possible blocked radiator?

hws

Hello, wondering if any of you could offer some advice on a situation I'm having on one of my recent projects.

I recently installed a system as part of a major whole-house renovation. Boiler and controls are new, all piping new, but at homeowner's request I used all the original cast-iron rads. It is a three-zone system: Basement, main floor, and upstairs. Each zone is two-pipe.

I'm having trouble with one of the rads on the upstairs zone. The rest of the system heats perfectly. Here's the problem: Got a call today that one of the rads is not heating. Tried bleeding it, got not air but water. My first theory was that the old valve was stuck in a closed position. I removed it and hard-piped the rad. The valve WAS stuck semi-closed, but when I Started the system back up again bled all the air and I still had the same problem. Rest of the zone heats very well, except for this rad.

I began bleeding again, this time water came out. I noticed that as I bled water out through the bleed key, the rad began to get warm, and the supply pipe to it was hot. Kept bleeding water, the rad got warmer.

What I think is happening is that the radiator is blocked internally somehow. Heat is getting to it but not flowing through. It seems that opening the bleed valve gave the existing water somewhere to go, allowing the hot water to slowly come in.

Apologies for the long post. Wondering if anybody had any opinions or suggestions. I do mostly new boiler installs, haven't had a lot of experience with the nuances and subtleties of these old cast-iron radiators. It may be worth noting that this is the last radiator in line, but it is a two-pipe system NOT a monoflo or series loop, and that the rad is fed & returned from the bottom tappings.

Thanks!

JStar

Rad

Definitely a flow problem. Like you said, bleeding water gives the hot water somewhere to go. Did you calculate head and flow for the new pump? What size pipe feeds the radiator? What size is the radiator?

Alan Welch

new piping/ old radiator

Is it possible some debris such as insulation  got lodged in the pipe?

hws

additional details

Joe, thank for your reply.

The zone is piped in 3/4" heating pex. It has a calculated heat loss of 11 500 btu. The radiator in question has 1/2" tappings but is fed up to this point with 3/4" pipe. I calculated 10 ft of head on this zone and am using a Taco 007 on high speed. The piping is two-pipe direct return. (I know that this arrangement can be difficult to balance but the job took place in a home that was very structurally compromised and thus I could only run lines a certain way.)

On this zone, there is a branch feeding three radiators.  It too is arranged in direct-return and feeds back into the zone main. We'll call this the "sub-zone" for sake of clarity. In the boiler room I can feel the supply and return of the "sub zone" where they tie back into the zone mains, and they are both hot. The offending radiator is at the end of this "sub zone". The other two rads on the "sub zone" are hot.

I am now thinking a few things:

- Maybe the 007 is working at its hardest (its highest head is 10') but can't do the job. Possibly upgrade to a 008 or 009?

-Perhaps this is a balancing issue? Flow not getting to the last rad in the sub-zone due to the direct-return arrangement? If so,  how can I balance without TRVs?

Hope this clears up a few details.

hws

Alan

I'm wondering that as well. However I'm also wondering about balancing issues/head issues to be sure. I'm definetly looking at taking the rad outdoors and blowing it out with some compressed air. However I'm also wondering if there is a more mechanical-based explanation (see my reply to Joe above)

Any help from any of you would be appreciated.

icesailor

No Flow:

The last radiator I saw that didn't work like you describe hadn't worked since it was installed 40+ years before I found it. A radiator on the second floor worked as you describe, It was an old 2 story house, on one zone of heat with mono-flows. I had heard vague comments about this one radiator not working correctly. The house was only used in the summer. When I filled the system in the Spring, it always started to get hot and I left it once the air was out.

A few of years ago, the owner stayed until Thanksgiving and complained about the radiator. Sure enough, it didn't get hot. I looked in the cellar to see if it had a backwards Mono-Flow.  In the corner, were a tribe of connections. Straight tee, Mono-Flow tee, Straight tee, Monoflow tee, etc. Some plugged where they either weren't used or a radiator had been removed in the past. The guilty radiator was connected to two straight tees. I removed a plug from an unused Monoflow and connected it properly to the radiator and presto, problem solved.

You either have a misplaced monoflow, or the length of the circuit is undersized and/or too long for the size of the radiator.

Circulators with the thrust of a Saturn 5 moon rocket will also create bad flow problems. 100' head circulators don't belong in Mono-Flow systems.

icesailor

Do that last:

Unless you feel the need to go to the Gym for exercise, don't do that. Go to the gym first, then try the low tech, low energy things first. Maybe some here have seen a CI radiator full of chit and wouldn't flow, but I haven't ever seen one. And unless it is water tight so the "Plug" was complete, it would still flow enough so the part of the radiator would get hot. The supply side. The radiator would dissipate the heat faster than the water flow. The fact that it doesn't get hot at all, tells me that it has a flow problem in the piping.

You maybe are suffering from my "Least Common Denominator Rule". That rule says that if you plan for the dumbest person on the job to screw you up, there is someone dumber so you need to think stupid.  Whenever I ran heat risers through a second floor, I have a box of 3/4" cop. nipples with caps soldered on them, which I solder onto the riser with a coupling. Some plaster will sooner or later (sooner) will drop a big splat of imperial plaster into the pipe. More than once, I had to scrape the plaster from top of the cap. I could always get a coupling off a pipe but not always a cap.

icesailor

Direct Returns:

With a direct return, the last radiator on the zone has the least pressure. If you can. can you close off the two radiators before the one that doesn't work? If you can and the offending radiator starts to work, water DOES care where it goes and takes the easiest path.

