dhw and aquastat

[maplewoodshelby]

I'm finally getting the materials to hook up my dhw. I do have a few questions. My boiler has the dhw coil that goes into the back of the stove with two hookups (water going and water coming back in).
I will need to use a pump as my electric water heater is 40 feet away from my boiler. I will be using pex to travel this distance and it will be under the house.
My questions relate to the aquastat and pump
Where and how should the aquastat be used. I know the aquastat will be wired to the pump and tell the pump when to turn on and off but I am confused on when and where. Should it be near the boiler and once the boiler water reaches a set degree it kicks the pump on to circulate (and stays on as long as it is above the set degree) and vice versa if the water at the boiler is not hot it keeps pump off? Or should it be near the (turned off) electric water heater and set that so when the water temp gets low (say 100 Deg) it kicks the pump on?
Also I'm guessing the pex will need to be insulated and do folks use the foam pipe sleeves like used on copper

 

[rowerwet]

I would have the temp switch on the hot water heater to keep it up. Don't know how you would make sure the boiler ran enough to make hot water for the hot water heater. You may want the aquastat to kick the boiler and pump on together all the time. I think this is how a super store works which is what you are making.

Pex doesn't loose heat like copper, but it will loose some so insullation will help.

 

[maplewoodshelby]

Are you saying that I do not need an aquastat and just wire the electric water heater thermostat to the pump. The water in my boiler is always going to be hotter than my water heater as I run 24/7 with no storage so having the boiler ramp up heat is not needed. I just need to figure out the most efficient way to wire my pump

 

[wantstoburnwood]

i have installed a circ pump on my dhw coil hooked up to my water heater tank. I have a strap on aquastat on the loop between oil and wood boilers as the wood isn't always hot set at 155 . And I also have the wires hooked up to the lower thermostat on the water heater so when the water tank gets cool it turns on the circ pump to store hot water. If you use the water heater in the summer as a water heater a DPDT switch to switch from circ pump to water heater elements will make it easier to change from season to season.

 

[maplewoodshelby]

Thanks for the info. I was hoping it would work off the water heater thermostat.

So what I am getting from this is that I do not need an aquastat. Just wire directly to the electric water heater thermostat and when it cools to the set point it will kick on the circ pump.

So I am guessing that the electric water heater will still need power for the thermostat. IS that the purpose of the DPDT switch? It allows the hot water heater thermostat to work without turning on the water heater heating element while using boiler and circ pump.

This probably sounds very simple to most folks but I'm learning as I go. Thanks to this site I have installed (my wood/coal boiler in conjunction with my propane boiler (which has not kicked on once) and heating nearly 5000 sq feet.

also any suggestions on the size pump I need for about a 80 foot run of level 3/4 pex to and from my water heater and do I need a special pump as it is potable water?

 

[wantstoburnwood]

The DPDT switch is so you can set the heater to summer or winter . There is a voltage difference between the heater 220 volt and the circ pump is 115 volt. I have just disconnected the water heater wires for the winter and installed the circ pump wires on the thermostat , so the thermostat only acts as a switch. You'll still need a 115 volt feed to the circ pump. If you install a cast iron circ pump it may fail sooner as domestic water usually is harder than boiler water. I have a taco 006-b4 bronze cartridge pump.