Manifold Gauge and Hose question

[lees8110]

Hi all,
Just a quick question about gauges and hoses really,
I work mainly on package units with the basic schrader valves (without service valves).
Now I have just carried out my 2079 I am now required to test all the units for leaks every 6 months, I would like to carry out this by measuring and recording the superheat/subcooling, but every time I engage my hoses I am probably doing more harm than good!
Now I am just wondering if there are any hoses out there that are specially designed to be put on and off these valves without loss of refigerant, for example with a longer end connection so it screws on far enough before it releases the valve so its sealed before releasing the refigerant.
I currently use a red hose with a tap on the end and before attempting to take the hose off I close the tap and open my hi and low valve to rid whats left in the hose before removing.
Any advice or help would be brilliant,
Thanks Lee

[glenn1340]

Hi Lees,
http://www.srw.co.uk/ do a set of hoses fitted with non return valves that`ll hold the refrigerant the line. Of course that means you`ll have to have a diferent manifold for each gas you deal with but that`s no bad thing as you`ll not have to purge the hoses each time you connect them.
You`ll need to register with srw to view them but they do lots more stuff at good prices.

[Gary]

Now I have just carried out my 2079 I am now required to test all the units for leaks every 6 months, I would like to carry out this by measuring and recording the superheat/subcooling, but every time I engage my hoses I am probably doing more harm than good!

Yes, you probably are.

You would be better off tracking evap delta-T. An increase in dT indicates airflow problems, while a decrease indicates refrigerant flow problems... or high humidity... or various other problems.

If these are heat pumps, you would want to track the dT of the indoor coil in each mode, as the temp and volume of indoor airflow is relatively constant.

Of course you would first need to establish a base dT for each unit in each mode (with everything functioning properly) to compare to.

[Gary]

I see no sense at all in periodically testing for refrigerant charge problems. Why not instead periodically test for any and all problems?

[lees8110]

I see no sense at all in periodically testing for refrigerant charge problems. Why not instead periodically test for any and all problems?

Thankyou all for your advice and input so far I appreciate it, I am sorry for all the basic questions but am just keen to learn properly.

What checks/precautions would you recommend for this aswell as what you have already suggested?

[marc5180]

IMO gauges should only be connected to systems as a last resort, not on a maintenance/ leak check visit.

As Gary says there are many ways to check if the system has a leak, firstly by carrying out a visual check of the system paying close attention to any signs of oil around joints, schraeders etc and maybe even using your leak sniffer.

Other checks that need performing are,to verify the airflow through condenosr/evap are clear and are not full of dirt by checking the Delt T (air on/air off).

[moondawn]

i am currently doing a nvq level 2 in ac and refigeration. i asked my tutor the other day about putting gauges on a system for maintenace. he said it is illegal to do so. you only put them on if you think the system is short of gas and as a last procedure really.

is this true what he is telling me?

[marc5180]

I don't think it is illegal but too many engineers think the first thing that should be done is put the gauges on when it isn't.

Firstly it should be to check correct water/airflow through both coils, take temperatures and then if there is still a problem i would connect my gauges to check subcooling and then superheat.

[laf100]

I always remember being told that gauges are diagnostic tool not maintenence tool.
Nuff Said.
:cool:

[nike123]

i am currently doing a nvq level 2 in ac and refigeration. i asked my tutor the other day about putting gauges on a system for maintenace. he said it is illegal to do so. you only put them on if you think the system is short of gas and as a last procedure really.

is this true what he is telling me?


If it is not, it should be!

[desA]

If it is not, it should be!

http://www.refrigeration-engineer.com/forums/images/VA_RE/header_05.png

Oh dear... will a logo have to change? :)

[moondawn]

http://www.refrigeration-engineer.com/forums/images/VA_RE/header_05.png

Oh dear... will a logo have to change? :)



no cos that engineer is on a call to a unit showing signs of Short of gas :D

[El Padre]

If the condenser coil is accessible, measure the temperature at the end of the coil, work your way down from the top and you should see a decrease in temperature, when you start to see no change in temperature that reading will be your saturated condensing temperature, subtract the liquid line temperature and you will have the subcooling value.

Cheers

[Peter_1]

You only have to check your system for leaks according to EN378, and it's not illegal to put your gauges on a system.
Why not use these http://www.drillspot.com/pimages/44/4442_300.jpg
I have 2 (1/4" and 5/16 " SAE) in each toolcase, it's a standard tool I use since years.

[lees8110]

If the condenser coil is accessible, measure the temperature at the end of the coil, work your way down from the top and you should see a decrease in temperature, when you start to see no change in temperature that reading will be your saturated condensing temperature, subtract the liquid line temperature and you will have the subcooling value.

Cheers

Cheers for this Would this apply to the evapourater too?

[lees8110]

You only have to check your system for leaks according to EN378, and it's not illegal to put your gauges on a system.
Why not use these
I have 2 (1/4" and 5/16 " SAE) in each toolcase, it's a standard tool I use since years.

Peter this is what im looking for, were would I find myself a set of these?

Cheers Lee

[El Padre]

Cheers for this Would this apply to the evapourater too?

I used the subcooling example as it would be very rare on AC systems to have access to the evaporator coil, because you are looking for the end of the latent heat gain the same principle would apply for superheat, on Daikin splits for example you can see the coil sensor values via the controller (setting code 41).
Gary makes a great point regarding checking air/water flow prior to anything, I have been caught out several times, especially on water chillers in the past.

Cheers

[clivemtk]

your location is manchester you have dean and wood +ryan aircon ref spares on your doorstep

[marc5180]

I heard Ryan Air Con Spares had moved/closed and was concentrating on internet orders instead?

[bangoman]

check with heatcraft,,,,australia there have some fittings u cn use on the schrader valve ...

[pipeman]

I heard Ryan Air Con Spares had moved/closed and was concentrating on internet orders instead?

They still have a trade counter, its in Irlam. About a mile or two down the road from macro