Hitachi RAC25/35 Unreliability Problem

[Spud G]

This one has been going on for some months now. Story so far - I installed a Hitachi RAC25 inverter heat pump single split in/outdoor system using thermoplastic pipework between the in/out door units. All was well for a couple of weeks, then unreliability started - In cooling mode, the output air temp would drop as normal, but after a couple of minutes, would rise slowly back to room ambient and stayed there. This behaviour continued for a few days so I called my supplier. He replaced the outdoor unit. All was was well for a couple of weeks then the same thing happened again. My supplier then very kindly replaced the whole system (apart from the pipework) with a RAC35 system. Meanwhile, he had other customers with Hitachi reliability issues but could not pin down the cause. He eventually considered the possibility that the compressor heater was not sufficient and so fitted a band type heater to a couple of other customers units - with apparently complete success. He advised me of this breakthrough and modified my unit for me. This was towards the end of last year, consequently I've been using the unit in heating mode and it has behaved perfectly. Yesterday I had cause to use cooling - the same old problem returned. I tried cooling mode again this morning and it worked perfectly - for 3 hours solid. I wasn't holding my breath. When I tried it tonight - initial temp drop followed by rise back to ambient:eek: The only common component here is the thermoplastic pipework, but WHY would that be causing the problem. The last ditch plan is to replace it with copper, but I'm not convinced it'll sort the problem - unless someone could explain what could be happening......

[eggs]

I have supplied and installed loads of these little units with no problems what so ever.
My guess is that your plastic pipes are leaking and your supplier doesn't know what he's doing.
The give away is in the plastic pipes.

eggs

[al]

what are themoplastic pipes?

al

[eggs]

what are themoplastic pipes?

al

These (http://www.airconwarehouse.com/acatalog/easy_fit_air_conditioning_hoses.html) typically used by diy'ers, B&Q and plumbers/sparks.
Us ducters do it proper;)
cheers

eggs

[Spud G]

typically used by diy'ers, B&Q and plumbers/sparks.
Us ducters do it proper;)
cheers

eggs

Thing is, my supplier is a fully qualified aircon engineer with many yrs experience. I know him well enough now to be sure he definately does know his business inside out and previous to running his own succesfull business actually worked for Hitachi. The "plastic" pipework is very well engineered. The reason for its use is to offer the kit for DIY installation - indoor unit comes with pipework fiited, vacced down - with high grade self sealing terminations. These are no mickey mouse fittings - the pipework is made to measure and have the appearance of high quality industrial hydraulic lines. The company supplying the lines assured compatibility with the refridgerant. Bottom line is - the lines have to be to blame - everything else has been swapped out. What I want to know is, why does the heating cycle work fine (the unit pushes out 40C+ air month after month) but cooling is so unreliable? Just tried it again - initial plumet to 7C (OAT 12C) then gradually rise to room ambient (21C). What is going on? - the pipework is SO well made, the nagging thought remains that even if I rip it out (not easy its behind plasterboard) I'll still have the same problem. Are the symptoms I'm experiencing consistent with a leak?

[al]

Sounds suspiciously like moisture or a partial or total restriction on the suction line, compressor could be tripping on high discharge temp, cools down, blockage clears temporarily and off it runs again.

sounds mad but could installer run a temporary line set from indoor to outdoor ,leave in test cooling and see what happens??

al

[Spud G]

Sounds suspiciously like moisture or a partial or total restriction on the suction line, compressor could be tripping on high discharge temp, cools down, blockage clears temporarily and off it runs again.

sounds mad but could installer run a temporary line set from indoor to outdoor ,leave in test cooling and see what happens??

al
Thanks Al, I've been in touch with my supplier and he's going to come and look at it for me after I get back from a week away (this'll be the last post I'll be making for a while). The problem is getting worse - 3 attempts at cooling this morning resulted in no cold air at all, then came in this evening, temp dropped by 10 degrees initially but then rose back to 22c ambient. I think you're on the right lines with your restriction theory. Will report back when my man has done some trouble shooting.

[nike123]

My advice is to change pipes with normal copper pipe which all manufacturers recommends.
These "thermoplastic" pipes are porous and refrigerant leaks thru them. If they are any good, every one would use it.

Heat pump air conditioner have need for different refrigerant quantities in cooling and heating mode due difference in condenser (and evaporator) size in different mode. If your installer weigh amount of refrigerant which is left in system, he will find that amount remained in system is smaller than what is stated at nameplate.
That is why you have problem in cooling operation.

[icecube51]

looks like the same trouble the plumbers had a few years ago.the pipes were 99% airthigt,so there is always a los of 1%.
i never going to use something else than copper for refrig.

Ice

[Spud G]

Still haven't managed to get my supplier onsite but latest symptoms are as follows.........

