The heatpump has 02 date on it, so it's 8yr old or less. when I flip the switch on and off the fan in heatpump doesn't always work. I tried like 6 times and it turned on by itself only once or twice. Also, I noticed that the circuit breaker (inside the house) makes a noise every time the fan is trying to start. Is that normal for circuit breaker to make this noise? The lights in the house flicker when it makes this noise, but once I start it up with the stick everything is back to normal. I had an oil service rep over at my place and he said it's normal for lights to flicker, but at that time I didn't know that the fan doesn't work. now I wonder if it really is normal. Another strange thing - it 70 inside and 70 outside, but when I tried to bring the room temperature to 68 the air coming out from the ducts wasn't cold enough, not nearly as cold as it was in the summer.I ran AC (with fan running) for about 45 min, but it's not the ice cold air that I was getting in the summer . Thanks

I may be mistaken as to what you are really looking for but what I think you want is a traditional 2 stage heat pump thermostat, you can buy them just about anywhere. It will control the heat pump. When the heat pump is not doing the job and more heat is needed or, when in defrost mode, the second stage kicks in the oil burner and hydronic system. This is a traditional heat pump thermostat however in a lot of cases heat strips are engaged only because that is the backup heat. There will be times when the heat pump and the oil burner are working at the same time, depending on the heating demand. To just automatically switch to the oil system at 35 degree outdoor temperature would not be energy efficient. Heat pumps do their job very well at 35 degrees. If your hydronic system supplies heat only and not hot water for bathing etc., then I understand your concern about the waiting period for the water to heat up to temperature and supply the supplementary heat but I suspect that not to be the case. If, with the 2 stage thermostat, you decide you do want the heat pump off and the hydronic system to supply all the heat, you merely switch the thermostat to emergency heat. That will disengage the heat pump and your heat will be supplied by your backup source, this case being the oil fired system.

If you have the burner serviced each fall then the probability of it failing during the middle of the winter is low. A competent oil burner technician will replace the nozzle and filter as needed. The motor should last many years especially if you supplement the heat with a wood stove. Does this tech work for a fuel oil company? I find it strange he is encouraging you to switch to propane. Maybe he doesn't know what he is doing and wants you to switch before you find out he has been doing a poor job of maintaining the oil burner. The whole thing seems suspicious.

weedmeister - Thanks you so much for the help. Just to follow up on that's going on in case you're interested" I also contacted Ecobee support a few days before I posted here. I was worried I wasn't going to hear back, which is why I posted here. But it just took a while. Now I've been going back and forth with somebody helpful at Ecobee. The Ecobee guy sent back the same wiring you did, except that he said I can't double-wire the transformer into the Rc and C contacts as you suggested. I did try wiring it up both the way you and he suggested (although without the Transformer), and confirmed the Mini Split would not provide power to the Ecobee. He then suggested it might provide power it I re-wired it using the "O" wire, but it still did not. At first he said that to use the transformer for power, it would need to be done through an Isolation Relay https://support.ecobee.com/hc/en-us/articles/227874527-ecobee-thermostat-installation-with-an-isolation-relay But he later updated that to say I can't use that method because then the Ecobee would send power out to the Min-Split. I actually don't think this is a problem - my reading of the Dry Contact manual is that that's why there's a "volt" switch in it - it's to set the Dry Contact to be OK with power coming into the Dry Contact from the thermostat. I'm hoping I'll hear back from him confirming that, and I can buy a relay and wire the transformer into the Ecobee that way for power. If it turns out that I really can't do that, then I do have an option of running new thermostat wire up from the oil furnace that so I can get another, powered "C" wire that way. Thanks again. Oh, and MiniSplit Heat, thanks for trying to help, but I don't understand how your comment answers anything I asked in my post.