Insufficient flow in radiant system (air removed via purge cart) looking for reasons?

chingo

To answer some questions on procedure.
I have the flow meters FULL OPEN
Adjustment to the run is done via the KEY NOT the Blue Adjustment Cap
ALL pumps are UPS 15-58 1 Main circulator 3 Zone Circulators.
There are 3 SS-Manifolds (see pic)
2 Are 8 Run ½” pex 250 feet +/-1%
1 Is 4 Run 1/2:” pex 250 feet +/-1%
ALL connections FEED and RETURN are ¾” pex from pump to manifold.
It has approx. 10 feet of connecting pex FEED and RETURN.
The other two zones are 40 feet and 70 feet away from pump FEED and RETURN.
The MAIN LOOP (Boiler,exp tank etc….) see pics is joined with 1-1/4” copper
It is approx 16 feet loop length.

This system was designed with country well water on property.
Rather than take a chance corroding system, I decided to use a closed loop.
I used and AXIOM MF200 System Feeder for my pressure/fill requirement on makeup.

When I first started system I used a purge cart
The main system was started up (call for pump start disabled) hose was connected to
Fill location and relief valve was left off (highest point of main loop.) hose attached and run back to purge cart. Ran system for 10 min. until filled and consistent flow.
NOTE: ALL Zone pumps were off.
Also water was prevented from entering or exiting zones. MAIN LOOP flow only.
Unhooked Purge cart and reattached relief valve and fill cap.

Started main system pump to circulate water. (MAIN LOOP only)
Zones are still isolated and pumps disabled.
AXIOM pres./fill is ON. Add water if needed. Pressure to 12psi.
Nice smooth operation (no crackle etc…)
Ran for 10 min. No Main flow meter to give reading. Assumed fine.
Pressure built to 12 psi, water was added (indicated by water line moving down in tank)
AXIOM turned off by itself and system continued to run with new settings for pres.

Turned off system and moved to manifold purge.

1hp pump in 53 gallons of clean water hooked to input of manifold on the FEED side.
On the RETURN side I attached a hose and ran it back to cart.

Pushed 2gpm through individual run on manifold and let run for 10 min.
Did each run on manifold individually. at same rate

Then ALL runs on flow meters read approx. 3/4gpm per run, STRONG AND STEADY
RAN for 10 min.
There should be no air left in the manifold system.
Turned off all Runs on manifolds at Feed and Return (Key and Meter)
Opened feed and return to MAIN LOOP.
Since I used shark bite fitting on OUT of pump and IN of Return manifold able to fill line by hand and reconnect.

LAST winter the system ran as follows.
Basement zone 8runs. 1 run ON 7 OFF ¾ to 1 gpm/ 8 run ON / flow by 8 (not readable)
Ended up using 4 outside RUNS down to 2 when it got cold.
Alternated other two zones which are upstairs and divided up runs to outside.
In other words, a lot of manipulation to keep house at 18C on cold days.

So you see I was hoping to have found my answer by now, but life has a way of getting in the way. So here I am back at it before winter starts.

I can get the same performance as last year but I need way better.

My problem assumes the following when sizing pump.

All circulator pumps are typically sized based on the heat load and head loss (pressure drop) for a given zone.

Knowing the heat load (in BTU's) for a given zone, allows to calculate the required circulator pump's flow rate in gallons per minute (GPM).


For hot water hydronic or radiant heating applications, the following equation can be used:

GPM = 0.002*BTU/(Temperature Drop, F),


where Temperature Drop is the difference between supply and return temperatures in the system and GPM is the amount of flow the circulator must produce.

Since most of the radiant heating systems utilize a 20F temperature drop, the formula can be changed to:

1 GPM = 10,000 BTU/hr,

meaning that for every 10,000 BTU's of heat load the circulator must output a 1 gallon per minute flow.

This system calls for 80,000 BTU/hr, circulator pump should have a minimum 8 Gallons Per Minute flow rate at a given pressure drop.


The next step is to calculate the head loss, or pressure drop in the system.


