monoflo trouble

Uni R_2

My guess would be flow. There simply aren't enough GPMs for the diverter tees to have enough pressure drop for those branches to flow. It's like a plane that can't go faster enough for its wings to get off the ground.

It's either the pump (not enough velocity at low head) or the piping (restrictive bends, valves, narrow tubing, long runs, some capped monoflos perhaps?).

The pump is easy to check... slip in the old pump if it is still around.

EdyLogicMstr.

monoflo trouble

Hello everyone. I would like to present a problem that I have recently come upon in the field. A customer of ours this past summer had an older Am. Stnd. or Nat'l. Rad. boiler replaced with a new Buderus G115 3 section oil fired boiler. I was not involved on the installation but have been back to the residence on three occasions due to insufficient heat. The system is a split monoflo with 1" copper mains that have 3/4" branch connections for the radiation on the 1st. floor & 1/2" branch connections for the 2nd. floor. The header is now piped in a "pump away" configuration and includes a # 15 Grundfos 3 speed IFC circ. The customer complains that several areas of the house no longer heat well since the new boiler was installed. In fact there are several pieces of radiation that barely get luke warm to the touch. There are new coin vents installed and there is no air present @ these vents. We have tried bleeding the system with the boiler water cold & hot and @ nearly 25 lbs. pressure to no avail. We have also tried changing the speed of the circulating pump again to no avail. The new header is piped in such a direction where the water leaving the header now has to make several 90 degree turns before entering the original piping. Have we perhaps changed the pressure drop through this system so dramatically that it is having an effect on several of the monoflo tees downstream ? I would entertain any thoughts or advice on this perplexing problem.

Thanks for your input !
Lawrence

Empire_2

Hello Lawrence?

Sorry to reiterate, buy are you sure the split header is in fact that?? meaning that the house takes off in two directions? What pump was in there before? are you sure that the flow is in the correct direction as far as the Mono- tee's? Don't mean to question, just trying to get a handle on what you see.

Are you able to isolate one brance from the other and check the results? SOunds like a flow issue not a pressure issue. 12 psi should be more that enough for a 2 story house.

Mike T.

EdyLogicMstr.

monoflo trouble

Hello Mike;

Thanks for your reply. Yes the system is definitely a split loop. There is a "Y" fitting at the beginning of the supply run just after the point where the new header connects into the old existing piping. One side runs to the front of the house and the other runs to the rear. On this "Y" fitting there are butterfly type isolators (like in some purge valves) that can be used to restrict either side of the system if necessary but there are no real isolation valves. The old boiler used a standard B & G 100 circulator on the return line. We have checked and double checked to make sure that the new piping did not get accidentally hooked up backwards and it is correct without any question. The mono tees here have arrows on them to indicate which way they are to be installed depending on whether they are in the supply or return pipe, so we are also positive that they are installed in the correct flow position. As I said we are puzzled because half of the radiation and or convectors in the house heat well while others do not and by the way the problem ones are located on either side of this split loop so there is no real pattern to discern here either. It certainly is not an air problem because like Dan Holohan says : If you bleed and don't get air it's not an air problem.

Lawrence

lee_7

Are the radiators that are not working on same "loop" are are they split between the loops? Is it the ones fed by 3/4 or 1/2 tees? Do you have pictures, they always help.

EdyLogicMstr.

monoflo trouble

3lees;

There is no pattern to the areas of the house that are not heating well. Some are on the 1st. floor (fed by 3/4" branches) and others are on the 2nd. floor (fed by 1/2" branches) and they occur on both sides of the split loop. Sorry, I do not have any photos at this time

Lawrence

Jim Franklin

Check the amp draw of the circulator, ya never know you may have a bad you right out of the box.

TimS

Pumping away

Is it possible that the circs on the old system was on the return side and now that you are pumpimg away the flow of water is going backwards to the monoflow tees??

TimS

oops

Sorry for the post, Mike T already mentioned this

Unknown

Are the monoflow Ts

spaced correctly and the system in general, beyond what you did, is it proper.
I had a monoflow system once that I subcontracted from a local gas company to just change the boiler, I did and when it was done the widow(newly widowsized)told me the bedroom in front did not get warm, so I went back and removed the drop ceiling to find the 15 ft of copper fin in her 2nd floor room was connected to the basement loop with 1/2 inch tube to monoflow t's that were 6 inches apart. I told her that it never got hot and her husband didnt care and now with her new found fortune she decided to replace the boiler(that there was nothing wrong with)because she assumed that would fix the problem. Some times the the saying that realestate people use...buyers are liers falls into our trade too... and a lie of omission is still a lie. Hopefully for you its something less cynical like a bad pump.

RonWHC

The Grundfos folks

never saw a monoflo system. B & G designed it & they have a dirty little secret. It's called the NRF 33 Wet Rotor Pump. Designed to match the Series 100.

