toshiba ras 26 - high discharge pressure on heating mode and very hot compressor

[sale]

hi,
i had problem with 3 same units toshiba ras26 heat pump.
On 2 units we repalced compressor and after we put all togheter we had problem aith high discgarge pressure on heating mode.
It is going over 350 psi on discharge line and compressor gets very hot.
Because we have only one service port when unit is working on cooling mode suction pressure pressure is arround 50 psi,which is little bit low.
Using same service port,when unit is working on heating,pressure jumps over 350 psi and after some time trips circuit breaker.
compressor is very hot and draws 22 amps on start up ,and on hetaing mode is ratted at 14.5 amps,but it draws over 18 amps and then trips circuit breaker which was on 16 amps.
I checked outdoor unit and capillary tube was not blocked,also i checked reverse valve,and that is also fine.
I was charged unit on critical charge which was 1.85 kg ,which was written on outdoor unit.
I was thinking that maybe there is some air in condensor which causes high discharge on heating cycle.
That happeens only with this model,and all 3 units have similar simptoms.
Why compressor is getting so hot?
also thart is toshiba un it,and when we ordered compressor to replace they send us mitshubishi eletric compressor.
I am not sure that that is correct compressor for that unit,but all ports on compressor looks same like on old one.
Anybody knows why the pressure is so high on heating mode please send me your opinion.
Thanks

[Brian_UK]

What is the state of the indoor unit coil, filter and fan?

[nike123]

Did you charged all 3 units with refrigerant from same bottle or same refrigerant manufacturer?

[goshen]

Hi what is the ambient temp??

[sale]

hi all,
indoor coil was clean on all 3 units,indoor fan was working properly and it was clean,all filters were clean.
Ambient temperature was arround 18 C.
That problem happened on all 3 units after compressor was changed.I used new R-22 refrigerant,i replaced compressor on 2 units and on third somebody else did it.
I folllowod all procedures and we ordered new compressor from toshiba,we were sent mitchubishi eletric compreessors,which fitted properly,but i dont know what mitshubishi compressor has to be installed in toshiba units.
I disconnected one outdoor unit and checked if capilary was bolcked,and it wasnt,also i checked reverse valve and that was also ok.
That unit has 2 sets of capilary tubes in outdoor unit,and i didnt see any strainer ,i ve seen something like check valve ,which was working only in one way,i know when you have so small units like this and it is heat pump,that should be 2 check valves.
After i red some books,i saw that maybe can be some air in condensor coil,but i did everything properly when i evacuated system,maybe some air went thru the manifold hoses,but i am not sure that that si problem for so high discharge pressure on all 3 units.
All same models and same symptoms.
Anybody have some ideas?
Thanks

[Gary]

What are the indoor coil air on and air off temps?

Is the indoor fan rotating in the right direction?

Is it set at high speed?

Are the fan motors single phase or three phase?

[goshen]

Hi gary ,so far many questions -no answers!,!

[Gary]

Hi gary ,so far many questions -no answers!,!

Life has far more questions than answers. :)

[nike123]

If refrigerant is common connection for all 3 units than it could be bad refrigerant which causes high discharge pressure.

Also what is full model number of your units and what is compressor model number?
It could be that compressors are pumping more refrigerant than old original compressors and therefore you got "restriction" at expansion device.

Also, I don't see 350PSIG or 24,2Barg as excessive discharge pressure if outdoor ambient temperature is 18°C.
Some units are not designed to work in heating mode above 15°C outdoor temperature.

What was problem with old compressors? What is cause of their death?

[mundow1]

I would say its the solenoid valves but here you are saying its happening on all three units,that leaves me with one thing in mind.If you follow the discharge pipe,from the solenoid valve to just before it leaves the condenser,I think you will find a small filter(very easy to miss as it is enclosed in the same size pipe as the discharge pipe). I experienced the same on a panasonic unit,hope this may help you.

