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Spence

Spence

Joined on April 16, 2013

Last Post on July 23, 2014

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Formula

@ July 23, 2014 8:37 AM in FREE ,FREE, NO CHARGE ,Schrader Tee.

How cool! A Carrier manual from 1961. Love it!

More Free

@ July 22, 2014 7:41 PM in FREE ,FREE, NO CHARGE ,Schrader Tee.

There is no formula for sub cooling. Again, it is the difference between condensing pressure converted to temperature and the actual liquid line temperature. If you have 6 and the maker wants 10, you have an issue to resolve. If the maker wants 9 and you have 11, you're within accepted tolerances. There is no 12 or 1/2 pound this or that. For SUB cooling to be present, the liquid line HAS to be colder than the saturated temperature. And you should always check superheat too. Sub cooling is not solely a means to an end.

The never check refrigerant first was not for you, because you are intelligent and you care. I shake when I see someone carrying refrigerant up the driveway when they have not even been in the house. Yikes!

SC

@ July 22, 2014 7:43 AM in FREE ,FREE, NO CHARGE ,Schrader Tee.

Sub cooling is, simply, the difference between the operating (saturated) pressure converted to temperature and the actual liquid line temperature measured at the condenser outlet ( LL service valve). This is compared to what the maker has stamped on the nameplate. We try to get as close as possible, yet +/- 3 degrees is almost universally acceptable.

The last thing that ever should be calculated is the refrigerant charge. System cleanliness, actual air flow, ducts, etc. ALWAYS come before refrigerant diagnosis.

PD

@ July 21, 2014 9:38 PM in FREE ,FREE, NO CHARGE ,Schrader Tee.

You're working too hard. Your maker knows how to maintain his desired sub cooling when he publishes limits to length and lift, and what adjustments to make when you're outside the box. Upsized lines and "x" ounces of refrigerant and other measures are for the purpose of maintaining his sub cooling and superheat and the other good things that go with a happy system.

Sub Cooling

@ July 21, 2014 7:53 PM in FREE ,FREE, NO CHARGE ,Schrader Tee.

Put a clamp-on, or other quality thermometer at the TXV and convert the reading to pressure. Subtract that from the pressure at the OD unit to get PD. Simple, easy, and no fitting to create another PD.

PD in the LL does not figure into a sub cooling calculation.

You have a big heart to make the offer, though. I like it.

Tee

@ July 21, 2014 7:25 AM in FREE ,FREE, NO CHARGE ,Schrader Tee.

Please share your thoughts regarding the purpose of this fitting. Thanks!

Equipment

@ July 16, 2014 8:28 AM in Replacing oil furnace w/ fan coil connected to new boiler. What brands to consider?

The point, for your comfort and economy, is you have some serious issues to consider prior to selecting equipment. The hydronic coil can have as much resistance as an entire duct system, so if you don't plan for it you will be stuck with a system that neither cools nor heats properly. Get your loads first, so you know what size coil you need and the pressure you have available. Then find a maker whose blower will give you what you need. An hour or two spent on this will save you years of frustration, high energy consumption, and premature equipment failure.

ESP Readings

@ July 15, 2014 10:04 PM in determing to cfm

Some manufacturers put a hole for you in the cabinet to save the drilling. Others give you a peep hole so you can see the IFC LEDs which you can pop out for the return pressure readings. On the supply side you can take out the high limit card.

Sub Cooling

@ July 15, 2014 9:52 PM in Height vs SubCooling vs Freon Charge

SC has to be measured at the outdoor unit, since it is part of the condensing process. SC ensures the condenser outlet is full of liquid refrigerant. Proper sizing and installation of the liquid line ensures that only liquid is available at the TXV inlet.

Fan Coil

@ July 15, 2014 9:22 PM in Replacing oil furnace w/ fan coil connected to new boiler. What brands to consider?

