Multiple Zones with high head and I may be in over my head

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Mid Michigan

Mid Michigan

Member
Oct 20, 2009
71
Mid Michigan
Help, I find myself involved in a renovation project for a Non-Profit. I may be slipping in over my head.

There are 6 zones of Radiant Base Board with head and GPM as follows:
Zone 1 - 16' at 2.00 gpm
Zone 2 - 25' at 2.64 gpm
Zone 3 - 29' at 5.28 gpm
Zone 4 - 24' at 3.60 gpm
Zone 5 - 21' at 1.80 gpm
Zone 6 - 28' at 2.88 gpm

2 Boilers piped parallel with the load in series. Main Boiler 2,000,000 btu has a TACO 0011-F4, Back-up boiler 80,000 btu TACO 007-F5. No pressure bypass valve in system.

I am asking if all the zone valves are open than I need a pump capable of 17.88 gpm at the highest zone head of 29. Is this correct? If so the 0011 will never move enough water and the 007 will do nothing.
It looks to me like I have to replace the main boiler pump with a TACO 1400-45 and re-pipe the Back-up boiler into the main boiler loop using two closely placed T's. The 1400-45 must run regardless of which boiler is in operation and the 007 will pump back-up boiler HW into Main boiler loop. Seems to be cheapest fix. Any ideas?
Also add a pressure bypass valve for when 5 zones are closed or add variable speed pump with delta T.
Are there any variable speed pumps with 29' head at 18 gpm?

Thanks for any assistance!
 
From the way I read the Taco pump data for the number 11 pump could not support Zone 3 or Zone 6 by themselves. However, I don't claim to be an expert on those charts.

What no diagram?
 
a picture is worth a thousand words.

I don't understand where your numbers are coming from for the various zones. I don't understand how different zones would be piped in series, or if this means something different than what I'm thinking of.

Also, what is wrong with the system? is it being added on to or improved?

sorry for the questions with no answers
 
That lools like a Wilo Stratos 1.25 3-30 to me.
Use the highest head loss for deign, add up the flow rates is correct for design purposes with everything running.
That is am ideal application for an ECM pump, as the pump can adjust to the flow. I believe Grundfoss makes similar products, but I've never heard of anything other than the Alpha, which is too small for what you describe.
 
Ok, Here is a drawing. It is from TACO software and it raises the head up even higher than I figured.
Another idea I think is possible is add Zone pumps. A 009 would work for all Zones except Zone 3 at 29' at 5.28 gpm that one would barely squeeze under a 0013.
I think changing out the Main Boiler pump to a 1400-45 at $400.00 is cheaper than 6 Zone pumps.

What am I missing?
 

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To answer some questions:

Why such high head on such low gpm zones? Small tube diameter, long loops? Is the 2 million btu boiler for a 180K load correct?
This building is a 15 year old church with all fin tube heat. Original piping was under slab with out insulation. Don't ask me???? The pipes are rotting out were they come up through the concrete. Re-piped all fin tube over head with over 2000' of copper. 26 pieces of fine tube varying from 8' to 48' in length. One too many zero's on the boiler. 200,000 btu's is correct.

I would like a variable speed pump. If anyone knows of one with that kind of head and gpm let me know.

Thank again, and keep the ideas coming!
 
Let me start by mentioning that I am not a professional (in this trade), just a home owner that comes here for boiler install info...

You could look at it another way... You need 20 GPM to move the 200k BTU's at a delta-t of 20 degrees. When all the zone valves are open, the pump will not see the high head pressure, but rather a much lower head pressure due to the parallel flow paths. Will you need to add some flow balancing valves into the zone loops to make sure the heat goes where you want it to?

One thing I experienced the other day is that running multiple boiler circulators in parallel does not necessarily result in more flow through the system. The other morning I accidentally had a Grundfos 15-58 (wood boiler) and Taco 007 (oil boiler) running at the same time. The Taco would not move any water. When I manually opened the flow check, the Grundfos pushed water backwards through the running Taco pump. Normally only one runs at a time. This is a single loop system, not primary / secondary piping...
 
scottb
I had the same pump problem hear on this project. The 007 on the back-up boiler will not move an ounce of water against the main boiler pump. I think I will be re-piping the boiler into a pri-sec. That way the to boiler pumps are not fighting each other. This should also lower head on the zones a little. I do have balancing valves on each zone. Right now they are all open trying to keep the head down. That is another question after I get the water moving. If my highest zone is 29' head, do I start shutting all other zone balancing valves down until all zones have 29' head? This way they are all getting the right amount of water???