[sale]

thanks for answers,here is model number of 2 units,they had same compressors.
Models are: RAS-26NZAH-AZ,and RAS 26NAH-A.
This are model numbers for outdoor units,in all 3 units we install compressors which has this model number:NH52VNHT.That is mitshubishi eletric compressor.
I called giu from Carrier(toshiba is part of Carrier) and he told me that for that units they make LG compressors and Mitshubishi eletric compressors.
I was also thinking that maybe that compressor dont match,he wasnt sure so he said he will send some Carrier people from Sydney to Canberra where i live at moment.
This units have 2 pairs of capillary tubes in outdoor units,one capillary is bigger size then other,they have some small muffler,i think they have one cgeck valve which is going just to one way,and i am not sure where is other check valve if unit is working on heating mode.I couldnt see any strainer in unit,or fillter,i couldn find any material to read about that units.
On 2 units we replaced commpressor and on third another company replaced compressor.
And all together have same symptoms,unit is drawing to much amps when working on heating mode(goes over 23 A ,and max.current is 18 amps ,compressor is so hot,and i charged with critical charge but still dont help.
Guy from Carrier told me that run of pipes has to be at least 5 meters,but some of units have 2 meters pipes.
The thing is that all this units worked fine before compressors failed.
Or it is comperessor problem(it is not like original)or it is some blockage in strainer which i cant see in indoor unit.
All fans working fine,coils are clean,i flashed outdoor unit with dry nitrogen in case that capillary tube is logged with some oild,and i didnt find any blockage.
I didnt see any filter which is same size like discharge line,i think there is only one check valve(it is saying something like 2.3 MPa on it,and i didnt see another check valve.
This is happening only with this model.
There are so many toshiba models here in Australia,that every is built different.
If somebody has some ideas please send me answer.
Thanks

[nike123]

By the compressor model # (and specification data)it has 9674 W cooling capacity and by unit model number (and specification data) it has 7500 W cooling capacity which is the reason for high pressure and compressor high current consumption and overheating.
Correct compressor model # is: NH41VNHT with 7570 W cooling capacity.
Someone has made costly mistake 3 times.

[sale]

Hvala,kako znas ove podatke?
To sam i mislio na kraju kad sam sve provjeravao.
Thanks for information,i was thinking this because everything else was checked.

[nike123]

http://www.ligajos-technika.lt/rotary-compressors-for-air-conditioners
http://homedealqld.com/PDFs/Toshiba%20Residential%20HWS%20and%20Consoles%20RAS%20Series.pdf

[goshen]

HI this is a very expensive mistake!!!!

[sale]

One more question,that capacity which is written on compressor is that cooling capacity or heating capacity?
On outdoor units we have both information,for heating and cooling and on compressor is just written one capacity.Is it the lowest capacity(cooling) on compressor?
Thanks for links

[sale]

it is not ours mistake,we gave them model numbers and they send us compressor,we didnt checked it,we were thinking that it is ok,but now because this is warranty job,they will check better and also we will as well

[nike123]

One more question,that capacity which is written on compressor is that cooling capacity or heating capacity?
On outdoor units we have both information,for heating and cooling and on compressor is just written one capacity.Is it the lowest capacity(cooling) on compressor?
Thanks for links

Refrigeration capacity is what is relevant.
Heating capacity is actually condenser rejected heat, which is sum of refrigeration capacity (heat collected at evaporator) and heat of refrigerant compression and heat generated by compressor motor.

Also you could compare old compresor data. Usually, compressor model number have displacement stated in some form.

For conversation on our native language, it is good to use visitor/private message (http://www.refrigeration-engineer.com/forums/faq.php?s=&do=search&q=visitor&match=all&titlesonly=0#faq_vb3_public_profile) system.

[sale]

hi everybody,
can you tell me if compressor capacity is measuring and compare to a heating capacity of heat pump or cooling capacity of heat pump?
if cooling capacity is 7.5 kw,and heating capacity is 8.4 kw,what should be compressor capacity of heat pump,for example when ordering new compressor to be replaced?
Thanks

[nike123]

hi everybody,
can you tell me if compressor capacity is measuring and compare to a heating capacity of heat pump or cooling capacity of heat pump?
if cooling capacity is 7.5 kw,and heating capacity is 8.4 kw,what should be compressor capacity of heat pump,for example when ordering new compressor to be replaced?
Thanks

When you order new compressor you should look for same displacement and same usage area.
Different compresos capacity is given for diferent conditions and may be misleading.
For first part of question, I have already answered in my last post.

