How to turn of Circ Pump to water/air exhanger when water temp is low

I have a forced air furnace that I am installing a water/air exhanger in . I have one thermostat for the propane burner and will have another to control my circ pump and turn the fan on inside the furnace. I know there is a way to turn off the circ pump when the water temp is too low but I dont' know how to go about it. I want to keep it simple and avoid any fancy controllers. I think I will need an aquastat. Can someone explain to me how this would work and how each component would control the other.

Thanks
Mike


EKo 40 with 500 gallon pressurized storage

If you only have one pump on your EKO it will control it for you 100% without the need for additional electronics. You'll control the "on" and "off" temp's on the EKO controller. It's usually only when you add another pump that you would need to add a relay or other device to control a pump with a thermostat.

I will have the EKO control the primary loop pump. I will need something else to control the additional pump.

This is a section from " Simplist Presurized Storage Design" Maybe it can be of some help!

In this system, each boiler has a circulator that runs whenever that boiler is hot. That's normal behavior - no changes are needed. These circulators need to have check valves to prevent reverse flow.

Each heating zone has a zone valve that's controlled by the zone thermostat (or aquastat in the case of the indirect DHW that I've shown). This is also the normal configuration - no changes are necessary.

Zone valves have built-in limit switches that close when the zone valve is open. Normally those contacts are wired in parallel and connected to the oil boiler demand input. Here, we have to make some changes.

First, the zone valve limit switches are removed from the oil boiler demand input and connected to the 24vac thermostat transformer (see schematic).

Second, we need a 24VAC relay that we energize when any of the zone valve limit switches are closed. This relay will turn on the Load Circulator.

Third, we need a 24VAC relay for the oil boiler demand input - when this relay is energized, it creates a closed circuit that turns on the oil boiler. This takes the place of the zone valve limit switches.

Finally, we need an aquastat at the top of our storage with contacts that close only when the storage temperature drops below the minimum usable temperature - we'll say 140 degrees for this example. The signal from the zone valve limit switches passes through this aquastat before going to the oil boiler demand relay. In that way, if the storage is above 140, the oil boiler will not come on when the zones call for heat.

A aquastat as pictured below can be used as a switch to turn the circulator on or off. It would be wired into the 110 volt power leading to the circulator .

Thermal snap disc controls are simple, inexpensive and very reliable. Some can be clipped right onto the pipe. This one on the left turns on a fan when the piping gets warm enough. It's used in a small kick space heater. Some have an adjuster dial on them to tune them to your needs.

They come as a "L" limit which means it opens the circuit on temperature rise. or a "F" fan to make contact on temperature rise. A F140 would turn on when the temperature reaches 140F, for example.

Commonly used on furnaces for both limits and fan switches. Most of the pump manufacturers offer pipe snap on ones to turn DHW recirc pumps off when the loop warms to 115F for example.

120V wiring should be in a flex or condiut for safety. Use a junction box to make up the connections. The pump ones generally have leads attached to them, so no opoen terminals.

hr

Why do you want to shut it off? I ran mine for 3 seasons with no controls very simple. Then i switched to a flat plate HX for my DHW and now i let my furnace thermostat turn the circ pump on and off as it calls for heat.

Rob

I want to turn it off because if the water temp is low and my propane furnace kicks on I will be trying to heat 500 gallons of storage with my propane furnace. Now to make this even more complicated. How do I turn the furnace blower off if the wood boiler can't meet demand. Lets say I set the wood boiler thermostat to 70F and have the propane furnace thermostat set to 66F. If the water temp is low and can't meet the 70F demand the blower would run until the temp in the house dropped to 66F which is when the propane would kick on. Is there a way to turn off the blower if the above situation? Remember I want to avoid computer controllers. Trying to keep it simple.

The fan limit switch in the propane furnace will turn the blower off !

It sounds like I have mine set the way you would like yours.

I have an aqua-stat at the heat exchanger it is connected to a time delay a a couple RIB relays. I have mine set so if the water at the exchanger is not 130 after 3 minutes it shuts off the pump and the gas furnace kicks in.

All my pumps just run on demand because I don't want to mix storage.

I only have 1 thermostat. It works great so far for the last 3 years.

gg

Goosegunner,

Thats what I want to do! Could you provide me some more details or a diagram of how you have it wired.

Im also curious about hobbyheaters comment about the fan limit switch shutting the blower off. I need some more info on that.

Here you go, I had a HVAC guy do it for me this is what he did.





gg

This sounds something like what I need. I plan to adapt my existing L6081 aquastat to control a replacement backup electric boiler. Currently, the aquastat starts the oil burner when there is a call for heat & the water isn't hot enough, by sending 120v to it. I want to change that so that rather than starting the oil burner, it will instead simply close a circuit - as there is connection in the electric boiler for a thermostat to control it, which I'd like to mate to the 120v wire now going to my oil burner. So I think I need a relay to make the 120 volts now going from the aquastat to the oil burner, simply flip a switch that I could hook up to the electric boiler connection and close that circuit the same way a thermostat would.

Would this do that?:

http://www.pexsupply.com/Honeywell-...ching-Relay-w-Internal-Transformer-11013000-p

If not, then what? Something cheaper/better?

(I'm knowing just enough about this stuff to be dangerous....)

When the thermostat for the propane furnace calls for heat, the burner or bar is ignited. When the air in the plenum reaches a set point, the "fan limit switch" turns the fan on. When the room gets to temperature, the thermostat turns the burner or bar off and when the heat is dissipated from the plenum, the "fan limit switch" turns the fan off.
When the second thermostat for the hot water side calls for heat, the thermostat turns the circulator on and the hot water heats the heat exchanger in the furnace plenum. When the air temperature in the plenum reaches a set point, the "fan limit switch" turns the furnace fan on. When the room gets to temperature, the thermostat turns the circulator off. When the heat is dissipated from the furnace plenum, the "fan limit switch" turns the fan off. The furnace "fan limit switch" may not be set low enough to respond to the hot air from the hot water heat exchanger and may require a parallel switching. An example would be the limit switch ( pictured earlier ) that snaps onto the hot water pipe leading to the heat exchanger.

Your second thermostat could be powered by a Honeywell RA 832 Relay or similar relay. This relay would switch your circulator on and off as well as the parallel limit switch for the fan.
If you do not want the water from storage to circulate to the plenum heat exchanger - say below 140 degrees - the line voltage from the relay to the circulator would be switched by an aquastat in your storage tank.