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Suggestions on balancing radiator heat system?

Howdy everyone,

I've owned a 2-flat (live in 1st floor, rent 2nd) for about 1.5 years and trying to balance the radiator heat is driving me crazy. During cold winter days, we have a sauna in the front of the building and a meat locker in the back. I've tried regulating heat by stopping down the front radiators with only limited success. My two key questions:
1. is there a way to better regulate the system (or perhaps something additional that should be installed?
2. Is there any type of water temperature booster for toe-kick type heaters?

The system details:
• 2 year old boiler (Weil McClain 175,000 btu, 83% efficiency)
•*water based system - not steam
• was originally gravity fed. Now has pump, but still uses the large pipes from original install (100 years old)
•*From furnace, pipe splits - 1 side = 4 LR radiators (2 per unit). Other side - remainder of unit (total 16 radiators).
•*Thermostat in front of building. When it reaches 72, back is still in mid 60's (63-67).
• Toe kick in 1st floor kitchen rarely kicks on because it needs 120 degrees. The system often doesn't reach this temp.

There is a diagram attached of the system. If you have any suggestions, it would be greatly appreciated. Thanks for your time!


Re: Suggestions on balancing radiator heat system?


Thanks for your post and the diagram you posted.

After studying your post I wonder 1) if you could say what is causing the heat to collect at the front of the building; 2) what is the total square footage of Flat 1 and Flat 2; 3) are there valves on the radiators that you can turn off & still get heat in the other radiator in the room?

Instead of thinking in terms of the diagram you posted study the diagrams of loop heating systems at the site below, & notice that they all flow in a LOOP; the blue box represents the boiler, the red line the hot water being pumped out of the boiler, & the orange line the cooler water that has given up some of its heat to the radiators along the way & returns to the boiler to be re-heated; thus, click onto "one pipe series loop", monoflo loop", "2-pipe loop", etc. to get the diagram of the various piping loops used in hot water heating.

Try to draw a loop of YOUR system on a piece of paper & see if it fits one of the 4 listed at the site.

Please post back.


Re: Suggestions on balancing radiator heat system?

Hello Nashua Tech,

Thanks for your reply. First, to answer the type of system question, I wasn't clear. Thanks for your link - I didn't know the proper terms to describe the system. The basement 4 radiators are on a one pipe series loop. However, the rest of the building is a 2-pipe direct return system. The basement radiators and loop are not original and were installed by some previous owner.

To answer your 3 other questions:
1. Total SF - roughly 1000-1100 per unit.
2. There are valves on each of the radiators in the 2 units. You can turn them off and still get heat in other rooms. However, since some of the radiator pipes run between the plaster and exterior walls, I'm hesitant to shut them totally off for fear of freezing on ultra-cold nights. I have turned the valves mostly off on the LR and DR ones, which helps some but doesn't completely solve the problem. Also, there are no valves on the main pipes in the basement, so zoning heat currently isn't possible.

Why the variance in heat? I don't know for certain, but here are some guesses:
1. Rear of building (colder part) faces west, so it gets more wind than front of building.
2. Kitchen toe kick in first unit rarely kicks on - water temp needs to reach 120, which it often doesn't. Since it doesn't kick on, this means the radiators in the 2 BR's off the kitchen must also heat it, so they're heating more SF. (Is there some type of booster I can connect to the toe-kick pipes?)
3. Since furnace is in front of building, I'd assume hot water reaches front radiators more quickly than back.
4. Since the main feed pipe running to back of unit is 3", I assume due to the higher volume of water it takes a long time for that water to cycle through and thus reach a higher temp.
5. I also assume that since the first spilt in the feed pipe from the boiler sends 50% of the water to the four living room radiators, that this also helps them heat more quickly.

Like I said, the above possible contributing factors are guesses, so if any of them are wrong, feel free to correct them. And if you have any thoughts on solving the issue, it would be greatly appreciated. I'd like to figure it out before we get into freezing temps.

Thanks again,

Re: Suggestions on balancing radiator heat system?


Finding it hard to provide you with solid suggestions when I can't walk thru your cellar & inspect the piping arrangements & try to figure out exactly where the hot water from the boiler is going; I'm also thinking of the complicated piping mess that is usually made when conversions are done on an old gravity system to a system with a pump.

This is common in conversion jobs going from a gravity system to a circulator pump forced hot water system.

What usually happens is the plumber who does the conversion connects the piping in a haphazard way, when the best solution is to put in new piping that goes as directly as possible to the radiators so the heat contained in the hot water reaches all the radiators.

Also inherent in conversions, as you mentioned, is you're stuck with large-diameter piping supply mains that contain a lot of extra water that the boiler has to heat to 180 degrees before it can heat any part of the house---this also leads to system imbalance---it also burns a lot more fuel than it should, taking all that much longer to heat the water.

