More info on Low Loss Headers?

Mike T., Swampeast MO

Here's the best diagram I've found. The purpose is to allow secondary flow to exceed primary flow without any chance of increasing the return temperature to the boiler.

Keeping return temperature is low as possible is great for a condensing boiler but not good for many other boilers. I have no idea of the requirements of the heat source(s) you are using. Can you provide links to the actual equipment.

Kind of hard to see, but the 2nd to bottom line reads "T2 = T4". In other words boiler return temperature equals system return temperature.

VERY important to note that the low-loss header ONLY works this way when secondary flow is higher than primary flow. If primary flow is higher (as certainly sounds possible with the whopping 24 gpm you're moving through your heat sources), the flow in the body of the low-loss header will reverse with boiler supply heading right back to boiler return--thus <I>increasing</I> return temperature to the boiler.

Unknown

Due to a suggestion by I think weezbo at my "critique" thread I looked at both Caleffi's and hotrod's low loss headers. I'm not totaly clear on what's happening with them, even though I read everything. Can someone explain or direct me to info that explains? Thanks!

Dave_4

Good desciption.........

Mike T,

Good description, I didn't know that.

I'm always happy when I can learn something new.

"VERY important to note that the low-loss header ONLY works this way when secondary flow is higher than primary flow. If primary flow is higher (as certainly sounds possible with the whopping 24 gpm you're moving through your heat sources), the flow in the body of the low-loss header will reverse with boiler supply heading right back to boiler return--thus increasing return temperature to the boiler."

JR

Unknown

> Here's the best diagram I've found. The purpose

> is to allow secondary flow to exceed primary flow

> without any chance of increasing the return

> temperature to the boiler.

>

> Keeping return

> temperature is low as possible is great for a

> condensing boiler but not good for many other

> boilers. I have no idea of the requirements of

> the heat source(s) you are using. Can you

> provide links to the actual equipment.

>

> Kind of

> hard to see, but the 2nd to bottom line reads "T2

> = T4". In other words boiler return temperature

> equals system return temperature.

>

> VERY

> important to note that the low-loss header ONLY

> works this way when secondary flow is higher than

> primary flow. If primary flow is higher (as

> certainly sounds possible with the whopping 24

> gpm you're moving through your heat sources), the

> flow in the body of the low-loss header will

> reverse with boiler supply heading right back to

> boiler return--thus _I_increasing_/I_ return

> temperature to the boiler.



Thank you, I'm more interested in using the device as a means to break the hydraulic connection between my primarys and secodaries. I'm not overlyt concerned with return temp but, given the low temps I am working with, I do wondr how mixing supply and return will affect output temps on the secondary side.

I have to go but will check back on all these subjects later today. I too am learning quite a bit and appreciate it all.

m

Unknown

Thank you, I'm more interested in using the device as a means to break the hydraulic connection between my primarys and secodaries. I'm not overlyt concerned with return temp but, given the low temps I am working with, I do wondr how mixing supply and return will affect output temps on the secondary side.

I have to go but will check back on all these subjects later today. I too am learning quite a bit and appreciate it all.

m

Brad White_9

What Mike T. Describes

for the LLH application is appropriate for a condensing boiler and assures that the coldest system water makes it's way back to the boiler without boiler return dilution (temperature rise) by primary boiler water. All of this is as Mike said.

The other part is, the LLH can be used for boiler protection when boiler-side flow is higher than the system side flow. Similar functions in a different location. Thus it allows cooler system water (deeper reset) with boiler protection. It is a natural application especially when you are using variable speed pumping. Something to think about!

Indeed though, the LLH is a superior hydraulic decoupler.

Unknown

> Here's the best diagram I've found. The purpose

> is to allow secondary flow to exceed primary flow

> without any chance of increasing the return

> temperature to the boiler.

>

> Keeping return

> temperature is low as possible is great for a

> condensing boiler but not good for many other

> boilers. I have no idea of the requirements of

> the heat source(s) you are using. Can you

> provide links to the actual equipment.

>

> Kind of

> hard to see, but the 2nd to bottom line reads "T2

> = T4". In other words boiler return temperature

> equals system return temperature.

>

> VERY

> important to note that the low-loss header ONLY

> works this way when secondary flow is higher than

> primary flow. If primary flow is higher (as

> certainly sounds possible with the whopping 24

> gpm you're moving through your heat sources), the

> flow in the body of the low-loss header will

> reverse with boiler supply heading right back to

> boiler return--thus _I_increasing_/I_ return

> temperature to the boiler.



Link:

http://www.robur.com/pag_prodotto.jsp?idp=17&idl=2&steps=0

Unknown

Link:

http://www.robur.com/pag_prodotto.jsp?idp=17&idl=2&steps=0

ALH_4

Low Loss Headers

I would attempt to describe their operation, but it would not come close to what Caleffi has done in their idronics technical journal.

The low loss header is "close tees", but more. It also provides an ideal place for air removal, some sediment removal, and connection of the expansion tank. Otherwise they are just a different take on hydraulic separation, and they may work slightly better than close tees because the boiler and system loops follow itentical mirrored paths.

Unknown

Another diagram...

Do you think this would serve to eliminate the hydraulic connection between the secondary pumps and the primary in a similar manner as the LLHs? Again, secondaries are pumping away and I am not concerned with water return temp. Let's say the circuit is doing the whopping 24 gpm. Would you do 1 1/2" copper for the whole thing? Or make the parallel branches smaller like 1 1/4? I'm imagining I could run two 12 gpm pumps in parallel to split the load again instead of running one 24 gpm pump all the time. Do you think the secondaries will add anything to the primary loop when operating?

