Poor dehumidification on new HVAC system

[docholiday]

amazing... simply amazing.

[lcimpala65]

I'll second that Doc................

[jimp]

I have seen this problem before with 410A.

[docholiday]

the coil temps are the same. thats propaganda unless substantiated.

[dash]

I'm not saying that there is a problem,but my experience is that the customer is often right,when "we" think every thing is normal.


Another possibility is that the old system had very low airflow,increasing the latent capacity(humidity removal),to beyond what you can get with the new system.

The one thing that that made me think the poster may be correct,is that changing fan speeds madde no difference,in humidity removal.If correct ,the accuracy of his test equipment,becomes mute.

To the comment regarding ,seen that problem with 410A before,it may be due to 410A system using TXVs more than what you saw with R22.

[rhblake57]

To Shophound 3-29-05

I understand what you are saying.

Interestingly, the Bryant dealer/tech read this site thread yesterday, and sent me e-mail denying he said super heat can't be checked on fixed TXV system. This,despite my writing down his answer while I was in his office and while I asked him to repeat it at least three times!!
He now claims he said "super heat can't be adjusted at TXV".
This resoundingly demonstrates the power of a good web site like HVAC-TALK.
Unfortunately and neglectfully he still refuses to come out to check out my system properly with sub cool and super heat readings.

Instead of looking at the ductwork he says in the e-mail "he would hope that the contractor sealed the ducts".
From this site, I think the leaking ductwork may turn out to be half of the problem.

Since last month the Bryant dealer/tech has come a long way thanks to info I have gotten from you and others on this HVAC-TALK site.
He is now aware that I know about checking super heat and sub cool and sensor bulbs, even though he insists that testing them is a waste of time. He says he doesn't want to buy the equipment to do the tests.

I hope, with my new found knowledge, to appeal for help from his superiors. Perhaps just a small adjustment in my AC system will do the trick. Wish me luck!!

What does the sensing bulb on the suction line look like and where is it supposed to be?

Which one is the suction line in the attic?

Thanks for being so positive. And giving me info, so that I could understand. Knowledge is always power. Many home improvement techs seem to prefer uninformed and uniterested customers. I once heard a home improvement tech say "dumb blonds make for good customers"!!!

Best wishes in your business and your life

rhblake57@comcast.net

They claim that there is no need to check sub cool at compressor if I have correct pressure reading there. They claim the pressure is right as of last June and was tested for leaks.

I'm known on this board as saying to fellow technicians that "pressures tell only part of the story". For you as a homeowner it only means that if a technician is going by gauge pressure readings alone, he's half blind to what's going on with your system when it's running. For the technicians, how many of you reading this would think that if superheat and subcooling readings were taken on this homeowner's system, something would turn up as out of whack?

Also Bryant says there is no piston in the FX4B air handler TXV valve, so there is no way or need to test superheat at the air handler.

I disagree. Again, for you the homeowner it may not mean much. I only address it as it strikes me they're saying there's "no way" to test superheat at an air handler. Sure there is. Directly downstream of the TXV bulb on the suction line, the technician can attach a type k thermocouple probe to the line, bury it in the insulation, and read the temperature of the line, Yes, he'll likely have to get his suction pressure reading at the condenser in order to obtain the saturated vapor temperature inside the evap for comparison. That's why for residential A/C, most superheat discussion revolves around suction line superheat vs. evaporator superheat. But a tech that knows his stuff can get a superheat reading at the sensing bulb and get an idea whether the TXV is maintaining good superheat or not in the evaporator.

Additionally, suction line superheat on a TXV system is just as useful to a tech as it is on a fixed restrictor system. A properly adjusted TXV will maintain consistent evap superheat with a normal to overcharge condition, but will show an increase in superheat if the system is undercharged or if the TXV is out of adjustment.

For you the homeowner all that carrying on I just did probably doesn't mean a lot. I just had to address what appears to me to be bad info. [/B][/QUOTE]

[Shophound]

He now claims he said "super heat can't be adjusted at TXV".

He may be thinking of a non-adjustable thermostatic expansion valve (TXV) or a fixed restrictor (flowrator, piston, etc) metering device.
Even so, on a non-adjustable TXV, improper superheat will show if the charge isn't right (in particular if it is too low) or if the bulb is not properly mounted. Also, debris in the TXV will affect its operation.

He is now aware that I know about checking super heat and sub cool and sensor bulbs, even though he insists that testing them is a waste of time. He says he doesn't want to buy the equipment to do the tests.

If he's really shooting straight about the not wanting to "buy the equipment to do the tests", that's hilarious! So he's saying his technicians don't have gauge manifolds, digital thermometers (most often used with digital multimeters that many techs already carry), a pressure temperature chart, and basic mathematic skill?


<shaking head> "Waste of time?" And going on callback after callback and the constant ringing of the phone from an unhappy customer is NOT a waste of time? My foot.

It could be this guy does know how to check superheat and subcooling but is handing you a line as part of expressing exasperation, but I would certainly choose a different subject to vent by, if at all! How does he know you won't take his words as tongue-in-cheek?

The suction line is the insulated line emerging from the air handler. It is possible the sensing bulb for the TXV is inside the coil where you can't see it. Otherwise it will be on the suction line immediately outside the air handler and should be tightly wrapped with insulation. The bulb underneath all that insulation should be attached tightly to the bare copper of the suction line, preferably with copper straps. Ideally the bulb should be on a suction line that is horizontal, downstream of the equalizing line, and not mounted on the bottom or top of the pipe. If the pipe is vertical it should be where the suction gas flows down, not up. Nor should the bulb be placed where oil inside the line may trap.

[dash]

If your guy needs help with superheat/subcooling,tell him to look in the "For your interest " section on this site.

[eduardo grueso]

To bud in late, it sounds as if the unit keeps humidity in check and the only real complaint is how fast a bucket used to fill.