capillary tube to expansion valve

Posted by nikos on July 5, 2007, 12:47 pm

I am in the unenviable position being in charge of retrofiting a "no
name" split unit domestic air conditioner (9000 BTU) for advanced
control within an R&D project

The unit comes with adjustable speed compressor (inverter) but has a
fixed capillary tube instead of an adjustable expansion valve. I want
to have the valve controllable too, so I need a bypass of sorts. The
controller will have an overview of the system, balancing compressor
speed and valve opening.

I would appreciate some advice on the following:

1. Is this conversion feasible? Would it possibly make the system
unstable, e.g. end up with moist refrigerant entering the compressor?

2. what type of expansion valve? There are "thermostatic" and
"electronic". What would be continuously controllable, e.g. my
algorithm may request 25% open. If they can both do the job I'll go
for the cheaper

3. I've read in this newsgroup that the compressor may need
retrofiting too for a "a hard start kit" whatever this is :)

Alternatively I would need an experienced HVAC engineer to do this
conversion for me, in the area of Bangor wales UK

thanks
nikos

Posted by on July 5, 2007, 1:12 pm

Yes and yes.

>2. what type of expansion valve? There are "thermostatic" and
>"electronic". What would be continuously controllable, e.g. my
>algorithm may request 25% open. If they can both do the job I'll go
>for the cheaper

Electronic is your only choice.

>3. I've read in this newsgroup that the compressor may need
>retrofiting too for a "a hard start kit" whatever this is :)

Nope.

>Alternatively I would need an experienced HVAC engineer to do this
>conversion for me, in the area of Bangor wales UK

Yep.

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Posted by nikos on July 6, 2007, 7:03 am

On 5 Jul, 18:12, .p.jm@see_my_sig_for_address.com wrote:

> >3. I've read in this newsgroup that the compressor may need
> >retrofiting too for a "a hard start kit" whatever this is :)

> Nope.

are you sure about that? Many posters talked about a SPP hard start.
Perhaps this isn't required for ELECTRONIC valves (?)

> >Alternatively I would need an experienced HVAC engineer to do this
> >conversion for me, in the area of Bangor wales UK

> Yep.

from your signature you look US-bound. Or are you in the UK and could
take the job?

thanks
nikos

Posted by on July 6, 2007, 9:30 am

>On 5 Jul, 18:12, .p.jm@see_my_sig_for_address.com wrote:

>> >3. I've read in this newsgroup that the compressor may need
>> >retrofiting too for a "a hard start kit" whatever this is :)

>> Nope.

>are you sure about that? Many posters talked about a SPP hard start.
>Perhaps this isn't required for ELECTRONIC valves (?)

>> >Alternatively I would need an experienced HVAC engineer to do this
>> >conversion for me, in the area of Bangor wales UK

>> Yep.

>from your signature you look US-bound. Or are you in the UK and could
>take the job?
>thanks
>nikos

US here.

Look up Marc o'Brian over there.

http://www.fridgetech.com/

--
Click here every day to feed an animal that needs you today !!!
http://www.theanimalrescuesite.com/

Paul ( pjm @ pobox . com ) - remove spaces to email me
'Some days, it's just not worth chewing through the restraints.'
'With sufficient thrust, pigs fly just fine.'
HVAC/R program for Palm PDA's
Free demo now available online http://pmilligan.net/palm/

Posted by Tony on July 5, 2007, 6:16 pm

It has lot to do with what are you really looking for
precise temperature control precise RH what is
your end project, end product your end achievement.
Tony

>I am in the unenviable position being in charge of retrofiting a "no
> name" split unit domestic air conditioner (9000 BTU) for advanced
> control within an R&D project
> The unit comes with adjustable speed compressor (inverter) but has a
> fixed capillary tube instead of an adjustable expansion valve. I want
> to have the valve controllable too, so I need a bypass of sorts. The
> controller will have an overview of the system, balancing compressor
> speed and valve opening.
> I would appreciate some advice on the following:
> 1. Is this conversion feasible? Would it possibly make the system
> unstable, e.g. end up with moist refrigerant entering the compressor?
> 2. what type of expansion valve? There are "thermostatic" and
> "electronic". What would be continuously controllable, e.g. my
> algorithm may request 25% open. If they can both do the job I'll go
> for the cheaper
> 3. I've read in this newsgroup that the compressor may need
> retrofiting too for a "a hard start kit" whatever this is :)
> Alternatively I would need an experienced HVAC engineer to do this
> conversion for me, in the area of Bangor wales UK
> thanks
> nikos
>

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