Half a zone not heating

drosner

i have a zone where it tees to 2 baseboards and the other tee goes to 2 radiators. Last season it all was working just fine. But this season I can’t get the radiator path hot. The piping is deep into a crawlspace so I can post pictures and I’m going off memory. But I think the piping goes to one radiator and the output on that goes to the next.

I opened the vent on one of the radiators and I could start to feel that incoming pipe get hot. So I know at least hot water is getting to the radiator and isn’t blocked. Any suggestions what to try to get to bottom of what causing lack of circulation in this section?

Ironman

What’s the pressure on the boiler gauge?

Big Ed_4

You mentioned crawl space , a addition where the heat was tapped into a existing system . You will need to post a diagram of your system ..Correctly trace the pipe work . Confusing ? You mentioned baseboard and radiators ? Two different animals ….It is hard to see from here :)

EBEBRATT-Ed

Check the pressure you may be air bound or you gauge could be defective.

george_culbertson

Air in the system or you don't have a pressure difference from input to output of your rads on the same piping circuit. You can accomplish this by closing off a tiny bit to create pressure differential for the rads or base board Depending upon which. Hence water will now start to move and now you heat.

LRCCBJ

I opened the vent on one of the radiators

Did you get air…………or water?

drosner

when I vent I get water only and no air…..pressure on main system looks solid where it normally is. Could, the air be downstream of the 2 rads on return line?

Ironman

https://forum.heatinghelp.com/discussion/comment/1827112#Comment_1827112

Please give the specific pressure: a generic answer doesn’t help.

drosner

gave up trying to debug myself and called plumber….he ventured deep into my crawl space where radiators were located. I always thought they were plumbed in a loop. Turns out the guy who did the install used pex T to split the supply and returns to go to the 2 radiators. Plumber said this ain’t good and if I had it working before I got lucky and it won’t last…picture shows supply coming off main branch with 2 closely spaced tees (which is ok)…but then tees to go to 2 radiators.

Stet

Radiators should be done mono flow with no chance of air pockets. They should on a separate zone from baseboard. And they should not be part of a loop system. Pretty much everything that could be done wrong on this install was done.

TheUpNorthState88

I’m not a licensed anything but I am a reader of the old texts including Dan’s. If I’m not mistaken, cast iron rads and slant fin baseboards need to be on separate zones. Sure, things may “work” initially but eventually balancing issues do arise where certain rooms aren’t getting hot.

MarkMurf

And if the radiators were left overs fron an antiquated system updated to pex, an outside chance there's an accumulation of rust in the bottom if them. Just had that occur on a job. Flushing revealed quite a bit rust .

hot_rod

weird flows can happen in bullhead tees like that. Sometimes both sides get equal flow, sometimes not

Not enough delta P to get them to work properly

In domestic water piping you have 40 -60 psi driving flow

DJDrew

https://forum.heatinghelp.com/discussion/comment/1831414#Comment_1831414

@hot_rod Would something like this be the correct fitting instead of a T in this situation?

RobertJordan

I would insulate those pipes being in an unconditioned crawl

hot_rod

https://forum.heatinghelp.com/discussion/comment/1831435#Comment_1831435

Yes that is a fitting that would work.

The bull head fitting seems to come and go from the plumbing and mechanical code books. I don't see this in any 2024 versions? It is easy enough to avoid them.

Screenshot 2025-01-02 at 8.45.32 AM.png

Adk1guy

You did not provide a complete diagram. My next step would be to purge the loop by forcing water in the supply side and out the return side by using shut off valves to isolate the loop and boiler drains, and use a pump to force water in and drain the return side into the same bucket. Use washing machine hoses and be sure to submerge the return side hose and circulate the water until bubbles stop appearing. The use of the pump increases the flow significantly over using the system pressure while adding water and wasting the return water down the drain, plus you keep most of your deoxygenated water in the system. This will eliminate air trapped in any high spots in the piping which opening bleeders will not do. Then bleed every heating unit and see if they heat. Also you need to check for balancing valves in the system or on the radiators .

Copper baseboard and cast iron radiators can be on the same loop but it isn't a good design. The copper baseboard is flashy meaning it heats up and cools off quickly and heat output is low where as cast iron is just the opposite. Yet like the bubble bee that can't fly I have seen it work. It certainly isn't in the 1970's IBR design books from sizing and design courses I took back then.

ccstelmo

NEVER use a tee in a closed loop heating system. That's what my mentor said. ccstelmo

Oracle

I would build a boiler side supply and return manifold and parallel your radiation and verify your differential. I would also do as Member Adk1guy suggest and flush clean your supply and return lines from your cast iron radiators. Cast iron radiators often gather debris, which is not usually a problem for steam, but can become an issue with fluid flow.

mikespipe

a monoflow tee might work but separating the radiators into their own zone would work better

sbachman7117

This is a longshot, but if the radiators were converted from an old 2-pipe steam system, make sure the guts of the steam traps were removed. I discovered this problem in a building that I bought in 2007. It had been converted by a well-established plumbing/mechanical company in the 1980s! Once I removed the resistance, it worked like a charm.