I recently inherited a job. The primary complaint is the cast iron baseboard are not all getting hot. The boiler is a dunkirk 150k btu, with domestic coil & 3 zones, circulators. The boiler is 2 years old, I don't know anything about the old boiler or if this was a problem with the old boiler also. The house is an average sized ranch. Main zone is cast iron baseboard monoflow. 1 1/4" supply splits to (2) 1" perimmiter supplys.
venturi tee is on the return side of the baseboard. On the opposite side of the basement, the supplies tee back to 1 1/4" and return down the center of the house. All air has been bled off . On a call for heat The burner and circ. start, the main seems to heat up in a reasonable time and the supplies to the baseboard are getting hot. The kitchen and 2 back bedrooms only 1/2 the base board gets hot, One section in the livingroom doesn't get hot at all. If the thermostat is raised 6 degrees, eventually all the baseboard is completely hot, but it takes 15-20 min for the water to make it through 10 feet of baseboard. There is a Taco 007 circ on this zone. There is 2 walls of baseboard in every room and a 6' length in the hallway. Today we moved the thermostat away from the hall baseboard. Other than a restriction in the pipes, I can't figure out why it takes so long for the water to move through the baseboard
Originally posted by hebegiant
The primary complaint is the cast iron baseboard are not all getting hot. All air has been bled off. Other than a restriction in the pipes, I can't figure out why it takes so long for the water to move through the baseboard
Apparently not all air has been removed from some of the rads. Bleed each individually. If they have no vents or vents that don't work, replace them and bleed.
All air bled
All coin vents are new and every baseboard was bled and then bled again
when they replace the boiler did they mix up supply and return
witch way do the aarrows face on the tees
old flow check
They connected the new boiler to the bottom of the old flow check. The supply water enters a standard tee, goes through the baseboard and returns to the main in a venturi tee with the arrow pointing in the direcion of the water flow
If the circulator has an internal check valve then that is your problem. Change it to a 007 with out a check valve.
If that is not the case then get rid of that old check valve at the supply (with the new boiler some crap might have stirred up and check valve might not be opening all the way) and install individual check valves for each zone except for the ones that might have internal check valves in circulators.
Even that might not solve your problem if the 007 doesn't have enough to overcome headloss in piping. You may need a circulator with a higher head rating on your g.p.m. needed. Most monoflo systems are very restrictive. Also if there is a bypass between the supply and return that may have to be closed off. But if there is one watch out for cold returns.
First off lets think about what you have.
Highmass emitter with a onepipe monoflow system.Which was
design what 40 or 50 years ago with the attention focus on
this zone only.
Now add acouple more zone somewhere else in the house and take away the 180 degree water from the main system and blend in lower water temps to the main system and whats you get.
Thats right a time lag of when your main system heats up.
Without doing the math I could say you may need a bigger circ to create more flow in the main..however from what I reading from your reply I'll stick to my first conclusion.
1 1/4 pipe is good for 14 gpm x 10.000 btu =140.000 btus.
Pretty close to your boiler size.
Now add some more zones,plus domestic that has priority over
the heat and a very cold day and what do you get?
May want to add a monoflow tee to the supply to increase flow thru the branch circuit. Water will take path of least resistance and that sounds like what is happening. Also need to check size of pump to make sure it is large enough.
Does the boiler short cycle? Does it hit high limit? Does the boiler temp rise quickly? Might be signes of poor flow on that flow check or pump.
No short cycle
The boiler does not short cycle. Once the main zone calls for heat, the boiler operates around 170 -175 until the return comes back hot, then the boiler will go up to high limit. The thing is its taking 10-15 min. for the water to go through the baseboard. And if I let the boiler run long enough for the return & all baseboard to get hot, it gets so hot in the house you cant breath.
I'm going to disconnect the baseboard in the hallway, I don't think ranches need it there especially when all the rooms have 2 walls of baseboard. We already moved the thermostat from the living room end of the hall to the bedroom end. We're also going to replace the old 1 1/4" flow check. I'm tring to convince the homeowner to also install air elimination ( Scoop or Spirovent) whoeverinstalled the boiler didn't put anything in.
Get rid of that 007.
Measure your pipe length, and baseboard to determine head.
May have to go with a 008 or 0011.
Bet the original circ was a high head circ, and some body though it was just a reg B&G 100 series.
You don't have to remove any baseboard, you just need the right circ.
now we're talking
When you measure your main pipe length, don't forget to add 10 or 12 FEET of pipe for each monoflow tee in the loop. THEN select a pump.
Never seen a 007 work on ANY size monoflow loop in my life.
Also look for "altered" radiators, where a bunch of piping was added to existing tees, like, maybe, during a remodel.
Monoflow systems had air vents installed at the radiation, and a compression style tank on them.
No air scoop, but an Airtrol fitting, instead, was installed.
Sometimes the "boiler guy" cuts out stuff and dings it. "If I don't know what it does, you don't need it."
"This system NEVER had an air scoop, I ain't adding one now!"
"Oh, so THAT'S what that was for...."