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[muffin]

I am having an issue with my flow.  Attached is my plumbing diagram.  The pump that runs the house Hx runs 24/7.  The pump at the boiler also runs 24/7 and is a Grundfos 26-99 I think.  The problem is that when the pump running the Pool exchanger is off, I am still seeing some flow through that loop.  That causes a problem because when the pool pump is off, then this exchanger get very hot which is bad for the PVC the pool is plumbed with; as well as the filter and sanatizer.  Any thoughts as to what I have done wrong?  I have tried to draw it as close to representative as possible as far as tee positions and distances.

Thanks

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[yoderheating]

 Its going to be normal to get some flow through that loop when the pump on the stove is on and putting pressure on all the water lines. It looks like the shortest way for water to get from the pump on the stove back to the stove is through the pool heat exchange. Water will naturally flow through the place of least resistance.
 Several things you can do. You could try adding another check valve in line on the pool loop, I have found that adding several places with slight resistance will greatly reduce unwanted flow. You could add a valve that you keep closed when the pool is not in use. However what I would do if I was installing the system was to put in a zone valve that would open automatically at the same time the pool pump is turned on.

[dwneast77]

I agree with yoder and intheoaks.   You could get away with a simple zone valve.  In my initial setup I did something very similar using regular zone valve as per my dealers suggestion feeding baseboard in my greenhouses.  However, I used a 007 "Priority" pump, in that you wired the thermostat (or aquastat in your case) and zone valve directly to the pump using also a 24V transformer.  I would suppose that if your pump didn't have that option, I would think you could wire the 24V transformer in with the pools circulator pump so when your pump is running the transformer would be powered thus powering the zone valve???  Anyone else have thoughts on that one??   Makes sense to me.  If you are worried about any lines freezing from sitting idle too long, or if it's a relatively long run, I would definitely use the 3-way zone valve (same wiring scenario) located near the pool. 

[RSI]

All you need to do it put both pipes to the pool heat exchanger in the same pipe and as close together as possible.

[yoderheating]

You don't want a three way zone valve because that would divert water away from something else. A line voltage two way valve would do, just wire it in with the pump. RSI is correct, if you plumbed both lines into the return line you would most likely solve the issue although I have had one job where I still got some flow though the lines and had to install a valve.

[RSI]

It might also work to just swap out the pump on the pool heater to a grundfos 15-58 with a flow check. It depends on how much is actually flowing through it if it can stop it or not.

[dwneast77]

yoder, he has a seperate pump feeding a designated line for the pool. The suggestion I made was for the 3-way zone valve to be placed next to the pool bypassing only the pool.  The 009 pump running the pool could be left running 24/7, or If the pump and zone valve were electrically connected to run together then the 3-way zone valve would only be bypassing the pool HX. 

To simplify a little, my thought would be 1: run pump 24/7 and use a 3-way zone valve. Simply shut the pump off if the pool is to be shut down at any time, or 2: (and this depends on one thing,  Are aquastats 120V?)  Wire aquastat to run pump (as I think it already is) and add 24V transformer to power regular zone valve.  Both options would stop the ghost flow with no question and neither would interfere with the rest of the system.

[RSI]

That makes no sense to run the pump 24/7 and a 3 way zone valve. If a zone valve were used it would not be a 3  way and get turned on when the pump does.

It should not be needed though. Just both connections in the same pipe or a flow check if left the way it is.

[dwneast77]

It is not in my nature to argue with someone I don't know esp. when I am no expert on the subject, but what I am suggesting is not far fetched.

 A pump running 24/7 with 3-way zone valve is a good solution for this issue if your suggestion of a check valve doesn't work.  This is exactly how my water/air heat exchangers are set up in my house and greenhouses.  I mean, what is the difference??  Nothing except this guy is using, I assume, a plate exchanger. 

My second option was to use a 2-way zone valve (not a 3-way)  in-line with the pump to open when the pump was turned on by the pool aquastat. 

Either option to me is workable.  If there is any concern about cold/freezing pipes, or if it is a long run to the pool, I would say that option 1 would be optimal as it would keep hot water close by the pool and there wouldn't be a blast of cold water rushing back to the boiler when the pool aquastat called for heat. 

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[willieG]

all sugestions will work...but if the pool pump is not running i can only assume you are not using it? if you are not using it  why not just put another ball valve in the line? they are abou tthe cheapest thing you could do (other than the suggestion of both lines to the pool on the same line as suggested by RSI)

[RSI]

I wasn't trying to argue, I just don't understand the reasoning of wanting to run the pump 24/7 if he isn't now. If the pump only runs when it needs to flow a 2 way zone valve would be much better.

Also, I see the pool pump is listed as a 009. What kind of heat exchanger is it and how many feet of pipe and what size? That sounds like a really bad size pump to use looking at the diagram.

[Scott7m]

I wasn't trying to argue, I just don't understand the reasoning of wanting to run the pump 24/7 if he isn't now. If the pump only runs when it needs to flow a 2 way zone valve would be much better.

Also, I see the pool pump is listed as a 009. What kind of heat exchanger is it and how many feet of pipe and what size? That sounds like a really bad size pump to use looking at the diagram.

There sure are a lot of folks that use 009's in questionable situations it seems.  The 009 is designed for a lot of head and a slow flow, not what you need in this situation.

[muffin]

all sugestions will work...but if the pool pump is not running i can only assume you are not using it? if you are not using it  why not just put another ball valve in the line? they are abou tthe cheapest thing you could do (other than the suggestion of both lines to the pool on the same line as suggested by RSI)

The system is automatic so I cannot use a ball valve.  The pump is on a timer and the heating is controlled via a thermostat on the pool water line.  If the pool water gets below the threshold it enables the outlet that the Taco 009 is plugged into. 

I had thought about the 2 tees close on the same line, but would that not chill the water to the rest of the house? 

Perhaps a zone valve or pump with integrated flow control would work.  Also wondering if a spring loaded check valve would work, or 2.  Mine is just a flap.  I have to imagine the flow has very little pressure behind it.  The least flow path should really be right at the beginning where it can simply loop back to the furnace.

[muffin]

I wasn't trying to argue, I just don't understand the reasoning of wanting to run the pump 24/7 if he isn't now. If the pump only runs when it needs to flow a 2 way zone valve would be much better.

Also, I see the pool pump is listed as a 009. What kind of heat exchanger is it and how many feet of pipe and what size? That sounds like a really bad size pump to use looking at the diagram.

I was using it because I had it laying around.  The lines are pretty short, only maybe 15' comprising the whole loop.  All 1" pex.  The exchanger is a shell in tube, 55KBTUs with 1" inlets/outlets as well.  The flow seems adequate.  I see about 10-15* delta across it. 

[Scott7m]

It can do that, u can put a pump on the supply of the first T