[sale]

thanks for reply,
last time you told me to check compressor capacity and cooling capacity ,and that compressor which i have got from Toshiba was 9.6 kw and that cooling capacity was 7.5 kw.
So that means that compressor is to big?
Can you explain me how displacement play role in this?
thanks

[nike123]

thanks for reply,
last time you told me to check compressor capacity and cooling capacity ,and that compressor which i have got from Toshiba was 9.6 kw and that cooling capacity was 7.5 kw.
So that means that compressor is to big?
Can you explain me how displacement play role in this?
thanks

Displacement is volume in time.
Compressor is pump and two compressors are of same capacity when their pumping volume in time is same.
In any time compressor pump same volume (fixed speed compressor).
With changing working conditions volume stays same and mas flow is different. Different mas flow mean different refrigeration capacity.
Now it is clear that by using displacement as comparison, you are not affected with different working conditions.
You only now need to find compressor with same area of application.
Area of application is divided in 4 categories.
LT=>low temperature
MT=>medium temperature
HT=>high temperature
AC=>air conditioning

[nike123]

So that means that compressor is to big?

Exactly that!

Edit: Now it appears it is not so "exactly"!:confused:

[sale]

thanks for reply,
when i asked before about what is right size of compresor,you told me that if cooling capacity is 7.5 kw ,and heating is 8.4 kw,that good compressor will be with 7.5 kw capacity,that means to match cooling capacity.
I was told from Carrier field supervisor here in Australia,that compressor should be matching with heating capacity not with coooling capacity.
Can you explain me is that correct or compressor has to be little higher capacity then when is working in heating mode?
Thanks

[sale]

NH 41 VNHT 25832 btu 7568 kw
NH 52 VNHT 33014 btu 9672 kw
NH 56 VNHT 36078 btu 10570 kw
which one of this compressor is good for next 2 units:
one is 7.5 kw cooling and 8.4 kw heating capacity
second is 7.2 kw cooling and 8.1 kw heating.
Whicone of this 3 compressor will match units?
At moment in first AC is 52 compressor,and in second is 56 compressor.
I have very high discharge pressure in both and very low suction.This happened after we replaced compressors,but we ordered by model number on outdoor units,and this is what they sent us.
I think that in both cases compressor is to big.Getting so hot.

What you guys think?

[nike123]

I was told from Carrier field supervisor here in Australia,that compressor should be matching with heating capacity not with cooling capacity.
Can you explain me is that correct or compressor has to be little higher capacity then when is working in heating mode?
Thanks
Are you sure that is exactly what was told to you. If yes, than that field supervisor has noting to do with refrigeration, or he is trying to fool you so that their mistake in delivering right compressor for right unit is covered with such stupid excuse.
Ask him that he give you service manual. In manual is stated right compressor model #. I cannot find manual for that units nowhere.
Also what happened to original compressors? Where are they?

Compressor capacity in kW is given for certain conditions. In compressor technical data it could be found that capacity of compressor is usually given at 7,2°C evaporation and 54°C condensation temperature.
When indoor WB temperature is around 19°C and outdoor DB is around 35°C than we probably have 2-4°C evaporation temperature and 45-50°C condensation temperature. That is close to that catalog conditions of compressor capacity. And that ambient temperatures are temperatures at which is given catalog data for unit cooling capacity.
Unit cooling capacity is given by measuring air flow and temperatures at unit and by calculating capacity based on air enthalpy and air mass flow in time.
Compressor cooling capacity is given by calculation of refrigerant mass flow at catalog conditions and by enthalpy of refrigerant.

In heating mode capacity of unit is given at condition of 20°C DB and outdoor 7°CDB/6°CWB. And that conditions make evaporation temperature below 0°C and condensation temperature below 54°C.
Which mean that that capacity is for different operating conditions and that they are not comparable.
Same as above, heating capacity of unit is given by measuring air flow and air temperatures.
We must consider that that mean that measured capacity in heating is actually rejected heat at condenser which is sum of heat absorbed in evaporator, heat of compression and heat of cooling compressor motor (and that is the reason why heating capacity of unit is higher than cooling capacity).
These other two heats are not mentioned in compressor catalog data.
Since heat absorbed in evaporator is actually compressor cooling capacity at that conditions it is obvious that heating capacity of unit in heating mode does not matches cooling capacity of compressor given in compressor technical data and cannot be used as guide for selection of compressor without considering what is said above

