lennox heat pump kfhk 28 vfc

[cool it]

Hi I have a lennox hp cond unit feeding a coil in a duct.
Problem is runs fine in cooling
put into heating suction pressure drops within 10 seconds and unit cuts out on LP as you would expect.
I have replaced the check(one way) valve by the indoor coil and still the problem remains. My thoughts now are swaying towards the reversing valve maybe not seating back enough when it is de- energized. the only to parts in the cond unit is the reversing valve and an expansion valve. Does my suspicion sound feasable as im racking my brains it surely could only be one of these two devices.
Any help would be truly appreciated.
thanks

[Brian_UK]

Hi Cool It, sounds like you could have identified the problem.

Had a similar problem with a Blue Box heat pump which was going into vacuum in heating mode. Main symptoms at the time where the two TEVs so I changed those out and replaced the filter/drier.

The TEVs were actually clogged up with carbon based debris so I thought all was well.

However upon recharging it I ended up with very similar pressures to what had been before the repairs.

I ended up cycling the reversing valve many times and eventually it all started working as it should. I hadn't actually suspected the valve because it made all the right noises at the time.

So yes, have a go at the reversing valve, use a magnet, before you continue pulling it apart.

See if you can get a sample of the oil for any signs of crud in the system..

Good luck with.

[cool it]

Hi Brian UK
Thanks for that information it has eased me quite a lot i have took over this site 3 months ago after 2 and a half years of another company lying there way through and not getting anything sorted. This unit has had nearly everything changed. The check valve was changed.we then found faults electrically on the motor protection module the optional phase monitoring relay was also blown while showing live it was actually burnt out. I have 100% sorted all electrical faults out and when we came to fire it up then for this to happen it was a bit of a blow. So hopefully tommorow il be ok the customer has not had these units working for 3 years so you can imagine all the links and bodge ups I have come across.
Thanks again Brian I will update on the outcome.....

[cool it]

update could not get the valve to free up as mentioned above. So have removed and replaced units is now on vac till the morning...... to be contd

[cool it]

follow up.... Charged system up to the required amount...... Left a while had a cuppa to let it settle crank case heater had been on all night so oil was fine...
Set unit of in cooling mode no problems working fine as I had expected.. now for the test... Set temp to 24 as room temp was 17 heat mode was called for waited the set 5 minute dely. Comp fired up cond fans came on and bang as before dropped out on LP.........
After speaking to Lennox technical apparently the reversing valve is only used in cooling and could not possibly have caused thes fault...???? The only thing left is the TEV on the cond unit possibly blocked... After looking at some of the joints on the site installed pipework it appears that the installer was not really a competent brazer.. So my only other possible thought to end this is that OFN was not used during the installation hence why there is a blockage.............................
If anybody can shed any light or maybe one of you have had something similar would be interested to hear from you. State of the unit at the minute . recovered the refrigerant ready for a replacement TEV on monday/tuesday....

[Brian_UK]

Sorry Cool It you've had a bad day

I thought that 'everything' had been changed earlier so must have misread somewhere.

It seems that the TEV is blocked by the crud that has slowly been moving around the system over time.

It may be prudent to change out the other TEV at the same time, costs more but cheaper than having to do it as a separate exercise.

If possible, although doubtful on a Lennox, try and isolate the TEV from the system and pull the orifice to check the condition of the internals.

Just had a moment.... does your TEV have an inlet screen? Is it blocked ?

[Brass Monkey]

Cool it,

Had similar probs. If it is a condensing unit, are you sure you can see the entire pipework between the indoor and outdoor units? In my case persons had intalled liquid line biflow dryers on the indoor unit, consealed out of view which were blocked. Only way i found it was as you have have done. I ended up with possible blocked outdoor TEV?, so I removed valve and soldered in straight section of pipe! therefore no metering device on heating and then run system to see suction pressure drop therefore problem in other part of system. Checked pipework to find poor location of dryers. Going by your comments on the past tradespersons anything maybe possible.

Hope this helps.
Peter.

[cool it]

Who is the happiest man alive !!!!
Yes its me. I have only gone and fixed the bloody thing.
This has been a big learning curve for me I cannot believe what some people are getting away with. The installation of everything in this job is disgracefull.
However I am glad to say that the manageress of the said bar is now over the moon as they are now able to take there cardigans/jackets of while being at work and they actually had 40% more customers this afternoon than they have done on a weekday lunchtime for a long time.
thanks for the advice and am only glad to say
WE GOT THERE IN THE END !!!!!!

[Electrocoolman]

So it was the TEVs??? You haven't actually said what was the cure.

[Brian_UK]

Hey, well done Cool It, I'm glad that it is resolved but, as ECM above says, what the hell was it

Still I suppose we won't get an answer for a while, he's gone down the pub for a beer

[cool it]

sorry guys should of explained a bit better.
The fault was NO OFN USED IN ORIGINAL INSTALLATION and blocked the outdoor TEV.............
While i had the old TEV out before I went any further decided to cut out 2 joints one from each pipe and end of the system..
Obvious installation bad practice....
Replaced with identical TEV (using OFN may I add)
tested my joints vacced down to 3 TORR worked out correct charge as after what we had found I didnt trust the commisioning data.
All working like a beauty.
Manageress happy as the preverbial pig in s***...
So there you go another one bites the dust.

I am now at another crap install job repairing the 7th refnet joint in 3 years........... Oh how I love my job.
JUST THINK IF THERE WASNT ANY COWBOYS I WOULDNT BE AS BUSY............
Take it easy out there..

[Brian_UK]

Than ks for the update Cool It.