified jobs have a call for brand X or equivelent and then spout out the add ons such as hard start kit, time dealy, etc. Often, this is specified by a building engineer who is calling for the same thing year after year and only changing the model numbers as they change. Remember, he runs the cost up for a reaon.

[ultratec]

MrBill, I installed a 12, 4 ton last week Ruud, Doesnt have a start kit. I called my rheem dealer to ask about the 14 seer. The hard start kit doesnt come w/ any model, Rheem or Ruud. The only time I found a scroll hard start, was because the internal discharge check was defective, again, very rare.. Love scrolls lol.

[Mr Bill]

We must be getting two different units in our areas, I just installed a 5-ton Ruud 14 seer about an hour ago and it had not only a start assist but a time delay also mow that is weird.

[ultratec]

No way lol. Really? And a time delay?? Maybe they thought it was a recip lmao. Was it a 50hz machine? lol. Can I have the model number please? I wanna call on monday and speak to someone else. Like I said, I am not a big resi company, I never seen a hard start on any scroll, I am not saying there not installed on some machines, After speaking w/ a PE friend of mine and talking w/ national compressor and copland, they do nothing for that compressor, but wont hurt it bla bla bla lol. I started up two carrier 3 ton cassets today, I hate them lol. No start kits, you can push that contactor in 10 times, once every second and that pump (copland sroll) wont even fart, just starts right up lol. Try that w/ a recip.. Dont try that at home!!!(its not good for the machine) If you dont mind, if you still have the model #??? Thanks Mrbill.

[Edited by ultratec on 06-24-2005 at 05:32 PM]

[Mr Bill]

UAPC-060JAZ 14+
don't know if it makes any difference but invoice say's
"was UAPB"

Maybe baldloonie will come along and give us his experience
to see if he is getting the start assist and time delay in his area with the Ruud units.

[Edited by mrbillpro on 06-24-2005 at 05:06 PM]

[duckman373]

Trane use a hard start kit in high eff units, because they believe it's a good marketing tool. It's not needed on a Scroll. The time delay is neccessary on a Scroll, to keep it from running backwards in case of a short cycle.

[Mr Bill]

I have never heard of a single phase scroll running backwards but I have heard of 3-ph.scroll running backwards, but hey I am still learning.

[ultratec]

Thanks Mrbill, I was kidding about the 50hz comment. I tried calling my guy just now, but I guess its Miller time lol. I think everything should have a time delay IMO, even 3ph. My Rheems and Ruuds, that I install or service(12 seer) dont even come w/ time delays, most delays I see on resi are from the stat. On carrier, like the little 3 toners from today had clo's, I believe correct me if I am wrong, dont act as a short cycle timer. Its for high/ low short cycling(makes them manual reset) and will break the control to the contactor if it doesnt see amp draw from the compressor, those things I know the clo does on the carriers for the crappy cassets I started up today, but did not notice a time delay, I kinda short cycled the compressors playing w/ the control wiring to them.. I am on Long Island ( New York). Again, Thanks Mrbill.

[resolutetech]

wow reading is a dangerous thing.

i went to sporlan's web sight and down loaded info on txvs.

it seem to select one you need to know the temp of the liquid at valve (generally abou 100 f) and pressure drop across the txv. with these values you find two numbers or correction factors to multiply the valves tonnage by. the tonnage is foung in a table for each valve at the evaporators design opperating temp in ac case about 40.

you are shooting fo the odu tonnage or a bit above after you multiply the factors times the tonnage at 40 from the table. wow

with this done you can now select the charge of bulb. sporlan has about 4 that can be used for r22.

now you choose the valve body type you need, there are about 8 if i remember correctly. (sweat, flare, and many shapes and sizes)


now for another question

in a heat pump application do i need to purchase a seprate check valve that is sweated into this set up to allow for flow around the valve in heat mode? little is mentioned about this in the literature i down loaded.

[Shophound]

now for another question

in a heat pump application do i need to purchase a seprate check valve that is sweated into this set up to allow for flow around the valve in heat mode? little is mentioned about this in the literature i down loaded.

Sporlan makes a TXV with a built-in check valve. Funny thing is, you won't see it in Sporlan's catalog or valve selection literature. But flip open your United Refrigeration catalog to the TXV section and that valve is practically on the first page in that section.

VGA is a very common thermostatic bulb charge on hi-temp (a/c) for R22 on Sporlan TXV's.

[resolutetech]

yes shophound. VGA seems to be their reccomended thermostatic bulb charge for R22 on Sporlan TXV's. Its pressure limiting chateristics and anti hunt abilities are mentioned in bulletin 10-9.

another question should the valve body be mounted outside of the ahu to keep it's temp above that of the bulb. (if the valve body temp is lower than bulb charge migration to body occurs when a vapor charge is used. when this happens the valve doesnt work. )

if you remove the piston inside of ahu that is positioned just before the distributor and mount the txv outside does the approximatly 10 inches or liquid line between the txv and the distributor interfere with the distributors job of equally feeding the evap coil.

i guess im asking should a distributor always immediatly follow the txv to make the equal distribution work?


it this is the case, then the valve body on a txv with vapor charge must go inside of the ahu where it can become colder than the charge in bulb which will cause it to stop working.

one more question is vga charged bulb a vapor r22 charged bulb or cross charged liquid or cross charged vapor

damn txvs are close to rocket science!

[beenthere]

UPG part numbers for their txv's.

2 to 2.5 ton----025-31988-000

3 to 3.5 ton----025-31989-000

4 to 5 ton------025-31990-000

[mark beiser]

Regarding units with scroll compressors coming with hard start kits from the factory.
I think you will find that it is heat pumps that generally come with factory installed hard start kits, but straight cooling units will generally come with no start kit from the factory.

Trane requires that you install a hard start kit on thier scroll compressors if you are going to operate a straight cooling system below certain outdoor ambient temperatures.
Heat pumps normally operate below those temperatures, so many units come with the start kit already installed.