new system injection problem

pat_3

after changing injection pump ,everthing works fine ,injection pump no longer running at full output.thanks

pat_3

new system injection problem

system is less than a year old.entire home is radiant heat,suspended floors,tube is embedded in mudd job throughout.btu load of about 75,000.piped primary/secondary,1 inch primary,3/4 injection lines,1 inch beyond injection lines with 3/4 secondary loops to various manifold locations.injection controlled with a tekmar 356.tekmar 356 indicates 90% output from variable speed pump continuously and doesnt seem to be able to reach current desired mix temp.boiler does not seem to have problem reaching aquastat setting.rooms not satisfying since temp went below 20 3 days ago.

marc

injection piping

sounds like there are a few things wrong.tekmar essays say injection piping to be at least 1 pipe size smaller than both boiler and low temp loop. 3/4 in. inj. piping is huge. also tee spacing on primary secondary piping and on low temp loop. what size pump on inj. we use the 356 all the time. if piped correctly they will perform perfectly.

kevin

what is..

the boiler temp? what is the primary suppy temp and return temp? Any baseboard loops? I had a problem like this just the other day.The boiler was not putting out 180/185...even though the boiler gauge said it was 180 it was in reality 165...kpc

pat_3

new system injection problem

injection piping is 1 pipe size smaller than boiler piping as well as low temp secondary header.pump is b&g nrf22,was throttled back on inj line until today.

pat_3

boiler temp aswell as primary supply temp 180,seems to cycle fine,just cant reach mix target temp

kevin

is there...

a boiler minimum temp. If so what is it set to.
Try boosting your boiler temp. to 190* kpc

pat_3

i dont think boiler temp is going to make that much of a difference.i didnt design or install the system,homeowner cant contact plumber that did.i dont know for sure what was done with the tubing layout but everthing i can see in the boiler room seems ok except mix temp seems to be about 20degrees off target.

eleft(retired)

new system

If you have a throttle valve in the variable speed injection return open it so the pump reaches 100% then reset after it reaches desired mix temp.

al

pat_3

opened throttle valve all the way,mix temp still didnt reach target temp

eleft(retired)

target temp

It takes a while

al

pat_3

thanks for your input al ,i'm thinking that maybe the flow rate on the secondary side might be too great for injection lines and pump to keep up with,if mix temp isn't achieved with throttle valve full open over night,i'll check delta t's on secondary loops and maybe throttle them back if possible.what do you think?can it be possible the water is moving so fast on the secondary side that its not picking up enough heat off the injection line.i've never seen this happen before.can't be the boiler right?if the boiler was under sized it wouldn't reach high limit?

Patrick_3

Had the same

problem this week on a new installation. It has been running fine up until a few wks ago. What I thought could not be happing, was. My injection loop was back flowing and just recirculating within itself and not drawing 180* water from boiler. All due to the screen of my y-strainer being plugged with flux and debris. I removed the screen and system is working great. Good luck, Patrick

eleft(retired)

Boiler not a problem

Pat,

Are you getting 100% V/S pump speed?

Are you on out door reset mode?

If so what temp? (you might need to raise it to start the heat curve higher ending up with a higher supply temp)

Is your ratio set correctly to achieve the temp you want at the colder than expected out door temp? (if on out door reset)

Is your supply temp set higher than the temp you want?

al

kevin

i didn't..

ask if the boiler size was too small. Iwas asking if the boiler temp was high enough. This just happened to me the other day boiler temp was too low. (8148 was wrong) as soon as I turned up the temp the injection loop zone came up to temp.kpc

pat_3

tekmar 356 says 90% output which i believe is the highest indicator.i am on outdoor reset,outdoor design temp was set at zero ,i bumped it up yesterday to twenty and it didnt make a difference,thats when i realized i wasnt maintaining desired mix temp regardless of outdoor design temp setting,mix temp only seems to be getting to about 86degrees...should be around 105,125 with bumped up outdoor design temp.if it was an older system i would think the injection pump was bad.

pat_3

kevin,boiler temp is set at 180 and actually is 180

hot_rod

Are you sure

the injection pump is spinning? May be time to pull it out and check. Could have a broken shaft, plugged impeller?

Is there a throttle valve on the injection riser? You may switch the tekmar control to setpoint mode and see if it reaches target.

In cold start up , it takes time to ramp around.

Doubtful the secondary pump is moving thre water too fast!

hot rod

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eleft(retired)

Pat,

Do you have this?

pat_3

pulled the pump ,looked fine ,replaced it just to make sure.system now runs the way it should.thanks to everone

pat_3

pulled pump,looked fine,replaced it just to make sure.system now running the way it should.thanks to everyone

Steve Eayrs

check the sensors.

I have run into a few sensors going bad. You can ohm them and test according to the spec sheets. I know you checked the injection pump, but what about the system pump? This would explain the injection running full bore, if you don't have circulation on the slab pump. Whats actual temp. at slab sensor?

good luck, Steve