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Joined on April 16, 2013

Last Post on July 30, 2014

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@ March 13, 2014 11:23 AM in High efficiengy heat pump connected to a single stage blower

This is your second stage cooling signal from the comfort control. There are a litany of reasons why you need an AHRI matched system; efficiency, performance, and comfort are just a few. Understand that when the CC calls for 2nd stage, the blower and outdoor fan ramp up to match the higher compressor output, so without this feature you have wasted a bucketload of cash in a two-stage HP that will never live up to expectations.

2-stage HP

@ March 11, 2014 4:19 PM in High efficiengy heat pump connected to a single stage blower

You're better off using a single stage heat pump with your existing furnace.

2-stage HP

@ March 8, 2014 6:24 PM in High efficiengy heat pump connected to a single stage blower

Can you connect to a single speed blower? Yes. Is it a good idea? No. You'll have to hook up Y2, losing the 1st stage and the benefits therein.

There is Nothing Wrong

@ March 3, 2014 1:29 PM in What's wrong with this?

It is the evaporator's job to convert liquid to gas.

Furnace Issues

@ March 3, 2014 1:25 PM in furnace problem

The first thing that is not right is the limit. Unless approved by the manufacturer, NEVER raise the cut-out temperature.

Dryness and comfort are independent issues. Check the thermostat reading against a high quality thermometer; the two should be within 3 degrees. Also check your TR and compare to the nameplate. The CFM numbers sound like the cooling dips, not the heating.

Check your RH with a psychrometer; 30% is the lowest on the comfort scale. If you don't have one, cut the tip off a clean white shoe lace, soak it in water, and slip it over the wand of your thermometer for a wet bulb value. You'll have to convert to RH. For example, 63 degrees WB is 50% RH.

The Evaporator

@ February 27, 2014 8:20 AM in Apologies!

Delivering comfort and economy is all about pressure, and how to manipulate it to your advantage. In the purest sense, the outlet of the blower is the highest pressure while the inlet is the lowest. Evaporator coils can easily be the system component with the highest PD, so you want to account for it where you have the most with which to work (blower outlet). The heat exchanger's PD is included in the blower selected by the manufacturer.

With this in mind, the furnace would have to be raised to get the coil directly underneath, and there are coils and accessory plates expressly for this purpose. Some have left the furnace in place and put the coil in the crawl (a horrible idea). Watch your RA though; raising the furnace for the coil can make changing filters a PIA.

Condensate Lines

@ February 26, 2014 8:28 PM in Condensate drain trap question:

Is it possible you have an ill-conceived secondary drain? Code requires an independent one, yet I have seen many incorrectly tapped off the primary. Also, could the other line be your neighbor's drain?

I Thought......

@ February 26, 2014 7:46 AM in Coil Material Opinions:

The blower has to overcome the duct resistance, plus the other pressure drops in the system, to deliver the designed air quantity. This is why many in the industry have the concept backward, residentially. You first have to find a blower that will deliver your required air, take out the PDs from your accessories, and use the remainder to calculate duct friction rate. A flex system will only increase the resistance against the blower, causing high energy use, noise, and substandard comfort, especially if distorted or not accounted for in the design.

UC Ducts

@ February 25, 2014 9:13 PM in Coil Material Opinions:

My comment was to TonyS (rip it) and was intended to be complimentary for recognizing the value of insulation. You mention two interesting issues: SEER and insulating ducts. First of all, if for example, your electric cost is $0.12/KWh and you have a 3-ton machine, a 14 SEER unit would cost $0.31/hr. while the 16 SEER model would be $0.27. Multiply that by cooling hours per season; you may find the small difference will make you feel better about not having room for the larger 16 SEER coil, and be better off having a well-performing duct system.

Flex duct moves 40% less air than sheet metal, so any distortion makes a bad situation worse; especially if flex was not considered in the original design. Compacting insulation lowers R-value. However, it sounds as if you are trying to do it right. I would check your ESP to see the effects any duct distortion has had on your blower.

Rip It

@ February 25, 2014 8:27 AM in Coil Material Opinions:

Your post certainly strikes a chord to those of us who advocate locating ducts in conditioned spaces, which I view as an underlying tone of your comment. In some applications, cost or physical limitations get in the way of doing the right thing; keeping ducts out of attics.

Your post also nods toward the value of insulation. Using your Delta T, a 6" duct would lose 15 BTUH per linear foot with R8 and 11 BTUH with R10, so if you aren't able to rip and tear then insulate, insulate, insulate.


@ February 20, 2014 1:12 PM in Coil Material Opinions:

Following all of the storm damage before Sandy, we had the now-famous "Chinese Drywall Era" which drove most manufacturers crazy. Hence, the movement to all aluminum coils, which appear to be less prone to off-gassing building materials creating champagne leaks in coil tubing.

R-8 duct insulation in non-conditioned spaces is code. However, check your local AHJ to see if they have a different requirement.

Wet AH

@ February 19, 2014 9:47 AM in Hydronic Air Handler in A Condo Issues

I'll bet my bottom dollar you have pressure issues. The PD of a hydronic coil can easily be .80 IWC. If this and other PDs were not considered during the equipment selection process, your duct sizes are too small. This results in noise, drafts, and poor performance. Have your contractor check the ESP!

