Zanotti problem

[glenn1340]

Hi guys.
One of my customers asked me to look at his freezer room, fitted with a Zanotti BSP123T0305F, as it only reaches -4c After climbing up a ladder in the wind and rain and balancing fifteen foot upon a ledge I found the condensor blocked I cleaned that out and now it manages -9c I checked the superheat @ 7k but was unable to get to the TXV to take an accurate measrement. The low side is 2.5 bar on 404a. I couldn`t take the high side as there`s no service valve. What I did notice was the condensate drain pipe from the evaporator tray was constantly warm. It`s bare copper tube with no trace heating on it. Could this mean the electic defrost is constantly on and that the heater is "fighting " the refrigerant in the evaporator. The electronic controller is showing the defrost off when compressor is on and vice versa.
Thanks in advance guys

[charlie patt]

the zanoottie usually runs a capialary system i pressume the pipe your on about is the discharge pipe in the reevap tray on the right hand side is that correct? the system would not achieve minus 9 with hot gas on

[glenn1340]

Wow, now that`s a quick reply!

Hi charlie. The pipe in question is the one out of the bottom, it`s definitley the drain pipe. Thanks for the tip about the capillary tube, no need to worry about a TXV being duff then.
According to the zanotti site this unit is electric defrost.
Cheers

[monkey spanners]

How long did you run it for after cleaning the condenser?
How much stock is in the freezer?
I think they are hot gas defrost, i have seen leaky solenoids on these as they seem to cook the oring in the discharge solenoid.

[charlie patt]

just got in from breakdowns does it have to mag valves? two pipes go to the tray the defrost tube and the discharge pipe of the comp when running if pressures ok it will burn your pinky useually a zanottie is speced right on its limit so you may have cured the problem but it requires a longer pull down time if condensor had been running hot i always manually df and run does it have fan speed control

[charlie patt]

that was two mag valves my spelling was never that good but i can add up a bill

[acb]

hi glen zannotti coldrooms are usually uniblock systems that are mounted next to the door, but your post makes it sound like you are working on a remote condensing unit. so that rules out hot gas defrost and with a hot drain line and deffo no drain heater, it sound like youve got a stuck on defrost relay/contactor. can you confirm that you are working on a remote condensing unit for me mate??

[glenn1340]

hi glen zannotti coldrooms are usually uniblock systems that are mounted next to the door, but your post makes it sound like you are working on a remote condensing unit. so that rules out hot gas defrost and with a hot drain line and deffo no drain heater, it sound like youve got a stuck on defrost relay/contactor. can you confirm that you are working on a remote condensing unit for me mate??
Hi ACB,
Sorry, I forgot to mention it is a remote system. The controller is a Thermomax RCX100 I checked the online manual and the heater is switched via an internal contact. I`ll check that out on my next visit.
I`ll also weigh the gas out while I`m looking at the controller, being a small system that`ll eliminate any problems there.

Thanks again

[charlie patt]

if its a remote it will be on a tev not a capiliary... which should have a sight glass to save weighing out gas

[acb]

hi glen. thanks for confirming that for me, well with that suction pressure id say check two things, defrost terminals on your thermomax controller, you shouldnt have 240v coming out while in cooling mode, secondly and its a long shot check the size of the condenser fan on the cond unit, make sure its got the right size of motor.

[glenn1340]

hi glen. thanks for confirming that for me, well with that suction pressure id say check two things, defrost terminals on your thermomax controller, you shouldnt have 240v coming out while in cooling mode, secondly and its a long shot check the size of the condenser fan on the cond unit, make sure its got the right size of motor.

Thanks for that. I`ll not be back there for a few days but when I`ve had a look I`ll let you know.

[glenn1340]

How long did you run it for after cleaning the condenser?
How much stock is in the freezer?
I think they are hot gas defrost, i have seen leaky solenoids on these as they seem to cook the oring in the discharge solenoid.

Sorry for the delay in replying. I checked the temperature after an hour or so (I had other stuff to check, a OMB has to do all sorts! Food mixers and generators etc). The freezer was 25o/o full at most

[monkey spanners]

I was just thinking it may take many hours to bring the room down if it has stock in that has warmed up, a freezer i looked at last summer took three days for example.

[jose-carvalheir]

hi, my experience on zanotti equipment tells me that you have some problems with the compressor, since you had the condenser blocked up mybe the oil carbonized the valves in the compressor bring lack of compression ratio, also had some problems with r404a on zanotti and only resolved changing the filter dryer and replacing the refrigerant with new r404a

[glenn1340]

Just an update by way of saying thanks to you guys who`ve offered their advice
I checked Thermomax controller and found no fault there.
I did mention earlier that the condensate drain pipe was warm even in cooling mode. I took the pipe off to check the wring in the evaporator and found it did have trace heating inside the pipe so this seems to prove the defrost is permantly on
On checking the connections on the condensing unit and junction box on top of the freezer room I found various "engineers" had linked out all and sundry to get the unit running. You know the thing, wire 1 into a chockblock to wire 4, into another coming out as wire 3 ans so on.
Looks like a complete rewire job is in order as to try to correct the "repairs" done by others will be a nightmare.
Luckily the room in question is overflow one so this quiet period gives me time to get it sorted.

Thanks again guys

[Tayters]

Hi Glenn,

The freezer rooms I've worked on have the trace heater in the drainpipe wired to a permanent feed - not just to come on with the defrost and if the defrost was stuck on then I reckon your superheat would be cosmic - way more than the 7K you roughly measured.

It would be interesting to see what suction pressure you are now getting assuming the room has had a chance to cool further. Hopefully it's around the 15psig mark.

Good luck with the wiring - at least the snows gone!

Andy.