Home>Discussions>PLUMBING>Radiator to Baseboard troubleshooting
2 posts / 0 new
Last post
Radiator to Baseboard troubleshooting

we recently purchased a home with no basement that had the radiators converted to baseboards. (1) section of heat on the main floor was ice cold, a bleeder was installed, good news - it got hot, bad news the cold problem transferred to another section of baseboard. Bleeders were added to the remaining (2) sections on the main floor, good news - they are hot, bad news - original cold line is struggling... water is hot going in, but is cold or luke warm in the fins.

We are considering the following before the massive task of tearing it all out and starting over.

(1) adding reducers to upstairs baseboard (goal - reduce temp upstairs, reduce flow upstairs to hopefully send more to cold line)
(2) add pump to cold line.

Appreciate some advice.

Re: Radiator to Baseboard troubleshooting


The condition you describe could be caused by any one of several conditions, pertaining to the actual arrangement of the baseboard piping & its supply piping as it goes from the water pump located at the boiler, travels thru each of the baseboard (on the 1st & 2nd floor) & then returns back to the boiler to be reheated, to repeat the circulating process thru the baseboard/piping all over again; try to draw as accurate a diagram as possible on a piece of paper as to the way the piping goes from the supply pipe at the boiler pump thru the various baseboards & then up to the 2nd floor & then back again to the return pipe at the boiler---of course much of the piping is liable to be hidden behind walls & floors---but I suspect that some of the baseboards have "dead ends" of stagnant water that is not being pumped because of the way that the piping arrangement is presently set up.

The fact that you have no basement can often compound the problem of working on the baseboards & its associated piping------this is because it's usually lots easier to see how the piping branches to different parts of the house & convectors, when the piping is visible from the cellar as it branches to the exterior wall cavities.

Consult the HIGH PERFORMANCE site below to see how the various different water heating piping loops are used in hot water heat baseboard systems---the BLUE SQUARE in the diagram is the boiler; the red line coming out the left of the boiler (where the pump is usually located) is the pumped hot water heated by the boiler going to the baseboards/rads; the orange line is the hw as it gives up its heat to the rads; the orange line on the right back to the boiler is the cooled water that returns back to the boiler to be reheated--the cycle repeats over & over until the T-stat in the room is satisfied & it shuts off the boiler's calling for heat.

The most common loop used is the ONE PIPE SERIES LOOP (direct supply/direct return)----but since you also have a piping loop that serves the 2nd floor, I'd be interested to know how the piping is divided somewhere at the 1st floor, so that a loop also travels to the 2nd floor to heat the baseboard on the 2nd floor---too often a previous owner has simply (erroneously) connected a "fork in the road" tee connector to supply the 2nd floor baseboard convectors & similarly connected another tee on the other end as a supply return to bring the cooled water from the 2nd floor baseboard back to the boiler to be reheated---the problem with this arrangement is that the pumped hw gets "confused" as to which way to go---should it go thru the 1st floor baseboard & back to the boiler, or should it go up to the 2nd floor baseboards & then go back to the boiler---water flowing in a pipe ALWAYS follows the LEAST PATH OF RESISTANCE as it travels thru the piping.

The piping arrangement you are describing seems to be tailor-made for the pumped hot water to follow the path of least resistance as it travels thru the house baseboards on the 1st & 2nd floor, and make some "detours" & thus BYPASS various sections of baseboard as a result, causing some baseboards to remain cold or only lukewarm---in other words, a DESIREABLE hw piping arrangement for a home heating system should follow something like the ONE-PIPE-SERIES-LOOP diagram as illustrated on the high performance site below---notice how the hw in this diagram is pumped (pump not shown) from the boiler thru a single pipe that subsequently flows thru each of the rads/baseboard, & then back to the boiler---note there are NO ALTERNATIVE WAYS that the water can go in this piping arrangement; thus, there are no cold or lukewarm rads/baseboards & the heated water gives up all its heat to the baseboards in the rooms---your task in rehabbing this problem is thus to follow the same plan---don't allow the pumped water going thru the piping to "make any detours" & you'll end up with a good system where all the convectors heat up & effectively heat the house.

What is the sq.footage of the 1st floor & the 2nd floor??? Are the rooms large & drafty w/high ceilings, or small & tight??? Do you have tight windows??? Is there insulation in all the exterior walls???

The best solutions in these situations (assuming you have access to the piping since you have no basement) is to 1) either re-solder (assuming copper tubing) all the piping/baseboards into a ONE-PIPE SERIES LOOP, as noted at the HIGH PERFORMANCE site below, or 2) (also assuming you can access the piping) to install 2 ZONE VALVES with a thermostat for the 2nd & 1st floors in order to make 2 separate loops; see the Caleffi site below (give it a minute or 2 to load, it's big) , Fig. 3-7, which shows how zone valves are installed ---this is the plan I would recommend using the high quality, low cost Taco 570 series zone valves (below), assuming you can get at the baseboard piping---you may have to cut holes in the plaster/sheetrock to get at the piping inside the walls; since this is an older system, the piping is probably copper (or possibly steel); when rehabbing these jobs hi-temp low-cost plastic PEX tubing is used, since it is much less expensive & easier to route thru the wall cavities & avoids extensive removal of sheetrock/plaster wall sections, thus keeping the rehab costs down; PEX is also much less likely to freeze & burst inside the walls during bitterly cold winter weather, which up to now has been a costly repair problem for houses in northern climes.

Zone valves typically also require a 24v step-down xformer, & 2 T-stats for the 2 separate zones; the ZV pictured is for 1/2" piping; 3/4",1" & larger piping models also available.


Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.