I just found this site and see the incredible amount of effort and info here. Wow.
With that being said I have a beginners question - I am looking for any info on what I might do to improve the efficiency of my current setup as far as heating is concerned - an off the shelf Fujitsu ductless heating/cooling setup. I have rooftop solar PV and with that the house is close to being energy neutral for the most part. I am within +/- $20 /year of zero electric cost which covers light, electronics, cooling, cooking, heat, and 2 plug-in hybrid vehicles. Gasoline cost of less than $50/year for both vehicles combined. Oil fired boiler is used for hot water and the rare moments when the Fujitsu goes into defrost cycle. One tank of oil lasts 15-18 months. The winter heating seems to be the big consumer in all of this. I have raised the heat pumps to stay above snow buildup and put a small cover on top to keep snow and rain from being sucked into the coils and to keep the sun from heating the unit in summer. I would be interested in any suggestions or info folks might have to lessen the energy usage of the ductless units (I have 3) in winter time. This might free up some KWH for me to look into electric water heating for us…
Thanks to all.
Hi Mark, welcome to the OpenEnergyMonitor community.
That’s an impressively low fossil fuel use.
Switching to a hybrid water heater would move some of your summer cooling load to water heating but increase your winter electricity usage.
Do you have any monitoring in place? Measuring the COP of the heat pump will be challenging.
Did you do a load calculation to properly size the heat pump? Does it cycle in summer or winter?
How is the insulation and air sealing on your home?
I imagine you control the set points in summer and winter using remote controls for the three ductless units.
Is the air distribution good, or do you have to freeze some rooms to cool off others?
-I have looked into the hybrid water heaters but see they have electrical heating elements to supplement the heat pump. After a good bit of head scratching I believe this would end up costing me much more in electric consumption than I would save in oil cost.
-
The monitoring that I do is limited to reviewing monthly and annual solar output to ensure everything is working correctly in the 3 separate PV arrays. Also reviewing the monthly electric company bill that shows beginning and ending electric meter readings, and net electric use. This way I can see that the “electric bank” is in the right range for an annual net-zero result that is reconciled each year in the spring.
-
The way things have worked out over the years as knowledge and technology progressed, I now have 3 Fujitsu ductless air conditioner heat pumps outside and a total of 6 head units in various rooms of the house including the basement. So temp is nicely balanced inside the house and we can condition or not condition in each room as needed. The one 15kBTU unit supplies the first floor and is responsible for the majority of heat demand in winter. Overall there is enough capacity to heat and cool at whatever level we desire.
-
Over the years I have improved the windows, insulation and overall sealing of the house which was built in the 1940’s to a pretty reasonable level.
-
Nothing is really automated as can be done today with smart thermostats etc. We essentially set all the units to cool mode in the spring and select a desired temp on the remote control in each room. That temp selection might change a bit based on our overall physical activity level. Say 72-76 degrees F. In the winter we switch over to heat mode and select typically 69-71 degrees F and leave it there for the season. The only change being turning a head unit on or off depending on if the room is being used. - example would be the basement and spare bedrooms.
| rsiddall Richard Siddall
28 July |
- | - |
Hi Mark, welcome to the OpenEnergyMonitor community.
That’s an impressively low fossil fuel use.
Switching to a hybrid water heater would move some of your summer cooling load to water heating but increase your winter electricity usage.
Do you have any monitoring in place? Measuring the COP of the heat pump will be challenging.
Did you do a load calculation to properly size the heat pump? Does it cycle in summer or winter?
How is the insulation and air sealing on your home?
I imagine you control the set points in summer and winter using remote controls for the three ductless units.
Is the air distribution good, or do you have to freeze some rooms to cool off others?
I think most hybrid water heaters offer a heat pump only mode where they won’t use the immersion heaters, or only when you’re almost out of hot water. The big box DIY stores often link to the user manual which would tell you whether a specific model offers this feature.
I don’t know how you’d set it to run only when you can best make use of the cooling. Since you’re on net metering you won’t have a time-of-day rate when it’s cheaper to heat the tank.
Sounds like you’re checking PV output from the manufacturer’s portal. You might want to consider installing an EmonPI2 or an Emporia Vue or similar to get more detail about what’s using electricity. See emonTx V4, emonVS in North America. You should be able to see how much energy each heat pump uses, and get an idea about whether experiments succeed in reducing energy use.
You could read Heat Geek’s article on why not to zone and decide whether it makes sense to turn head units off in unused rooms.
You may want to measure humidity levels. Mini-splits get high SEER ratings by not running very cold and so not using much energy to dehumidify, but you could run the house hotter in summer if it’s drier inside and still be comfortable. It may be worth running a dehumidifier to reduce the electricity the heat pumps use.
You may also be able to adjust the set points to make the upstairs do more of the cooling and let it fall to lower floors, and the downstairs do more of the heating and let it rise to upper floors.
Thank You for the info.
I have some reading to do.