Monoflow system does not heat well
Comments
-
So I changed the pump to another 007 a couple of weeks back but it did not improve the situation. As far as I know nothing else has changed.
0 -
Yes I saw your post and it makes a lot of sense, but nothing has changed with the system. Could there be a restriction in the air separator?
0 -
The 007 runs out of gas at 8.5 feet of head your down on flow. If you have places to get a pressure gauge on the suction and discharge of the circ you subtract the two. 2.3' of head =1psi
Gauges are not that accurate but it will give you csome kind of an indication
Your boiler is 106000 btu so you should move 10.6 gpm. An oo7 at 10.6 gpm will only move that much water at 4.2 feet of head.
4.2feet of head is about 1.8 psi differential across the pump.
Change the circ to a 008. @Ironman has a lot of experience and I respect his opinion and he said the same thing
I learned my lesson at my own house and it ran me in circles and twisted me up for a few hours until I figured it out.
My house was an 1 1/4 monoflow loop and it worked for years with the 007…no issues. But as soon as I added a 1" zone valve that was enough to make the system heat very slow……and that was the only change.
0 -
I'd look at the separator when you swap the pump as @EBEBRATT-Ed suggests.
Trying to squeeze the best out of a Weil-McLain JB-5 running a 1912 1 pipe system.0 -
All of the above recommendation are all well and good, but none address the conundrum.
You are supplying water at 180°F and it is returning at 160°F. Nobody can argue that you have insufficient flow. If the flow was insufficient, you would return at 140°F and then you can make an argument to change the pump. With 1 1/4 piping, you have very low head relative to 1" systems or, god forbid, 3/4" systems (which I am VERY familiar with ) and all the recommended suggestions are pointed at 3/4" systems.
My only thought is that it is significantly colder in this cold snap that it ever was before. In this case, just raise the SWT to 200° and call it a day.
You won't solve this issue by changing the pump. It might close the DT slightly if you do but it will not be a magical solution.
0 -
If there was a restriction, the DT would climb significantly. It doesn't.
0 -
The delta t won't go up if there isn't enough flow to encourage the water to take a route through the emitters, if it is just taking a trip through the runs of the monoflo tees and only losing what the piping and a little flow through the emitters can dissipate.
The boiler is cycling on the aquastat so it isn't dumping a lot of heat out of the boiler.
0 -
Incorrect.
You have a DT of 20°. If the boiler isn't dumping heat, just where do you think it is going? A round trip loop would result in a DT of 5°.
Just about every boiler cycles on the aquastat. Irrelevant.
0 -
it is heating some
0 -
"Some" ?
You can't have a DT of 20 unless it is heating "significantly".
If you increase the flow rate, the DT will drop to………..maybe 15………….but you won't get much out of that with exception of the last rads on the loop.
The temp of the supply and the return to the very first rad would be of interest. I don't expect any surprises. Supply will be 180° and the return will be 176° give or take.
0 -
All I can say is what I posted above. I had a perfectly good operating system with the Monoflo and an 007 circ. When I installed the new boiler, I added a 1"zone valve to the existing Monoflo loop and it would not heat
But thats why I asked for temps in and out of the baseboard and circ suction and discharge pressure.
0 -
I would take the boiler output in BTU and divide it by 10,000. That will give you the GPM you need. Then find a pump that will deliver that gpm with a head slightly higher than the pump you now have.
Ed, this presumes that the radiation can deliver all the BTU's that the boiler can provide. We both know that this occurs once in a million. The boiler is nearly always oversized.
The flow that he requires is simply based upon the emitters. If a building has emitters that can deliver 60K @ 180°, he doesn't need to move more than 6 GPM. On a 1.25" system, a 007 can easily move 6 GPM. The headloss is minimal.
Note that he mentions that the boiler frequently shuts down on limit despite the fact that the supply is maintained at 180°F and the return is 160°. Proof that the boiler is much too large for the radiation.
I suspect that something changed in the building…………..more air leakage somewhere? It wouldn't take much to skew the results and attempt to cure the heating system…………when it doesn't have a problem.
0 -
The delta t is a function of both flow and energy removed. Little flow with little energy removed will give you your 20 degree delta t just as well as normal flow and a normal amount of energy removed.
e =500 btu/(hr * fdeg * gpm) * gpm * dt
500 btu /(hr * fdeg * gpm) * 2 gpm * 20 = 20,000 btu/hr
500 btu /(hr * fdeg * gpm) * 8 gpm * 20 = 80,000 btu/hr
The delta T alone tells you nothing about the flow.
The duty cycle of the boiler will give you some idea of how much energy is actually being dissipated.
0 -
Unfortunately, you are hung up on the formulas and fail to pay attention to the radiation.
There is NFW that you can increase the flow from 2 GPM to 8 GPM and improve the energy dissipated by the radiation from 20K to 80K. That's a fools errand. It's a non-linear relationship.
