No flow?

Paul S_3

I went on a service call today " not enough Heat" area will not get above 65f.... It's a series loop baseboard system 3/4" baseline 2000...This home has 2 hot water boilers 1 for the basement and First floor and the other which has the problem is for the 2nd floor. .... customer called me because the company who installed this system could not fix it..... previously the home had just one boiler which heated the whole home. ... customer wanted to separate the 2 floors. ... The 2nd floor has a heat loss of 23,000 btus..... There is a total of 55 feet of 3/4" element. .... total loop length I estimated about 150 feet.... The loop is ran in mostly 3/4" pex with some parts using 3/4" copper. ....I counted from what I can see about 37 3/4" pex elbows and 12 copper to pex adapters. .... boiler is oversized 130000 btus.... boiler is piped properly pumping away from expansion tank on supply. .... No air in system.....The pipes get hot but there is very little heat radiating from baseboard elements. ... system pump is a 008... temp drop across loop is about 5f... No flow. ... need bigger pump? .... Paul s

Unknown

bigger pump???

Its bigger pipe is what u need!! Def not a hdyronic heating guy... look inside of those pex fittings.. every one of them is a restrictive fitting, limited the full flow .. tear it out and install with proper piping and fittings.

Unknown

bigger pump???

Its bigger pipe is what u need!! Def not a hdyronic heating guy... look inside of those pex fittings.. every one of them is a restrictive fitting, limited the full flow .. tear it out and install with proper piping and fittings.

Paul S_3

gpm

What is the max gpm that can flow through 3/4" pex? All I need is 23000 btus .... explain if I'm wrong.... Don't I need just 2.3 gpm? Paul s

Unknown

its not the pex

Its the fittings u have to overcome the restriction.. so u figured all you need is 23,000 btus, so how's the bigger pump gonna help you as you stated in first post? Proper repiping is needed.. and don't know what kind of boiler there, that may also needs a by-pass

Zman

Temps

How are you measuring the delta t?

If you had inadequate flow, you should also see a much wider delta t. Can you get a good measurement at each baseboard?

You are correct that you only need about 2.3 gpm. 1/2" pex with that circ would move that much water.

Air lock? Bad circ? Incorrect piping?

Is the air flow good around the registers.

Carl

Harvey Ramer

You know

it sounds like you are not getting any convection across the baseboard fins. Make sure the vents are open and there is nothing hampering the air flow.



While the setup is less than ideal, you should be getting about a 17°Δ with the equipment that is currently installed. That is, with 180° water. According to your heatload calc you also have enough baseboard.



Harvey 

Ironman

5* Delta T?

If you are getting a 5* delta T, you don't have a flow issue. To be sure, 37 pex Ells would be very restrictive, but a 5* delta indicates more than sufficient flow - provided your emitters are properly emitting.



Could it be that the elements are installed with the fins rotated 90* in the wrong direction? Any knucklehead the would put 37 pex Ells in a loop is subject to do that too. I just had to correct that on a job last week.



Low delta T and low heat emittance indicate a problem with the radiation.



Once you get the rads working, you may find that then the 37 Ells are also an issue if your delta T goes too high.



3/4 pex has about the same flow as copper. It's the barb fittings that are restrictive.

Harvey Ramer

Bingo!

You might just have hit on it Bob. Rotated 90° I have not seen it ever but it would definitely cause the symptoms this system is having.



You can probably look like a hero on this one Paul.



Harvey  

Paul S_3

baseboard

the baseboards were indeed blocked by a bunch of junk that the tenants put there....i opened all dampers and moved everything....previously with the same baseboard the home was heated by a single boiler and the basement, 1st floor & 2nd floor were ALL one series loop of 3/4" baseboard, and it worked correctly. im measuring delta T with a digital strap on thermometer at the supply and return of boiler.going back tomorrow.... Paul S

M Lane

Amps

At the pump motor. Be sure to check them. The electrical junction cover lists what amps should be drawn

Harvey Ramer

Mr Lane

brings up a good point. According to my calculations the circulator will be running at low flow rate 90% or more of max head.



That is not a good duty point for a pump.



Harvey