Danfoss Return Water Protection Location Question

[avc8130]

Does there have to be a pump between the boiler and either the Danfoss valve or the crossover between the supply/return?

Or can the pumps be located outside of that square?

The picture I attached shows what I am talking about.

I ask the question because the way my plumbing is done currently makes the config on the right MUCH easier. In fact, I am not even sure I can do the config on the left.

ac

 

[ewdudley]

The pump can go either after the mixing valve and before the boiler on the return line into the boiler, or it can go after the boiler and before the bypass crossover tee on the supply line leaving the boiler (as shown in left hand drawing).

Most often it's on the return line because may as well let the pump have cooler water to pump in order to be cooler, although manufacturers of modern pumps quote maximum fluid temperature limits way up over 200 degF and we can probably take their word for it. Advantage of having pump on supply line would be that if air eliminator is placed between boiler and pump then air eliminator sees slightly less pressure and could work a little better, FWIW. I think convenience is more important than either of these considerations.

In drawing on right, consider situation where mixing valve is cold. When mixing valve is cold then the port coming into mixing valve from the crossover is open and the port coming into mixing valve from system/storage is nearly or completely closed. When port from system/storage is nearly or completely closed then pump in right hand drawing can push little if any water and boiler will (hopefully) shut down on high limit.

 

[avc8130]

The pump can go either after the mixing valve and before the boiler on the return line into the boiler, or it can go after the boiler and before the bypass crossover tee on the supply line leaving the boiler (as shown in left hand drawing).

Most often it's on the return line because may as well let the pump have cooler water to pump in order to be cooler, although manufacturers of modern pumps quote maximum fluid temperature limits way up over 200 degF and we can probably take their word for it. Advantage of having pump on supply line would be that if air eliminator is placed between boiler and pump then air eliminator sees slightly less pressure and could work a little better, FWIW. I think convenience is more important than either of these considerations.

In drawing on right, consider situation where mixing valve is cold. When mixing valve is cold then the port coming into mixing valve from the crossover is open and the port coming into mixing valve from system/storage is nearly or completely closed. When port from system/storage is nearly or completely closed then pump in right hand drawing can push little if any water and boiler will (hopefully) shut down on high limit.

That was my fear. My system currently has 3 separate circulator pumps (DHW, House Zones, Shop) and I'm just not sure how I can get it setup to have the pump between the boiler and the Danfoss on either the supply or the return.

ac

 

[avc8130]

Any chance a check valve would work by the ball valve to only allow the flow to go INTO the Danfoss from the T on the supply?

ac

 

[ewdudley]

Any chance a check valve would work by the ball valve to only allow the flow to go INTO the Danfoss from the T on the supply?

ac

I like it, that's pretty clever, but we know that if you're clever enough to come up with that you must already know the unfortunate answer.

 

[avc8130]

I like it, that's pretty clever, but we know that if you're clever enough to come up with that you must already know the unfortunate answer.

I figured...

Is it possible to have boiler protection when using multiple circulator pumps?

ac

 

[ewdudley]

I figured...

Is it possible to have boiler protection when using multiple circulator pumps?

ac

With or without storage?

 

[maple1]

Can you reduce your three pumps to just one & put it where it needs to go, tying all your heat call signals to the one pump?

Or are you zoning by pump as well? If so maybe swap a pump for a zone valve at two of the three places?

I've got two pumps - one for moving from boiler to storage when burning, and the other does all my loads.

Actually three, but the third is on my backup electric boiler and only ran one day last winter.

The newer variable speed pumps are sweet units for multiple zones - might reduce your power bill some too.

(Thinking out loud...)

 

[avc8130]

With or without storage?

No storage.

 

[arbutus]

Is the difficulty with fitting the piping in the current space or is it with the overall plumbing layout?

If it is overall layout can you make the boiler circulator and return protection part of a primary secondary system?

 

[avc8130]

Can you reduce your three pumps to just one & put it where it needs to go, tying all your heat call signals to the one pump?

Or are you zoning by pump as well? If so maybe swap a pump for a zone valve at two of the three places?

I've got two pumps - one for moving from boiler to storage when burning, and the other does all my loads.

Actually three, but the third is on my backup electric boiler and only ran one day last winter.

The newer variable speed pumps are sweet units for multiple zones - might reduce your power bill some too.

(Thinking out loud...)

Maybe.

My system is very unique so let me try to explain. All pumps are on the supply side. I have 3 "loops".

1. Indirect DHW. This is fed from supply and has a small TACO circulator pump. The return T's in just after the house zones.
2. House zones. There is a 007 right AFTER the indirect T which feeds 5 zones with zone valves.
3. Shop. This isn't installed just yet but the "future" hookup is right out of the boiler and returning after the others. I'm not 100% I like this as it will steal priority water from the house unless I do some other controls.

I don't know about using 1 pump. I could probably replace the indirect and house setup with a Bumblebee or similar, BUT the run to the "shop" will be 150' of underground pipe to an 18x18 heat exchanger. I don't think I can do that AND the whole house with 1 pump reasonably.