First of all, the 007 on 1.5" is not flowing 2 GPM. I'd conservatively estimate that it is flowing 5 GPM and it might even be 6 GPM. The 1.5" presents almost no resistance at these flow rates.
So, 5 GPM with a DT of 20° gives you 50K. Do you think you can possibly increase this 50K to 80K by increasing the flow to 8 GPM?
Impossible.
0 -
You don't know what the flow is. The point of this is to try to determine if there is a restriction somewhere like in the air separator or a strainer or valve somewhere we don't know about. Unless we are measuring flow somewhere we are just guessing that we are getting what the circulator specifies.
0 -
On that point, do the emitters have valves on them? Are any of those closed? That will affect the flow in the whole loop.
0 -
Of course I know what the flow is. I have the DT and I have the pipe size and I have the circulator. It's not difficult to estimate the headloss in such a system (which is not that high in 1.25") and determine that the 007 can easily send 5 GPM through it.
Now, IF you can show that 50K is woefully inadequate based upon the radiation, THEN I buy the argument. But, I am ASSuming that the zone doesn't have the capability of delivering more than 50K. That's a LOT of radiation for a residential building.
The most important point to note is that nothing has changed on the system since this "problem" has surfaced. You are trying to chase ghosts.
0 -
On that point, do the emitters have valves on them? Are any of those closed? That will affect the flow in the whole loop.
You're grasping at straws!!!
0 -
All I know it what happened at my house ran me in circles because I could not believe the flow was restricted …but it was.
My system operated fine a 1 zone monoflow 1 1/4" with 1/2 in branches to the radiation. Originally had a Taco 110. When that failed I put in an 007 and it was fine, no issues and it heated quickly.
I installed a new boiler CI Peerless with an indirect and 2 zone valves 1 for the indirect and 1 for the monoflow heat.
The zone valves were Honeywell 3.5 Cv. I only have a 50,000 btu load
I started the heat with the indirect zone valve closed and it wouldn't heat. With the heat off the indirect heated quickly. Water movement was very sluggish running the heat. The house is a 5 room ranch about 1000 square feet with about 95 feet of fin tube.
I made sure everything was bled
The house was vacant because I was selling it. I left it as it was (sluggish) for a few days and went back and checked it and the water traveling around the main just wasn't moving well.
I had 8 monoflow tees in this system and the 007 would not do the job
I took the Honeywell 3.5Cv valve out and put in a Taco with a Cv of 8
That solved the problem
Monoflow requires enough flow in the main to drive the water up to the radiation and to make the monoflow tees work. less flow in the main =less flow to the radiation.
I suspect with the op that he is down on flow in the main and the baseboards do not heat well JMHO
0 -
With all due respect, Ed, the DT tells the tale. He is not down on flow and he does not have a 3.5 Cv valve on it to my knowledge.
Do you recall the DT on your place when you had this issue?
Do you recall the capability of the radiation?
In this situation, if there was insufficient flow, you could not get a DT of 20.
He could easily confirm sufficient flow in the radiation by measuring the temperature at the outlet of the first emitter. I sincerely doubt it will be anything less than 175°F.
I've been down on flow on a 3/4" system. DT of 35. Put in a Taco 011. Brought it back to a DT of 25. Still excessive but that was about the best I could achieve using 3/4". Ridiculous.
0 -
128K Btu/hr input doesn't suggest to me that an 007 shouldn't work. But, maybe the impeller or something else deteriorated? Can you valve out one loop and see what happens when the flow to the rest of the system is increased?
0 -
The radiation is typically far less than 128K. Figure the values on 60K…………and that is generous.
0 -
My radiation was about 95 feet of fin tube so 95x 550=52,250. My heat loss was about 50,000. I am just saying the monoflow tees are restrictive. All my piping was 1 1/4" The only reduction in size was about 2"6" pieces of 1" where it reduced to the 1" valve. When I would start the heat the hot water moved around the main very slowly. I would feel the main where it was hot then move downstream 3-4' and wait and wait it would finally get hot and that is how the water moved around the main very slowly.
The system worked with the oo7 before. just adding the valve stopped it. I just think the restriction of the monoflow tees is a lot. That gpm in 1 1/4 tubing is nothing
0 -
Remember in a monflo system the monoflo tees divide the flow between the main loop and the emitter. A restriction anywhere in any emitter will increase the flow resistance of the whole system. If the circulator was just on the edge of having enough flow to make the water follow both paths, any restriction in an emitter could reduce the flow enough that there is little flow induced in any of the emitters. That could be a valve, that could be some debris that found its way to the outlet of an emitter. It could be debris in one of the tees itself.
Something changed, the question is what.
0 -
Gentlemen,
The problem you face with any of those arguments is the DT. If the flow is returning to the boiler with a 20° DT, you don't have a good argument that increasing the flow will result in more heat being emitted.
