Fancy Thermostat - Do I need Aquastat?

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Tennman

Minister of Fire
Mar 4, 2009
993
Southern Tenn
Changed HVAC service guy so now have someone more knowledgeable about the controls stuff. Have had two thermostats for my previous 2 boiler seasons; first for the original propane furnace/downstairs AC, second to just control the furnace fan when the boiler is running. We don't have storage so for 2 seasons, I wake up to a cold house, manually turn off the tstat #2, turn on #1 to burn a little propane to knock the chill off while I restart the boiler, then before leaving for work reverse tstats since the boiler would be up to temp. Yeah I know you controls types out there are shaking yer heads, but we all have different skill sets. I'm good with mechanical stuff but allergic to wires. So NOW bought a Honeywell Pro9000 multistage to automate the stuff I was doing above. SO.... out in the boiler barn I can set the pump off temp on the boiler controller so I don't waste electricity when the water gets cool. And the fancy new tstat will switch to propane as some programmed temp lower than my primary which will be the boiler..... So do I really need the aquastat I bought last year to turn off the furnace fan because the house was calling for heat, but there is nothing but cold water?? I'm thinking not.... Down the road if we add storage, I presume then I'll need the aquastat somewhere, so it's not wasted, but until then???? I think the fancy tstat does it all... Am I missing something?

Fired her up last week for one day when nites got chilly and the next day temps went into the 70's with 60's at nite!! Looking forward to my first year of burning 2 year seasoned wood! On that one burn could tell a BIG difference in output.
 
I would think that you would want your Aquastat to interrupt your boiler thermostat circuit anytime you don't have usable water temps.

1. you will just be circulating cold air through your duct work.
2. If your circulator is circulating cold water while you are burning propane you will be transferring heat from your furnace to your boiler shed.

I would never try to talk you out of a new more efficient thermostat but there is no reason to shut the original furnace thermostat off,if you have it a a lower setting it will only function when your house has cooled to this point and of course your boiler thermostat will have already be disengaged by your aquastat.
 
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