Water circulation loop ?

[Dave B.]

Sorry if this seems so simple to some but I keep going round and round with this question and several related having to do with pressurized and non-pressurized water circulation loops. Using this simple sketch as an example the question is : will this water circulate as indicated ? The standard tank is closed the larger tank is open. I say it should and with that answer I can answer many other combinations myself. I'm not lazy but with no means of decent lab equipment for experimentation I really don't want to tear down my own plumbing for testing several different combinations of circulation loops. Yes, I have googled and learned much but I always seem to convince myself it will and it will not work when it comes to certain plumbing combinations, most confusing being open and closed loop and pump locations. Thanks for a little direction on this.  Dave B. 

[Wolvenar]

Don't take what I say as expert opinion, it's just the way that's been successful for me thus far.

I have ( simplified )  a system of both an open unpressurized heat storage tank, and a closed system with expansion tank, air bleeder, and secondary circulation pump. So I have had to plan for the worst of both worlds, but its not all really that complex.
At least its working ok circulation wise for me.

Are you planning a secondary circulation system, or do you plan to place the radiator loops in this as well, it could make a big difference.

In this system in the image if it used as it appears without the circulation moving through circuits that radiate heat,
I would place the pump in the lowest output of the open tank

The pump would then fill the water heater on it's (water heater's) lowest input or anything other than the top most out of the water heater. It might also be a plus for keeping air from building in the hot water heater if the filled water level of the large storage tank was higher than the water heater by at least some measure.

This kind of setup should minimize priming and air collection.
There is debate over if this loads the pump more because of the cooler water temp,
but then there is the argument that the pump will stay cooler so its windings are not as stressed.
I'm not an expert, I just go by whats working for me.

[Wolvenar]

To answer the first question, will it work as pictured.
The system may work, particularly if the open ( larger ) tank water is higher than the water heater and the pump.

It has a couple risks, mostly if the larger tanks water level is lower than the pump, or heating elements.
In a fully closed system, these concerns seem to be lessened, and pump placement can be more determined by other factors.
This may be more prone to air lock too, again just my opinion.

[ghurd]

I agree with Wolv, especially the purpose, distances and placements of the other parts are unknown.

If there is no reason to have the left red side with pipe going down in the U shape where the pump is shown, then keep all the red pipe going up.

Also, depending on how long the 'mostly horizontal' pipe runs are, may be a great idea to install automatic burpers at the highest point in the runs.  Expensive little buggers, and prone to failure with hard water.
In some open systems, can get away with just a T with a tall open vertical pipe at the high point (top right corner of the red pipe).

If it is for a RE dump load, to store heat somehow, might be able to pull it off with no pump at all.
G-

[frackers]

Take a look at the website http://www.deals4homes.co.uk/diyprojects/centralheating.htm.

 

This is the correct way to do it in the UK (i.e. complies with local code), note the positioning of the vents with respect to the pump & feeds.

YMMV

[Dave B.]

 Thank you for the feedback. I am using the open tank for heat storage from my solar thermal system. There is a heat exchanger coil in the tank for that transfer (closed loop) as well as another coil heat exchanger straight through from my cold water supply to heat my DHW.

 The idea here is to use the electric tank to suppliment the large tank temperature when the solar large tank temp drops below a certain level. In effect adding another 50 gallons of heat storage. (many options to circulate this, time and temp etc.) Often the large tank temp will rise and be well above the low set point of the standard tank, if not the standard tank will act as the heat source to keep the system storage from going below a certain temp.

 I can put the pump any where in the system and I was thinking right on top of the standard tank. I guess my question is if there is an ideal location in the system for the pump and basically if my idea is sound ? Total loop will be no more than 50' and highest rise from the floor maybe 7'.

 Thanks to anyone for the help.  Dave B.