FHW Zone is "weak"

WalksInDarkness

Hi All,

I have a 3-zone FHW system in my house, it was a completely new install 7 years ago (formerly steam heat).

The basement zone is acting very "weak" lately, especially when the main floor and second story zones are running. The problem seemed to start last year, when we had a 10'x16' room added to the basement; the contactor tapped into the basement zone, and added one radiator (maybe 10' long). I didn't really notice any problems last year, but I was using a supplimental heater in the bathroom.

This is the symptom:
1) if the two upstairs zones are running, the flow seems to be very little. The first radiator in the TV room gets "warm" but not "hot". The second radiator in the bedroom gets "lukewarm". The last radiator, in the bathroom, does not warm up at all.
2) Once the upstairs ones stabilize, then: the 1st radiator gets "hot", 2nd gets "warm", and the third gets "lukewarm". But it still takes at least an hour for the basement to raise 1F, which is much slower than it used to be.

The zone valve (TACO 570 series) seems to open, but the flow is lousy; I am not sure if it is only opening part way? Also, I am wondering if the addition of the new radiator is causing some sort of line pressure phenomenon or air bubble situation? Hopefully, the contactor did not accidentally block the line by putting a rag or something in there (to stop drips when tapping into the line).

Any ideas are greatly appreciated!

LawnGuyLandSparky

It sounds like your system is simply undersized. Rarely will the basement zone fall victim to vaporlock when there are 2 more zones higher than it. How does the basement zone perform when neither of the 2 other zones is calling for heat?

WalksInDarkness

Hi,

When the upper floors' valves shut off the flow definitely "improves", and the last radiator in the basement loop finally heats up; but it still seems like it is "weaker" than before the addition of the new room. This might all simply be attributed to the fact that we added one large radiator to the zone, and since it is the "first" in the loop it might be sucking out all the heat for the new 160sq-ft room. Really weird! Could this be solved by going with a more powerful pump?

Thanks In Advance!

biggles

hows your boiler setting that maintains the temperature of the water going out,and the actual reading on the temp guage on the boiler as the system calls.you have 3 zones now with the basement being and seems the last on the loop.if the others are satisfied the circulator should be banging the heat 140F-160F into that basement zone...the zone on the same level should have the least problem due to no rise on the piping????check out one zone run and all the others not calling (stats all the way down on temp 55F)

WalksInDarkness

Well the problem is solved, but I am not sure exactly what the problem was. Yesterday had mild temps, so by the time I finished dinner the boiler had shut off and cooled. I decided to try purging the air and manually filling the water. The first time I did this, I forgot to purge the air and the manual water fill did not need to add much (a few seconds). When I purged the air it only "whooshed" for no more than 1 second before stopping itself; however, the manual fill ran for about a minute. I am surpised that so little air would need to be displaced by so much water. I am wondring if I dislodged so air bubbles or pressure phenomenon when I forced the zone to manually circulate the other day (I shut off the other two zones, and used a c-clamp to manually open the affected zone). I will make sure to repeat the procedure every fall. Does anyone know what the actual problem was, maybe vapor lock or something?

sgthvac

Your problem is more than likely 2 issues. By the way this is speculation because you didn't post what your water pressure and water temp. is set at, 1) Air in the system will restrict water flow and can even stop heat all together, so make sure you bleed your system and check your auto vent if you have one. It will bleed the air from the system on it's own. Usually it's located at the boiler somewhere. 2ND) Water pressure is probably the other issue. You stated things improved when you bled the system and manually filled yuor system. Water pressure should be at least 12psi and hi should be no more than 15psi. Though it depends on how big your home is and how much distance vertically the 2nd floor rads. are form the boiler. In my house, b/c my boiler is in the basement and my 2nd floor rads. are about 20 ft. up I boosted my press. to 18psi. You should have an auto fill you can adjust the pressure with. 3rd) water temp. your limit can be set between 160-180 degrees. That could also be another problem, but if it ran for 7yrs. without a problem it's probably the first 2 possibilities.