Mike T., Swampeast MO

That's not any form of primary/secondary, that's merely a primary loop directly connected to secondary loops with their own circulators!

The primary circulators are not isolated from the secondary circulators--in fact they will appear in series to one another! I won't even imagine attempting to estimate the flow!

See the greatly simplified sketch. The common piping on the primary (heat source) side must be sufficient for the full primary flow. Assuming 24 gpm that's 2" copper or 1 1/2" steel. The LLH must be capable of this flow as well! The individual piping (suited for 12 gpm) should be 1 1/4" copper or steel.

On the secondary side the main piping must be suited for the total flow when ALL secondary circulators are running. If this flow rate is greater than 24 gpm, then THIS will determine the minimum size of the LLH.

I'm still VERY confused by your desire to "split the primary load" by using two circulators in parallel. Are there two different sources of heat? If so, you will need some form of staging control. May be as easy as an outside temp sensor that puts the 2nd heat source on-line when the temp falls below some point (preferrably with controller that changes the "lead" boiler periodically to even wear); may be as complex as a sophisticated electronic controller that determines if one, the other or both heat sources are on-line depending on the current number of zones calling and/or the current load on the system.

If you're only using one heat source then I'd be looking hard for a single variable speed circulator plus controller.

Unknown

Thanks Mike, I moved this to over here because I was getting too lost trying to follow the critique thread and answer everything. There are two heat sources, they each require 12.5 gpm. The Caleffi models are too small so apparently I must build my own. What if, instead of the loop I drew, I make it a tank. The system wants a buffer tank anyways. Would that suffice in terms of the breaking the hydraulic connection? Would that become a large LLH? If so and keeping it upright, what would be the best locations for boiler in/out and secondary in/out. They are NOT boilers. They are reversible air to water ammonia based heat pumps. They each have a board that controls their own pump, that's why I want to split the load. ie, in the winter only one will run ~85% to 90% of the time. Why run 24 gpm if you only need 12? Both boards are connected together and then to a "Mother" board digitally. This DDC board controls all the aspects of operation you speak of including balancing the run time and staging. They've each got about 1700 hours of run and last I looked they were within 10 hours of each other. It logs and transmits alarms, all kinds of fun stuff. Soon there will be a way to access it from the net. The only thing it doesn't do is outdoor reset, and I've been on them about that.

ALH_4

separation

Caleffi makes some pretty large hydraulic separators. The threaded version is available up to 1-1/2" and the flanged version is available up to 6".

From what I understand, the diagram posted by Glenn Sossin in the other thread is the best way to pipe something like this without a low loss header, and the diagram posted above by Mike makes sense with a low loss header. Both diagrams are essentially the same thing.

Unknown

Aha! Somehow I missed those, I'll take a look, thanks.

Unknown

Found the local Caleffi rep and yes, the 1 1/2" 548 separator is the answer. Thanks again!

Mike T., Swampeast MO

A buffer tank won't offer hydraulic separation. To achieve hydraulic separation you need a low-loss header or traditional primary-secondary piping. Since this [seems] to be an existing system and is piped similar to your original sketch, I'd suggest that a low-loss header would be MUCH easier to install as it would require fewer piping changes.

While traditional primary-secondary and low-loss header both perform the function of hydraulic separation, primary-secondary is often considered a way to keep return temperature UP for conventional boilers while a low-loss header is considered a way to keep return temperature DOWN for condensing boilers. While both can work both ways, the flow path of the low-loss is elegantly simply and easy to understand while the flow paths with primary-secondary piping rely on flow reversals along the primary path. Simple demonstrations prove that such does occur, but I have a feeling that such doesn't occur perfectly--especially with lots of zones.

With regards to buffering you first have to understand the purpose of the buffer.

With hydronics a buffer has two purposes--it serves both as a "dummy" load and as a potential heat source to the system. The assumption is that the load is significantly lower than the minimum output of the heat source. Store the difference between minimum output and load in the buffer and then let the buffer supply the load until it is exhausted.

Unknown

I agree on the separator fix being the easiest. Not a big deal at all, relatively speaking. The questions have all been twofold as I am looking to do another system with another two HPs and a total of 11 tons of cool hooked into 3 air handlers. Another 25 gpm-er. I've also been looking at Dan's "Pumping Away" and I'm considering this configuration as well:

Unknown

Oh,,,

The buffer tank IS a false load as well as a storage for "extra heat/cool" and is recommended by Robur. Here is another problem. To accomodate 25 gpm through a tank I need at least 1 1/2" connections in and out. Best I can find is 1" on like a 40 gal Superstor, if I recall correctly. I'm thinking diverter tees in the primary loop right after the pump down to 1" and at least bypass SOME of the water through there. What do you think of that idea? That's why I thought if I could put it in there and double it as an LLH I might be able to kill two birds with one stone. I'd just take it to my local welder and have hime add all the proper sized connections I'd need including the 1 1/2" ones.

Moses

idronics

If you look on page 14 figure # 19 , that's our project.

Here is some more pictures from that job.

Unknown

Final Diagram?

This is what I'm ending up with. Any problems here?

ALH_4

Yes

I like it.

Unknown

Very good! Thank you all, especially for your patience, again!

m

Unknown

I beg to differ that a buffer tanki does not offer hydraulic separation; here's one that does (thanks to Siggy for pointing us toward it):

Unknown

I figured it would work. Looking at the innards of the 548 the only difference between it and a tank is the perforated baffle which I believe has more to do with air removal than hydraulics. I could lighten the materials list quite a bit doing it that way. I just checked with a welder, ~$100 plus parts to weld 4- 1 1/2" stainless nipples on a tank for me. So I can take the $400 tank I need anyways, put another $150 into it and eliminate the $700 #548. Seems like a winner to me.