Head loss is associated with friction of the water against the internal surface of the pipes/tubing in the hydronic or radiant heating system and restricts flow rate a circulator can produce.
Although radiant heat manifold and PEX tubing sizing are a different topic, this systems manifold has 8 outlets with 1/2" PEX tubing installed at 250ft length per loop and the system calls for 80,000 BTU's.
Using the formula above, we can determine the flow rate required for our given zone: 80,000/10,000 = 8.0 GPM.
Flow rate through every selected circuit of the manifold equals Flow Rate divided by number of Circuits:
8 GPM/8 circuits = 1 GPM per circuit (assuming that the circuits are equally balanced).
Using a Pressre Drop Table or Pressure Drop Chart, supplied by the PEX tubing manufacturer, a pressure drop per ft of tubing can be calculated at a given GPM flow rate.
NOTE: Pressure drop data supplied by manufacturers may be available both in PSI (lbs per square inch) and in foot (ft) of head.
For conversion, I used the following equation: 1 psi = 2.3 ft of head (for fresh water), and 1 ft of head = 0.43 psi
In this example, pressure drop per 1 ft of 1/2" PEX tubing at 1 GPM flow rate would be approximately 0.03 ft of head).
Considering that each individual PEX tubing circuit is 250 ft long, pressure drop per circuit would be 0.03 x 250 = 7.5 ft of head.
Since PEX tubing circuits are in parallel to each other, pressure drop per circuit is always the same as the total zone pressure drop. So, the total pressure drop is: 7.5 ft of head
We now have the complete specification for the circulator pump available: 8 GPM flow at 7.5 ft of head pressure drop.
I understand that other components installed within a given zone (such as the radiant heat manifold itself, fittings, check valves, mixing valves, balancing valves, heat exchangers, PEX tubing length (different diameters), etc.) also have to be considered when sizing a circulator pump (see Scheme 1 below). Pressure drop information is usually available in a form of technical specifications or submittal sheet supplied by the manufacturer. Given real conditions, we may add extra 2 ft of head just in case, making pressure drop 9.5ft of head. NOTE: Pump head is a term used to describe the force the circulator develops to overcome pressure drop (pipe, fittings and valves). In a Closed System, "pump head" is NOT the height of the building. Height (on the Scheme above) is not taken into consideration. Regardless of this the zone manifold is below the pump, only rise is as pex comes out of top of pump to curve around and down to manifold. As per pics

The next and final step, is to match the obtained data with a correct pump on a Circulator Pump Curve Chart Which should be the Grundfos 15*58 on mid speed??????

But it is not the case.

Hope you can help, i'm not sure if the pump is functioning properly, from startup last winter it has never pushed what i had hoped it would. The previous system ran with same configuration giving me an output of 1/2 gpm per run, which works out to 4 gpm into manifold out of 15-58 pump. It was hooked to town water via a check valve.
AGAIN
Its not that it does not work, it is that it does not provide what the specs said it would.This system is on a pressure/fill tank which provides a system pressure of 12 psi on input to pump.

Thanks neil

Jamie Hall

You have added 2 feet additional drop for "just in case". Have you actually figured out the additional loss through the manifold and valves? It may be more than that.

Also, how steep is the pressure/flow curve for that Grundfos (I don't have the curve). Some pumps the curve is pretty steep, and if your head loss values are even slightly different the flow can be quite different.

Just some thoughts.

chingo

grundfos UPS 15-58 can provide 8gpm and tolerate between 7 (med. speed) to 12 ft (hi speed) of head.
I put same pumps in another system and was able to acheive 4gpm to manifold and .5gpm per run. This system also ran to same manifold configuration of (8) runs of equal length.
If i take spec of curve that would be 13 to 16 ft of head.

However on this current system i can not acheive even that.
I am stumped to explain the additional head to overcome in system. All components are on same floor.

Somehow I have all this extra resistance to flow in my system.

Ironman

Have you tried the circ on high speed. IDK why you chose to use those external check valves: they add a lot of head. The 15-58 comes with an internal one that adds very negligible head.

