Sporlan Thermostat assy replace

[daveca]

Went tripping down the Rabbit Hole on the question of cutting the cap tube, Parker says "wont work" (in another thread)

Thats a refrigerant cross-charge head and apparently always has vapour phase which would be lost.

Next point of disorder, changing the thermostat assembly without recovery.

General concensus is "cant do it without refrigerant loss" which is true, as it has no isolation valves.

so, how about 'minimise vapour loss over the 15-20 seconds needed to swap the head?"

Trane XL14C heat pump. Externally equalized TXV via a long cap tube.

According to Sporlans data, that external TXV has no pressure commuted to the bottom of the thermostat disc from the input or output lines (sealed), only the Eq cap tube, which is a long, small restriction which is only seeing vapour-phase.

This change could be done at night when the outdoor temps are ~ 60F. The indoor coil cover must be removed to access the TXV, which also exposes the indoor coil to cool air. The inlet (cold air return in the dwelling) can be blocked, windows opened and indoor fan run to draw outdoor air thru the indoor coil to cool the sealed system down to outside ambient, which will reduce the system pressure from ~230 psi down to about 170. That would means much less vapour loss.

???????

PS it is VERY easy to stop a Trane.

[seanf]

170psi is still a good amount of pressure, if you were talking about 5psi fair enough.

Recover the gas, lets you mess around with any seal it might have and leak test it before putting expensive gas back in.

[daveca]

170psi is still a good amount of pressure, if you were talking about 5psi fair enough.

Recover the gas, lets you mess around with any seal it might have and leak test it before putting expensive gas back in.

Improper response. Rejected

Your responses are correct, but one- dimensional. Citing pressure only.

That ignores the Elephant in the Room. The equalising cap tube pressure drop due to its large flow restriction as an orifice.

"Expensive gas," not acceptible. Expensive liquid. Gas cost is a small fraction of the liquid cost. Much smaller volume.

1 ounce liquid lost versus 2 hours reciver/ recharge time is irrelevant

2 oz,= ~ $ 2 USD.

Ill waste that much using hoses to recover and recharge.

You figure 2 hours = $2 US? I hope youre not running a business!

.R&D engineer here, you must do better than that...I can calculate the orifice flow and loss if you need further education.

Or better yet, you do so. 0.107 inch cap tube, 24 ins long.
How much flow lost in 20 seconds?

[frank]

I find your post above a little condescending of the helpful advice seanf was giving.

Remember the forum rules do not allow insulting fellow members.

We all have differing levels of knowledge so please be a little more respectful, and remember that this forum is not HVAC.COM

[Grizzly]

Well said Frank.

[seanf]

Improper response. Rejected

Your responses are correct, but one- dimensional. Citing pressure only.

That ignores the Elephant in the Room. The equalising cap tube pressure drop due to its large flow restriction as an orifice.

"Expensive gas," not acceptible. Expensive liquid. Gas cost is a small fraction of the liquid cost. Much smaller volume.

1 ounce liquid lost versus 2 hours reciver/ recharge time is irrelevant

2 oz,= ~ $ 2 USD.

Ill waste that much using hoses to recover and recharge.

You figure 2 hours = $2 US? I hope youre not running a business!

.R&D engineer here, you must do better than that...I can calculate the orifice flow and loss if you need further education.

Or better yet, you do so. 0.107 inch cap tube, 24 ins long.
How much flow lost in 20 seconds?

I'm just a daft fridge parts fitters so, I wouldnt take anything I say too seriously. And yes I should have given a bit more context to my answer.

Gas loss during the planned 20s quick change, yer I can see it only being a relatively small amount. But could that planned length of time end up getting extended if you find theres more to it than just unscrewing and fitting a new power head?

What if there is a leak past the push pin?

What if the pressure pushes the push pin out? Its been awhile since I've looked at a Sporlan, so that may be irrelavent.

What if you loose a relatively large amount of vapour from the R410a system?

Potentially working against the 170psi dosnt sound the best idea. But maybe the calcs are saying the pressure build up will be slow enough for reassembly and during disassembly?

Its been awhile since I've done any calcs on flows, so I'll leave it to you.

Safety and making a good repair is what would concern me more than the cost.

[al]

I believe that even in the land of the free, intentionally releasing refrigerant is an offence? If engineers with many years experience won't' do this "live", why on earth do you think you should?

You don''t mention what refrigerant it is, if 407c then loosing even a small amount of "gas" would result in changing composition of charge, but hey, you'r'e the expert, go for it.

[seanf]

..............

[monkey spanners]

Can you pump the system down to a few psi?
Failing that if you are determined to cut corners, pinch the equalising line flat change the head and then round it back out with flaring block (assuming its 1/4")