VERY long story short: 2 zones: 1 for 1st floor and basement works fine. 1 for 2nd floor has had problems since day 1 in house 5 years ago. Although AC seems to work OK. When outside temps are below 32, we have freezing Heat Exchanger, Reversing Valve, Accumulator, and all the lines in between. FHP split runs constantly but does not satisfy stat. Have replaced everything except the line set, ductwork, and loop. Replaced FHP split twice. Ducts in attic have been inspected. Line sets have been cleaned and pressure tested. Loop fluid has been replaced. Manual J indicates 2.5 ton, but our FHP is 2 ton, which is what original HP was.
With proper loop mixture freezing should not occur, ever regardless of the ewt. Was a blower door test ever done? Or an energy audit of your home? When the infiltration rate of a given home exceeds "normal parameters" it does really bad things to your manual j load. At 39 degrees ewt your unit should have more than adequate capacity to meet the load /if it is 2.5 tons/. The reason for the freezing needs to be identified, and the manual j backed up by energy audit or blower door. Others will chime in but it sounds to me like unit is running at capacity and not meeting the load. Freezing? What was put in the loop to prevent freezing when the fluid was replaced? What was the concentration vs.volume? Eric
THIS is a problem: "freezing Heat Exchanger, Reversing Valve, Accumulator, and all the lines in between." NONE of that should be happening regardless of EWT, house load, or whatever. System could be one or more of: 1) Severely undercharged 2) Restriction upstream of the iced parts 3) Bad metering device (overly restrictive) Odd that we are seeing a little rash of undercharged systems this year. Last year we seemed to be chasing loop issues ad infinitum. I wonder what's up with the change?
Mark, I am not a newbie to this site because I have had problems for so long and I have posted here about them. I appreciate everyone's suggestions, because many of you are experts in the field and I am not. But, I have learned a lot about geothermal systems over the past 5 years, much more than I ever thought I would know. I think that we are slightly undersized and the 2 ton FHP can't keep up when we have temps below 32. But we have not changed the ducts, line set, or loop, so one or all of them could be contributing factors. Several people have told me that the FHP unit should not freeze up the way it is, but no one seems to know why it does. Has anyone ever experienced this?
Eng, we have looked at all 3 of your ideas at one time or another. None of them panned out. We have tried almost everything.
Maintenance varies with water quality. When you say starting from scratch......? Slightly undersized simply makes geo cost a little more to run.mIt doesn't nix the system all together. Make sure new company starts with manual J load calc. Share that as well as existing equipment info. Let's see if we agree on the "slightly undersized"...... J
Eric, the loop solution (about 65 gal) used was 4 parts water to 1 part Propylene Glycol. We never had a blower door test or an energy audit done. Our home is 12 years old, all brick exterior, well insulated. We did not build it, but it should be fairly efficient.
Find a better pan With EWT in the upper 30s, there should not be heavy icing on the low side pieces parts. To be fair, I was overly broad in saying that icing should not occur "regardless of EWT" Just because the investigation failed to pan out doesn't mean the symptom may be ignored. I'd like to know low side pressure when this is occurring. Somewhere along the way a tech should have measured / recorded that figure.
Looking back through my notes I have the following range: Hi=215 Lo=45 to Hi=265 Lo=50 in Heating Mode during repairs/analysis When the second new FHP was installed early March, the following were recorded: Refrig High Pressure in Heat = 200 Refrig Low Pressure in Heat = 58 Refrig High Pressure in AC = 120 Refrig Low Pressure in AC = 52 EWT at startup = 46 degrees F LWT at startup = 40 degrees F Pressure Drop on Loop = 7 pounds Return Air Temp in Heat = 71 degrees F Supply Air Temp in Heat = 95 degrees F Return Air Temp in AC = 69 degrees F Supply Air Temp in AC = 46 degrees F High Volt Contactor with Compressor Running 245 Volts Low Volt Contactor with Compressor Running 26.5 Volts Amperage at Contactor with Compressor Running 5.7 Volts Within 4 hours after these measurements were taken, the FHP was frosting up.
That indicates a 25% mixture that may or may not be adequate, especially with the propelene glycol. The way to test is with a hydrometer and the chart at the next service, or schedule the test. We use 20% methanol in our systems which works out to about 15 degrees for protection. I know that the environal product yields less significantly less protection at that concentration. Sooooo you may not have enough protection to operate at or around 32 degrees. Without an energy audit combined with a blower door test in your situation I would never feel warm and fuzzy about manual j results given your history with issues to date. If you have a new contractor on deck ask if he can help. Frankly I have been contacted to "start from scratch" with bad projects in the past. Not identifying what made the first attempt fail is crazy. Eric
I apologize if I am getting slightly off topic. Specifically what is it that a homeowner should request of the auditor? Is it a manual J, or something else? The reason I ask is so that homeowners (myself included) can confirm with the auditor ahead of time that the needed information will be provided. I assume some energy auditors are better than others (like home inspectors.) I may get these tests done soon, but I'm unsure if I should address obvious air leaks first.
Some installers do an energy audit and blower door test prior to filling in the values on manual j software. Other installers fill in the values using best info available. Other installers hire independant energy audit and blower door test to fill in values. Yet other installers do none of the above. Like a lot of things in life: Garbage in = garbage out, GIGO Eric
I do a pretty comprehensive audit for about $300. It reports Manuals J and D calculations compared with measured supply airflows room-by-room I also evaluate and report on a half dozen other significant energy consumption centers including, but not limited to: water heating, pool pumping, laundry, cooking, lighting, and home entertainment, as well as anything else that catches my eye. My basic premise is to gather and evaluate a year's worth of utility bills along with degree-day history data and endeavor to apportion costs among consumption centers in a manner supportable by measurement and analysis. I mix in some home inspection, listing any obvious problems that come to my attention within each center. $300 barely pays the bills for such an analysis. Adding to it Blower door, DuctBlaster and TED5000 / Envi measurements would blow the costs out of the water. Attempting to pass such costs along in an initial analysis would cause sticker shock and lead to the whole endeavor being rejected. Therefore I reserve such drilling down for follow-up investigation. On the other hand, if my initial analysis fails to supportably apportion costs among centers such the the total equals the sum of the parts, then I feel obligated to suggest and supply the required additional measurements.
$300 for that service is very fair; it is more here in NYS. I highly doubt you'd find a contractor to provide that level of detail in my area w/o a design retainer of $500.00. I know so. But, no state income tax in Florida helps. No sales tax either, no?
Thanx Urthboy, that is why I don't do ratio deco in my head like others!lol That enlightenment makes the freeze protection even higher. It may be slightly better than raw water around 34 degrees. In regard to the testing I brought up. It all costs money, when it is billed or called for is the trick. A lot of the hvac here are doing it when they believe a problem may exist and after an initial contract has been entered into. Thier is also a new audit company in town that has some kind of support from the gummint. They have been charging the customer 100.00 for the full audit service. Eric
My costs are lower, and the assessments are loss leaders. Fl is a fairly cheap place to do business...labor costs are half or less what they are up north. We do have sales tax, but not on services, which to me makes no sense...
