Strage Pipework Configuration

[chillerman2006]

Chillerman,
A suction line accumulator should be sufficiently sized to hold the entire charge of the system.

Hi Marc

should it ?

you got me, when it comes to designing and component choice

but does seem excessive to me mate

If correct ...would you say this units accumalator is big enough ?

R;s chillerman

[install monkey]

http://www.stara.co.kr/parker_catalo...og/40-10-7.pdf

Hi Marc

should it ?

you got me, when it comes to designing and component choice

but does seem excessive to me mate

If correct ...would you say this units accumalator is big enough ?

R;s chillerman

[marc5180]

On a heat pump air conditioner the defrost is nearly (if not always) carried out by the hot gas method, i.e. the reversing valve is energised to flood the outdoor coil with "hot gas". As this coil will be 90% full of liquid it will be pushed down the suction line and has to be collected by the accumulator to protect the compressor - hence the accumulator must be able to hold the entire charge.

[install monkey]

Systems with a thermostatic expansion valve (TEV), the
accumulator holding capacity should be approximately 50%
of the system charge.
from parker

[chillerman2006]

On a heat pump air conditioner the defrost is nearly (if not always) carried out by the hot gas method, i.e. the reversing valve is energised to flood the outdoor coil with "hot gas". As this coil will be 90% full of liquid it will be pushed down the suction line and has to be collected by the accumulator to protect the compressor - hence the accumulator must be able to hold the entire charge.

Argh, I see cheers

So does the hidden accumalator have that capacity, mate

(marc's thinking ''I started this thread for answers not starting up a training school )

R's chillerman

[stufus]

I could be wrong but....I always thought a suction accumulator should be sized for 50% of refrigerant charge and a liquid receiver was 100% of charge.
Cheers
Stu

[install monkey]

http://www.refrigerationbasics.com/1...eat_pumps1.htm
in defrost mode the liq still travels through the 4 way valve and creates cooling in the evap thats why ur indoor fan slows down whilst in defrost mode

[install monkey]

stu u are wrong,but u are correct! brownie point for u!!

[chillerman2006]

http://www.stara.co.kr/parker_catalo...og/40-10-7.pdf

Thanks Install

have kept a copy of that, a useful bit of info Cheers

I could be wrong but....I always thought a suction accumulator should be sized for 50% of refrigerant charge and a liquid receiver was 100% of charge.
Cheers
Stu

Hi Stu

as per 'Installs' link you would be correct mate on refrigeration systems

But it does not state clearly for systems with reverse cycle or for heat pumps

And 'Marc s' comment makes sense, would you agree ?

R's chillerman

[marc5180]

Haha far from it CM,
Install, i've read what Parker say that and by the size of the accumulator that is fitted then i would say they have probably used one that is 30-50% of the entire charge but what happens if a componet fails.
The size of an accumulator is based upon the size of the error, and the likelihood of the error you think can occur

[marc5180]

Haha far from it CM,
Install, i've read what Parker say that and by the size of the accumulator that is fitted then i would say they have probably used one that is 30-50% of the entire charge but what happens if a componet fails.
The size of an accumulator is based upon the size of the error, and the likelihood of the error you think can occur

[chillerman2006]

irrelevant

[install monkey]

you dont have the power to give fractions yet! haha-nike 123 give me a pic of a pint of guiness and a bird wrapped in duct tape- that wasnt frowned upon!!

[marc5180]

http://www.refrigerationbasics.com/1...eat_pumps1.htm
in defrost mode the liq still travels through the 4 way valve and creates cooling in the evap thats why ur indoor fan slows down whilst in defrost mode

Liquid travels through a 4 way valve?? Where?

On a 4 way rv you have discharge and suction vapour pressures not liquid.

[install monkey]

my bad

[stufus]

Suction accumulators are also system specific IE you should not use a standard SA on a heatpump system due to the orifice size being to big and allowing liquid slugging to the compressor especially in heating.
http://www.henrytech.com/Tips/HT-TT14.pdf
Cheers
Stu

[chillerman2006]

irrelevant

[monkey spanners]

I've heard half system charge as a rule of thumb for accumilator sizing.

Jon

[install monkey]

chillerman

[al]

Thanks Marc

You've had one electrical fault and the other sounds like liquid flood back, i'm with install on this,these dx units must be held off in ambients below 16c, i know theres plenty of heat at the minute but i doubt that was the case before this week? If the units are required to run in lower ambients you've a sizing issue. I can't imagine a heat pump with no accumulator, so look at control strategy and airflow first, see Gary we do listen!!

al

[install monkey]

hmmm-post missed with all the chat over accumulators-other points to consider-
no crankcase heater on the pot, system is within the airflow so exposed to 10-40deg ambient, no jacket on the compressor, as u say no suction accumulator or evap press reg, as with air handling units normally 100% fresh air then sticking a cooling coil in there there is not a constant load so theyve done well sticking an electronic expansion valve-at least it will be more responsive, also them check vavles will need checking to ensure theyre not passing as with the 4 way valve as its too easy to chuck a pot in and watch it destroy itself, also i would look at the control strategy, comp restart delay, setpoint differential it should have a free cooling setpoint that usually is set around 16 deg which will stop the mechanical cooling and rely on fresh air.
are the v belts ok,if fitted,panel filters blocked as they normally last 3mth also check alarm history, is there a lp swith on it or transducer, may be sartup of the compressor causing pipework to flex and the lp being auto reset??
are the fans inverter driven whats the minimum speed or is it controlled of duct pressure?
i could nip up to site as its in my hood!!haha

[chillerman2006]

Install

Just because no-one replied to your post the last time round

R's chillerman

[install monkey]

my post co

[MikeHolm]

irrelevant

[install monkey]

molson per

[MikeHolm]

irrelevant

[MikeHolm]

irrevelant

[chillerman2006]

irrelevant

[install monkey]

is that ur

[MikeHolm]

irrelevant

[chillerman2006]

irrelevant

[chillerman2006]

irrelevant

[marc5180]

11 posts spamming.....

