Metering a comp

[taz24]

.

On a new or rebuilt comp why do they state..

Do not MEGGA compressor if it is in Vacuum???

Any ideas..


Cheers guys


taz

[Quality]

Got Me thinking if thats any idea

[taz24]

Got Me thinking if thats any idea

Thankyou.

I had it asked of me today and could not answer.

I did not know if it has anything to do with vaccum and temp??

Cheers taz.

[monkey spanners]

Without any pressure in the comp it could ark under the high voltages meggers give out, same reason for not running comps in deep vacuum (apart from no cool of motor)

[taz24]

Without any pressure in the comp it could ark under the high voltages meggers give out, same reason for not running comps in deep vacuum (apart from no cool of motor)

But I thought the vacuum was a perfect insulator??


taz.

[monkey spanners]

I think it insulates thermally but not electrically.

[taz24]

I think it insulates thermally but not electrically.

Ah ok.

That was one of my thoughts acctualy.

That the vacuum could put undue stresses on the winding varnish (shilack ?) and that could cause a short.

Thanks taz.

.

[Toosh]

Ah ok.

That was one of my thoughts acctualy.

That the vacuum could put undue stresses on the winding varnish (shilack ?) and that could cause a short.

Thanks taz.

.

Hi taz A vacuum has no insulation properties hence it would arc, atmospheric pressure has, ie 0 psi

Norm

[US Iceman]

The dielectric quality of the insulation goes down in a vacuum from what I remember. Therefore when you use a megger to hi-pot (high potential) test the motor windings the insulation can be weakened resulting in an arc from winding to winding. Effectively destroying a new motor.

You can hi-pot test under pressure, but never a vacuum.

You also do not want to hi-pot test a motor where moisture may be concerned. Same effect and end result.

[taz24]

Hi taz A vacuum has no insulation properties hence it would arc, atmospheric pressure has, ie 0 psi

Norm

The dielectric quality of the insulation goes down in a vacuum from what I remember. Therefore when you use a megger to hi-pot (high potential) test the motor windings the insulation can be weakened resulting in an arc from winding to winding. Effectively destroying a new motor.

You can hi-pot test under pressure, but never a vacuum.

You also do not want to hi-pot test a motor where moisture may be concerned. Same effect and end result.

Thanks guys.

I can tell the lads today and pretend I know the answers to everything

But in all seriousness lads thanks.

taz

[Suffolk Fridge]

Busted Taz! now i know where you got your answer from!
Thanks for all your help over the last 3 days, ive actually learnt something on a course! Actually i learnt a lot!
As for the tshirt i must confess i think i accidentally left it in the travelodge up the rd!

Thanks again Taz, (especially for passing the 4 of us)
from the annoying one in the class asking all the obscure questions.......

Now wheres my local arco, some git has robbed my gloves! LOL

[taz24]

Busted Taz! now i know where you got your answer from!
Thanks for all your help over the last 3 days, ive actually learnt something on a course! Actually i learnt a lot!
As for the tshirt i must confess i think i accidentally left it in the travelodge up the rd!

Thanks again Taz, (especially for passing the 4 of us)

Your welcome, but you earnt it, you all did.

from the annoying one in the class asking all the obscure questions.......

Its the annoying question that I like. I learn from them.
You would be supprised how mich I learn each week from
each group of people on the course.

Now wheres my local arco, some git has robbed my gloves! LOL

Your welcome..

Gloves are good, they were used this week

All the best.

taz.

[Brian_UK]

Congrats to you then Taz but did they get you doughnuts on the last day?

You've got to get doughnuts for the teacher on the last day, it's test day after all.

[taz24]

Congrats to you then Taz but did they get you doughnuts on the last day?

You've got to get doughnuts for the teacher on the last day, it's test day after all.

Nah they were fridge engineers and they all forgot to bring any money Tight gits

Cheers taz.

.

[Suffolk Fridge]

No need with the chocolate eclairs that were included as part of the lunch buffet! roll on the next lot of legislation that requires a 3 day course far enough from home to warrant a travelodge!
Question for you taz, i did a small custom built fridge cabinet recently with a danfoss optima cond unit, but the hrp tech guy said that as i had a capillary tube and not an exp valve, i would have to remove the reciever? This i did of course, but what difference would it have made leaving it on?

[Yuri B.]

as i had a capillary tube and not an exp valve, i would have to remove the reciever?

While Taz rests...
exp valve systems (excluding EEVs' ones) include the solenoid valve.
If I understood it right,it is said that the charge in the cap system would migrate from the receiver into evaporator and at the start the comp is at risk of heavy slugs. So, no receiver there.

To add to the answers to the original post.
Vacuum's electric permitivity is better than that of the gases. So in relative absence of gas's particles an el arc is easier to form (and be breaking in its wake the winding insulation).
It sounds paradoxical because in HV switches it is just vacuum they use for extinguishing the arc of opening contacts. But it's becuse there takes place ionization of air which is sustaining the arc. Vacuum does not allow it.

[taz24]

Question for you taz, i did a small custom built fridge cabinet recently with a danfoss optima cond unit, but the hrp tech guy said that as i had a capillary tube and not an exp valve, i would have to remove the reciever? This i did of course, but what difference would it have made leaving it on?

As Yuri explains it so well I don't think I could answer better.
One thing that a capillary tube does is, it allows the pressures to equalise in the system when the comp shuts down. This makes it easier for the comp to start back up again and therfore the start winding can be smaller, cheaper to make. But as Yuri stated if there was a reciever on the system the liquid would flood the evap on shut down and run the risk of flooding back on startup.

While Taz rests...
exp valve systems (excluding EEVs' ones) include the solenoid valve.
If I understood it right,it is said that the charge in the cap system would migrate from the receiver into evaporator and at the start the comp is at risk of heavy slugs. So, no receiver there.

To add to the answers to the original post.
Vacuum's electric permitivity is better than that of the gases. So in relative absence of gas's particles an el arc is easier to form (and be breaking in its wake the winding insulation).
It sounds paradoxical because in HV switches it is just vacuum they use for extinguishing the arc of opening contacts. But it's becuse there takes place ionization of air which is sustaining the arc. Vacuum does not allow it.

Thanks Yuri.

taz

[US Iceman]

I can tell the lads today and pretend I know the answers to everything

Never let them see you sweat Taz!

[taz24]

Never let them see you sweat Taz!

I'm like a Swan.

All graceful and elegant above water, but paddling furiously underneth to keep moving.



Cheers taz