Hybrid Hot Water Heater with Existing Tankless Boiler (that I don't heat with)

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Maestro232

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Hello. My apologies if this has been asked before. The following two threads are close:

https://terrylove.com/forums/index....lectric-hot-water-question.82334/#post-593937

https://terrylove.com/forums/index....ess-coil-or-keep-with-hpwh.83242/#post-599972

I have an oil-fired boiler for water baseboard heat with a tankless coil for DHW. I installed minisplits on one side of the house and use wood for the other side, so we don't need the oil heat (maybe a half a dozen times a year in dead of winter we'll kick it on in the morning because we're lazy). In any event, I purchased a hybrid electric hot water tank and I'm trying to decide the best way to do integrate this into the existing system. Ideally I'd be able to shut down the boiler for 9-10 months out of the year, and maybe just use it for the possibility of heat (not using the hot water coil) in the coldest months. But I'm not sure if these boilers are really designed to just turn off and leave sitting for months with water in them. Another possibility is to really shut it down for good with the possibility of easily reviving the system if I go to sell the house (some people may be turned off by needing wood for one side of the house). But then I'm guessing I have to drain the oil from the tank, water from the system, etc...

I am looking for advice.
 

Maestro232

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I've been doing some hunting on the forums while awaiting a reply and there are a couple of conflicting ideas that I might need clarity on:
1. I have seen some suggestions to turn the boiler off for the many months that it's not in use, but I have also read elsewhere that the cast iron sections can leak from the contraction of the cold. I have a Dunkirk Empire 2 which does fit the description of cast iron sections with push nipples, but I don't know if it would be prone to leaks or not? If I can just cut the tankless coil out of the loop and only turn my boiler on for heat for a couple months out of the year, that would be great.
2. If I have to keep the boiler on even though cutting out the tankless coil for hot water, it is not clear to me what the safe, minimum, least fuel consuming aquastat settings would be.
3. It looks as if some have successfully installed their hybrid-elec, elec, or heat pump water heater tanks "in series" such that the hot water coming out of the coil is the cold intake to the tank, but I have also seen some suggest that it can't be done. Any word on that?
Just to reiterate, I'm looking for the best way to pipe in a hybrid-electric water tank into an existing oil-fired tankless system where heat is not used or only super rarely.
 

Fitter30

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Minimum water temp for heating is 140* return temp. Adding boiler treatment would help it's the oxygen in fresh water that is detrimental to a boiler. My main concern would be on the oil side. Conensation in the tank, nozzle stopping up. Water heater just pipe it without boiler coil.
https://www.supplyhouse.com/Rectorseal-68712-8-Way-Boiler-Water-Treatment
One way to add treatment. Valve boiler off, drain, pull pressure relief valve add treatment.
 
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