Weird pipe runs

[SkyWalker]

System install,

hi guys one thing i have noticed when going on any course, manafactures specify pipe max/min runs, max/min height diff of evap/cond, max distance from first refnet ect ect, but i have never seen them specify certain conditions to be avoided......

for instance say you had a really weird and wacky pipe run lots of ups and downs 45' 90' ect i mean REALLY out of the ordinary,

what im trying to ask is, are there any situations you guys try to avoid when installing pipe work or are you completely oblivious as long as pipe run doesnt exeed max (taking into acount bends ect)

[BigJon3475]

That's kinda a loaded question IMO. If it has "lot's of bends and 45º, 90º"...." Then most likely you'll be well above the normally recommended 2-3 psi pressure drop. So it would depend specifically on how many 45's 90's and how long the line set was weather or not you use risers or long radius couplings instead of reg. couplings. The manufacture doesn't have every equation out their to give you every scenario. You have to use your best judgment and go by the min/max the manufacturer can recommend.

[Jez]

Manufacturers frequently state a maximum 'equivalent' pipe length which would include for bends etc.

[SkyWalker]

thats what i do just wonederd what you guys thought on the situation!

[BigJon3475]

Probably contact manufacturer and get them involved with anything outside the "box"

[vac-man]

could someone explain to me what would happen if you exceed the recomended pressure drop and what exactly long radiius couplings involve..thanks

[BigJon3475]

http://www.refrig.com/Ref%20Pip%2002.pdf


This will at least give you some ideas.

[hendrag]

Most manufactureres have a max pipe run and max equivalent pipe run. The equivalent run assumes a few bends are included but figures are never given. On VRF or VRV systems it is not uncommon for the systems to compensate for long runs with high pressure drops by altering the compressor speed. The unit calculates the pressure drop during during an oil recovery cycle the outdoor unit knows the back pressure so therefore the evaperator temperature, by asking the indoor units what the real evap temperature is the unit can determine the pressure drop. To see this in action go to 2 similar systems (same manufacturer) and measure the back pressure units with long runs will have lower back pressures than those with short runs, this overcomes the pressure drop.
splits dont know the real back pressure so they have to either guess or some have a long short pipe run switch which is a crude way of doing the same. Non Inverter units just struggle on with reduced capacity

If you want more explanation come to our vrf service course go to www.mylg.co.uk and click training for details

hope to see you all soon.