Parallel pump to reduce idle

[goosegunner]

I would like to add an additional pump to my system to increase flow when I get near the end of storage charging. I would control it with an aqua-stat that would activate the pump at a desired supply temp to increase the gpm.

I am thinking about placing a T in the supply line near the boiler and back in before the storage tank.

I need some advice on where to place the T and if there are any drawbacks or concerns.

Some of my concerns are location of new pipe in relation to;

1. Air separator

2. Bypass for Danfoss

I have included a picture with my initial choice.

gg

 

[hobbyheater]

I would like to add an additional pump to my system to increase flow when I get near the end of storage charging. I would control it with an aqua-stat that would activate the pump at a desired supply temp to increase the gpm.]

If you put the second pump in a by pass loop you will need a one way check valve or the flow to storage will take the path of least resistance when just the first pump is working and will just go around in circles at the by pass loop .


Very nice installation!

 

[ewdudley]

Probably first need to plot your piping resistance curve against candidate pump curves to make sure that you need parallel pumps and not series. Probably parallel would give more flow, but it's hard to sure without running the numbers.

And as hh says, need check valves. If the new pump had IFC that would take care of it, but if the first pump fails it would be nice if it had IFC as well for automatic failure mode operation.

The Danfoss has a nice Cv of about 20, IIRC, so not much to be gained by bypassing it. I suppose you could add an EBV to the hot leg of the Danfoss for a positive shut off, but seems hard to justify. As for the air separator is seems like bypassing it from time to time would be harmless, or just move it upstream of the tee-in point if you're worried about it.

But here's something else to consider. I built my system with two parallel pumps from the get-go thinking that would be the trick set up, based on what I had learned here, and it works as expected when storage is heated in two phases.

However I have since decided that the two-laps-through-storage strategy is not preferable and buys you nothing. Now I have simply increased my boiler supply temperature setting to the desired final storage temperature. Then when all of storage is hot instead of idling I shut the draft fan off and let the fire go out.

This one-lap-through-storage-and-done strategy simply gets storage to the desired temperature with no fuss, and if I get the fuel load about right it leaves a nice pile of charcoal for starting the next fire.

 

[hobbyheater]

I would like to add an additional pump to my system to increase flow when I get near the end of storage charging. I would control it with an aqua-stat that would activate the pump at a desired supply temp to increase the gpm.

I had a similar problem. The boiler would start cycling when storage would hit 170 so I went to a pump with about 30% more capacity.
On using a second pump - installing it in a by pass loop at the storage tank on the return side may give better results.

 

[goosegunner]

I have been using a timer to shut off my fan. I try to set it so it leaves coals in the boiler for restarts.

The parallel pump would also serve as a safety if the main pump would ever fail.

I have considered placing it in a bypass off the return line like the picture below.


gg

 

[goosegunner]

My current pump is a Grundfos 26-99 with flow check. I run on low at about 13 gpm through 1 1/2" copper. It keeps hotter water at the top of the tank.

As the the return temp climbs I sometimes put the pump on medium to flow 18 gpm. It reduces idling but I don't like have to switch it. I thought if I had another small pump kick in it would solve the problem on its own.

I was going to use a 15-58 with a flow check for the parallel pump with a 1" cooper bypass line.

gg

 

[Fred61]

I have the Ecoster 2 controller on my Eko which tops out at 180 so I moved the temperature sensor bulb up into the insulation and now only goes into idle at about 210 so when I installed my unpressurized storage I incorporated a copper coil in the bottom of the tank which serves as my overheat dump zone. I installed a well and aquastat in the top (unused tapping) and set it to come on at 200. It returns to the boiler side of the Danfoss and has everything needed for a zone, ie; flow check and air eliminator. I'm running a Taco 007 and the circuit is plugged into a 1500 watt switching inverter. By the time the boiler reaches 200 I don't have to worry about the return temperature being too low. When the circulator launches the rate of temperature climb in the boiler really slows.

I should point out that I do not use the Eko controller to control the main circulator. I am controlling with a Techmar 156 so therefore I am able to view the true temperature of the boiler and also make use of the differential temperature feature which stops the combustion fan at a preset temperature upon cool down. The only thing that is controlled by the Ecoster controller is the max temp which brings the unit to idle which, like I said is now about 210. Other than that, the controller is nothing but an on/off switch.