Pressure Switch Test

@ February 11, 2014 7:02 AM in draft simulator

You can inexpensively obtain vacuum hose sections and plastic barbed tees from an auto parts house, which will put your manometer in series with the switch and gas valve or inducer. Pull the factory hose off the switch so you're not cutting tubing that requires a coupling to reconnect. You can also check calibration by pinching the tubing and tubing condition at the same time.


@ February 10, 2014 6:10 AM in manometer

Existing ducts are a different animal, since you weren't in the driver's seat. So now you determine your ESP and subtract individual pressure drops. The pressure left is what the blower "sees" as the distribution system. In most cases this will be sky high because the installer does not understand that you choose a blower FIRST, not that .10 IWC thing. The good thing is the system doesn't care where you relieve pressure. It is easier to do RA mods than SA in most cases.

CFM/ton is a RESULT of your calculations, NOT the basis for them. If your load is 22,000 BTUH sensible and 30,000 BTUH total, your target CFM is 852. You now have to find a blower that will give you that at hopefully not over .72 IWC when you add in your duct pressure from above and other components. Try to get your target on medium speed so you have room to adjust up or down.


@ February 8, 2014 4:13 PM in manometer

Oh yes, my fellow duct guru. I'm an ACCA blue blood. When I finally got the secret of comfort from them, I have never looked back.

In Jersey, I have found the housing stock to be reasonably well-constructed, so my latent loads are on the small side. This is great, because I can take a credit from the latent capacity of the machine I have selected and apply it to the sensible load. I love this because I can use smaller units and still neutralize both of my loads. With a light latent my CFM can hit 500+, yet I can still guarantee 75/50 on a design day.

Duct Design

@ February 8, 2014 10:39 AM in manometer

Using either static regain or equal friction is purely what you prefer, and I applaud your use of either. Here is the more important issue: before even thinking about ducts, you have to choose a blower that will provide the correct pressure to get the CFM required to the conditioned spaces, less the pressure drops of all components in the system. CFM is NOT 400 per ton; rather, it is the air needed to satisfy the sensible load gathered from your load calculations. For example, a low sensible load (high latent) requires a colder evaporator (low CFM), while a high sensible (low latent) needs higher air flow and you will have a warmer coil. This can be anywhere from 300 CFM to over 600 CFM per ton. Oddly enough, if you average CFM research from years of studies, the average is 400, so the manufacturers believe if you base air flow on this number it will "work" but it is rarely correct. Once you calculate the load-required CFM, you then pick a blower that will give you that amount at a decent pressure; try to stay within .50 to .70 IWC if you can. Once you back out your pressure drops (dampers, coil, filter, etc.) you have the pressure left for your duct design.


@ February 7, 2014 2:27 PM in Flue liner size for new gas water heater ?

I would be happy to send you a copy of the GAMA tables.

Power Vent

@ February 7, 2014 6:25 AM in Flue liner size for new gas water heater ?

You certainly got a bucketful of fabulous comments from Steve. Taking all of that into consideration, and not discounting his input in any way, there still may be a nod toward the PV. Venting is a serious business in which many contractors and building inspectors are not on top of their game. With the PV, the venting instructions are in the IOM, so you have pipe sizes, equivalency, pitch, connection requirements, termination configurations, and termination locations. As long as you follow the IOM to the letter you can't get hurt. With the atmospheric model, the maker assumes that you understand the GAMA tables and will vent accordingly.

The efficiency difference Steve mentions would indeed be the vent motor's consumption, yet his comment about combustion air (another life-safety issue most disregard) is more important than a few watts of power, assuming both atmospheric and PV tanks have the same 1st hour rating (how you size your tank) and energy factor (the higher the EF, the more "MPG").

Liner Sizing

@ February 6, 2014 9:12 PM in Flue liner size for new gas water heater ?

Never insulate a vent connector or a common vent section! Use the GAMA Tables for a single appliance to size your vent system. This is a life-safety issue and should not be taken lightly. Choose a liner that is stainless steel; the aluminum liners have a very short lifespan.

HP Operation

@ February 2, 2014 1:38 PM in York heat pump/auxilliary element heat

If you have installed a fairly sophisticated programmable thermostat, you can set parameters for heat pump and electric heat operation by choosing options in the installers guide. However, I fail to understand why you would want to do this, as locking out either HP or back-up heat is normally reserved for fossil fuel combinations. The COP of electric heat is 1; a heat pump will always be more than 1 as long as the ambient is above -17 degrees. Run a heat loss, then plot that loss on a balance point chart. Look up the capacity of your HP at 47 and 17 degrees and plot that on the chart. This gives you exactly how much heat you are producing as compared to the heat loss at given ambients. I believe you will find that adding ODTs on the strip heaters to stage them based on your BP chart findings will make your client more comfortable and happier with their energy consumption.

Heat Loss

@ February 1, 2014 5:42 PM in Temperature stuck at 64 degrees

Follow icesailor's lead. No heat loss equals no way you know what is needed, so don't spend a dime without one.

64 Degrees

@ January 31, 2014 2:23 PM in Temperature stuck at 64 degrees

Does the upstairs unit have an independent thermostat? If not, you won't have heat if the downstairs portion satisfies the heat demand. Did anyone run a load calculation before choosing the size of the heater? If not, then no one properly knows the amount of heat needed to replace the heat you are losing to the outside of the structure.
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