Circulator questions / tuning

[MrEd]

Question,

As I have stated in another thread, I am up and running with my tarm, (storage I am still waiting for a part before it can come on line).

I am using a modified version of the "simplest pressurized", in particular I have two circs)Grundfos 15-58 3 speed w/IFC), one on the back of the tarm, and one after the "T" that pulls from either storage or tarm. So, if any zone is open, both circs are running. Right now I have them both on "high", but theoretically I have 9 different combination I could use (LL,LM,LH,ML,MM,MH,HL,HM,HH).

What is the different things that come into play when choosing the settings? In other words, without actually trying all different settings and then monitoring the results, what "symptons" might I see in the performance of my system that would cause me to want to speed up or slow down on or both of the circs?

 

[stee6043]

I'd say one simple way for you to get an idea of which setting to use would be to put temp guages at both the in/out on your heat zone loop. Play with the speeds until it looks like you're getting the best heat transfer at your zone. You want to maximize your temperature drop without the return dropping below 150 or so. That's just my guess though.

As far as your main circ - as slow as possible but still enough to move your heat to storage when the zones aren't calling for heat. Lower speeds burn less juice. So go as slow as you can without idling the boiler. Again, just my thoughts...

 

[Nofossil]

Question,

As I have stated in another thread, I am up and running with my tarm, (storage I am still waiting for a part before it can come on line).

I am using a modified version of the "simplest pressurized", in particular I have two circs)Grundfos 15-58 3 speed w/IFC), one on the back of the tarm, and one after the "T" that pulls from either storage or tarm. So, if any zone is open, both circs are running. Right now I have them both on "high", but theoretically I have 9 different combination I could use (LL,LM,LH,ML,MM,MH,HL,HM,HH).

What is the different things that come into play when choosing the settings? In other words, without actually trying all different settings and then monitoring the results, what "symptons" might I see in the performance of my system that would cause me to want to speed up or slow down on or both of the circs?

I'm not sure that I understand what's 'modified' in this case. Does the circ on the back of the Tarm run even when the Tarm isn't providing heat?

The intended balance is that the circulator for the wood boiler should provide a flow rate appropriate for the output of the boiler. Rough rule of thumb would be 1 gpm for every 10,000 BTU/hr. That will result in a roughly 20 degree temperature rise through the boiler.

By the same token, the load circulator should be sized based on the heat load and desired temperature drop. In a zone valve based system, the zone valves provide a good deal of flow restriction, so the load circulator will be at a different point on its operating curve depending on how many zone valves are open.

Again, about 1 gpm for every 10,000 btu/hr will give a 20 degree drop. If you can tolerate a higher drop, then a lower flow rate will work and you'll get better storage performance.

You can get a sense of whether things are out of balance by checking return temperatures.The input protection on the boiler will complicate things, but look for a 20 degree rise across the boiler and a 20 degree drop across the zones as a starting point.

Hope this helps.

 

[MrEd]

So, I should measure the temp coming out of the boiler, and then measure it again as it is returning, and if it is more than 20 degrees difference, then what? Turn the pumps up, or turn the pumps down? Can't figure out if moving water faster gets more heat to the baseboards, or moving it slower does. Everything is more-or-less working as planned, the whole house is 72 as I write this, and the boiler hasn't had to idle yet it 2 days of using it, so I think I am not far from an 'optimal' solution. Just trying to figure out the interplay between the two circs, and the consequences of slowing one or both down and/or speeding one or both up.

Still got lots of tweaking to do - most of my controls are all manual right now (i.e. I turn the fan on, I turn the pump or pumps on, I turn them off etc). I wanted to run everything in manual mode as I really got a feel for how things worked. In this way I hope that as I design my control logic I have a much better understanding of what needs to do what, and more importantly why.

 

[Nofossil]

I'm going on my fourth season now, and I'm still making fine-tuning adjustments. Just can't help myself....

If you're seeing a temperature rise of more than 20 degrees through the boiler, then you might want to increase the boiler circ speed. More water per minute will result in less temperature rise and a small boost in efficiency. The upper limit is when the boiler can't raise the temperature enough to be useful.

If you're seeing a temperature drop of more than 20 degrees through the zones, then increasing the load circulator speed will result in less temperature drop and a bit more heat transferred into the zones.

The system will work well over a fairly wide range of settings. Probably the most important idea is that the flow through the boiler should be at least a hair more than the flow through the zones. Typically the output of the boiler is more than the zones can absorb, so that works out well.

 

[deerefanatic]

Ok, here's a question. When I designed my boiler, I was hoping for 320,000 btu's...... I put a 0010 on it and according the the flow curves and my (wild guess) at headloss, I should be flowing 20-26 gpm. Running full-on, my boiler can only achieve about a 10-12 degree rise.... (And I verified this buy doing gpmxrise in temp when I was filling my tank with well water..... The boiler was pushing about 148,000/hr)

So, does it hurt anything to do it this way? I know the 0010 pulls more juice than say, a 007. But, does it hurt boiler performance? Would I be better off with a slower running 007? My pump logic is tuned around the 10 degree rise and therefore cycles the pumps to keep the boiler temp up. I guess what I'm asking is, if I pumped my water slower, would my boiler operate better and push more BTU's? If not, I really don't have the money to be buying different pumps right now.

Thanks!

 

[Nofossil]

Ok, here's a question. When I designed my boiler, I was hoping for 320,000 btu's...... I put a 0010 on it and according the the flow curves and my (wild guess) at headloss, I should be flowing 20-26 gpm. Running full-on, my boiler can only achieve about a 10-12 degree rise.... (And I verified this buy doing gpmxrise in temp when I was filling my tank with well water..... The boiler was pushing about 148,000/hr)

So, does it hurt anything to do it this way? I know the 0010 pulls more juice than say, a 007. But, does it hurt boiler performance? Would I be better off with a slower running 007? My pump logic is tuned around the 10 degree rise and therefore cycles the pumps to keep the boiler temp up. I guess what I'm asking is, if I pumped my water slower, would my boiler operate better and push more BTU's? If not, I really don't have the money to be buying different pumps right now.

Thanks!

No - lower temp rise is actually more efficient. If designing from scratch, you might not want to buy the bigger circ, but it hurts nothing except fro drawing a bit more power. In testing the EKO 80 for max efficiency, they pump 36 GPM through it with a very small rise.

 

[deerefanatic]

Ok- Cool.