Cant get correct flow on system- Pic Attached

[fin5281]

I am beating my head against a wall here. I can only get .6 gpm out of each loop on my 6 loop system. Loops are in the neighborhood of 270 ft. Longest is 272 1/2" Pex. The pump I am using is Grundfos S15-58 which by all accounts should be the correct pump for my system. Take a look at my setup and see if you see anything that I am doing wrong. I feel that I should be at least getting 1- 1.5 GPM on each loop. Any suggestions would be greatly appreciated. Yes I a aware that the Seisco SH-22 Water Heater is not wired correctly in the finished state. I just hooked it up fast to see if adding a little heat to the system would have made a difference. It did not. HELP

 

[fin5281]

Sorry the Pic came in sideways

 

[fin5281]

New Picture attached. Hopefully it is not sideways

 

[forAK]

Are balancing knobs opened all the way? All 6 loops show .6 gpm? How long has it been running? Meaning, all of the air out of it.

 

[fin5281]

Are balancing knobs opened all the way? All 6 loops show .6 gpm? How long has it been running? Meaning, all of the air out of it.

Yes. Balanced and air removed. I ran if for 2 days


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[forAK]

I'm running a 26-64 pump and am getting .8 gpm on my 8 loops. So, you could be fine. Mines been running for a couple of months like this and have good heat. Fast isn't what you're going for. Slow and steady even heating. As long as your return heat isn't too far off of your supply, you're good to go on your pump size.

 

[Radix2]

How did you calculate that you should be at 1-1.5 gpm?

Head loss in seisco at 6-9 gpm?
Head loss in pex at 1-1.5 gpm?

 

[koditten]

I have to agree. I'm not moving much water either. What are your in and out temps?

 

[larry_g]

That is a three speed pump? Have you tried all three speeds? Where is your flow sensor?

lg
no neat sig line

 

[fin5281]

I have to agree. I'm not moving much water either. What are your in and out temps?

In temp 100 return 60. Did not allow to run for a long time cause I was not sure my flow was working correctly.


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[fin5281]

That is a three speed pump? Have you tried all three speeds? Where is your flow sensor?

lg
no neat sig line

Yes it is a 3 speed pump. .6 at the fastest speed. .4 at lowest


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[pstnbly]

Lots of headloss through the WH.

 

[Radix2]

The wh claims "no loss"....

I don't know what tubing you are using, but at 1.33gpm, on the uponor calculator, 250 ft of 1/2 in tube is 17ft of head. Your pump on high at 6x1.33gpm= 8gpm has only 12ft of head possible.

So there is no way possible you could get that flow since we added nothing for wh loss or your pipe main loop and elbows.

Going the other way you say .6 gpm. Total flow=3.6gpm. Pump head available at 3.6gpm is about 16. Tubing loss is only 4.3 ft. So somewhere you have 11ft of head.

.6 seems too low, but your 1-1.5 is too high.

 

[fin5281]

The wh claims "no loss"....

I don't know what tubing you are using, but at 1.33gpm, on the uponor calculator, 250 ft of 1/2 in tube is 17ft of head. Your pump on high at 6x1.33gpm= 8gpm has only 12ft of head possible.

So there is no way possible you could get that flow since we added nothing for wh loss or your pipe main loop and elbows.

Going the other way you say .6 gpm. Total flow=3.6gpm. Pump head available at 3.6gpm is about 16. Tubing loss is only 4.3 ft. So somewhere you have 11ft of head.

.6 seems too low, but your 1-1.5 is too high.

What would be a good gpm to target?


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[Radix2]

What would be a good gpm to target?


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Your boiler is 75,000 BTU.

If we assume you want to operate with 20F across your loops (and boiler of course) then 1gpm = 10,000 BTU

So to get full power out of your boiler, you need to move about 7.5 gpm

So in the loops 7.5/6= 1.2gpm

The thing to do then is figure out your head losses at 7.5/1.2gpm and get a pump that can do it.


Or operate at bigger temp differences across your loops. At 30F you need 5gpm or .83gpm over loop.

As you sit, at 3.6 gpm, you will see about 42F across your loops when your system is at full power. How much if an issue this is depends on how often you really need that kind of power.

 

[Radix2]

Looking at your rig, I don't see where the losses are...seems like you should be close to 1gpm . You could put a test pipe in instead of the boiler to see what the effect is.

Is that main loop 3/4 or 1 in?

 

[fin5281]

1" main. That's what is so confusing to me


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[fin5281]

Your boiler is 75,000 BTU.



If we assume you want to operate with 20F across your loops (and boiler of course) then 1gpm = 10,000 BTU



So to get full power out of your boiler, you need to move about 7.5 gpm



So in the loops 7.5/6= 1.2gpm



The thing to do then is figure out your head losses at 7.5/1.2gpm and get a pump that can do it.





Or operate at bigger temp differences across your loops. At 30F you need 5gpm or .83gpm over loop.



As you sit, at 3.6 gpm, you will see about 42F across your loops when your system is at full power. How much if an issue this is depends on how often you really need that kind of power.

