Monoflow Continuous Circulation System

franco b wrote:It seems like a lot of fuss and expense to simulate a gravity hot water system when it seems the original system was gravity to begin with. (2 1/2 inch main).

This is not what is being suggested, it is a conversion to a modulating temperature controlled radiation loop. The water temperature in that loop will be adjusted from 90* to 180* to supply continuous, even heat.

If you wish to get an idea of what it would feel like just lower the water temp to 125 or so or even less, which will cause the circulator to run for much longer periods keeping the water in the mains warmer than now. This would be only for the mild weather we are having now. As was pointed out domestic water would suffer.

The DHW will not suffer, it will improve from its current state as he is currently dumping massive amounts of cold water into the boiler when the pump starts. The coil is in the boiler and the radiation loop does not affect it in any way. The pump will run constatly in this configuration until warm weather cuts the call for heat.

coaledsweat wrote:This is not what is being suggested, it is a conversion to a modulating temperature controlled radiation loop. The water temperature in that loop will be adjusted from 90* to 180* to supply continuous, even heat.

That is exactly what a gravity system does. The water to the radiators gets no hotter than needed to satisfy the thermostat. What I outlined will do precisely that. Please re-read the post as I added some things in an edit which you might not have read.

All that is needed is a relay activated by the thermostat to control both the stoker and circulator, plus a high limit aquastat in case one is not already there. The present low limit would not be used or converted to high limit. You are right though that the domestic water would not be satisfactory.

Cost, under $100 and no pipe fitting. Might be better off with a separate tank for hot water tempered in the winter with heat from the boiler in a gravity setup. Also the circulator would not run continuously which saves on electricity and wear on the pump.

Richard

I would never go back to a simple gravity system

too many benefits can be reaped by modern controls --- without screwing up a well designed system.

And to folks that say the old gravity heat rise systems were not well designed -- Well if they were incorrect, they didn't work AT ALL - not like the crap installed today by the lowest bidder. It sort of works in spite of the poor craftsmanship.

Sorry to make the analogy to the old steam heat systems that produce a great comfort in large old structures -- I should have simply stopped the testimonial to coaledsweats advice.

franco b wrote:

coaledsweat wrote:This is not what is being suggested, it is a conversion to a modulating temperature controlled radiation loop. The water temperature in that loop will be adjusted from 90* to 180* to supply continuous, even heat.

That is exactly what a gravity system does. The water to the radiators gets no hotter than needed to satisfy the thermostat. What I outlined will do precisely that. Please re-read the post as I added some things in an edit which you might not have read.

All that is needed is a relay activated by the thermostat to control both the stoker and circulator, plus a high limit aquastat in case one is not already there. The present low limit would not be used or converted to high limit. You are right though that the domestic water would not be satisfactory.

Cost, under $100 and no pipe fitting. Might be better off with a separate tank for hot water tempered in the winter with heat from the boiler in a gravity setup.

Richard

Won't work in a mono flow system -- well I shouldn't say it won't work at all.

Sting wrote: Sorry to make the analogy to the old steam heat systems that produce a great comfort in large old structures -- I should have simply stopped the testimonial to coaledsweats advice.

I appreciate all opinions and advice, keep it coming

Sting wrote:I would never go back to a simple gravity system

too many benefits can be reaped by modern controls --- without screwing up a well designed system.

I personally like the idea of using the modern controls, over having it go back to the ole gravity system

Sting wrote:Won't work in a mono flow system -- well I shouldn't say it won't work at all.

franco b wrote: That is exactly what a gravity system does. The water to the radiators gets no hotter than needed to satisfy the thermostat. What I outlined will do precisely that. Please re-read the post as I added some things in an edit which you might not have read.

All that is needed is a relay activated by the thermostat to control both the stoker and circulator, plus a high limit aquastat in case one is not already there. The present low limit would not be used or converted to high limit. You are right though that the domestic water would not be satisfactory.

Cost, under $100 and no pipe fitting. Might be better off with a separate tank for hot water tempered in the winter with heat from the boiler in a gravity setup.

Richard

Won't work in a mono flow system -- well I shouldn't say it won't work at all.

From the size of the mains I assumed it was gravity. Mighty large house to have monoflo that large.
Single pipe should still work though. The only thing different from the present setup is the control.

Richard

franco b wrote:From the size of the mains I assumed it was gravity. Mighty large house to have monoflo that large.
I agree that if it is single pipe then it would not be practical.

Richard

From what ive been told and I don't know for sure, I was told it was originally a gravity system. and now its a monoflow. Maybe thats not even possible, I have no idea

All that I know for sure is that there is one huge pipe that runs around the entire basement in a huge loop branching off to each radiators supply then the return goes back into that huge loop and back to the boiler.

make sense?

Yep, that is a mono flow. I had it in my house. Big, clunky, and it sucked. Pipes everywhere, some rooms were hot, others
cold, constantly bleeding baseboards.....so I tore it out, and piped baseboard to baseboard, one loop. WAY better heat, simple,
constant, NO issues.
Modulating the supply heat effectively can save you 15-30% on your energy use. If your house is old and not well sealed, it
is not a great candidate for modulated constant flow. You need that big heat in the pipe to overcome drafts, etc. I know, just put in
a condensing gas boiler in my Moms house. I basically ended up programing the outside reset high and lows so close and high
to keep the baseboard temps up, because she was COLD. Only you know how tight your house is. If it is big, old and loose,
save yourself the trouble. You will still save, just not huge. Good Luck!

