[stevehull]

This year, humidity is a problem here in Oklahoma this year (lots of rain). Our yearly rainfall is ~ 35 inches and we have already had that with almost 15 inches in the last month.

I misspoke about the 100% humidity . . . , it is very high and unusually so for this geography. In the early AM, the pasture grass is wet, wet and walking through it will soak your boots and pants. Unusually damp. This is more like Mississippi/Alabama weather!

Just looked at the weather data at 6 AM and the temp (75F) is just above the dewpoint (68F) with a relative humidity of 79%. Last night, before midnight, the dewpoint was 76F. This is very humid! In the daytime, the air temp goes to mid 90's F and the dewpoint may drop a bit, but it is still quite oppressive.

The guest home is built up on piers, the dirt floor is completely covered with plastic and "skirting" surrounds the periphery. Moisture is not coming in there and the skirting allows ventilation without snakes. No roof leaks either. The only sources of water in the house are the drains, toilets, sinks, etc. When not in use, I turn off the water valve to all those so there is not an inadvertent flood from a blown out valve or something. This house can go for weeks with little use. Accordingly, not much need for AC or heat. No mold, no inside condensation, but if no AC at all, then a slow gradual buildup of relative humidity up to the 62-64% range. And at that level, you will get mold.

Therefore the need to run the AC to remove moisture and therefore the conundrum of the AC capacity being too large. The existing geo heatpump, running at stage 1 (~16,000 BTU) kept the house at 75 F in the coldest of winter nights (0-5F) running almost 100%. This delta T (70F) with an 16 KBTU input shows a remarkable amount of insulation. I mention this as a summer delta t of only 10F (inside to outside) means the AC geothermal unit hardly runs at all and consequently does not remove sufficient moisture.

Normally, our July midday dewpoint is in the high 50's to low 60'sF. With a breeze, this is certainly tolerable. And at night, we don't normally have the oppressive high dewpoints with wet grass in the AM.

This 12 K BTU hack may even be too big for the guest house to remove moisture. It is in the SIP shop now and doing a GREAT job of removing moisture and lowering the air temp. The volume of that space, 36K CF, cools to about 25F off the daytime high with Frankenstein running. The condensate continues to pull out moisture (8 oz every 18 minutes). This floor of the SIP shop is made of concrete pavers on dirt and that subsurface dirt is drying out rapidly.

I have a broken dehumidifier (broken fan motor) and the compressor is an R22 unit with a 6 KBTU capacity that draws about 250 watts (according to plate). That may be about right just to dehumidify the guest house when not in use. I can use the evaporator in that unit, coupled to a coaxial heat exchanger, to serve as a small AC open loop unit.

The local dealer's boneyard has a lot of old geo units and I bet I can scrounge up a coax exchanger for the cost of killing wasps. If I am correct (please check), I can use a coax unit that is larger in capacity. I can use the existing dehumidifier box, the scroll compressor, electronics and evaporator in place.

I know, . . . there are new variable speed geothermal compressor units out there that can modulate between 5 and 110% compressor speed. They do a simply outstanding job of removing moisture at very low cost, but the purchase price is astounding.

Today's job is repairing the blower motor with bad bearings. They are sealed in, the shaft wobbles and, when turned on, they squeal and then the shaft binds up. I oiled them before and got the shaft to spin, but the bearings are shot. Hard to find a 3 inch diameter 1/12 HP AC motor . . . The large squirrel cage blower, from an old 3 ton ac unit, is simply too large. I have to restrict the air output to allow a lower air flow across condenser. That just loads blower and is not a solution.

Will see if I can resurrect a small DC motor (more efficient than split capacitor AC motor), but then I have to build a high amp DC power supply. But wait, I think I do have one of those that used to power a 6 meter ham radio rig!


Steve