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Question regarding one pipe loop hot water heating

I currently have a one pipe loop system in place. There are 2 heating zones and one DHW zone. The boiler is new as well as the indirect water heater. Radiators were existing.

The first floor is big old heavy rads and there is no problem there.
The second floor has all baseboard.
The second floor was modified to become a second zone and the loop
goes up to the radiators on the south side of the house which contains one bath and two bedrooms.That side of the house seems fine. The loop then returns to the basement and crosses the width of the basement where it then goes up an outside wall to the Master bedroom with approximately 14 feet of baseboard before returning to the boiler.

This bedroom never seems to get warm enough. It is on the north side of the house.
The house is 120 years old with very little insulation but that is a project I am working on.
I've begun insulating the pipes in the basement but I was wondering if it was possible to have just this radiator configured with a monoflow tee arrangement so I can have some hotter water feeding that radiator.

Thank You

Re: Question regarding one pipe loop hot water heating

If you are saying the second floor zone goes from the basement to the south side of the second floor and back to the basement and then up to the north side of the second floor before returning to the boiler, that seems like a bad idea. If the boiler is in the basement, why not make the second floor north side a third zone?

Re: Question regarding one pipe loop hot water heating

I agree completely with ZZZ.

I think you'd get more heat to the Master Bedroom with a separate zone & you would give the MB its own t-stat, which is also important---I have doubts that you'd get sufficient heat with just a monoflo modification----if the water temp in the supply piping to the MB is only 40 degrees now, a monoflo change won't make a difference.

Do some detective work while the system is heating, by going around the cellar & touching the piping to make sure the water supplying the baseboard, as well as the rads is hot enough to do the job---that means it should be close to or at 180 degrees---water hot enough so that you can't touch the piping for more than a second or so without burning your fingers.

With all those radiators and baseboard in the other parts of the house calling for heat at the same time on a cold day, I'm willing to bet there's a lot of lukewarm (if not cold) water in the supply piping---it also sounds like the boiler may be unable to keep up with the demand for hot water in all 3 parts of the house at once, & at the same time be able to satisfy the indirect HWH to have hot tap water ready at all times.

The indirect is often wired to get the hot water first (priority) before the rest of the house & if you have a lot of large, cast iron rads, the boiler will have trouble keeping up (cast iron rads are good, but they contain a LOT of water that has to be heated up before the rest of the house can be heated)---most heating techs install a thermostatically controlled 1 1/4" bypass loop for this reason at the boiler directly from the main supply to the main return so that the water has a chance to get hot enough to serve all the convectors----otherwise the boiler will fire all day & burn a lot of fuel.

The first thing to try is to stand in front of the boiler with a timepiece when the system is calling for heat & watch the temp gauge; the system should promptly go up to 140-160 degrees; you should then hear the circulator pump kick in to distribute the water & the gauge drop below 140 as cold water is pumped from the rads; the circ goes off till the boiler heats the water to the 140-160 range & the pump kicks in again---the boiler will keep doing this until all the t-stats are satisfied, then shut down at 180-200 degrees---it should be within 1/2 hour, but it could take hours in a poorly operating system.

Another thing you might try if the rooms with the large cast iron rads are overheating & they have shutoff valves on the end, is to turn down, or shut off completely several of the lge rads & see if this increases the hot water to the Master bedroom.

You also mentioned a lack of insulation in the exterior walls---this is a no no; it only cost a few hundred $$$ to have cellulose insulation blown into the walls (R19 recommended) and the attic (R40 recommended)---you have to do this ASAP--for the few hundred $$$ you spend on insulation it will make a tremendous difference in fuel savings & prevent any heating pipes in the exterior walls (especially in north-facing walls) from freezing & (dread) rupturing to create a real expensive mess.

I would have an experienced tech come over the house to look at your system & do some "pipe feeling" while the system is running & make some recommendations as to what should be done first.

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