Danfoss Return Water Protection Location Question

[Coal Reaper]

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?

shouldnt air elimination be on hot side of boiler?

 

[Coal Reaper]

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

yes, and isolate it so it doesnt kick on circs that are not calling for heat.

 

[ewdudley]

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

Everything on the right of your 25 Sep 3:11 drawing stays the same except might need a check valve in shop circuit.

The boiler loop circulator would run all the time whenever the boiler is burning. I would say you'd want at least 15 gpm, so a 007, 15-58, small Alpha or Stratos.

(If you have room, a 30 or 100 gallon propane tank could take the place of the rightmost pipe in my drawing, which would give you some buffering to help with short-cycling the boiler.)

 

[avc8130]

Everything on the right of your 25 Sep 3:11 drawing stays the same except might need a check valve in shop circuit.

The boiler loop circulator would run all the time whenever the boiler is burning. I would say you'd want at least 15 gpm, so a 007, 15-58, small Alpha or Stratos.

(If you have room, a 30 or 100 gallon propane tank could take the place of the rightmost pipe in my drawing, which would give you some buffering to help with short-cycling the boiler.)

Would the boiler circulator run whenever there was a call for heat, or just whenever the boiler was firing?

ac

 

[ewdudley]

Would the boiler circulator run whenever there was a call for heat, or just whenever the boiler was firing?

ac

Both. I believe the following would be simple and correct, but there may be a better way:

"Boiler-call-for-burn" would go active when boiler supply temperature descends below (for example) 150 degF and would go inactive when boiler supply temperature rises above (for example) 185 degF. Boiler goes idle when boiler-call-for-burn goes inactive.

"Load-call-for-heat" would be active when any zone is circulating.

Boiler primary loop circulator would need to run whenever boiler-call-for-burn or load-call-for-heat is active. Ideally it would also run for a couple minutes after boiler-call-for-burn goes inactive.

 

[Coal Reaper]

Would the boiler circulator run whenever there was a call for heat, or just whenever the boiler was firing?

ac

I WOULD THINK CALL FOR HEAT
I THINK AQUASTAT FOR WGs IS IN A WELL, NOT ON THE RETURN

 

[avc8130]

Both. I believe the following would be simple and correct, but there may be a better way:

"Boiler-call-for-burn" would go active when boiler supply temperature descends below (for example) 150 degF and would go inactive when boiler supply temperature rises above (for example) 185 degF. Boiler goes idle when boiler-call-for-burn goes inactive.

"Load-call-for-heat" would be active when any zone is circulating.

Boiler primary loop circulator would need to run whenever boiler-call-for-burn or load-call-for-heat is active. Ideally it would also run for a couple minutes after boiler-call-for-burn goes inactive.

What is the benefit to running the circ when the "call for burn" is occurring? Better mixing of the boiler water? Less stratification in the boiler itself?

I think it would just about always run after the call for burn as chances are there would still be a "call for heat" from one of the zones.

ac

 

[avc8130]

So this would be the "proposed" setup with a 007 as the circ?

I could then use my current 007 from my "zones" and replace that with a Bumblebee for a more efficient distribution of heat probably.

ac

 

[ewdudley]

What is the benefit to running the circ when the "call for burn" is occurring? Better mixing of the boiler water? Less stratification in the boiler itself?

Right. When boiler is burning need to move heat away from top of boiler, and mixing the boiler gives you longer burn cycles.

I think it would just about always run after the call for burn as chances are there would still be a "call for heat" from one of the zones.

No need to leave things to chance. Boiler primary circuit needs to run for either of two independent reasons: to bring heat to closely spaced tees where the load circuits can draw from; and to bring the whole boiler mass up to temperature during each burn cycle.

Latest proposed drawing is missing the right hand end of the boiler primary loop and the closely spaced tees that the load manifolds connect to.

Also, Bumblebees have their uses, but for multiple zone valves an isobaric pump like a Grundfos Alpha or Wilos Stratos would be the better choice.

 

[Fred61]

I have poor eyesight and don't have the best screen on my laptop but I think I see your Danfoss is not oriented correctly on your drawing. Unless things have changed with the danfoss, the bypass normally would be connected to the center tapping with the thermostat bulb oriented toward the boiler side. It can only be installed one way in order to work. You don't have multiple choices.

 

[ewdudley]

I have poor eyesight and don't have the best screen on my laptop but I think I see your Danfoss is not oriented correctly on your drawing. Unless things have changed with the danfoss, the bypass normally would be connected to the center tapping with the thermostat bulb oriented toward the boiler side. It can only be installed one way in order to work. You don't have multiple choices.

(Although the thread keeps mentioning Danfoss, that looks like a drawing of a Termovar lifted from the Tarm reference designs, they're oriented differently than Danfoss.)

 

[avc8130]

Right. When boiler is burning need to move heat away from top of boiler, and mixing the boiler gives you longer burn cycles.

No need to leave things to chance. Boiler primary circuit needs to run for either of two independent reasons: to bring heat to closely spaced tees where the load circuits can draw from; and to bring the whole boiler mass up to temperature during each burn cycle.

Latest proposed drawing is missing the right hand end of the boiler primary loop and the closely spaced tees that the load manifolds connect to.

Also, Bumblebees have their uses, but for multiple zone valves an isobaric pump like a Grundfos Alpha or Wilos Stratos would be the better choice.

Oh, so I would have to replumb all of my current stuff into a "close T" configuration off the boiler loop.

I was hoping to avoid that.

PS: The orientation of the thermostatic mixing valve is just shown for reference/location. Whatever valve I chose would be installed in its proper orientation. If I tried to draw that schematic to actual locations it would by hysterical.

ac

 

[ewdudley]

Oh, so I would have to replumb all of my current stuff into a "close T" configuration off the boiler loop.

