Primary/secondary problems

Greenpoint

I have 3- 007 circs. with built in flow checks, and then 2 Grundfoss circs. for a primary/secondary circuit for a radiant manifold. The 2 Grundfoss run all the time, but when any of the 007's run, their loops don't get hot. What's wrong?

Mark Eatherton1

Need a schematic..

Need to see how its piped to be of assistance. Use MS Paint, save as a JPEG and post it here along with pertaining notes.

ME

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Tony_8

Probably

the 007's are airbound.

Mark Eatherton1

Greenwoods system schematic

I see some problems, but would like to use this as a teaching/learning tool to see if anyone else spots the reason. I've already responded to him directly so as not to hold up the heat.

ANyone else care to take a shot at it?

ME



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kevin coppinger_4

he should have....

use close spaced tees on the 007's...don't cross over the primary loop with the supply and return...kpc

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jim lockard

content

Looks like the water is very content to just travel around the primary loop. I would move the primary circulator to a spot between the exp tank and the boiler, but thats not the answer Prof. Mark is looking for nor will it change the 007's problem.

kevin coppinger_4

and move the circ..

to just after the air scoop...the PONPC...007 can't overcome the Diff.? To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Uni R

Greenwoods system schematic

May not circulate back to the boiler when it could just do the loops backwards with the primary circulator where it is...

Constantin

Here is my solution...

...probably overkill, but what they hey.

This is a bit of a hybrid pri-sec design to keep the IDWH on just one pump in the summertime. Still pumping away from the air-sep and all that. I suspect that the Tacos are currently full of air due to the present piping arrangement. Nevermind issues such as how the water is actually flowing in that mish-mash of piping... closely-spaced T's for the secondary loops is where it's at with pri-sec piping.

Here is a quick sketch with one system design one could consider: The baseboard gets the hottest water, sends the tempered stuff downstream, where V1 modulates it down to temp for the Radiators. With constant circulation, a measure of control should be possible in both the radiant and the radiator circuits. Otherwise, I think one would run out of cold water to temper with in a hurry. Naturally, all pumps must have a FC to prevent ghost flow and all that.

If the heat loss is quite proportional between the different loops, the 4-way valves may not even need to be motorized. However, this is quite unlikely the case over the course of an entire heating season.

However, I have the feeling that the system solution that is being sought is supposed to work at a lower price point than one with two four-way mixing valves. If that is the case, only use closely-spaced tee's, and arrange the stuff on the primary circuit in the following order: AirSep/ExpTank, primary pump, IDWH, BB, Radiators, Radiant injection loop.

Weezbo

i dont underestimate anything

if the recirc is pumping back at the return which is comming off the supply tapping, then in essence it appears the flow in the "primary is counter to the boilers supply and return ,and while i belive you should pump away and also that it is better to pull through a three way valve,it seems to me the radiant wont work very well and the baseboard will have two pumps fighting each other every time there is a call for heat,as the system pump is returning ahead of the returns on the loops controlled by ifc's and pumping back at the pressurized boiler and the checked taco recircs..

hr

A true series PS

would have all the loads teed off closly spaced tees.

The primary loop pump should be closer to the PONPC or move the tank to the circ if you want to pump into the return.

All the secondary loops need flow protection (check valves or check pumps), possibly on supply AND return if they take off the top of the primary loop as pictured.

The loads need to be arranged in order of the temperature they need. Think I would have the BB before the panel rads.

A temperature drop calc should be run to see what temperature each takeoff tee will see when all loads are running.

Not sure the radiant loop is pumping away from the PS loop in that drawing??

The indirect could be left as a parallel loop if it is on priority (primary pump shuts down on call)and has check protection on the primary and indirect loop. Of course this circ would need to be sized to the boiler and indirect needs if used in parallel.

I'm sure pipe size and iso valves have been left out for clarity

What else...

hot rod

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Weezbo

oh....Could it be \"Checkvalved?\"

:)or could the gate be shut of and the boiler header is getting"Hot" because the water has no where to go and the main circ is deadheading:) thats a strech buh maybe not

hydronicsmike

Constantin...

You ever run into pumping issues for pumping in series? When your Mixing Valves are open, that's what you have. Two closely spaces tee's can eliminate any potential for problems.