As you mentioned both a boiler and a fan coil, I will assume the boiler will heat water to pass through a hydronic coil in the air handler, which again I assume is connected to an existing duct system. Way before choosing a maker, you need a load study to determine what capacities the boiler and hot water coil should be. A hydronic coil usually has an extremely high pressure drop. You have to make sure the blower and ducts will work properly, especially if you have air conditioning.

CFM

@ July 12, 2014 11:37 AM in determing to cfm

Place one manometer probe at the entrance to the blower compartment downstream of the filter. Place the other at the outlet side of the furnace downstream from the cooling coil. The result will be the external static pressure that your blower "sees" which you will compare to your performance table.

Vapor Barrier

@ July 11, 2014 7:26 PM in Thermostat and humidity settings when away in coastal FL

These posts are an incredible perception. Vapor barriers have traditionally been installed on the warm side, as should be. Easy if you live in Canada, and easy if you live in Florida. So what happens in between, when there are two seasons to overcome?

Vapor barriers retard moisture flow from warm to cold; never the other way around. This means if I live in the Midwest, for example, I have to change my VB to one side of the wall in winter and the opposite side in the summer. No wonder there is confusion!

What we have learned (among other things) is incorporating an air space within the wall, to allow moisture to condense and fall to the lower quadrant of the wall. That is why you see tuned-in builders adding weep holes in stucco or brick (for example) to wick out the juice.

Bonding

@ July 11, 2014 7:00 PM in Bonding CSST:

Let us not forget the root goal of bonding, which is not really grounding, but to make everything in the circuit electrically neutral. If so, even a strange electrical potential will go to ground rather than seeking a path of less resistance.

Suggestions

@ July 11, 2014 6:45 PM in Suggestions for new forum

They simply MUST make the security math for responses easier. Sometimes it takes me hours to be able to respond to help requests. Perhaps it is my fault; I have a new phone and can't yet use the calculator function.

Bonding CSST

@ July 11, 2014 7:37 AM in Bonding CSST:

Nice job, Rich! For those of us who have worked with lightening strike incidents, even the cable TV line can be a superhighway for destruction.

IFM

@ July 8, 2014 7:21 AM in Goodman blower motor won't start.

Your air handler has a variable speed motor controlled by a system of electronic "languages" involving the thermostat and the controls in the air handler. Your parts are under a 10-year warranty. In your best interests, call your installer for diagnosis and solution.

Options

@ July 8, 2014 7:12 AM in Need help with options for converting from oil to gas. Steam, IWH, and furnace involved.

Just to start your process: there is no reason, provided your conversion burner specialist really knows steam, that you cannot reach a combustion efficiency of the mid to high 80s.

Indirect tanks are generally more efficient and easier to size properly for your needs than are the combination units.

RV Issue

@ July 3, 2014 6:53 AM in Heat Pump

If it works then doesn't and repeats, we most likely can eliminate the leak. Either the piston is sticking or there is an undesirable on the seat. Before replacing, you could try this: pump down, take out the Schraders, and introduce dry nitrogen up to factory test pressure. Blast it out both sides and repeat. A strong magnet helps, too, as you can pull the piston back and forth.

RV

@ July 2, 2014 5:34 PM in Heat Pump

Way too much. It may be leaking or just stuck. Kill the HV and bang the RV on and off several times with a low voltage signal. No change means it should come out.

AC

@ June 27, 2014 7:40 AM in My Hvac system not working

It sounds as if you're not getting a low voltage signal to the compressor contactor, the relay that energizes the compressor and OD fan simultaneously. Perhaps the mower severed the wires. Turn the high voltage off to the OD unit and call for cooling. You should see (+/-) 24 VAC across the two control wires. Does your indoor fan run?

Leak

@ June 25, 2014 11:32 PM in Freon leak

So, someone just popped by, said the pressure was low, and added refrigerant?

Church

@ June 25, 2014 7:28 AM in Whole house de-humidifier

Don't forget about ERVs.
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