I try to never connect anything complicated as a direct return, only reverse return. For the extra pipe and fittings, it is cheap compared to fixing it when it doesn;t work. I even connect manifolds as reverse returns.

Where do the Mono-flows come in? You described the system as a monoflow system, now you have direct returns?

hws

diagram

This is a diagram of the piping arrangement. two-pipe Direct return. Not a monoflo system. (Like I mentioned earlier, I was very limited in where I could run the lines due to the building being structurally unsound. the structural repars were done, but we were not allowed to drill holes through joists, certain stud walls etc).

Forgot to mention the radiator size: 4' long by 2' tall, 3 tube.

icesailor

Circuits:

That's tough.

The way it's drawn, and the actual installation is always different because it is difficult to draw accurate complicated piping systems.

The "Sub-Zone" needs to be its own zone and not sharing the resources of the other three radiators.

If you can close the radiator valves on the three left hand radiators, and force all the resources to the three on the right, the "Sub-Zone", you will see that it is out of balance. The top two left hand radiators will be like birds in a nest, demanding the hogs share of the resources.

If you can shut off the 3 left hand radiators, and the Sub-Zone works, can you install three ball valves to add resistance to the three circuits? You need to get more pressure to the Sub-Zone. You can install a bigger flow circulator but it might get noisy. I personally think the 007 will work. There just isn't enough resistance on the left side.

And if the left side is on the old monoflow side, and the monoflows are still in place, you definately need to separate it. They don't mix well. The flow characteristics are so far off.

IMO but not worth much.

hws

.

Sorry Icesailor, if I said monoflow it was accidental. Meant to say direct return, NOT monoflow or series-loop

hws

revised diagram

Icesailor, let me see if I understand you so far.

In the revised version of the diagram attached, the area inside the black square symbolizes exposed piping in the basement (everything else is behind finished walls).

I could install ball valves to shut off flow to the rads on the left side of the house, leaving only the sub-zone open. If I'm understanding you correctly then the sub-zone will work, because if doesn't have to share pressure with the low-resistance left side. The longer runs on the sub-zone offer higher resistance and are now getting less flow.

If this ball-valve experiment works, it would be safe to assume that, if the sub-zone became its own zone, all three rads in that line would work. Right or wrong?

Another thought: Instead of ball valves, install balancing valves (or globe valves) at the points indicated by white circles in the diagram?

And one more: The system is now running at the usual pressure, 12 psi. I generally don't ever set residential systems any higher than that. Would a pressure increase help things, do you think?  

Anyway thanks everyone for your help thus far.

Henry

Seperate risers

Old cast iron systems were piped with risers serving at the most two radiators. When we re pipe steam system to hot water, we always use reverse-return in the basement while keeping the risers. We do the same when the owner wants to remove the gravity mains in the basement for more ceiling height. Unfortunately, I doubt that you can balance the system the way you piped the second floor. It is DEFINITELY not a blocked radiator. We have encountered radiators that don't heat well if bleed ed but this was caused by improper radiator level, a sag that upset the natural flow.

icesailor

Flow:

Your last drawing shows the black lines in a thumbnail but goes away when it is blown up.

I understand that what is inside the black lines is in the cellar. If you can pipe a circulator into that added zone and if you connect at the return and put the circulator there, it shouldn't counter-flow. If you put it on the supply, the same applies.

I can't explain it but there is a way to pipe a zone into existing piping that when done in that way, the zone won't flow. If you put two ball valves into that upper loop, it may start working. But the problem piping has to do with one loop being fed through the run and the other passing through the branch.

You'll fix it.

hws

here are some things I'm thinking of trying this week.

-Installing some valves in the lines feeding/returning the left side of the zone, allowing only the sub-zone to operate. If I can get all 3 rads in the sub-zone to heat sufficiently, I'll slowly open the valves to the left side of the zone, hoping to achieve a balanced flow. I may use globe valves to allow for throttling flow.

-I might also consider a larger circulator. Although the 007 on high speed will generate enough head (10ft), it has no head to spare. Some flow noise might be acceptable as there is virtually none now.

-If I have to, I might consider making the sub-zone it's own zone with dedicated zone valve. I'm trying to see if I can get it working without doing this though, because running the thermostat wire will invovve a small amount of tear-up.

Sidd

*Please HELP!* 3 Zone system hot water system, certain radiators not heating.

*QUESTION!!*



I have a 15+ year old, 3 zone, hot water honeywell system. all the zones are working except a few radiators on the 3rd zone (2nd floor). 1 radiator on that zone is working correctly, but 2 radiators on that zone are not providing any heat or heating up at all. This is a recent problem, as all the radiators were working adequately for the last few years.



Any ideas what the problem/obstruction could be and how could i go about removing it?

Any suggestions or advice are greatly appreciated!!

Weezbo

Sidd ,

have you any place on the radiators to let air out of them?

try that first.

,

if that "Works" then we got lucky quick.



it is good to start a new thread if that does not work .



that way folks will answer your questions and this person 's thread won't get mixed up..

Go check ...



Weezbo.