Mike

Constantin

Hi Mike!

We meet again! Though I am not sure what exactly you are describing, the cascade idea I had in the first GIF was simply meant to allow constant circulation... while using temperature drop from each previous "user" to the advantage of the next heat emitter.

Below is a similar scheme. Perhaps it's better suited for the application? Naturally, one could use closely spaced T's and 3-way mixing valves as well. I just thought 4-way valves look nicer in a diagram. ;-)

hydronicsmike

(sorry if you seen my first reply. Missed something and decided to pull it). Am hoping to get you a better response later on in the evening)

Tim Doran

Delta P issues

You have some Delta P issues due to the piping arrangement. Consider piping it something like this to correct it.

Tim Doran

Delta P

You have some pressure differential problems due to piping and pump placement. Consider re-piping to something like this.

Tim D.

hr

Tim

I think you would want a check or check pump on the primary circulator also, in your drawing??

hot rod

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Tim Doran

Agreed

I agree due to the DHW configuration. If priority is not used/required the dhw can simply go with the rest of the high temp loads.

Tim D.

Sweet

Ill take a stab, what the hek

Couple of possibilities, move the primary circ to exp tank,air seperator.Second cheks on all three high temp loops. Third move the radiant circ touotlet side of inject. valve.???

marc

primary pump size

maybe to big, not allowing the smaller pumps to start moving the water in their pipes, what controls the boiler temp. does the outdoor reset control in the drawing for the low temp. radiant. what enables the primary pump to run, is this one of the 2 that run all the time, or is it only ran during low temp. heating. marc

Tony_8

He just needs to

Move the 007 returns to be close-spaced tees with their respective supplies. That will probably require moving the primary circ just for room.

Right now he has a hybrid system P/S and reverse return.

Mark Eatherton1

AHA!!

Pressure, like temperature flows from high to low. If the returns from the Taco 00 pumps are exposed to a higher pressure from the Grundfos, they WILL NOT FLOW.

This was verified by Greenpoint in a later response where he said he could get water to flow through the Tacos by choking the G-fos primary pump. Essentially, the Tacos can not overcome the pressure being generated by the Gfos pump.

Good eye. More to come...

ME

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Mark Eatherton1

Except...

the Tacos are internally checked.

ME

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marc

thanks mark

> Pressure, like temperature flows from high to

> low. If the returns from the Taco 00 pumps are

> exposed to a higher pressure from the Grundfos,

> they WILL NOT FLOW.

>

> This was verified by

> Greenpoint in a later response where he said he

> could get water to flow through the Tacos by

> choking the G-fos primary pump. Essentially, the

> Tacos can not overcome the pressure being

> generated by the Gfos pump.

>

> Good eye. More to

> come...

>

> ME

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 88&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Mark Eatherton1

Good ideas, all of them...

but as Mike-eh pointed out, the fourways present the possibility of having 2 or 3 pumps in series at some point, which may cause problems. You last sentence gets real close to a simplified system, and I think that was Greenpoints intent. K.I.S.S.

Thanks for thinking (and drawing) outside of the box though.

ME

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Mark Eatherton1

My thoughts exactly...

until he told me that he could get flow by choking back the Gfos he had on the primary side...

ME

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Mark Eatherton1

That would work...

The 07's would then be able to move water through their respective circuits. But he still has some physical location problems, probably dictated by space available.

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Mark Eatherton1

Greenpoint Fix(s)

As HR said, some valves have been left out for dwg clarity. Greenpoint 1 is a low watt design. Pump must be sized to actual loads imparted, and I'm not sure the 007 is the right one. If high head pump is required, an pressure activated bypass (PAB) should be installed around the secondary output pump.

Greenpoint 2 is with all the pumps, a high watt system. Note checks on the secondary returns to avoid unwanted ghost flow. Again, some valves were left out for clarity, and the pumps should be sized to their loads.

I making a LOT of assumptions here, like the panel rad circuits are being called by a t-stat. If not, then a PAB should be applied to it too.

Comments welcome, and thanks for playing along. That's what this place is all about. Learning and teaching. Thanks Dan for the opportunity.

ME

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