The high head in the long zones is what it is going to take just to move the water just through all the pipe. The 0011 is just barely moving water. All 5 zones that have any exterior wall in them have not shut off in days. The interior zone has shut.

That's another thing that has been making this a challenge. When I leave it has to be running.
 
I don`t know much but wouldn`t using zone pumps lower the head of the main pump? And control flow through those long runs better?
 
Bricks said:
I don`t know much but wouldn`t using zone pumps lower the head of the main pump? And control flow through those long runs better?
Click to expand...

Yes it would. I have thought of that also. Keeping in mind the cheapest route yet efficient, 6 zone pumps probably need 4 - 009 and 1 - 0011 and 1 - 0013, That's gotta add up to $1000.00 with flanges and all. I still need to re-pipe to a pri.-sec. system I would think for best performance.

With the help of member of this forum I have found a variable speed pump capable of 38' head @ 20 gpm. Leaning in that direction. aprox. $700.00. Power rating is .16 - 1.37 amps for this pump. That seems like a good benefit of this route too.

I still have never found out for sure on balancing zones though. Any help in that area would be appreciated. Make them all match with circuit setters and let her rip????
 
I am assuming that the back-up boiler will only be used to supplement capacity of the main boiler as load demands. If that is so, one way you could go is to keep the single loop plumbing that you had in the earlier diagram and pipe the backup boiler into that loop with a closely spaced T. In that case, the main boiler circ needs to always run and the backup boiler can add it's BTU's into the system even with the small pump.

The amount to restrict the smaller zones is complicated. It would be easy if you wanted the same flow rate in each zone. In that case, you would make them all match 29'. If they all had the same head, the flow would be even through all. With one zone open, the pump would need to move 5.3 GPM into 29' head (1 zone open) or 32 GPM into 4.8' head (all 6 zones open). This might be good enough, but it gets more complicated if you want to keep the flow velocities consistent. You would need to restrict the smaller zones more.

I think that the way to calculate effective head pressure with multiple zones open would be:
1 / (1 / zone1 + 1 / zone2 + 1 / zone3)
So if zones 1,2 and 3 were open per your data it would be 1/ (1/16 + 1/25 + 1/29) or 7.3 ft of head at the pump.
If you sized the pump to move 32 GPM into 29' of head, I would think that the flow would be way too high with just 1-2 zones open, you would definitely need a bypass. That VS pump seems like a great deal both in cost and power.
 
I had one final thought this morning. I think Brick suggested using zone circs and also keeping the boiler circ. Rather than sizing zone circs to do all of the work, let the boiler circ generate most of the pressure you need and use small zone circs to fill the gap. A Grundfos 15-58 is good for 14' of head pressure at 5 gpm when set on high. The Taco 011 is good for 13 ft head at 20 GPM so you are pretty close with these 2 pumps in series. These little pumps only cost $75 each and 3 speed settings let you adjust the flow.

I would think that you could balance the zones by adjusting based on the zone return temperatures.
 
scottb said:
I am assuming that the back-up boiler will only be used to supplement capacity of the main boiler as load demands. If that is so, one way you could go is to keep the single loop plumbing that you had in the earlier diagram and pipe the backup boiler into that loop with a closely spaced T. In that case, the main boiler circ needs to always run and the backup boiler can add it's BTU's into the system even with the small pump.

The amount to restrict the smaller zones is complicated. It would be easy if you wanted the same flow rate in each zone. In that case, you would make them all match 29'. If they all had the same head, the flow would be even through all. With one zone open, the pump would need to move 5.3 GPM into 29' head (1 zone open) or 32 GPM into 4.8' head (all 6 zones open). This might be good enough, but it gets more complicated if you want to keep the flow velocities consistent. You would need to restrict the smaller zones more.