Unit was reluctant to cool, but after a couple of rests/restarts cooling did happen. Strangley though, each cooling op (2-3hr duration) showed significantly different output air temps e.g.
day 1 12c +/- 1c
day 2 14c +/- 2c
day 3 9c +/- 1c
day 4 zippo - nada - NO cooling until I tried heating and then cooling, which gave initial cooling then rising back to ambient.
NO fault indications on any LED in the unit (or on the front of indoor unit)
So no real consistency with output temp. One thing I noticed on a couple of cooling ops was a distinct "sizzling" sound (temporary) from INdoor unit. Would these observations be indicative of low refridgerant content. Heating seems to be consistently fine (heating requires less refridgerant?):confused:

[nike123]

Still haven't managed to get my supplier onsite but latest symptoms are as follows.........

Unit was reluctant to cool, but after a couple of rests/restarts cooling did happen. Strangley though, each cooling op (2-3hr duration) showed significantly different output air temps e.g.
day 1 12c +/- 1c
day 2 14c +/- 2c
day 3 9c +/- 1c
day 4 zippo - nada - NO cooling until I tried heating and then cooling, which gave initial cooling then rising back to ambient.
NO fault indications on any LED in the unit (or on the front of indoor unit)
So no real consistency with output temp. One thing I noticed on a couple of cooling ops was a distinct "sizzling" sound (temporary) from INdoor unit. Would these observations be indicative of low refridgerant content. Heating seems to be consistently fine (heating requires less refridgerant?):confused:

Stop using that unit until someone change pipes and charge required amount of refrigerant by weighing.
You could only damage unit.

[Spud G]

Thanks for your reply braniac. Sorry to keep harping on about this one, but the symptoms are so erratic that it's hard for me to get my head around what's going on. Your explanation of different amounts (indeed different effective system volumes for heating/cooling) of refridgerant goes along way to satisfying my curiosity. I haven't noticed the sizzling before, and so I'm thinking this is due to there being even less refridgerant in the system now?

[nike123]

I haven't noticed the sizzling before, and so I'm thinking this is due to there being even less refridgerant in the system now?

Maybe yes, or maybe no, we cannot know until someone recover and weigh in recovered refrigerant. Possibility that refrigerant has leaked with these pipes is 99,9%.
Symptoms described in your post point to that, also.

And keep away from your supplier, since it appears (by service history of your unit) that he has no clue of what he doing.

[JerryG]

Does the indoor unit have backup electric heat by any chance?

Jerry

[Spud G]

Backup electric heat? - pretty sure answer to that one is no. You're thinking the heating is working because there's a (heating element) backup to the heatpump heating - no because on rare occasions the heating has been erratic too.
The pipework is finally in the process of being changed out - by my supplier - yes I'm sticking with him because he's tried so hard to help me, and I firmly believe he knows his trade. Pretty sure he's regretting going with the plastic pipes though!!
I'll let you all know what happens with the copper pipes. Meanwhile thanks for all your suggestions.

[Spud G]

OK - System up and running with copper pipes. Too early to say whether it is now reliable. Supplier did not determine exactly how much 410A was still in unit saying the operating pressure would tell all. On checking it said that the pressure was low indicating refrigerant had indeed been lost, and so charged more 410A until he was happy with the reading on his gauge.
Something I've noticed is that a mild "kettling"/sizzling sound is evident from the indoor unit shortly after cooling cycle startup which soon goes away. Any comments on this behaviour? Is still more gas required?

[icecube51]

i think its the speed of the refrig passing a narrow opening,from big to small. maybe the tube is 3/8" coppeling and the other is 1/4". so if the refrig was resting in the pipework,its possible to hear a sound at start-up.

Ice

[nike123]

As I said earlier:

And keep away from your supplier, since it appears (by service history of your unit) that he has no clue of what he doing. And he blew it again.
He should recover refrigerant, weigh in recovered, determine quantity to know for sure what is cause. And then change pipes leak test it, vacuum dry whole unit and new pipes and weigh in correct amount of new fresh virgin refrigerant, if amount of leaked is more than 10% of total weight, because of component fractionation problem of new refrigerants.
Now, you don't know if it is correctly charged, what is chemical composition and if it is going to overheat compressor because of lack of refrigerant, or it is going to kill compressor because of excess refrigerant. By looking only in pressures, no single one technician cannot correctly and accurately charge refrigerant in Split-system heat pump modern inverter air conditioner. It must be weighed in.

Get rid of that supplier and find competent person to recover refrigerant, pressure test for leaks vacuum dry unit with measuring end vacuum and weigh in correct amount of new fresh refrigerant if you wish trouble free operation of your unit, before more damage is done to it.

[Spud G]

Nike - you are right of course - absolutely right. The more enquiries I make, the more it is obvious. I believe my supplier knows what should be done, but because he's not charging me (because it's basically warranty work) he's doing the absolute minimum to get the system up and running. To do it properly takes time - time is money, but apart from that, time, clearly, is something he does not have. You live and learn - I have certainly learnt ALOT from this experience. Done properly from day one, I'm sure my system would have been trouble free and reliable. Isn't hindsight a wonderful thing.....
Thanks for all your contributions :)