[nike123]

NH 41 VNHT 25832 btu 7568 kw
NH 52 VNHT 33014 btu 9672 kw
NH 56 VNHT 36078 btu 10570 kw
which one of this compressor is good for next 2 units:
one is 7.5 kw cooling and 8.4 kw heating capacity
second is 7.2 kw cooling and 8.1 kw heating.
Whicone of this 3 compressor will match units?
At moment in first AC is 52 compressor,and in second is 56 compressor.
I have very high discharge pressure in both and very low suction.This happened after we replaced compressors,but we ordered by model number on outdoor units,and this is what they sent us.
I think that in both cases compressor is to big.Getting so hot.

What you guys think?

For both units corect one should be NH 41 VNHT!

[sale]

Hi nike 123,thanks for nice explanation.
He said that in first 2 units was originaly NH 52 VNHT 33014 btu 9672 kw compressor,and that in third one,which is toshiba ras 28 nah (cooling 8.0 kw,heating 9.5 kw) was originally NH 56 VNHT 36078 btu 10570 kw.In that third one RAS 28 nah,we have installed NH 52 VNHT,and he said that is to small,but like in first 2 we also get high discharge pressure.

He also said that we have to look heating capacity,and you nicely explained us that we have to look cooling capacity plus all other things you explained.
I am very confused,he is like 30 years working for Carrier,maybe they try to hide their mistake,but he ordered again 2 new compressor for this units and none of them is NH 41 VNHT.He ordered NH 52 VNHT 33014 btu 9672 kw compressor for toshiba RAS 26 NAH cooling 7.5 kw,heating 8.4 kw, and he ordered NH 56 VNHT 36078 btu 10570 kw compresor for toshiba RAS 28 NAH(8.0 KW COOLING ,9.5 KW HEATING ).
Old compressors are thrown in garbage,and i cant compare it,but i am not sure that any of them was NH 41 VNHT compressor.He didnt give me any information abot what was in that units in first place.
Still confusion for me..

[nike123]

I just checked in my service documentation simmilar, only cooling unit, Toshiba RAS 27BKX/BAX with 7,95 kW cooling capacity at standard conditions (27DB/19WB-35DB/24WB)
which have old Copeland piston compressor CQRJ- 0300-TFD of 9170W capacity at ARI conditions. You will notice that difference in given capacities exist but it is not that dramatic.
Difference (between unit nominal cooling capacity and compressor ARI capacity) is only 1200W as oppose to your case where that difference is more than 2500W.
And, when I choosing replacement, I always choose one with smaller rather than one with higher capacity.

Buy that, it looks like that your replacement compressors are maybe correct and that their pumping capacity is matching to your unit.
Therefore it is important that replacement compressors are compared by displacement since cooling capacity of compressors is influenced by many factors in circuit like subcooling, evaporation temperatures and condensation temperatures etc..

Ok, I was maybe harsh about that Carrier guy, but it stays as wrong statemant that capacity of compressor should match heating capacity of unit.
If we have all construction details of unit and we know all parameters required for calculating capacity of compressor than we will found that chosen compressor cooling capacity matches amount of heat absorbed in evaporator and not heat rejected at condenser.

Now, if we presume that compresors are corect ones (wich I am not that sure) you need to check other possibilities for High discharge pressure and low suction pressure.
First we need measurments, not opinions (as Gary always point out)!
Give us folowing:



Evap air in temp
Evap air out temp
Saturated suction temp (convert from pressure)
Suction line temp at evap outlet
Suction line temp at compressor inlet

Cond air in
Cond air out
Saturated condensing temp (convert from pressure)
Liquid line temp at condenser outlet

[nike123]

He didnt give me any information abot what was in that units in first place.


I am still finding weird that no one doesn't know what are original compressors in these units!

[sale]

i replaced 2 compressors,but because new we have got loked same i dint pay attention to check.
i sent them model number of outdoor unit and they sent us this ones.
I left compressors in my company and they throw them next day,so because i never had this issues before i didnt check,and all this new compressors are made in thailand ,siam compressors,rotary,they dont write to many information on them.
if they write it is half on thai language.