Go get one. Put it on. Watch the problem disappear.

Perry_5

System Pressure Drop & Pumps - Speculation

OK - the Engineer in me made me dig into this.

But - as a background I have a single loop monoflow T system - 1 1/4" Black Iron main - with 1/2 Black Iron risers on a 2 story house.

My old boiler also used a B&G Series 100 pump (other than oiling it twice a year - very reliable).

I struggled mightily with the question on which pump for my new system (Vitodens 200, Primary/Secondary, Boiler relocated (lots of new 90 deg elbows in 1 1/4" copper).

In the end the local heating contractor installed a Taco 007-F5 (he stocks it and the parts); which circulates a lot more water than the old B&G 100 (system temperature drop on cold days used to be a bit less than 20 F, now about 7 F). To me this indicates that the monoflow T loop pressure drop is about 8 Ft of head (i.e. The series 100 was not mooving much water at all... and the Taco 007 is moving a bit more than twice the water).

------

So lets speculate about your situation:

Assuming that you have not changed the monoflow T system - and its pressure drop is the same.

The old boilers had virtually no pressure drop them (very large areas and connections).

Could the new boiler have added head? I see that it has a 1" return connection, and 1 1/4 supply connection to the system. A lot of old boilers had 1 1/2" or 2" connections.

I doubt that a few more 90 deg elbows in and of itself added much head.

What is the comparison of the pump curves. How much water are you pumping at what pressure.

The B&G pump curves can be found here:

http://www.bellgossett.com/homeowners/A-50J-PumpCurve.htm

The Grundfos cureves for Series UP pumps is here:

http://www.grundfos.us/web/HOMEus.NSF/Webopslag/PAVA-53CT8Y


Unfortunately - based on your pump description (#15 IFC) I have no idea which pump it is - and I could not find a reference to that pump on the Grundfos site. If you are using a different pump find the pump curve.

However, There are 3 #15 pumps listed:

UP 15 10F/FR will almost certainly not work (it has less capability than the B&G 100).

UP 15-100F appears to have adequate pressure - but a much lower flow capacity than the B&G 100 unless the old system drop was near 8.

UPS-15-58F/FC (on Speed 3) has much better pressure and flow characteristics - and exceeds the Series 100 at lower flows; but....

Copper tubed monoflow T systems could have less pressure drop than the old Black Iron pipe systems.

If the old system/boiler drop was 5 Ft of head... The Series 100 pump would have put out about 22 GPM. The UPS-15-58 (Speed 3) would only put out about 15 GPM at this point(2/3 of the flow of the old pump).

-----

Now exactly where the old system head was - and the new system head is is unknown (unless you measured it); but, here is my guess: The new pump is too small. I suspect that the new boiler has raised the system head too (and even the Series 100 may no longer work).

I have not followed home heating pumps (I am a homeowner afterall - not a heating professional); but I do understand that there are some new multispeed pumps - or variable speed pumps out there. I would look for a pump that has a capability of say 15 ft head and the ability to move 25 GPM at 5 Ft head. I note that the fixed speed Grunfos UP26-64 seems to have those characteristics (curve 5). Other pumps may provide a better fit.

Perry

Perry_5

You may want to ask the Boiler Mfr...

What the boiler pressure drop is at 25 GPM.

That may tell you that you need different pump too.

The key is matching the system/boiler pressure drop with the required system flow. You have changed the boiler and slightly modified the system. Unfortunately, you do not know the old pressure drop and flow. My pump suggestion above may not work well (but is an educated guess).

Note that the reason that many mod/con boilers need primary/secondary piping is due to the pressure drops through the boilers.

Perry

Perry_5

Great Point - The pump Cureves are here and

the NRF 33 should do the trick (from an engineering perspective) as long as the new boiler did not significantly change the system pressure drop.

Note that I am posting this after I had posted my other two postings below.

Here are the NRF curves:

http://www.bellgossett.com/productPages/NRFcurves.jpg

If the NRF 33 does not work. The 3 speed NRF 45 certainly will.

Perry

EdyLogicMstr.

monoflo trouble

Hey Everyone;

Thanks for all the responses to my problem. I am sorry that I was not able to post any responses today until now. I had a busy day on call today. After all it is winter and its snowing here in CT.

I will be chewing all this stuff over with my fellow co-workers and will let everyone know what our final outcome will be.

Talk again soon.

Have a great holiday !
Lawrence

B.BART

bleeding monoflo system

We have a large amount of monoflo systems in our area and run into these problems often after boiler replacements.Just because your getting water out of bleeder dosn't mean there isn't any air left there are two pipes off the main you may be getting water out of one side and still have air in the other.Usually raising the radiator while bleeding works or ckecking the pitch of the pipes between main and raditor.At times we have had to add a purge set-up on the individual loop off the main.I would try that before changing pumps and checking pressure drop.Sometimes things did "work fine" before you got changed the boiler