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Joined on April 16, 2013

Last Post on July 30, 2014

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The Light Just Came On

@ July 30, 2014 7:26 PM in increasing length of AC cycle

Right you are; I didn't understand the question. I believe you are referring to the droop adjustment, which allows the compressor to operate to a setting lower than your comfort temperature.

If you live in an area susceptible to high humidity, three degrees is a good choice, provided you do indeed have the correct size. Dry climates should have the factory settings since you're mainly concerned about the sensible load.


@ July 30, 2014 5:57 PM in increasing length of AC cycle

How long the thermostat takes to reach the set point is related to several things. For example, the effects of a passing weather system, the thermal integrity of the space, the size and design of the equipment and distribution system, orientation of the structure, location of the thermostat, and others. Contact your local service professional who will be happy to diagnose the reasons your system isn't happy.

Yes, we are very concerned about cycling. We want your "comfort line" to be as flat as possible, meaning on and off events are less noticeable. This helps to keep even temperatures throughout and efficiency high.

Sub Cooling

@ July 30, 2014 7:12 AM in height length line set

In residential applications, until you can obtain the manufacturer's data, you most likely are safe with 10 degrees.

AC Cycle

@ July 29, 2014 4:52 PM in increasing length of AC cycle

On the average, it takes 10-12 minutes for a properly sized air conditioner, components in good working order, to remove humidity and bring the space to the set temperature. The time between cycles depends on how quickly the space gains heat and moisture from the atmosphere. However, most thermostat makers build in a nominal 5-minute delay to protect the compressor.


@ July 28, 2014 8:31 PM in HVAC options for 400 square foot addition

Sounds as if this is a wonderful system, and I have no doubt the homeowner would be comfortable after your work. We are all in the comfort business and want the best end result for our clients.

However, my point is this: if you're lucky to be working with a ground-up, we have a real advantage here, and that is exactly the root of your slogan regarding conservation. We make people comfortable by replacing heat at precisely the same rate as it is lost to the atmosphere. The smaller that loss is, the heating and cooling plants need less capacity to neutralize the losses. No matter the size of the structure or design temperature; balance loss with the identical rate of comfort conditioning. It's rather simple, really. Don't lose anything so you don't have to replace anything. This logic lends itself nicely to having one unit heat and cool.

Spending Wisely?

@ July 28, 2014 7:13 AM in HVAC options for 400 square foot addition

So, you expect the homeowner to create two distinct systems, when he is building from the ground up, and should be able to heat the room addition with a light bulb.

Wise Spending

@ July 27, 2014 12:16 PM in HVAC options for 400 square foot addition

Since you're building from the ground up, why would you want to install two different systems? Your mini-split heat pump is a fantastic idea; heating and cooling in one unit. Make sure the one you choose has rectified DC compressor operation so you have the modulating benefits for different load days.

1/2 Tank

@ July 25, 2014 6:59 PM in Cut oil tank in half, now what?

I'd love to help. For once I'd like to get off work a little oily.


@ 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!


@ 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.


@ 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.


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

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


@ 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.


@ 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.


@ 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.


@ 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.
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