I've got systems with 16 250' loops and one 15-58 on medium is flowing about .6 GPM on each loop. Get rid of the external checks.

chingo

The higher figures that i have quoted are on hi speed for UPS15-58 taken right from mfg. curve charts. the reason for the check valves is that system was built by Watts, who pulled out the factory check valves and added the ones in the picture as a replacement. They look alot more rugged but you are right it could be the chech valves, but all 3 seems weird.
If you break it down to its simplest form.
I run system with just one loop 20 ft 3/4"pex to and from manifold shown in pic. above, then from that i allow only 1 run to be on ((other 7 off) run is 250 ft of 1/2" pex) Run on Med speed i can acheive .8gpm of flow max., switch to high speed i can acheive .85 gpm of flow max. if i turn on other runs it drops by number turned on. 8 on .1gpm of flow max. to run .85gpm to manifold. max.
Where all this additional head is coming from i am not sure. But a check valve that is not funtioning properly could explain it.
I will have to try bypassing it. Of course the way they built system will not make it easy.
I would love to get the flow that you have with your 15-58 but even with the other system adequate is .5gpm when on per run.
Part of other system shown below.

hot_rod

I doubt those checks are the problem unless something is stuck inside them, very low pressure drop in the 3/4 size.

Flux gobs and teflon tape are common examples of junk found lodged in check valves. that would be one of the first places to look.

There was a time when Watts cleaned all those Hydro Control Panels in a large vibrating drum machine that had a bunch of steel beads in a mild acid and the whole tank vibrated. We found those steel beads in all sorts of places they didn't belong

A flow meter would confirm actual GPM, after that lack of heat could be due to tube spacing, excessive heat loss, insulation or lack of?

Kinked tube in the slab?

gennady

20F temperature drop S/R is for high temperature systems. Radiant system generally requires 10F drop. I design my systems at 5-7F drop to create evenly heated floor. it calls for much higher GPM. Double at least.

chingo

I appreciate the input on my issue.
To address gennady point.
Boiler set at 100F on floors upstairs which are plywood sleeper.
I get a drop of 20F between SEND and RETURN if i push .5gpm through runs. This is sufficient for the house which has R66 insulation in ceiling, R32 walls, ICF foundation.
On 8 runs this gives me .5*8=4gpm=40,000btu.

However this is not my problem.
Given 2 exact same runs with same equipment but different locations.(houses)
In one location i can acheive above. in other location i cannot get above .1gpm per run.
This does not make sense, which is why i am stumped.
I i rule out check valve, pump,etc... i am left with run,
BUT with purge cart i can push 2gpm through a run which to me means there is no blockage.
Could it be mixing valve which is common to all 3 zones.
ALL 3 zones are exhibiting same result.
Flow that as calculated above in previous post should be giving me 8 times what i am getting now based on pump curve.

To address hot rod point.
Flow is my issue and as stated above i don't think i could get 2gpm through run if it was kinked.

Again it is like i have a ghost in machine.

Guess i'll have to start replacing components to see if i can get different results.

I appreciate ALL input and thank you guys for your information.

Gordy

deleted

Ironman

I doubt it's your mixing valve: you should still get full flow no matter what position it's in. It just wouldn't give the proper mix temp if it was malfunctioning. There could, however, be a blockage there.

I would pull the pump and the check valve for that zone and look for a blockage. Look at the impeller particularly.

If you turn the water temp up higher, you may be able to feel along the lines and see if there's a temp drop at a particular point that may point you in the right direction. If you have low flow in all zones, then look at the components and piping that are common to all.

Ironman

Your other system is variable speed injection mixing; this one uses a thermostatic mixing valve. So they're not exactly the same. The mixing valve adds more head to this system, but it looks to be of sufficient capacity not to be an issue. I can't believe Watts would have mis-sized it, but there could be a blockage there.

Zman

You are placing a lot of faith in cheap plastic flow meters. Can you measure your exact delta t on each loop.
You would be wise to start disassembling and cleaning parts that could be gunked. Flow and check valves would be a good place to start.
Was the tubing protected from contamination though the entire install? A carpenter working near an unfinished manifold would be an example.

chingo

Cheap plastic components isn't that the way life is going.
Watts also replaced the key vavles in manifold with plastic,they used to be brass.

hot_rod

chingo said:

Cheap plastic components isn't that the way life is going.
Watts also replaced the key vavles in manifold with plastic,they used to be brass.