Say you double the flow. The DT comes down to 10°. Your increase in output is probably 7% or so. I have to repeat to both of you that it is a very non-linear curve. You can flow 2 GPM and get 65% of the output as when you flow 5 GPM.
In your situation, Ed, the DT must have climbed to well over 40. Sure, that tells you that you're not flowing anywhere near what is necessary. Clearly you must find the restriction OR increase the capability of the pump.
I still do not believe anything "changed" in the current situation. The numbers don't prove it.
0 -
I could be wrong but I am not sure delta T is the whole answer here. I think we can all agree that the flow in the main determines the flow through the branch piping with a monoflow system. Low flow will cause low baseboard output. You need the venturi effect to get flow through the branch and you won't get that with low flow
This is why I two of my posts above I mentioned taking temps in and out of the baseboards and getting pressure increase across the circ. That pressure converted to head even if the gauge readings are a little inaccurate will tell the story
1 -
I make the DT argument as follows:
If you are correct and the flow is so slow that you're not getting much flow through the branch (es), the radiator (or fin tube) will have a huge DT. I'd expect to see at least 40 as a DT in such a situation.
I'd also like to see temps coming into and out of the baseboards. Maybe one of them has a branch that is clogged thereby severely limiting the flow in the entire system due to the huge rise in head, but the system can still manage a DT of 20. That baseboard will not heat at all. Fix the one issue with that baseboard and the DT will drop to less than 15 due to the significant capability of the 1.25". The entire system will deliver more heat……………especially the baseboards at the end of the loop.
0 -
Hi to all, sorry for delay and I appreciate all the feedback.
About two weeks ago I bumped up the supply temperature to 200 (that's why you will see 200 in some of my temperatures) and it made a big difference, the house was able to maintain 3-4 degrees higher after the bump up (but still cannot maintain on cold days)
The unit cycles on for 3 1/2 minutes and off for 2 1/2 minutes (the supply differential is 10, cut out 200 cut in 190) It did this consistently.
At the unit the supply was 200 and return was 180. They have 8 emitters. 5 are cast iron steam type standard column rads and 3 are 3/4 baseboard. I took all the temperature readings just as the unit shut off at 200. I will start with the rad closest to the boiler and continue in order until the last one on the loop.
- in 200 out 180
- in 190 out 120 this is a small bathroom rad that is not heating well, no air comes out when vented.
- 200 in 180 out
- 195 in 163 out (long loop of baseboard)
- 192 in 185 out (6ft piece of baseboard)
- 190 in 178 out (11ft piece of baseboard)
- 186 in 164 out (thermostat room)
- 181 in 171 out (blocked in front by dresser)
The only place I could get a pressure reading was at the tee by the boiler, it was 22 PSI. Pump is on the return side. So reading is right after the pump before boiler. Where one would drain the boiler. The gauge on the boiler is not accurate (didn't think to change it when I changed the pump)
I also noticed for the first time when I was checking all the rads that there was one rad that was removed and capped. I know Dan says you are supposed to complete the loop. I see from some of the comments that this and also the bathroom rad not heating well will be of interest to some of you.
I's sorry if I did not respond with all the info asked for. I was not able to properly look at the comments from Friday/Saturday but I wanted to get this info out (its 3:20 in the morning) because I see from the comments this is important.
Thanks again!
0 -
Looks like you have enough flow except for #4.
Looks like not enough baseboard or radiation
0 -
in 190 out 120 this is a small bathroom rad that is not heating well, no air comes out when vented.
I was checking all the rads that there was one rad that was removed and capped.
These are your problems that must be corrected to increase flow.
The small bathroom rad has a buildup of sludge on the supply or the return. This can easily occur over 30 years on 1/2". Drain it………..take it apart……….and find the blockage.
The rad that was removed cannot have the branch capped. Either you reconnect the branch or you remove the monoflo tee. No other options.
I also note discrepancies in your data. If radiator 5 follows radiator 4, I'm sure you'll agree that it is impossible for radiator 4 to discharge water at 163° and have that water magically increase to 192° by the time it reaches radiator 5. Do you have a small boiler between them? 😁
0
Categories
- All Categories
- 86.9K THE MAIN WALL
- 3.2K A-C, Heat Pumps & Refrigeration
- 57 Biomass
- 425 Carbon Monoxide Awareness
- 109 Chimneys & Flues
- 2.1K Domestic Hot Water
- 5.7K Gas Heating
- 105 Geothermal
- 160 Indoor-Air Quality
- 3.6K Oil Heating
- 70 Pipe Deterioration
- 975 Plumbing
- 6.3K Radiant Heating
- 386 Solar
- 15.4K Strictly Steam
- 3.4K Thermostats and Controls
- 54 Water Quality
- 44 Industry Classes
- 47 Job Opportunities
- 17 Recall Announcements