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Thermostat/Aquastat Riddle

My wife and I recently bought an 1891 farmhouse that has a lot of curiosities and 3am emergency fixes that became permanent fixes over the years. One curiosity is the heating in our living room..

We have forced hot water throughout the house; however, the living room does not have plumbing to a radiator in it. As a "fix," a previous owner put a flat radiator in the basement below the living room with a fan on it to blow hot air into the room through two floor vents. There is a thermostat in the living room (an electric baseboard thermostat) that turns the fan on and off; however, there is an aquastat, hooked to the pipe that feeds hot water into the radiator in the basement, also controlling the fan.

The hot air that comes from the vents warms the room up incredibly fast; however it sometimes gets too hot. I am assuming the idea was that the the thermostat would turn the fan "on" if the room gets cold, and the aqaustat will turn the fan "on" when there is available heat to blow. If either "stat" is not "on" there is no action. That is not the case. The thermostat in the living room might as be a light switch. That fan will run 24-7 if the thermostat is not in the off position - 40 degrees, 90 degrees, it doesn't matter. Of course after there is no more heat to blow, the fans bring up the 49 degree air from the basement efficiently cooling the room down - this might be nice in the summer time, but the Vermont winters are colder than the summers are hot.

It's not ideal, and we plan on replacing it with a radiator, but there are many other items ahead of it. Any ideas on where and how to start to troubleshoot this so it is functional now?

Re: Thermostat/Aquastat Riddle

You might try partially covering the floor heat exchanger with heavy duty aluminum foil to cut down on the heat output, until a more permanent fix is arranged.

Re: Thermostat/Aquastat Riddle

Late on a reply...

I'm really perseverating on this. I could toss a radiator in the room and call it a day, but I feel I need to solve this...I don't know why.

I'm focusing on the aquastat right now. Here is what I have done

I've left the fan running and adjusted the temp dial until the fan turned off, then I adjusted just enough so that the fan would start again. This was from 160 to 140 degrees. Now the fan will not kick in when the boiler fires up until 10 or 15 minutes after. It then runs non-stop blowing luke warm air (because the pipe has cooled some) then cold air after the heat has dissipated.

If I leave the aquastat at 160, the fan runs 24-7.

Is it possible that the aquastat has been wired incorrectly?

Re: Thermostat/Aquastat Riddle

Your best bet is to get the mfgr name & model # off the aquastat & Google it to see if there is a wiring diagram (there usually is) that can help you figure out how the circuit is wired.

Honeywell makes an L6006 surface mount aquastat that can act on a temperature rise or fall---there are numerous other mfgrs that also make aquastats.

Older Honeywell surface aquastats are LA409A and LA409B.

Then, Google the model # and mfgr name to get the wiring diagram, like "L6006 Honeywell"

Aquastats are basically a switching device that take a low signal from a thermostat, or a bellows temp pressure rise or fall & kick in a fuel burner, circulator or fan, each individually or all at the same time, depending on how they're wired, until a certain temperatue condition is met.

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