I think those replacements key valves are hygroscopic vents, perhaps.

lchmb

just curious...in your pic's to start the discussion, your return to the primary loop is closed ..was this just while trouble shooting or done for a reason?

chingo

I believe you are asking about return by mixing valve. shut while purging zone's. But everything open when normal operation.

Mark Eatherton

I loaded your system into Siggys software, using the following parameters.

8 port manifold, each 1/2" PEX circuit at 250', 3/4" PEX at 70 long, 1" manifold, Grundfos 1558 on speed 2.

Total flow to manifold = 4.78 GPM, individual circuit flow = .6 GPM. With just one circuit open, flow = 1.33 GPM

When I take the pump to high speed, total flow = 5.46 GPM, individual tube circuit flow = .68 GPM/circuit. With just one circuit open, flow = 1.43 GPM

Sometimes you can "hear" the hydraulic resistance, especially if it is a pinched situation that will cause a HISSSssss. May have to use a screw driver pressed against your ear to confirm.

The one component that all three pumps do have in common is the mixing valve. Might try pulling the guts out of that, look it over and see if you can re-assemble (temporarily) with out the guts and see if that makes a difference. Most mixing valves do have a low CV, meaning more pressure drop... As flow increases, so does the associated pressure drop.

Can't be of much more help without actually being there to see and hear whats going on.

Drawing of test results is attached.

ME

Dave H_2

I would definitely look at the mix valve. If it is thermostatic in nature, there is a high pressure drop associated with it. Even if sized based upon 80,000 BTU's of a 1" valve.
Thermostatic valves have high pressure drops typically. I took a look at a project I did a while ago with a Taco 1" 5000 mix valve and it had a Cv value of 3.8.
When plugged into the formula to find the head loss, (flow/cv)squared x 2.31 = head loss;
(8gpm/3.8)squared x 2.31 = 10.18 foot of head.

Add that to the head loss of the manifolds and pex.

Best solution is to change the valve to a manual valve rather than thermostatic. A manual valves can have Cv's in the 8 and above range.

Enjoy

Mark Eatherton

Yeah, Siggy has mentioned that this (Cv issue with mixing valves) is a real issue within our industry. People keep forgetting about its inherent pressure drop...

hot_rod

Here is an example of the pressure drop graph included with some brands of mix valves. Read the gpm across the bottom axis, then up to the pressure drop on the side axis.

I know Watts has been using thermostatic valves since day one, over 20 years now on their panels. Properly sized they work fine.
Too high of a Cv valve and they will not respond to a low flow rate, maybe one small zone calling, for example. the valve will have a min. flow requirement also.

I think installers get confused when they see spec sheets that show 20 gpm flow rates published on a mix valve, not understanding the pressure drop issues with the flow rates in a low Cv valve.

Here is what 20 gpm looks like in a 2.3 Cv valve.

SWEI

Very true, Bob.

I just want to mention again that bigger is not necessarily better when it comes to a proportional control valve, and that mixing is definitely a form of proportional control. Oversizing the mixing valve will result in a lack of control authority, resulting in unstable mix temps. This seems to affect 4-way valves less than it does 3-way valves.

Ironman

@chingo
I would highly recommend that you carefully look at the last four posts in light of your application.
I personally would have never connected a one inch mixing valve to three circulators and that many loops, but I give Watts the benefit of the doubt assuming their engineers are more knowledgeable than I am. So I assume.

I would ask them for the Cv rating of the valve, but it's still not the correct component for a slab.

hot_rod

The Watts 1"mixer shows a 3.2 Cv. What is the total required flow?

If it is 8 gpm, that equates to a 14' pressure drop, doable with a pump shown. on speed 3

Also zone 6 is priority for some reason, as such only two zone pumps run at one time? If so what is the gpm load of those two?

I suspect the valve and pump selection is workable, the product number is on that Watts board, the rep or factory should be able to supply the original design criteria.

