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3 Answers

Making sense of the first month of minisplit heating data

I have 4 Fujitsu mini splits (non xlth) hooked up to (2) 24k condensers. They were primarily for AC but I'm trying to reduce usage of my aging 199k/152k steam boiler while the temps are relatively mild (Boston). Right now I'm using a 12K head per condenser, per floor, so 2 total. Dana had some good advice as the min modulation range was about 6200 BTU/hr per unit, and to run both units, so this weather seems to be the sweet spot for efficiency and load.

Asked By Kjmass1 | Dec 12 17
16 Answers

Help selecting a heat pump

Hi Guys,

I'm going to be meeting with my builder this week, and he wants to show off the furnace of his choice, which is a Dettson Chinook. It's a small modulating natural gas unit, that can be paired with their Alize heat pump.

It's a pretty neat unit, designed to allow for very long cycle times, often measured in hours. The problem I have is that the heat pump portion kind of sucks in cold weather, it uses proprietary small high velocity ductwork, and a proprietary thermostat to control it all. It also has a short~ish warranty.

Asked By Stephen G | Dec 11 17
10 Answers

Drain Water Heat Recovery

I plan to install a drain water heat recovery unit in my new home. Does anyone know of any guidelines on sizing? For example,there will normally be 2 people in the house, but on occasion that could easily double or more as we have extended stay guests (a week or even more). And we will have a 65 gallon heat pump water heater.

As the DWHR units tend to get pricey due to the copper involved, I want to make sure I get the most bang for the buck.

Asked By Norman Bunn | Dec 11 17
1 Answer

Horizontal ducted minisplit ducting

I plan on using a Mitsubishi 12K BTU horizontal ducted mini split, Model: SEZ-KD12NA4R1.TH to provide both heat and AC to two second floor bedrooms. The unit would be inside the building envelope in a dropped ceiling in a hallway between the bedrooms. I'm having trouble determining what adequate ducting would be.

The Mitsubishi submittal document has graphs for different static pressure that relate to CFM but I struggle to relate this to a duct design.

Asked By Jim Sweazey | Dec 12 17
4 Answers

Choose between window condensation or gaps in hardwood planks?

I built a new home in 2017. This is our first winter living in the home, and I'm running into a humidity problem.


Asked By Ryan Lazuka | Dec 11 17
9 Answers

Indoor Humidity - dew point & monitoring condensation

I live in Colorado, Zone 5, where our winters frequently drop down to 0-20F and outdoor humidity levels might be in the teens.

I recently figured out my chronic congestion gets about a hundred times better at 45% humidity. Despite all the sealing & insulating we've done, the plants and three dogs, our house drops down into the twenties in winter, sometimes even the teens. Because this is a retrofit, I probably can't hit 0.6ACH. I'm around 1.5ACH right now, and the next sealing & insulating step will require ripping off the roof, so that's on the back burner.

Asked By pshyvers | Dec 11 17
1 Answer

Desuperheaters in a high performance house

Does anyone know if there are any guidelines for using desuperheaters with HPWHs and ducted mini-splits in a high performance house? I will have a 65 gallon HPWH in my basement near the location for the outside AC/HP unit. There will be a 2 ton ducted mini-split HP serving the main floor, as well as a wall mount 1 ton in a loft/office area.

Does a desuperheater make sense in such a home and do mini-splits work with this?



Asked By Norman Bunn | Dec 11 17
4 Answers

Mini split head blowing cool air

I have 4 half ton heads and a 1.5 ton head in my house that were recently just commissioned. One head seems to blow considerably cooler air than the rest. I have checked almost 100% of the lineset into the unit from the branch box and we no kinks. The branch box does recognize I have 5 heads hooked up. It did seem like it was blowing a bit warmer when it was the o my head running.

Any ideas? Thanks in advance.

Asked By Mike M | Nov 26 17
2 Answers

Cycle Stop Valves

Has anyone looked in to Cycle Stop Valves for residential use? Do the motors really reduce their power consumption when throttled? How does the use of a pressure reducing valve effect the pump and motor cooling? Any other side effects I haven't considered?

Thanks guys.

Asked By Calum Wilde | Dec 7 17
0 Answers

Digital vs. VRF Scroll Compressors?

I'm looking at two different heat pumps, one using a digital scroll and the other a VRF (variable speed) scroll compressor.

The digital scroll compressor modulates output by separating the scrolls on a duty cycle, essentially a mechanical way of turning the compressor on/off as necessary while keeping the motor running. Modulation is from 100-10%.

The VRF scroll compressor modulates output by varying the speed of the compressor. Modulation is from 100-30%.

Asked By Lance Peters | Nov 29 17
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