HX pump control

[bowsky64x]

Ok so A big thanks to everyone who has helped me along my path to storage. For those of you who are not familiar with my issue
it is that I use a water to air heat exchanger. I was stuck on the idea that I have to have hot water at my air handler at all times. That makes it
impossible to store water without mixing it up at all times. So Now I have read and understand how to plum a system with storage but it would require me
to somehow turn my pump on and off when my house calls for heat. So I have 2 questions.
1 , How do I control the pump, I would guess that there is a control box I can buy that will take a input from my house thermostat and turn my pump on and off.

2 my house is 400ft round trip of 1' A pex . would there be any major issues with letting the water sit and cool in the lines between calls for heat.

Once again, I wouldn't be heating with wood without this forum. thanx

 

[taxidermist]

If you have storage you can use your 2nd pump to turn on and off when your thermostat calls for heat. I have mine this way but my DHW cools off with my side arm because there is no water circulating to keep my DHW hot. I am going to switch my DHW sidearm to a plate HX with a flow switch and a small pump so I can have on demand hot water.


Rob

 

[leaddog]

Ok so A big thanks to everyone who has helped me along my path to storage. For those of you who are not familiar with my issue
it is that I use a water to air heat exchanger. I was stuck on the idea that I have to have hot water at my air handler at all times. That makes it
impossible to store water without mixing it up at all times. So Now I have read and understand how to plum a system with storage but it would require me
to somehow turn my pump on and off when my house calls for heat. So I have 2 questions.
1 , How do I control the pump, I would guess that there is a control box I can buy that will take a input from my house thermostat and turn my pump on and off.

2 my house is 400ft round trip of 1' A pex . would there be any major issues with letting the water sit and cool in the lines between calls for heat.

Once again, I wouldn't be heating with wood without this forum. thanx

PM sdrobertson as he has a similar system and uses a pump with a sensor to vary the speed so he returns water to the tank at a lower temp so doesn't mix. It works very well for him. It may take a couple days for him to get back because of his schedule but he will.
leaddog

 

[pybyr]

Use a single-zone switching relay control (Google it to see some options) to turn on the pump to send the water to the air HX.

Then put a temperature control switch of some sort on the air HX to turn the blower on once the HX has come up to temperature. I use a Johnson Controls A419. That way (as compared to switching the blower along with the circulator) you don't start moving cold air while you wait for the HX to warm up, and you also extract the remnants of heat from the HX when the circulator turns off.

 

[bowsky64x]

Now that is a great idea pybyr. That would simplify the setup and would be the most efficient. THanks very much for the info. I am starting to get my head wraped around how this will work.
Any issue with letting the water in the lines cool between operation.

 

[ewdudley]

Any issue with letting the water in the lines cool between operation.

You're going to lose some heat into the ground any time you're pumping hot water through there. If you stop pumping between cycles the water will cool off as much as it's going to, but that's just the cost of doing business.

If you control the air-side to not run the fan until the HX is up to temp, then cool water in the line just means you'll have to wait for the hot water to arrive before the fan starts. 200ft one inch PEX would be about 7 gallons, so maybe a minute or so. Certainly preferable to running the pump full time and losing heat constantly at the highest rate possible on both supply and return.

--ewd

 

[rkusek]

If you have storage you can use your 2nd pump to turn on and off when your thermostat calls for heat. I have mine this way but my DHW cools off with my side arm because there is no water circulating to keep my DHW hot. I am going to switch my DHW sidearm to a plate HX with a flow switch and a small pump so I can have on demand hot water.


Rob

If you added a small pump(bronze or stainless with a check valve) to the potable side of your sidearm would that help give you all hot water you need and not require constant boiler water flow. Overheating the water a little but with a mixing valve like Nofossil uses would also help keep up with demand I would think. I'm no expert but I wonder why nobody ever just puts a small pump on the sidearm instead of going to a flat plate setup that seems to be expensive. I'm not heating DHW yet but plan to someday.

 

[rkusek]

Ok so A big thanks to everyone who has helped me along my path to storage. For those of you who are not familiar with my issue
it is that I use a water to air heat exchanger. I was stuck on the idea that I have to have hot water at my air handler at all times. That makes it
impossible to store water without mixing it up at all times. So Now I have read and understand how to plum a system with storage but it would require me
to somehow turn my pump on and off when my house calls for heat. So I have 2 questions.
1 , How do I control the pump, I would guess that there is a control box I can buy that will take a input from my house thermostat and turn my pump on and off.

2 my house is 400ft round trip of 1' A pex . would there be any major issues with letting the water sit and cool in the lines between calls for heat.

Once again, I wouldn't be heating with wood without this forum. thanx

Many ways to go with this. I'm currently working through my own solution just as you are. Just want to throw in my two cents.
I have about 330' of 1 1/2" underground pex (660' round trip) and no storage (yet) with an EKO 40.
Right now I am keeping the UG pex hot all the time and just cycling the blower with a 2nd thermostat set 2-3 degrees warmer than the heat pump.
Even though buried the pex 4-5 feet (42" frost line here) to have it somehow freeze would be a disaster. I think a guy could hook some sort of timer that would make sure they pump ran for 60 sec every 30 minutes to prevent this it would be wise. I would consider tying the pump to the thermostat if I did this.
I bought a Johnson Controls A419 (like Prbyr has) but use it to sense the temp on my incoming Pex line. If water is >130 degrees the relay closes on the A419 and energizes the coils on a DPDT relay. One side of this DPDT connects the heat request wire from my 2nd thermostat (24vac) to the blower relay coil wires and the other entergizes the circ between the hot UG pex loop and my HZX. So basically it is like turning the fan to the ON position instead of AUTO. When the boiler water is cold the A419 is open and nothing happens until temps cool a couple degrees and the Heat Pump thermostat kicks in.

Prbyr is using the A419 to delay his fan until the HX lines are hot and then continue blowing air after pump shuts off until the water in HX cools beyond useful temp. Most gas furnaces use a sensor to do the same thing. On my own I found out that my heat pump furnace has a fixed delay from solid state timer than runs the fan about 30 seconds after the heat pump quits.