I doubt Watts would send out a panel with mis-sized components, they have been at this a long time and learned some lessons

Ironman

hot rod
That would be 14.4' of head just for the mixing valve. If we add in the 1/2" pex, the manifold and the 3/4" pex, that puts it above 20' of head which is past the 19' that a 15-58 can produce. That's assumuming 8 GPM through the valve and 4 GPM going to the manifold.
With just one circ and 4 GPM, he would have 14" of total head which would be just at the far side of the 15-58's curve. So he should see the desired flow with just one circ running, but not multiple ones. Correct?
We don't know if Watts had all the data on the project given them when that board was selected. It seems somewhat doubtful given the fact that the wrong mixing component was chosen.

hot_rod

True at 8 gpm flow rate, somewhere in the thread 4 gpm was mentioned? What is the flow rate required?


If it is the Watts 1-1/4 valve, cv 6.2 I believe.


Usually a Watts Radiant design included heat load, tube layout, spacing, flow rates, loop temperature, all the required data.
Rare they would build and send a Hydro-Control panel out to a job without all the necessary data to build it to.

As I remember they were all custom built and well documented with a job name and number stamped right on the board. also the build requires a sign-off sheet from the rep requesting the build, acknowledging the build criteria was correct.

An important form was the Assumption Report which detailed the design and build to the specification submitted. Any jobsite changes, all bets are off.

chingo

Thankyou for pointing me in the direction of HWTCV

The following is off spec sheet i obtained.
based on labeling on device.

Hot Water Temperature Control Valves
Watts 1170M2
Min Supply Pres (Static) 30psi
Inlet Temp. hot 120F-200F
cold 40F-85F

Could it be that because my system runs at 110F and 12psi.
I am not able to make the temp control valve operate properly

If i was to hook it up to city water at 35-50psi 140F would it not operate efficiently???????

Country water system which is why i used AXIOM MF200 to provide pres./fill for bungalow in country. 12psi 110F

To operate similar to glycol system.

Ironman

Static fill pressure is only necessary to overcome elevation in a closed loop. The higher water is lifted, the more gravity is trying to pull it down. Since static fill would exert equal force on all sides of the component in a closed loop, it should have no bearing upon the flow rate. What you've posted for the valve appears to be for an open potable water system.

Did you have Watts engineer this from your ACTUAL job site data?

hot_rod

chingo said:

Thankyou for pointing me in the direction of HWTCV

The following is off spec sheet i obtained.
based on labeling on device.

Hot Water Temperature Control Valves
Watts 1170M2
Min Supply Pres (Static) 30psi
Inlet Temp. hot 120F-200F
cold 40F-85F

Could it be that because my system runs at 110F and 12psi.
I am not able to make the temp control valve operate properly

If i was to hook it up to city water at 35-50psi 140F would it not operate efficiently???????

Country water system which is why i used AXIOM MF200 to provide pres./fill for bungalow in country. 12psi 110F

To operate similar to glycol system.

That valve will have similar performance to the other brands mentioned.

You need about 20- 25° warmer water on the hot port than the desired mixed temperature to allow those valves to regulate accurately. What temperature is the boiler supplying when you are trying to mix down to 120°.

When you use city or well water to purge you have that available psi to drive through all the pressure drop components, maybe 40- 60 psi.

When the system is closed and using only the circulator pump pressure difference you do not have near that much available.

So make up water purges flow real good and you see adequate gpms on the loops, the pump will not provide that same amount of flow.

As everyone mentioned you have flow constipation somewhere. Not you, but your heating system.

About all you can do is track down the cause, pump size, plugged device, valves not opening fully, etc. It needs to be done at the jobsite, get out the tools and start digging through the list of suggestions.

I have had systems where we removed the guts from 3 way mixing valves and corrected a flow blockage. Oddly enough they mixed fairly accurately with a manual balance. That is certainly a very easy first step to running down the problem. As all the numbers show it is the most restrictive device in the circuit that we can see online here.

chingo

Concentrating on bsmt zone (one shown in pic). other zones isolated.
More test results, raised system pressure to 25psi at fill point.
changed 15-58 1/25hp to 26-99 1/6hp
Boiler not on. but Relays active. Water temp 60F

RESULTS. System on but idle all points approx. 25 psi.
Call for heat 25 psi at fill points and boiler 14.5psi at gauge after mixing valve. Very little improvement in flow.
Getting .85gpm for 1run ON 7 OFF on Zone manifold.