[marc5180]

Thanks Marc

You've had one electrical fault and the other sounds like liquid flood back, i'm with install on this,these dx units must be held off in ambients below 16c, i know theres plenty of heat at the minute but i doubt that was the case before this week? If the units are required to run in lower ambients you've a sizing issue. I can't imagine a heat pump with no accumulator, so look at control strategy and airflow first, see Gary we do listen!!

al

These units are only designed to temper the air and so run all year round using a recouperator and a mixture of fresh air and return air
When the outdoor temp gets to cold they use full return recirculation with minimum fresh air.
The minimum air onto the coil is 18DegC.

[al]

Check the accumulators for size and correct piping (inlet/outlet), could be worth getting a thermal camera for a day to see what's going on?
al

[marc5180]

no crankcase heater on the pot

Not all compressors have visible crankcases though do they? Many of them have a voltage going through the windings to heat the compressor a few degrees.

system is within the airflow so exposed to 10-40deg ambient, no jacket on the compressor

Minimum air onto these coils/compressors is 18DegC

also i would look at the control strategy, comp restart delay, setpoint differential it should have a free cooling setpoint that usually is set around 16 deg which will stop the mechanical cooling and rely on fresh air.

Compressor restart delay is 6 min. These have a recouperator that mixes fresh air and return air and if the temp is still too high/low then the compressors will be brought on. The setpoint for the building is 21/22 degress C so the compressors don't need to be on often....supposedly.

are the v belts ok,if fitted,panel filters blocked

Filter/belts ok

alarm history, is there a lp swith on it or transducer, may be sartup of the compressor causing pipework to flex and the lp being auto reset??

Yes theres an LP switch on it, looked at alarm history and found only the 1 LP fault.
Compressor flex and reset the LP alarm ?? Can that happen??

are the fans inverter driven whats the minimum speed or is it controlled of duct pressure?

Yes the fans are inverter driven and have been commissioned to run at 50hz

i could nip up to site as its in my hood!!haha

Lol, Nip up to the site to do what?

[marc5180]

Thermal camera? To check what?

[al]

check the accumulator for a start, also check your 4 way valve and NRV's.

In fairness this is either the site completely screwing up the units or they have been misapplied or specced?

al

[mad fridgie]

Copeland say that the scroll is compliant, it can handle liquid flood back ( a slug of liquid), say after defrost, in this case it is the position of the EEV temp and pressure sensor causing prolonged oil dilution,
Accumulator size, without knowing all the data I would just go for one which is has the same size pipe as the comp inlet. You could even look a suction/liquid line heat exchanger (between the EEV sensor and the comp)

[al]

MF, i've found scrolls less tolerant of flood back, more inclined to wash oil out and not return it, accumulator would be essential as you say.

al

[marc5180]

Thats a good idea al, I may suggest that.

When i find out more i'll update the thread, thanks for your input. Much appreciated

[chillerman2006]

Gents

just a quick thought as bed time for me

dont certain copeland scroll models have built in accumalators that allows them to take full liquid and boils it off by compressor heat ???

R's chillerman

[mad fridgie]

MF, i've found scrolls less tolerant of flood back, more inclined to wash oil out and not return it, accumulator would be essential as you say.

al

Before I starting producing my units, I did considerable testing on the scrolls, and found that under certain circumstances liquid return was a problem, so even though the tech data says i do not need a accumulator, I do fit one, in my mind it is cheap protection.

CM; copeland scrolls do not have a built in Acc, Maneurope recip comps do. (twin shell)

[chillerman2006]

Before I starting producing my units, I did considerable testing on the scrolls, and found that under certain circumstances liquid return was a problem, so even though the tech data says i do not need a accumulator, I do fit one, in my mind it is cheap protection.

CM; copeland scrolls do not have a built in Acc, Maneurope recip comps do. (twin shell)

Thanks Mad

Thought I was going 'mad' when the thought appeared in me head, argh so its maneuropes (recips) Cheers for correction

Also picked up a site with a right mickey mouse abortion of a setup (1st visit today) with 4 copeland scrolls, it looks a right b*tch to change 3 of the four compressors

Mad, in your eyes, whats the perfect suction superheat for copeland scrolls (as I need them to purr for ever)

R's chillerman

[r.bartlett]

Is anyone doing a failure test on the failed compressors

[install monkey]

Can Copeland Scroll compressors handle liquid?

ANSWER: Scrolls handle liquid better than most other compressor types, but still can require additional accessories for optimal protection. Those accessories include: Accumulators are recommended for systems with large refrigerant charge or those that allow for uncontrolled refrigerant floodback. Crankcase heaters are required for three-phase systems with large refrigerant charge and in/outdoor applications.

ref copelands website

[marc5180]

Just to update the thread. The system was found to have a leak on the equalising line. The manufacturers went back to site to repair.
Thanks to everyone who contributed

[al]

Nice one Marc, thanks for the closure!!

al