BillyPilgrim
New Member
Wire in a switch sounds fairly simple. Which terminal would I use to get the 28vac
Run fan only on old gas furnace
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DonL
Jack of all trades Master of one
The 24V power is on the R Terminal.
So a jumper / switch from R to G should make the fan run.
Good Luck on your project.
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Jadnashua
Retired Defense Industry Engineer xxx
Basically, right now power comes from the R terminal at the furnace, goes up to your thermostat, and when it wants heat, it simply connects that R terminal to the W terminal. If you want the fan to run continuously, it would just connect that R terminal to the G terminal. So, the thermostat is essentially just a fairly simple switch or switches. If you had a/c, moving the heat switch on the thermostat would make the connection to the Y wire instead of the W one to make the a/c run.
Tom Sawyer
In the Trades
A short jumper on the 9141 between G & R. Stick a toggle switch in there if you want.
Wireless thermostats allow you to put it where y0u want, when you want, or even take it with you when you go up or downstairs.
Sealing off ducts does not save energy- it creates pressure imbalances that only increase the amount of air handler driven infiltration. (This effect has been measured both in laboratory setting and in-situ in existing houses by researchers at the Lawrence Berkeley National Labs.) Better balance can also be achieved by increasing the duct or register capacity on the "cold" part rather than taping off supply ducts in the "hot" part of the house. Ducts need to be balanced too- the lack of dedicated returns on the lower floor are part of the problem.
In earlier posts you mention "...a full first floor gut in the plans...", then later on "...until I can gut basement." Is this a 2-story + basement, a walkout basement with a floor above or something else? The heat loss characteristics of basements are fairly different from fully above-grade floors, which makes running as a single zone nearly impossible to temperature balance, since the balance changes with the weather.
A pair of mini-splits can work, provided the floor plans on each floor are sufficiently open. It becomes an issue for doored off rooms down the hall from the room with the wall coil. Sometimes mini-duct cassettes feeding a few adjacent rooms is more effective. More so than single speed hot air furnaces, sizing a modulating mini-split correctly to the load is important for both comfort & efficiency.
Sealing off ducts does not save energy- it creates pressure imbalances that only increase the amount of air handler driven infiltration. (This effect has been measured both in laboratory setting and in-situ in existing houses by researchers at the Lawrence Berkeley National Labs.) Better balance can also be achieved by increasing the duct or register capacity on the "cold" part rather than taping off supply ducts in the "hot" part of the house. Ducts need to be balanced too- the lack of dedicated returns on the lower floor are part of the problem.
In earlier posts you mention "...a full first floor gut in the plans...", then later on "...until I can gut basement." Is this a 2-story + basement, a walkout basement with a floor above or something else? The heat loss characteristics of basements are fairly different from fully above-grade floors, which makes running as a single zone nearly impossible to temperature balance, since the balance changes with the weather.
A pair of mini-splits can work, provided the floor plans on each floor are sufficiently open. It becomes an issue for doored off rooms down the hall from the room with the wall coil. Sometimes mini-duct cassettes feeding a few adjacent rooms is more effective. More so than single speed hot air furnaces, sizing a modulating mini-split correctly to the load is important for both comfort & efficiency.
Jadnashua
Retired Defense Industry Engineer xxx
I saw an interesting concept on the Panasonic website about heating/cooling air distribution when using mini-splits in combination with their ventilation fans. Things would have to be carefully designed to achieve even temperatures, but would overcome some of the disadvantages of that type of system when you have rooms closed off verses an open floor-plan.
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The problem with redistributing the air with a vent fan is the piss-poor heating efficiency of moving 20-22C air into a room, even with the highest-efficiency vent fan. The amount of temperature balancing you get is quite small, and there will always be some temperature difference in the remote rooms.
By contrast, the heating efficiency & balance of heating rooms directly with the split output of a mini-duct cassette is quite good, supplying 45-55C air to those rooms, bringing 18-20C air back, and you can adjust the flows to optimize temperature balance to your liking.
By contrast, the heating efficiency & balance of heating rooms directly with the split output of a mini-duct cassette is quite good, supplying 45-55C air to those rooms, bringing 18-20C air back, and you can adjust the flows to optimize temperature balance to your liking.
Jadnashua
Retired Defense Industry Engineer xxx
Similar to a radiant system...you'd probably want things running continuously, as trying to recover from a setback would take time. My father's house went with a heat pump a long time ago (locally really cheap electricity), and I'm sure it is nowhere near as efficient as the modern ones, but they had a single speed fan, set to optimize cooling in the summer, and the cooler air from the ducts was uncomfortable if you were anywhere near one of their outlets even though the room temperature was reasonable.
THis would depend on the thermal mass of the structure and how well it was insulated and tight as to how well it would work out.
THis would depend on the thermal mass of the structure and how well it was insulated and tight as to how well it would work out.
Like ductless wall coil type mini-splits, mini-duct cassettes run continously if you size them correctly, since they are a modulating system with at LEAST a 3:1 turn down ratio. They typically have ECM drive motors that are at least as efficient as better-class ventilator motors, but would be driving at least one order of magnitude lower cfm to achieve the same amount of heat distribution.
The HSPF of the Mitsubishi SEZ/SUZ dedicated single cassette mini-duct mini-split is about 10- which is lower than a best in class wall coil types (HSPF of about 12-12.5), but would be clearly more efficient than something that also has the background power load of a continuous ventilation system running (that doesn'teven really resolve the temperature balance issue, since the air it's delivering is barely above the desired air temp.)
The HSPF of the Mitsubishi SEZ/SUZ dedicated single cassette mini-duct mini-split is about 10- which is lower than a best in class wall coil types (HSPF of about 12-12.5), but would be clearly more efficient than something that also has the background power load of a continuous ventilation system running (that doesn'teven really resolve the temperature balance issue, since the air it's delivering is barely above the desired air temp.)