When boiler active set to 110F

hot_rod

The fill pressure will have no bearing, just be aware you may be close to popping the safety relief as it heats up, most safety valves are 30psi relief.

The expansion tank pre-charge needs to be adjusted to fill pressure, and the elevated fill pressure decreases the expansion tank capacity. None of those steps help determine or fix a flow restriction condition.

Are you sure about the loop lengths? Kinked tubes and excessively long loops behave about the same. You have plenty of pump to make this work.

Did you dig up any of the initial design docs?

chingo

I have the system design
It was done in Loop Cad by a BCIN registered designer
Thermolec electric 4 stage 80,000BTU boiler relief valve came with boiler and stated must use their relief valve 100psi in system.

Loops are 250' max. (majority under that.)

3zones of 8/8/4 loops all zones are behaving the same.

If i hook it to potable system 35 psi do you think this will improve performance??????

hot_rod

How did the Watts Radiant panel get into the job? It should have been designed and built to your requirement. As such all the valves and pumps should be sized correctly.

The output of the boiler is not necessarily the same as the heat load. The heatload should be a number in BTU/hr at design conditions for your area. Maybe the designer you mentioned has that number?

So one of two things... either the Watts board was not designed to the actual load you have, or you have a flow restriction preventing it from working properly.

So run down one or both of those. Find out who sent in the design for the Watts Radiant board, and or run down the list of suggestions above. Most agree that mix valve could be the problem, undersized for the load, or plugged up.

So you have 20 loops total, at .5gpm per loop you need 10 gpm.

One of the zone pumps is labled priority for some reason. Usually that indicates the other two shut down when that zone calls. If so, only 2 zones, maybe 16 loops call at once, so 8 gpm. that mix valve can handle that flow rate.

Ironman

No. Again, the static fill pressure has nothing to do with the flow rate in your system. It only needs to be sufficient to overcome the highest elevation in the system.
If Watts didn't design the system, then I think you've found your answer as to why the wrong component (the thermostatic mixing valve) was used. Your problem lies there. You're grasping for straws to look elsewhere.
You've been given sound advice by some of the top people in the industry (Bob "hot rod" Rohr, Mark Eatherton and others). If you won't follow that, then what else can you expect from us?
I'm not trying to be unkind, just reasonable.

Zman

If you look at the resistance curve of the device, it matches perfectly the performance difference you are experiencing.
As others are trying to explain, the static system pressure does not matter.
That valve is really not appropriate for the application, it does not matter who specified it.

Gordy

I think you are confusing potable pressure, and its ability to drive through component restrictions with pressure differential of a circulator in a closed system. Raising static pressure will do nothing to increase the circs differential, or its ability to drive through restrictive components.

This is why piping diameter, loop lengths, valve cv's, glycol % are so crucial in a closed loop radiant design. The goal is using the smallest circulator possible.

hot_rod

Maybe this visual helps. Circulator pumps add head energy, shown by the pressure gauge.

All the "stuff" in the piping circuit uses up that energy. This is why we ask about valves, flow rates, etc.

It sounds like you have too much flow resistance.

Not to sound like a broken record but... removing the guts from the Watts mixing valve essentially turns it into a 1" tee, as such very low flow resistance. If it flows correctly on the manifold meters with the guts out, theirs you problem, Vern.

chingo

Let me first say
I APPRECIATE ALL OF YOUR HELP, INPUT, AND IDEAS.
I have no doubt that you are some of the smartest people in your field.
That is why i came to this forum in the first place.

I am not trying to be difficult.
I ask questions different ways in order for me to understand all aspects of a problem. I'm not the sharpest tool in the shed. Sorry :-(

Watts know's about the system and have kindly agreed to send someone to site. (behind the scenes I have been trying to make this happen and they have gaciously agreed)

I will post the results on this link.

System was designed using Loop Cad by BCIN registered tek

The UPS 15-58 should be more than capable of providing flow as per calcs. (see typical zone below).

