Circulator Question

Warren Licht_2

Here is my system:

I have a steam boiler with three water zones tapped off of the steam boiler; two are small and only circulate no more than 8 feet over water level. The third floor (circulating 20-25 feet above water level) is the largest of the three zones. The piping for the water zones are 3/4 inch. The boiler itself seems to have plenty of energy to supply the various zones (in fact it often overheats the steam zones at the expense of heating the water zones).

Over the years the system often needs "purging" as air gets in, despite it being a "closed" system. I have a heating guy coming to look at this issue this week.

But my question here pertains to the fact that the smaller and lower zones "circulate" fine with all of the return water going straight to the boiler return (without any of the return water returning to the circulator). However it seems that the larger and higher zone needs some water returning directly back to the circulator to allow for normal circulation in that zone (i.e. maintain the siphon effect). I carefully examined the circulator and realized that it is only 1/25 horsepower and then realized that it might be too weak to "assist" the siphon effect in the larger and higher zone - which could also add to the "air-trapping" and the need to repeatedly purge this loop over the years.

Could you tell me if 1/25 horsepower seems to weak for the system I have? If so, what size do you recommend and do you recommend 2 circulators instead of 1? (If you need more data about my system to assist you in the answer, please ask - thanks.)

Warren

Warren Licht_2

It does seem to work after a full "air" purge with total water return to the boiler, but it seems much more prone than the lower and smaller zones to get "air pockets". Would a stronger circulator help this as well?

Warren

Mark Eatherton1

Warren...

THe system you're speaking of can be REALLY tricky to get properly purged. If you're purging into your boiler, it doesn't sound to me as if you have a good and proper set up. When I set these up, I always set them up such that I can truly isolate the upper system from the boiler condensate so that I can perform a good solid power purge. Once thats done, I release the closed loop back into the hot condensate side of the system and I've never had a problem.

Sounds like you may need to add a couple of valves.

The pump is not actually "lifting" water to the highest side of the system. The weight of the water falling counters the weight of the water rising. If your pump is actually having to lift the water to the top of the system and establish a siphon, you're system is not set up correctly. Can you hear a bunch of bubbling in the boiler (air, not steam) when the closed system circulator starts up? If yes, its not set up right.

As for over heating on the steam side, it also sounds as if you're short some controls. When I set mine up, on a call from the condensate heating system, I limit the boiler to 180 degrees F with an add on aquastat that is looking at the condensate temperature, and not the steam chest, which is WELL below the threshold of producing steam. If I get a simultaneous call for both sides of the system, the steam side takes precedence.

It is EXTREMELY important that cool condensate be mixed with the hot condensate, otherwise the upper portions of the system could flash to steam, thereby casuing further problems of maintaining flow.

Go to Hot Tech Topics and you will find additional information on your system. (On the pipe to the upper left of your screen.

Good Luck and welcome to the Wall.

ME

Warren Licht_2

Thanks for the reply.

Yes I can and do isolate the loop when I purge it. I purge the loop into a bucket or sink, not back into the boiler.

Question: When you say mix the cold with the hot condensate, do you mean "mix" in the returning colder condensate at the circulator level (I have a "mixing" valve that could allow me to do that) or do you mean return all of the return colder condensate to the boiler itself - or a bit of both i.e. mixture. When I have "mixed" in the return condensate at the level of the circulator and not all to the boiler, that is when I think I have added or should say have perpetuated "air bubbles" back into this supposed closed loop. I believe if I can return it all to the boiler then it prevents these air bubbles from recirculating back up the loop. On the other hand, perhaps allowing some return condensate right back to the circulator might prevent "flashing into steam" that you mention that may also contribute to the air bubbles.

Help, which of the 2 makes more sense.

Thanks

Bill Nye_2

Warren , did

...did you have a look here?


http://www.heatinghelp.com/heating_howcome6.cfm

Warren Licht_2

Did do all the above and it still seems to be taking in air. Let me clarify that there are 2 air release valves at the top of the loop that I shut tightly. There are also two air release valves at the end of the return before it splits to go to the boiler or to return to the "loop". I had a "spirovent" installed on the outgoing part of the loop right after the circulator.

Where and could any of these be pulling in air? If so, which if at all should I have removed. Should there be any air release valves at all in the loop - and is it safe if there are no air release valves in the loop? Without any air releases can the pipes explode if too much expansion occurs?

Thanks....

Mellow_2

warren

The system you speak of should have no vents installed. The vents will let air in to the line. This system also sounds like the circs are on the return or pushing in to the boiler. Without the vents the circs will work in the return but I have had great results putting them in the out going pipe or supply.

"syphon" Dose this mean you are sucking the water back to the boiler with the circs........Try pushing with the circs in the supply....the air in the line will push its way back to the boiler....... with them in the return the air gets caught in the circ......good luck

Warren Licht_2

No there is just one circulator on the outgoing loop.

There are also two air release valves at the end of the return before it splits to go to the boiler or to return to the "loop". I had a "spirovent" installed on the outgoing part of the loop right after the circulator, because of my air issues.

Where and could any of these be pulling in air? If so, which if at all should I have removed. Should there be any air release valves at all in the loop - and is it safe if there are no air release valves in the loop? Without any air releases can the pipes explode if too much expansion occurs?

Thanks

kevin coppinger_4

get rid of....

the spirovent...it is 1/2 of the problem. kpc

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Warren Licht_2

so the concensus here is to rid of all of the vents....

again, is there any danger of "pressure" build-up in the pipes?

Warren

kevin coppinger_4

no danger beacuse....

the steam boiler runs under low pressure and is and open system. kpc

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Warren Licht_2

what about the 2 small screw vents on the baseboard at the top of the loop; I shut them very tightly, is that enough or do they need to be removed as well?

Mellow_2

two types of systems

One has a heat exchanger (closed loop system,this is not yours). The other is using the water from the steam boiler and circulating through the loops or zones( open loop system). This sounds like yours.......in this system the water can expand in the boiler and you want NO vents. The reason is to prevent air from getting in the line when it is not running. If air is let in to the line the water will fall back to the boiler. You might want to look in to Dans book "how come" chapter six explains it all.

It is safe without the vents and if it was me I would cap off the vents and make sure the lines were bled. This would solve the air problem. The best way is to remove them but you can see it work this way first....

Mark Eatherton1

Get rid of the vents...

Spiro AND giro. Make sure that all (if any) packing glands on valves are as tight as they can be. Also make sure that you have adjusted your mixing valve set up so that the water going to the zone never exceeds 180 degrees F.


ALso, go the the link (cut and paste) and read the information on this application. It's much simpler than you'd think.

Happy New Year

ME