I was hoping to avoid that.

An alternative would be to go past the last load supply point, tee in, and run a line from there to a point [edit:] before the first load return and put a check valve in that line.

 

[avc8130]

An alternative would be to go past the last load supply point, tee in, and run a line from there to a point past the last load return and put a check valve in that line.

I have drawn a more "clean" version of what I have and what needs to be added for the return protection.

Where on this would the line/check valve go?

ac

 

[ewdudley]

I have drawn a more "clean" version of what I have and what needs to be added for the return protection.

Where on this would the line/check valve go?

ac

I think you could come straight from the inlet of the third load pump back to the mixing valve. However without sufficient resistance from a weighted check valve or a zone valve there will be non-zero flow through the shop and DHW circuits even when their respective circulators are not running.

 

[avc8130]

I think you could come straight from the inlet of the third load pump back to the mixing valve. However without sufficient resistance from a weighted check valve or a zone valve there will be non-zero flow through the shop and DHW circuits even when their respective circulators are not running.

With valves...

 

[ewdudley]

With valves...

Tada! Close the thread, quick!

 

[avc8130]

Tada! Close the thread, quick!

Hey man, I just wanted to thank you for the help and bearing with me.

This "final" schematic won't be that tough for me to implement. I'm probably going to wind up using what I had originally planned for my "shop" as the loop for the mixing valve and just adding the shop back in where it makes sense the most. The check valve will be pretty easy and I just have to add one to my current DHW setup.

ac

 

[avc8130]

Tada! Close the thread, quick!

Wait! Open it back up!

Quick question:

Would Integrated Flow Check circ pumps work rather than having a check valve on each pumped loop?

ac

 

[ewdudley]

Wait! Open it back up!

Quick question:

Would Integrated Flow Check circ pumps work rather than having a check valve on each pumped loop?

First of all, now that I think of it, don't need to worry about parallel flow through the DHW indirect. It's no-harm no-foul, assuming you're going to be tempering the indirect DHW tank output anyway, as you would need to for fail-safe code compliance.

For the shop circuit, without running the numbers, I think it's fair to speculate the pressure drop of 15 gpm or so running through the supply-to-return-bypass-check-valve-section -- i.e., from P-1 inlet to shop circuit return -- would be small enough not to open either a weighted check valve or an 'Integrated Flo-Chek'. Worst case is you'd need to add a zone-valve to the shop circuit down the road, but it's unlikely the piddling amount of 'unwanted' heat going that direction would be a problem to begin with.

 

[avc8130]

First of all, now that I think of it, don't need to worry about parallel flow through the DHW indirect. It's no-harm no-foul, assuming you're going to be tempering the indirect DHW tank output anyway, as you would need to for fail-safe code compliance.

For the shop circuit, without running the numbers, I think it's fair to speculate the pressure drop of 15 gpm or so running through the supply-to-return-bypass-check-valve-section -- i.e., from P-1 inlet to shop circuit return -- would be small enough not to open either a weighted check valve or an 'Integrated Flo-Chek'. Worst case is you'd need to add a zone-valve to the shop circuit down the road, but it's unlikely the piddling amount of 'unwanted' heat going that direction would be a problem to begin with.

I was kind of wondering about that. With how long the run is to the shop I would have figured the pressure drop would have prevented flow. The old "path of least resistance" thing. The house zones are already zone-valved.

I currently do not temper my indirect water so that is a consideration.

ac

 

[ewdudley]

I was kind of wondering about that. With how long the run is to the shop I would have figured the pressure drop would have prevented flow. The old "path of least resistance" thing. The house zones are already zone-valved.

I currently do not temper my indirect water so that is a consideration.

No, it's not the path of least resistance, it's all the paths of equal resistance. Pressure drop is a function of flow rate, so if water sees parallel paths will always flow to all alternative paths and the rate of flow through each path will 'adjust itself' to equalize the pressure drop through all paths.

Unless there is some thresholding mechanism in play that stops any flow through a particular path until that threshold pressure is reached. This is what weighted check valves and IFCs provide. It takes on the order of one psi to open a WCV or an IFC. They are designed to stop gravity flow through a circuit when the circuit pump is turned off, but when there is some other pump that might or might not pop open the valve it gets tricky to figure out what's guaranteed to happen or not happen.

 

[avc8130]

No, it's not the path of least resistance, it's all the paths of equal resistance. Pressure drop is a function of flow rate, so if water sees parallel paths will always flow to all alternative paths and the rate of flow through each path will 'adjust itself' to equalize the pressure drop through all paths.

Unless there is some thresholding mechanism in play that stops any flow through a particular path until that threshold pressure is reached. This is what weighted check valves and IFCs provide. It takes on the order of one psi to open a WCV or an IFC. They are designed to stop gravity flow through a circuit when the circuit pump is turned off, but when there is some other pump that might or might not pop open the valve it gets tricky to figure out what's guaranteed to happen or not happen.

Gotcha. So realistically to be "safe" I should be using zone valves on my indirect and shop loops.

 

[ewdudley]

Gotcha. So realistically to be "safe" I should be using zone valves on my indirect and shop loops.

I would definitely not bother. The amount of unwanted flow will likely be none if the IFCs do the trick, or very little if there is enough head to force some flow.

For now I would simply identify where a zone valve would go if it was needed and then wait and see if there's actually a problem.

For the shop I assume there will be a ball valve that can be used to shut if off entirely when not actively heating, and a small amount of idle flow won't hurt anything when you are heating the shop.

As for DHW, without a tempering valve you already run the risk of overheat due to some failure mode or another, so another small risk doesn't worsen the situation much.

 

[avc8130]

Is the Danfoss the "best" or should I be looking at Termovar or others?

ac