Conversions have become easier in recent years with the introduction of PEX plastic piping that can withstand high temps & is low-cost (copper pipe is now very costly); the PEX can be fed thru small drilled holes even to 2nd floor locations; however, in your case, you may have to work with the piping you have now, especially if you don't intend to live a lot of years at your present location.

If you watch Richard Trethewey on TOH when he installs HW piping, the pipe diameters are all 3/4" (sometimes 1")---even the mains (aside from the boiler itself); and are all zoned off with multiple zone valves or small circulators; as many as 5 to 10 zones are created (in new unfinished housing they have easy access to all the radiators---such a modification in your case might not be feasible.

It would probably be best to find a pro in your area (there must be tons of them in a city the size of Chicago) who knows his stuff & concentrates in hydronic (hot water systems) & can make some of the changes recommended below.

Your present piping system is inefficient because of the conversion; the piping flows are not balanced; if you have no insulation inside the exterior walls, this should definitely be done ASAP; service companies blow in cellulose from the outside, usually done in one day---this is money well-spent, as it pays for itself in lower heating bills as well as lower AC bills in the summer.

It sounds like you have approx 3300 sq.ft. total including the cellar---you should be able to heat this with a boiler capacity of 128k---but your present boiler can be down-rated to that amount easily if you can make the house & the heat delivery (piping) system more efficient.

Any overhaul of your heating system would definitely include a separation of the 2 flats; the new boiler can be kept, & zone valves or zone circulators can be easily used to allow a thermostat in both flats to accomodate the different temperature preferences of the occupants---often, 2 boilers are installed & the piping is completely separated---that way the tenant is responsible for paying their own heat.

With your current system, balancing valves (see Illustrated Home site below) can be installed at the main pipe split near the boiler to better control the hot water distribution; radiator covers can be fabricated for the rads that are putting out too much heat (stuffed with pink fiberglass insulation)--you can keep the rad valve ON so the pipes in the walls won't freeze---you will have to troubleshoot the kickspace problem by feeling the cellar piping while the system is running to see if any hot water is reaching the kickspace, & if there is any balancing valve that can be adjusted to push hot water toward the kickspace.

You can read up on gravity system piping and different loops at the "Heating Help" site below.

This site is tailor-made for those of us who have HW (hydronic) heating systems--the site owner is Dan Holohan, who has written long & well on HW systems---click onto "Systems" once you get to the site, then onto "hot water", then on the various topics.

The illustrated home site has many diagrams on a hot water system; to navigate around this site, use the "+" key to enlarge the drawing, and hit the "close" or "back" word on each page to back out of a drawing.

Page 1 has "mixing systems", "covering radiators", Page 2 has "Extending HW system", "Balancing methods" (important); "Two-pipe system-indirect", "Two-pipe direct";"One-pipe system","Series loop piping"; Page 3 has "Zone control with valves", "Zone Control w/pumps", Page 4 has "Hi Efficiency gas boiler"; Page 5 has "How boilers work".

If you want to DIY on some parts of this project, you can certainly try to make some radiator covers & stuff them with pink fiberglass insulation on those rads that are too hot; you can also spend some time in the boiler room when the boiler is running FEELING THE PIPING as you hear the circulator running to ascertain exactly what parts of the house are getting the heat, and which are not---check the boiler temp dial to make sure the boiler is getting up to approx. 180 degrees---the piping delivering the hot water should be almost too hot to touch---this is the verification that 180 degree water is traveling thru it.

You may already have some balancing valves on the piping; if not, you will need a plumber/technician to come in to put a few in at key spots so the hot water is shared by all the radiators.

Consult the Yellow Pages under "Heating Contractors" if you don't have a regular tech coming in---the tech will look the system over free of charge & probably make some recommendations on the spot; there's nothing like getting a boiler tech with a trained eye in your cellar to look over the system---you may have to go through 2 or 3 techs before you find the right one who knows his stuff---usually, the older the guy is, the better---it's a good idea to go to the local heating supply parts distributors in your area & ask the counterman to recommend a tech who's experienced in HW conversions, or works exclusively on HW heating systems.


Re: Suggestions on balancing radiator heat system?

Wow, thanks so much for your detailed response - it is greatly appreciated! I'm going to study the site links you sent and I like the idea of finding a guy through a local heat supply store. I wish I would have known all this when we bought and rehabbed the place a couple years ago. I had a new boiler installed because the old one was very inefficient. I had 3 guys in to give quotes. One of them mentioned the old gravity pipes but none of them mentioned that this might cause imbalance problems or wasted energy.

I'll also look into insulating exterior walls. However, in the places where I've opened walls for other reasons, there's been virtually no space between the brick exterior walls and the plaster lathing. So I don't know if there's enough room to get much good from blowing in insulation, but I'll definitely have someone out to look at it.

Thanks again for your help!

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