House details... uninsulated 2 1/2 story victorian built in 1908. with an old 138,000 BTU new yorker oil burner with Bock Sidekick 40 indirect holding tank. first issue i have is the sidekick seems to have been plumbed in wrong. Their is no check valve on the return to the boiler so when the heats on it back flows up the heat return pipe. according to the bock install manual the circulator pump (taco 007) is on the from boiler side and the check valve is on the return to boiler side. Also they piped the to boiler side through the taco 007 instead of T in after the pump. So over to the heating... I believe i have a two pipe system with huge iron pipe & stand up cast radiators (supply and return from bottom of all radiators) There are 5 radiators on the 2nd floor & two on the first floor. The kichen Bedroom & bathroom are on their own loop of 3/4 copper to fin tube baseboard that they tapped off the old iron pipe instead of adding its own zone which i imagine worked okay possibly until the sidekick was improperly installed - i can't imagine they went 50 years with out heat in the back half of the house - just the year in-between them putting the sidekick in and me buying the house. I have a progress tool & pex expansion tool & i can sweat pipe but with the cold weather incoming i don't care about spending more money on fittings. Especially considering plumbers that have come in missed half of what I've discovered and want to charge $5,000 - $8,000 to add the separate zone.

I have two hydroair units in the house. The blower is controlled by a [url=https://www.supplyhouse.com/Taco-HAFC201-4-Hydro-Air-Fan-Control-w-Time-Delays]Taco HAFC201-4[/url]. I want to attached a sensor/probe/aquastat (whatever the correct term is) to the return line after the exchanger to trigger when the fan will turn on (the HAFC201-4 already has a TT connection for this). So the sensor should be normal but close when a set temperature or above it is achieved. Ideally the set temp is variable and the thing is cheap. lol. Does a cheap sensor/swtich like this exist? Thanks.