If the return from each radiator goes back into the same main, then it is single pipe. If the returns from the radiators go into a separate main loop, then it is two pipe.

What I outlined would work just like your system does now, except the boiler and circulator would run only on a call for heat. At present the boiler is kept at a high temperature for standby and for domestic water use. When there is a call for heat the circulator starts and pumps that hot water to the radiators.The temperature of that water may be far hotter than the radiators need to heat the house in mild weather. As a result they probably overshoot a bit causing long off times and cooling of the mains.

By not having the boiler up to heat all the time, when a call for heat occurs then relatively cooler water is circulated and is gradually brought up to the heat necessary to satisfy the thermostat; no higher. So the radiators and mains tend to be mildly warm all the time instead of hot ,then off for a long time. The water temperature is governed by the needs of the house. Fuel needed for standby is greatly reduced, even eliminated. So the domestic water will not be hot enough in mild weather. The house will be more comfortably because the heat will be far more even.

This is the least costly in material an labor and except for domestic water would work just fine. If you are not happy you can always go to what Coaldsweat recommends having lost very little.

Richard

I have been watching this thread evolve hear and I have to say I agree with freddy it is more trouble than it is worth. Those old radiators probably not going to take to a valve change reall kindly. I have changed a few in my time and it always ends as freddy says with a few coice words being said and some bloody knuckles/pinched fingers etc. I agree than the constant flow will give less fluctuation in room temps and will probably save some coal but in reality the biggest problem is the gross oversizing of the piping. For every linear foot of 2 1/2" piping you have 108.33 sqin of surface area that wastes heat by washing it into a room you are choosing not to heat. Conversely a modern system with even a large 1 1/4" main only has 56.56 sq in per linear foot to radiate heat into your basement. If you don't have a good working knowledge of plumbing I would definitely shy away from the new valves on the radiators however danfoss does make great products. The 4-way valve could be added by a plumber and would definitely make you and your boiler more comfortable but as for the cost savings of opreration, I can't see were you will see great gains in overall efficency probably less than 5%.

Paulie wrote: Only you know how tight your house is. If it is big, old and loose,
save yourself the trouble. You will still save, just not huge. Good Luck!

Yeah my house is drafty and old, but ive been doing what I can to seal up drafts.

franco b wrote:If the return from each radiator goes back into the same main, then it is single pipe. If the returns from the radiators go into a separate main loop, then it is two pipe.

it all goes into the same pipe. so its a single pipe loop

franco b wrote:What I outlined would work just like your system does now, except the boiler and circulator would run only on a call for heat. At present the boiler is kept at a high temperature for standby and for domestic water use. When there is a call for heat the circulator starts and pumps that hot water to the radiators.The temperature of that water may be far hotter than the radiators need to heat the house in mild weather. As a result they probably overshoot a bit causing long off times and cooling of the mains.

yes that is what was happening when it was a little warmer out, overshoot by a degree or so. then all the pipes would get cold till the thermostat called for heat again.

jpen1 wrote:I agree than the constant flow will give less fluctuation in room temps and will probably save some coal but in reality the biggest problem is the gross oversizing of the piping. For every linear foot of 2 1/2" piping you have 108.33 sqin of surface area that wastes heat by washing it into a room you are choosing not to heat.

thats what the danfoss valves are for. a room where I don't want much heat I just turn down the thermostat on the valve and the radiator doesnt get all the hot water and it passes on down the loop to find a radiator that does want the heat.

If I do try to change out these valves I will do it during the spring or summer when I don't need to worry about, and if I have a problem it wont be that big of deal unless it totally Fd' up a radiator. I think those valves are they way to go and make so much sense, id be stupid not to use them. unless its absolutely impossible to get off the old ones.

jpen1 wrote:The 4-way valve could be added by a plumber and would definitely make you and your boiler more comfortable but as for the cost savings of opreration, I can't see were you will see great gains in overall efficency probably less than 5%.

Why do you say less then 5%. Ive seen reports of 15 - 30 percent possible ... not claiming thats a fact just what I herd.

i can't remember ever seeing a gravity monoflow system that being said it's either a reverse or direct return and if you wait till it gets cold out you probbably won't notice a problem . if you got the $$$ then go with the modulating valves ect . that is a good way to go but from looking at your ealier post you are either quite parcimonios or your like the rest of us just plain broke thanks jim

I wasn't refering to the radiators themselves or the balancing valves on each. I was refering to the main house loop that is in your basement and its connecting piping. That is where the root of all the evil lies. They are responsible for a considerable amount of your systems poor effciency. To achieve those loftty 20% fuel savings that are claimed you would have to properly re-size your loops. I could be wrong however but In every commercial refrigeration system or steam system I work on line size is one of the most critical elements in the systems overall efficiency. The danfoss valves will definitely help you to maintain more even heat at a cost. Anything that we get from Danfoss is $$$. They are the cadillac so to speak in both heating and refigeration products. I'm not trying to discourage you from bettering your system, I'm just concerned that you are going to spend quite a great deal of money and not realize expected returns from the project.

It sounds like it was a 1 pipe steam system and they converted it into hot water baseboard. If it's not set up as a loop, it should be re-plumbed as 1 or 2 zones with the proper size copper pipe. You are dumping very cold water back into the boiler, it needs some constant circulation as it stands now. If it was steam, I would either convert it back, or rip it all out and put finned baseboard in. I'm not a plumber, but I did see one on tv once.

This is monoflow.

http://media.photobucket.com/image/monoflow%20hea ... tertee.jpg