why icing on the suction valve

[ong]

i came across a split system unit with under size piping.
The unit is a 12,000 BTU Sanyo unit.This unit should be install with 6mm diameter piping(discharge line) and 12mm diameter piping(suction line),but the installer use a 9mm diameter pipng on the scution line.Why icing occur on the suction valve on the condensing unit?

[chemi-cool]

Hi Ong,

First, enlighten me, how do you connect a 3/8 pipe to a 1/2 connection?

In recent mini splits, this is the suction pipe diameter,
the icing has nothing to do with it.

Check the indoor unit first for: blocked filters, dirt on the fan blades, free air movement.
If all the above is OK, I would check, lack of refrigerant, add a bit and check if the suction pressure have raised, if it did, fill up to the point when the the valve is sweating and check on your gauges that the pressure is about 5°C.

If the suction pressure remains low and does not change, check the capillar tube for blockage.

Chemi

[frank]

First, enlighten me, how do you connect a 3/8 pipe to a 1/2 connection?

I've had this Chemi where it seems that the guy installing the split had run all the pipework in and then discovered that it was the wrong size and won't fit onto the outdoor unit so he's left the pipework in and sweated it to a short piece of correct size pipe to make the connection.

A reduced size suction line will always result in low back pressures no matter how much additional refrigerant you put in. (obviously you know this Chemi but it's for the benefit of Ong)

[chemi-cool]

Hi Frank,

For a year now, all the mini splits with up to 12000btu capacity, come with 1/4 and 3/8 pipes.

No problems recorded.

The procedure you have have just described can be very dangerous in heating as the pipe, under high pressure and can pop out.

Chemi

[Peter_1]

.Why icing occur on the suction valve on the condensing unit?

Uhmmmmm,...perhaps because it's cooling.

[bobjob]

Hi Ong

There are a number of reasons why you may see icing on the suction valve entering the condensing unit.
I know of a number of units which sometime freeze over on the valves for a short period.
If it is an excessive freeze over
one of the reasons could be due to the diameter of your suction pipe on the Sanyo system

If the pipe dia. is too small the refrigerant pressure drop would be excessive in the suction line between the evapourator and the condensing unit and hence the refrigerant pressure would drop so you may see icing on the brass valves which are not insulated.

Chemi is correct in saying that all new 12,000 BTU unit working on R410A refrigerant seem to be manufactured with 6mm exspansion and 9mm suction lines.

I would recommend contacting Sanyo for guidance on this one, You have to make sure that the pipe sizes are correct for the length of run before you start checking capillary lines etc

Regards Bob

[ong]

[QUOTE=frank]I've had this Chemi where it seems that the guy installing the split had run all the pipework in and then discovered that it was the wrong size and won't fit onto the outdoor unit so he's left the pipework in and sweated it to a short piece of correct size pipe to make the connection.

A reduced size suction line will always result in low back pressures no matter how much additional refrigerant you put in. (obviously you know this Chemi but it's for the benefit of Ong)

[/QUOTE=ong]The installer use a small length of 1/2" piping connect to the valve...and then braze 3/4" piping on to it for the remaining length... this way the installer are able to earn more ...cause 3/4" piping is cheaper...but they will quote 1/2" piping price.All 1/2" pipng are visible,but 3/4" piping are hidden.

[ong]

[QUOTE=ong]Hi bob

this sanyo unit use R22 gas... the nut joint for the suction valve is for 12mm pipe.installer joint it with a 12mm pipng intially but half way he cut the pipe and baze it with a 9mm pipe

[Deejey]

you will get icing on the suction line or SSV if the temperature of the refrigerant in the line drops to below 32F or 0C...so look at the problem from the point why is the temperature falling to this level...what is causing this.....tell me if your using imperial or metric figures and I'll get back to you

[ong]

i use metric... i think this is due to undersize piping use by installer and i discover a slight twist on the piping the following day i went to check... this 2 may be the problem leading to icing...

tks deejay

[benncool]

Always look at the history of this system.

How long has this system been installed? Are the filters clean?
How big of a room is it cooling. Is there any thing such as curtains or plants that is causing a short cycling of air across the evaporator?

If this unit has been in operation for 2 or 3 years and now it is icing back then I don't think it is a piping problem.

Nobody mentioned checking the superheat at the compressor.

[ong]

i went back the client house an cut off the twist pipng and baze it with a new pipe...the undersize pipe i didnt not meddle with it... the system on the suction valve no long icing... but the off coil is 15 degree celcius... the efficiency is not that good ...but at least no icing on the valve anymore

[Peter_1]

[... this way the installer are able to earn more ...cause 3/4" piping is cheaper...but they will quote 1/2" piping price.All 1/2" pipng are visible,but 3/4" piping are hidden.

3/4 is cheaper then 1/2? Deliver me a container of it.

[Abe]

It may be 3/4" plumbing pipe Peter............not refrigeration quality.

And Im not joking....................in other " economies" they will use what ever is available and I have seen it done!!

[Peter_1]

We twice installed seamless steel lines (in the range of 5") for R22 - +/- 10 years ago - because copper wasn't available or we had to install multiple suction lines between each other which as too expensive.

We hired then for some weeks specialised TIG welders.

The units are still running.