The Watts system was bought with following in mind.
1 primary panel to handle main loop issues
1 3 zone panel to handle 8/8/4 loops
1 Boiler modulated to handle heat reqirements
1 Axiom MF200 to provide pres/fill capabilities.

Each panel is designed to deal with its function so you can plug and play the zone manifolds without huge site expense.

Everything is swappable and checkable.
Which I have done.
Except the mixing valve. which i will now do.
@ I left it till last and was hoping it was not it.

If it is the wrong one I am to blame obviously i didn't take into account some of the things that were mentioned previously.

Once the solution is found i will never make the mistake again i can guarantee that.

But i have learned an awful lot and can tear apart and put back together almost anything in the system now.

Mixing Valve my curse is the last thing on my list.
I really don't need a mix valve.
From the pics. if i 90 feed from boiler into supply manifold before pres/temp gauge and cap feed coming back from return manifold does anyone see an issue????

Below I try to show what i took into account for the head calculations on the pump curve.

I understand that the circ. pumps have only the resistance of the circuit to overcome.
That the pressure from the Axiom pres/fil tank overcomes height of building and makeup water that evaporates from system.

The mixing valve see's same pressure on all points H/C/M as provided by the Axiom.

Bsmt. Zone Only/1 Run on 7 off (Same as parallel)
The Grundfos pump overcomes resistance of
check valve
Zone Shut off Supply
3/4" pex pipe
Manifold Supply Shut off
Manifold
Flow Meter
Loop Connection
250' approx. 1/2" pex
Loop Connection
Loop Shutoff
Manifold
Manifold Return Shut off
3/4" pex
Zone Shut off Return
Return Manifold
Main Loop Piping
Mixing Valve C
Pressure/Temp Gauge
Back to pump
Grundfos UPS15-58 should over come this and provide .5gpm of flow to zone.

Main Loop Pump
Main Loop Pipe resistance
Various shutoffs
Boiler
Relief Valve
Air bubbler
Pres/Temp gauges
Feed Into Mixing Valve H

Blockage or restriction in the Mixing Valve OR
One not designed for application OR
Just bad.
Could restrict flow and would be experienced through out the system.
Bad System Shutoff (not opening all the way would restrict flow)
However, wouldn't it be noisy.
System when on operates smoothly and quietly.
Heat transfers through out (restricted flow) but still gets there on any loop.
Mixing Valve does mix

Again thankyou for your time and patience with this problem
you have given me great insight.

Neil Please excuse my bad spelling or terminology

hot_rod

Maybe I already linked you to this journal, if not take a look. By the time you get into this 30 pages or so you will have a good feel for how a system is sized and how the pump and system interact.

With the info you have you could develop a system curve. Lay the pump curve from Grundfos over the system curve and it defines the actual operating point.

Maybe we have overwhelmed you with bits and pieces of info, not defined the terms properly, jumped into the middle of the design without explaining the beginning.

This Idronics will step you through the process and help clear up some of the termanology.


http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_12.pdf

Zman

Why not just replace the mixing valve with one appropriate for your system.
A properly sized Taco I series valve would give you Outdoor Reset and boiler condensate protection without the flow penalty you have now.
Your problem is not that you have a mixing valve, you just need one that is designed for your application.
Carl

chingo

Thankyou everyone for your input.

I took mixing valve out of system.
Cleaned mesh filters and replaced.
Purged sytem and repeated.
Ran system and had much better flow at last.
This was the problem all along

It is still not what i was expecting from calcs.
but would do just fine to run house.

I am now looking into the TACO I series in order to make performance better.

I did not realize when ordering system as per design that a mixing valve would cause that kind of resistance.

I guess if i had known better, I would of verified flow characteristics of the device, but they don't give you choice on such a basic system.

Again thanks to all, i have learned valuable lesson's.

Neil :-} CHEERS!

Ironman

Just keep in mind that the I series valve will add some resistance too. Check its CV rating and use the formalu given to determine how much.
The only way to avoid any more head is by using some form of hydraulic separation (low loss header, closely spaced Tees, etc.). Injection mixing would accomplish that.
Go to Tekmar's site and read their essays on variable speed injection mixing.