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Joined on April 16, 2013

Last Post on August 21, 2014

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@ June 16, 2014 7:39 AM in Whoops!

The manufacturer may not insulate the feeler bulb at the evaporator exit because the ambient surroundings will not have an effect on the target superheat. If the bulb is mounted outside the coil enclosure then insulation is critical.

I am not familiar with manufacturers who do not mount the bulb. If you need to do this, make sure it is in either the ten o'clock or the two o'clock position on the vapor line.


@ June 11, 2014 9:31 PM in Air handler with DX A/Cz and hydronic heat.

My fault; I missed that you were using a ceiling cassette rather than a wall unit, which requires a 10' path for the blower to circulate properly.


@ June 11, 2014 7:38 AM in Air handler with DX A/Cz and hydronic heat.

It sounds as if you have chosen a machine, and that you're using a mini-split. You have an interesting issue to overcome. With your high LL, you'll need a lower fan speed to neutralize it. At the same time, you have one indoor unit that has to wash cooling around 570 ft2, which would dictate a higher speed. With this contradiction in mind, indoor unit placement becomes tantamount, plus you'll need at least 10' of throw to keep the unit happy.

Since you're covering the bills, at least you can choose an OD unit that will accept multiple heads. Now we need to find out the heating capacities of the model you like.

By the way, you can determine the operating cost comparison in this manner: divide the BTUH capacity by the SEER (watts); then divide watts by 1,000 to get Kw. Electric is measured in Kw, not therms. Multiply your answer by your local cost per Kw. The answer is cost per KwH to compare different SEERs.


@ June 9, 2014 7:47 AM in Air handler with DX A/Cz and hydronic heat.

Your latent loads are quite a surprise; rather high for the property as you have described so far. Yet we can't select equipment until we have this in the bag. Latent loads come from two "Ls": leaks and lifestyle. You seem to be leak-savvy if you've insulated and weather-sealed. Do the residents have 1,000 orchids or have large cooking vessels in extreme use? If not, I would double-check the Wrightsoft (a program sanctioned by ACCA-fantastic!) weather station, ventilation, and people load inputs. If all OK can we do more to the envelope? I'd like to see your sensible heat ratio in the 90s instead of the .68 you now have.


@ June 7, 2014 8:53 PM in Overcharge Question

Remember that the PT chart is saturated; LL temperatures are going to be roughly ambient temperature. Hence, a "cold" line would point to a possible overcharge. However, the point remains: let's not fall into the charge trap until we're certain the system is clean and has a tolerable air flow.

Cooling Load

@ June 7, 2014 6:43 PM in Air handler with DX A/Cz and hydronic heat.

We now need the total load. My error for not asking earlier; I assumed the numbers you gave us were total loads. If we have total and sensible we then know your latent load.


@ June 5, 2014 7:43 AM in Overcharge Question

First of all, the LL shouldn't be cold. Are ALL components clean? This is important to know before we talk about the refrigerant charge. Also identify your metering device.


@ June 5, 2014 7:36 AM in Air handler with DX A/Cz and hydronic heat.

OK, so now we need to think about this, since you're the one with the checkbook. We have three immediate goals: comfortable residents stay longer, making sure your first costs are in line with your budget, and ensuring an acceptable ROI and life cycle. You gave us a total cooling load; what is the sensible portion?

Sight Glass

@ June 4, 2014 7:19 PM in Ductless vs ACID vs SightGlass/MoistureIndicator vs Suction FilterDriers



@ June 2, 2014 9:41 PM in Air handler with DX A/Cz and hydronic heat.

Do the homes have separate electric meters now, or do you have to split them?


@ June 2, 2014 9:31 PM in mini-split use advice

Most models will cycle the compressor on the set temperature yet allow the indoor blower to run as long as you are in the cooling mode.


@ June 1, 2014 9:16 PM in 410A pump down

This refrigerant, although a blend, does not fractionalize at conditions most of us will see, so those rumors of R-410A separating are false. Unless you're in Arizona with an ambient of 125, of course. More to worry about is that R-410A is a sponge, so more care is needed when brazing, evacuating, and choosing a drier.

AC with Oil

@ May 26, 2014 1:43 PM in cased coils

Check your IOM for both furnace and coil.  There was an issue a few years ago with older oil furnaces and the heat from the combustion chamber/heat exchanger effecting the drain pans, so a higher stand-off was needed.  A new furnace with higher blower speeds changed the ball game.  However, check your coil PD, the duct system pressure, and the blower capability before you select any components.  Oil furnaces by nature have a high PD, so it could be difficult getting the performance for which you paid and expect.


@ May 23, 2014 9:34 AM in Compressor contactor.

I would think the washer and the wire will not be happy together for very long. I would get all back to original. The other benefit will be your bumper will stop vibrating.

Heat Loss

@ May 23, 2014 9:20 AM in Loss Calculations

The first step is to ensure your software program is blessed by ACCA. That way, you know the software designers have not added assumptions beyond those already in ACCA's design manuals.

Heat Pumps

@ May 17, 2014 7:50 AM in Cold Climate Air Source Heat Pumps

Even a reasonably efficient HP will be 1.7:1 at -17 degrees. At that frigid ambient, you will still get 1.7 cents of heat for every penny you put in. Electric heat has a COP of 1. HPs will always be more than 1 because they do not create heat; they transfer it. Moving is always cheaper than making! Heat pumps don't work properly ONLY when they are not properly sized, the duct system is not right (that .10 crap), the terminal units are wrong, and a balance point chart was not used.

Electric vs. Gas

@ May 10, 2014 8:24 AM in Cold Climate Air Source Heat Pumps

Your post is accurate under two conditions. (1) you are below the thermal balance point, and; (2) you are at or below the economic balance point.


@ May 9, 2014 2:57 PM in Cold Climate Air Source Heat Pumps

I'm still laughing!

FYI: my design temperature is 14. The worst day last winter was 12 with a 25 MPH wind, gusting to 30+. At 8:00 pm my HP was maintaining 69 degrees inside, and the house faces West, right into the wind. By the way, I don't have back up heat of any kind.


@ May 9, 2014 7:52 AM in Cold Climate Air Source Heat Pumps


HPs in Cold Weather

@ May 9, 2014 7:44 AM in Cold Climate Air Source Heat Pumps

Plot your structure heat loss on a balance point chart. Choose a HP of your liking and check the rated caps at 47 and 17 degrees and plot that output. This will immediately show you how much heat you will get with and without back up. Always choose a high HSPF; a 9.5 will produce 2.82 times the amount it uses in energy (HSPF x .297).

Equipment Matching

@ May 6, 2014 7:52 AM in 2.5 Condensor with a 5 ton coil

First check AHRI to see if your OD unit and ID coil have been certified. If not you may have a humidity issue. Then compare the SH and LH capacities of your OD unit at your design DB and WB (not AHRI conditions; yours!) to your load requirements. Remember, you can take "credit" for half of your excess latent should you have any to apply to your sensible, which always allows for smaller OD units if yoi can neutralize both loads.


@ May 6, 2014 7:31 AM in figuring CFM required

This is a wonderful practice; one of which our industry should have more followers. However, it tells you what you have yet doesn't address what you need (load). With these two bits together, we learn how closely the CFM required by the load and the field conditions (as your point states) can meet. The more narrow that gap is means everything to the occupants and the equipment.
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