Duct insulation and electrical rates question?

[Larry2]

Some folks may be weary of my postings concerning my failing air conditioning/heat pump system. I think my immediate issue might be solved by replacing the fan motor cap with a correct value part.

I have even more design questions that are just beyond my reach as a EE in the radio frequency field. I installed quite a few systems in the late 60's, charged them and went on my way back then, but I didn't do any load calculations on those. Thas was done by others. I guess I am lazy and should research and learn this stuff myself since I am the one in need answers, but anyway, I am asking for more help on my questions. Those more experienced can help focus my attention on the calculations for planning future direction. Since the questions are somewhat different from my failing unit, maybe I can get new help in this area.

My upper floor system has never kept up with summer heat gain. In fact, in September while outdoor temperatures moderate but solar gain increases with a lower sun angle, this unit has always failed to keep up with it's peak load. My first floor has 150 or so square feet of low-E glass facing West. My second floor has slightly more Western facing glass. I had my original contractor exchange the original 3 ton system for a 3.5 ton system. Without my consent or following our contract, without notice etc., he downsized the second floor unit to 3 tons. I think 3.5 tons was his original "seat of the pants" quess. He never showed me any load calculations. I don't think he calculated anything beyond a walk through the house.

This increase to 3.5 tons provided moderate improvement. Three and one half tons cooling was contracted performance. I don't believe he ever did a proper manual-J heat gain calculation on my home, even though provided him with my architectural drawings. I don't think he considered first floor heat gain on the second floor . My home has loads of Western facing glass at both levels. The rest of major glass area faces South. Some of this was by intent since heating is our major season here. Mostly it was by esthetics and I was the architect to blame for excess glass. It is "low E" glass, but the glass vendor installed the lessor of the available efficency glasses available at that time.

The home is otherwise well insulated 6" frame and brick construction. The calculated R value of the composite framing and insulation is 19.8R. The Brick is currently 112F. The attic is currently 97F, I have no patience to measure it in the current heat, so could be higher in spots. At the thermostat it measures 74.5 and this is the coldest point on the second floor. The unit has run all day without cycling and these measurements are as the sun load is decreasing. The attic installed duct work appears to be inadequately insulated from the start, as I mentioned in a different thread. I was amazed to see 15-20% cooling loss through the longer duct.

From late morning, until dark is when the second level proves to be a problem. It always has. My first complaints about the sytems unable to "satisfy the thermostat" caused my contractor to alter the thermostat level to make the thermostat shut off earlier rather than to improving cooling. Later, when I discovered the sytem he installed was only 3 tons, not the 3.5 tons under contract, I had him swap out the system for the contracted equipment. At that time, the system still would not keep up with outdoor temps of 78 F or lower when the a lower angle sun caused high solar gain through the windows. So, such is the background on my questions, problems and concern.

The home has a two story open design with a foyer that is open two stories. Heat from the first floor quickly rises through the foyer and family rooms to the second level. All of the first floor is an open design, so heat gained there promptly rises to the second floor. I have a lot of Western facing glass at both levels. Most glass is Southern and Western facing and is of considerable area, maybe 10% of the building walls. Solar gain, even through low-E glass is considerable. For cooling, the second level system has always proven inadequate. The second level system is a Lennox HP22-461-3P condensor while the blower/coil is a CB18-511-2P which folks tell me can provude 4 tons cooling at 1600 + CFM air flow. I can't say I ever received 3.5 tons cooling from this system, the rated capacity. I've not meaured unti now. It has never caught up with afternoon loading during summer, even on early September days when sun load was the important issue, rather than heat gain through the 2X6 construction brick faced walls. This home has a great deal of West-facing, though "low-emissivity" glass. When the sun hits the glass, the unit mostly cuts on early morning until the sun goes down late afternoon.

My questions are about fitting the system to provide efficent and adequate cooling. It seems like the outside system is well worn and will need replacement. (I await comments on that question) I need to know if the second floor system ever provided the spec cooling and I need a larger system, or if I only need only correct worn out gear.


Windows are mostly 32" wide and 72" tall.

Sat dishes are how I reach my friends here on the fridge net.

Thanks, all!