Please continue to think out loud. It's the best way to get complex problems like this sorted!

ac

 

[ewdudley]

I figured...

Is it possible to have boiler protection when using multiple circulator pumps?

ac

One way would be to add a boiler loop pump and have one crossover pipe as shown in left diagram (with boiler loop circulator on supply or return), and another crossover further to the left. Then connect all load pumps to draw from closely spaced tees on the leftmost crossover. Could use a single pair of closely spaced tees if the load circuits are check-valved correctly.

This Greenwood design would be schematically equivalent to what I'm describing:

 

[avc8130]

One way would be to add a boiler loop pump and have one crossover pipe as shown in left diagram (with boiler loop circulator on supply or return), and another crossover further to the left. Then connect all load pumps to draw from closely spaced tees on the leftmost crossover. Could use a single pair of closely spaced tees if the load circuits are check-valved correctly.

I'm going to try to draw out my current plumbing arrangement this evening, along with a few pics.

I really appreciate the help!

ac

 

[avc8130]

Here is what I currently have using my best MS Paint skills. Thanks to Tarm for the figures.

ac

 

[Coal Reaper]

you have a woodgun, an oversized WG knowing that you were going to add heat to shop. and no storage. only want to heat shop to 55* most of the time. why not tie the barn loop into the other side of the woodgun independent of the house loop (assuming multiple in/out ports, or T off). use the woodgun itself as sort of a buffer so the two loops dont interfere with eachother. water to air heat exchanger with thermostat controlled fan in barn, right? use a set-point pump such as bumblebee with ECM motor. put a switch on this circ and run it constant through the time that you will need heat out there. perhaps only three months out of the heating season since you only want 55*. dont guys do this for in floor heat? the ECM motor will draw very little power and you wont need to worry about return water protection on that loop since your setpoint can be above 140*. thermostat kicks fan on, return temp to set-point falls and the circ increases hot water going out there with no warmup period, only 150' worth of lag. you go out there to work on something and want it warmer and it is real quick to react when you adjust thermostat. also, no control wires needed between house and shop. in fact you can even have that pump in the shop. do need well insulated underground pipes. now you can move the pump on house loop to where it should be to do return water protection, like everybody else does. i wonder if i splained what i am thinking clearly enough...

 

[avc8130]

What about plumbing in a T after each circulator pump and tying them all into the "supply" side of the Danfoss. Then mount the Danfoss right before the boiler on the return.

ac

 

[maple1]

That won't move water around your bypass loop.

Will it?

It also wouldn't move water through the supply side of the Danfoss with the cold water a pump would send it on a zone opening.

Would it?

 

[Fred61]

The hot water circulating through the bypass is what activates the Danfoss. You must have an adequate flow in order to open the thermostat. When the water circulating through the bypass reached the temperature value of the thermostat within, it starts to open and the colder water from the system starts to flow and mix with the hotter water circulating within the recirculating loop.

The thermostat at that point could actually pulsate as the colder water hits the sensing bulb on the automotive thermostat. When the water returning from the loop reaches the value of the thermostat it will stay at its fully open position. If a slug of cold return water passes through the Danfoss it will close and will again depend on the bypass water to open it again. It is important to have the circulator either on the supply or the boiler side of the danfoss in order to maintain flow through the bypass.

 

[maple1]

My thinking also was it is best to have the pump right before the boiler inlet on the return, or I guess just downstream of the Danfoss, so it would pull all the water through it no matter which way the thermostat was needing the flow to go.

 

[avc8130]

So the thought is that without a pump within the "loop" between the boiler and the Danfoss there just won't be any flow. So I either need to figure out how to get the current pumps between the Danfoss and the boiler, or figure out how to add another pump.

What about this?

 

[ewdudley]

Here is what I currently have using my best MS Paint skills. Thanks to Tarm for the figures.

ac

Just add a circulator and make a boiler primary loop.

 

[Fred61]

Wow! Having a little trouble getting my head wrapped around it. Confused right now! Gotta go right now but will be thinking about it

 

[maple1]

So the thought is that without a pump within the "loop" between the boiler and the Danfoss there just won't be any flow. So I either need to figure out how to get the current pumps between the Danfoss and the boiler, or figure out how to add another pump.

What about this?

That might work.

Quite the spiderweb though - kinda like mine in places.

 

[ewdudley]

So the thought is that without a pump within the "loop" between the boiler and the Danfoss there just won't be any flow. So I either need to figure out how to get the current pumps between the Danfoss and the boiler, or figure out how to add another pump.

What about this?

Would work when one or more loads are calling, but I think you need to maintain constant flow through the boiler when it is active and boiler supply is above what is called the 'launch temperature'.

 

[avc8130]

Just add a circulator and make a boiler primary loop.

Would that require any other reconfiguring or would I be able to just add the circulator and valve? In other words, do I have to reconfigure all of my loads to close T or anything?

I guess I would have to wire that circulator so it was running any time any other load was running? I could probably use a ridiculously small circulator?

ac