I knew I got those numbers somewhere . Just could not remember. Any suggestions to get me closer to that 1.2 would be greatly appreciated


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[DenisG]

Here's something that might help you explain what you are seeing – see “Reading Flow Without Flow Meters”:
https://www.taco-hvac.com/uploads/FileLibrary/PumpCurves.pdf

Your pump specs/pump curve:
http://s3.supplyhouse.com/manuals/1249544647674/Grundfos_ups15-58fc_Product_Data.pdf

 

[forAK]

I knew I got those numbers somewhere . Just could not remember. Any suggestions to get me closer to that 1.2 would be greatly appreciated


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Grundfos 26-99 three speed or a 26-64 single speed. Put an add on Craigslist and get a used one to try it out. Put an add in the wanted section. Or just cough up the $280. Either way, you get close to 33 gpm and 28 ft of head loss. Big difference compared to the 15-58 at 17 gpm and 19 ft of head.
Another thing to consider is you lose head when pumping glycol vs. water. What are you using?

 

[R.Anderson]

Grundfos 26-99 three speed or a 26-64 single speed. Put an add on Craigslist and get a used one to try it out. Put an add in the wanted section. Or just cough up the $280. Either way, you get close to 33 gpm and 28 ft of head loss. Big difference compared to the 15-58 at 17 gpm and 19 ft of head.
Another thing to consider is you lose head when pumping glycol vs. water. What are you using?

This, glycol in the system was my thoughts here.

 

[fin5281]

Ok been running the system for last 2 days. Outside temp is 30. Inside temp up to 48. Supply side is at 120 return side 80. So my delta t is 40. Any suggestions how to get that delta number closer to 20?


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[Radix2]

Ok been running the system for last 2 days. Outside temp is 30. Inside temp up to 48. Supply side is at 120 return side 80. So my delta t is 40. Any suggestions how to get that delta number closer to 20?


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As you see, the numbers work out as predicted.

So the solution is to get more flow.

Are you using glycol ?

Is there any possibility that there is junk in a filter on your manifold or boiler?
The input connections often have screens and stuff gets in during construction.

Any possibility that you are missing something on setting the flow controls?

Other than finding some source of pressure drop, the only other thing is a bigger pump.

 

[fin5281]

As you see, the numbers work out as predicted.



So the solution is to get more flow.



Are you using glycol ?



Is there any possibility that there is junk in a filter on your manifold or boiler?

The input connections often have screens and stuff gets in during construction.



Any possibility that you are missing something on setting the flow controls?



Other than finding some source of pressure drop, the only other thing is a bigger pump.

Water. Will have to check out the path but I think your right that i need a bigger pump. Out of curiousity.....I have an old bell and gossett laying around. Would having 2 pumps on the same main be a possibly to increase flow? Not sure if that's do able. Just to try it out before spending another $300 on a system I'm not sure is ever gonna work.


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[Radix2]

Water. Will have to check out the path but I think your right that i need a bigger pump. Out of curiousity.....I have an old bell and gossett laying around. Would having 2 pumps on the same main be a possibly to increase flow? Not sure if that's do able. Just to try it out before spending another $300 on a system I'm not sure is ever gonna work.


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It will definitely work.

What is your building like - sq ft, insulation? 75,000 BTU should be able to heat a big space

Two pumps should work, not the most efficient, but I don't see why not.

I hope you find a gob of stuff in your strainers. See if there is one in your air vent too.

 

[fin5281]

My builiding is 40x40x16' Insulation is moderate and I have high cielings. I can maintain 55 degrees no problem just seems like the pump runs all the time. With the setup I have i wish there was a way to make it run less therefore not running the high amperage of the boiler continuously. I am expecting my electric bill is going to be like a $1000 this month ughhh.

 

[forAK]

Thinking out loud here. I've got a 40x40x14 and I'm running 8 loops in. They go between 260' to 305' and I'm sitting at .8 gpm. I'm also running a gas boiler at 120 in and 100 back out. To get to a higher ambient temp, have you increased your over all in temp? Also, what is your ceiling temp at? You might need a ceiling fan to bring down the wasted heat that's just sitting up high. Your lower flow though still should go up a little more. A 40 degree delta seems a bit much. What is your outside temp?

 

[American Locomotive]

My builiding is 40x40x16' Insulation is moderate and I have high cielings. I can maintain 55 degrees no problem just seems like the pump runs all the time. With the setup I have i wish there was a way to make it run less therefore not running the high amperage of the boiler continuously. I am expecting my electric bill is going to be like a $1000 this month ughhh.

The physics don't really work like that.

If you want it to run less, you need to insulate the building better. A lower temperature delta will make your slab temperatures more even, and increase efficiency somewhat, but nothing really major.

If your system/boiler is running at full power continuously, then your system is giving everything it has to keep your set temperature, and more flow is not going to solve that.

As mentioned, you should probably get some ceiling fans to bring hot air near the ceiling down low.

 

[fin5281]

Thinking out loud here. I've got a 40x40x14 and I'm running 8 loops in. They go between 260' to 305' and I'm sitting at .8 gpm. I'm also running a gas boiler at 120 in and 100 back out. To get to a higher ambient temp, have you increased your over all in temp? Also, what is your ceiling temp at? You might need a ceiling fan to bring down the wasted heat that's just sitting up high. Your lower flow though still should go up a little more. A 40 degree delta seems a bit much. What is your outside temp?

Outside temp is in the 30s. I am happy with a a 55 degree ambient temp. It would get hotter if I turned it up but have not yet done so as I'm still fine tuning the system.


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[biodiesel]

Double check your flowmeters if they are like mine you can also turn them to restrict flow. I have a manifold that looks to be the same as yours and also had the same issue with flow. I found that in addition to the flow regulation valves with the white knobs the flow meters themselves can be turned to restrict flow. Not sure why they are built that way since one adjustment would be enough..