I think that the way to calculate effective head pressure with multiple zones open would be:
1 / (1 / zone1 + 1 / zone2 + 1 / zone3)
So if zones 1,2 and 3 were open per your data it would be 1/ (1/16 + 1/25 + 1/29) or 7.3 ft of head at the pump.
If you sized the pump to move 32 GPM into 29' of head, I would think that the flow would be way too high with just 1-2 zones open, you would definitely need a bypass. That VS pump seems like a great deal both in cost and power.
Click to expand...

Yes back up boiler is there just for emergencies. Originally two of them. One got a crack heat exchanger so replaced it with one high eff. boiler that was large enough for entire load. Didn' see any reason in taking second one out when it still worked. Having different flows in each zone does make it a bit more complicated. This is good information you gave me. I will continue to go down that line with some research. I noticed yesterday all but one zone finally caught up. It got up to 30* though too. Where I get lost is if it takes 29 foot to push the water through one zone just to overcome the friction of the pipe, then that number can not ever be lower. So balancing between zones gets tricky.

Thanks
 
scottb said:
I had one final thought this morning. I think Brick suggested using zone circs and also keeping the boiler circ. Rather than sizing zone circs to do all of the work, let the boiler circ generate most of the pressure you need and use small zone circs to fill the gap. A Grundfos 15-58 is good for 14' of head pressure at 5 gpm when set on high. The Taco 011 is good for 13 ft head at 20 GPM so you are pretty close with these 2 pumps in series. These little pumps only cost $75 each and 3 speed settings let you adjust the flow.

I would think that you could balance the zones by adjusting based on the zone return temperatures.
Click to expand...

Another good idea, I knew that two pumps in parallel would double gpm and keep same head. So you are saying two pumps in series the head is added together and probably take the lower of the two for gpm?
 
As long as the pumps are in series, they don't cavitate, and their operating pressure is not exceeded. I am no expert, but they must function pretty close to the advertised performance curves.
 
Another good idea, I knew that two pumps in parallel would double gpm and keep same head. So you are saying two pumps in series the head is added together and probably take the lower of the two for gpm?
Click to expand...

According to Taco http://www.taco-hvac.com/en/faq.htm :

Code: 
Q:  What happens to the performance of pumps when they are piped in parallel or in series?

If pumps are piped in parallel, the flow produced by each pump will be additive, 
at the same head of each pump. For example, if one pump puts out 20GPM at 35 ft. 
and another puts out 30GPM at 35ft., the total flow at 35ft. head will be 50GPM.

If pumps are piped in series, their heads will be additive, at the same flow rate. 
For example, if one pump puts out 20ft at 15GPM and another puts out 25ft at 
15GPM, the total head will be 45ft at 15GPM.
 
scottb said:
I have seen installs with 2 circs bolted flange to flange, but I would want some length of pipe in between to let any turbulence settle out.
Click to expand...

Taco agrees:

Q: Do you have any data on putting two 009 in series or possibly combining the 009 in series with another circulator to boost head and flow rates?

If any pump is put in series with another pump, the heads are additive at the same flow. To increase the flow, the pumps have to be put in parallel. With pumps in parallel, the flows are additive at the same head. When pumps are put in series, install a nipple between 2 flanges. Bolt the discharge of one pump to one flange, and the suction of the other pump to the other flange.
 
I would have to assume that if you have two different pumps in series, say a boiler pump and a zone pump, the heads pressure would be additive but the flow would be equal to the pump with the lower of the two flow rate.
As far as my situation goes this would mean 6 new zone pumps in series with the TACO 0011 boiler pump. If I need 18 gpm @ 45 foot of head - A 0011 at 18gpm is around 14 foot of head. I still need a pump with 31 foot of heat for each zone with the right gpm for that zone. Now if only one zone is open that's a whole new deal. Say a zone of 2gpm, that same 0011 is up to 29 foot of head leaving me to find a pump with 16 foot at 2 gpm, much more doable, but prabally not practical. Need to size for all zones open.
So help me here. It would seem easier to switch to pri-sec and find one pump capable of the total gpm @ total head. Each boiler dumping into the secondary loop. The new boiler is a high head boiler, so there may not be too much left over for the 0011 to give away to the zones.
That is my last two drawings, a variable speed or a constant speed with pressure reducing valve.

Am I missing something? I do not need to spend $1000.00 of a non-profits money to see it not work. That would not be good.
 
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