HVAC-Talk: Heating, Air & Refrigeration Discussion banner
Cancel
Create thread New Forums

Temperature difference above and below TXV valve

Jump to Latest
1 - 17 of 17 Posts
B

bulldog13

· Registered
Joined
·
12 Posts
Discussion starter · #1 ·
I have been fighting a re-ocurring problem with my HVAC unit. Periodically it trips into a low pressure fault state.
It seems fine now, but it tripped twice the day before yesterday. It is a Miami Heat Pump HPX041V-RF-A heat pump

The only thing I have noticed is around the time it trips, when I am trying to bring it back to life, sometimes the condensor (I think it is the condensor) will kick on, but the fan will not. Or the fan will be humming along fine and just turn off. I cannot reliably reproduce this. I keep the fan in continuous mode. A few months ago they replaced the fan motor. If you are so inclined, you can read about it further if you search posts from my name (I cant link).
The high pressure fault mentioned in the article was unrelated (was the communal roof cooling towers).

Anyways, I had a different company come out.

First he thought the coolant was low, it was sitting at 80ish when it should have been 110?
After further diagnosis though, he thought we had a "TXV valve liquid line restriction".
He showed me with equipment that it was 75-76 degrees below the TXV valve and 47-46 degrees above it.
He said the normal temperature difference should be 8-12 degrees.

They recommend replacing the TXV valve. Does this diagnosis and fix sound reasonable to you all ?
 
#2 ·
bulldog13 said:
I have been fighting a re-ocurring problem with my HVAC unit. Periodically it trips into a low pressure fault state.
It seems fine now, but it tripped twice the day before yesterday. It is a Miami Heat Pump HPX041V-RF-A heat pump

The only thing I have noticed is around the time it trips, when I am trying to bring it back to life, sometimes the condensor (I think it is the condensor) will kick on, but the fan will not. Or the fan will be humming along fine and just turn off. I cannot reliably reproduce this. I keep the fan in continuous mode. A few months ago they replaced the fan motor. If you are so inclined, you can read about it further if you search posts from my name (I cant link).
The high pressure fault mentioned in the article was unrelated (was the communal roof cooling towers).

Anyways, I had a different company come out.

First he thought the coolant was low, it was sitting at 80ish when it should have been 110?
After further diagnosis though, he thought we had a "TXV valve liquid line restriction".
He showed me with equipment that it was 75-76 degrees below the TXV valve and 47-46 degrees above it.
He said the normal temperature difference should be 8-12 degrees.

They recommend replacing the TXV valve. Does this diagnosis and fix sound reasonable to you all ?
Click to expand...
From what I am gathering from your post this is not the proper way to diagnose a TXV. If you think about it on a 90 or 100 degree day that line temp is going to run somewhere over 90 degrees if the valve only drops the temp 10 degrees that makes your coil temp 80 degrees. Not much cooling done with an 80 degree coil when you want it 75ish in the house, is there.
 
Save
Like Like
#3 ·
bulldog13 said:
I have been fighting a re-ocurring problem with my HVAC unit. Periodically it trips into a low pressure fault state.
It seems fine now, but it tripped twice the day before yesterday. It is a Miami Heat Pump HPX041V-RF-A heat pump

The only thing I have noticed is around the time it trips, when I am trying to bring it back to life, sometimes the condensor (I think it is the condensor) will kick on, but the fan will not. Or the fan will be humming along fine and just turn off. I cannot reliably reproduce this. I keep the fan in continuous mode. A few months ago they replaced the fan motor. If you are so inclined, you can read about it further if you search posts from my name (I cant link).
The high pressure fault mentioned in the article was unrelated (was the communal roof cooling towers).

Anyways, I had a different company come out.

First he thought the coolant was low, it was sitting at 80ish when it should have been 110?
After further diagnosis though, he thought we had a "TXV valve liquid line restriction".
He showed me with equipment that it was 75-76 degrees below the TXV valve and 47-46 degrees above it.
He said the normal temperature difference should be 8-12 degrees.

They recommend replacing the TXV valve. Does this diagnosis and fix sound reasonable to you all ?
Click to expand...

Pressures without temperatures are worthless like the tech. Find a different contractor!
 
#5 ·
Try looking on this site for techs. There is a spot for it. Someone else will likely chime in.

But yeah, that diagnoses sucks. LOL
 
Save
Like Like
#10 ·
Maybe go to that website and tell them the diagnoses you got and ask does that sound correct (?). When they reply that the the diagnoses is grossly flawed, tell them they are the ones who told you that.

Then wait to see how they respond to that.


bulldog13 said:
Unfortunately, I got this tech from this site. :(
http://servicesunlimitedofraleigh.com
Click to expand...
See that link for AOP contractor map a couple of posts above . . . ?
 
Save
Like Like
Discussion starter · #12 ·
BBeerme said:
Maybe go to that website and tell them the diagnoses you got and ask does that sound correct (?). When they reply that the the diagnoses is grossly flawed, tell them they are the ones who told you that.

Then wait to see how they respond to that.




See that link for AOP contractor map a couple of posts above . . . ?
Click to expand...
That kind of worked haha. I sent a message over the website. I explained the situation. Now they are sending a more senior technician without additional charge.
Thanks for the advice.
 
#14 ·
I don't quite understand why people want to complain on the internet and out a company with potentially wrong information without even contacting the company with their concerns?

We don't know if what you heard and the tech was "trying" to explain are one in the same.
 
Save
Like Like
#15 ·
The service call should be in writing.


mgenius33 said:
I don't quite understand why people want to complain on the internet and out a company with potentially wrong information without even contacting the company with their concerns?

We don't know if what you heard and the tech was "trying" to explain are one in the same.
Click to expand...
 
Save
Like Like
Discussion starter · #16 ·
Just wanted to wrap this thread up with the fix. After years of struggling with a malfunctioning hvac blower motor and replacing it twice, an enterprising tech finally diagnosed the root cause.

There was a short in the wires / wire harness that powers the HVAC blower motor. After the second replacement of the the HVAC blower motor, it was exhibiting the same symptoms. The fan would not turn on in auto mode and would not run continuously when set to always on.

He flipped it on and jammed his hand into the wiring harness and saw sparks. Also depending on how he shook the wires leading to the blower motor, it would cut out.

They replaced the wiring harness (apparently a small repair) leading to blower motor and it has been flawless ever since.

YAY !
 
#17 ·
bulldog13 said:
Just wanted to wrap this thread up with the fix. After years of struggling with a malfunctioning hvac blower motor and replacing it twice, an enterprising tech finally diagnosed the root cause.

There was a short in the wires / wire harness that powers the HVAC blower motor. After the second replacement of the the HVAC blower motor, it was exhibiting the same symptoms. The fan would not turn on in auto mode and would not run continuously when set to always on.

He flipped it on and jammed his hand into the wiring harness and saw sparks. Also depending on how he shook the wires leading to the blower motor, it would cut out.

They replaced the wiring harness (apparently a small repair) leading to blower motor and it has been flawless ever since.

YAY !
Click to expand...
So, you finally found a good tech. Hope you took real good care of him / her (Tip) and kept there # on speed dial.
 
1 - 17 of 17 Posts
You have insufficient privileges to reply here.
About this Discussion
16 Replies
7 Participants
Last post:
pecmsg
HVAC-Talk: Heating, Air & Refrigeration Discussion
posts
5M
members
275K
Since
2000
The #1 HVACR Community
Full Forum Listing
Explore Our Forums
AOP Residential HVAC/Refrigeration(Beenthere Zone) General Discussion Tech to Tech Chat - Residential Controls Refrigeration & Ice Making