Condensation in cast iron boiler

Dave_12

CONDENSATION IS A HUGE PROBLEM THAT DESTROYS CAST IRON, COPPER FIN, AND STEEL BOILERS. I LIKE TO USE A MINIMUM RETURN TEMPERATURE OF 140F TO BE SAFE WHEN TRYING TO AVOID FLUE GAS CONDENSATION.

CONSIDER A THERMIC VALVE PRESET FOR 140F IN THE RETURN LINE WITH A BY-PASS FROM THE HOT BOILER OUTLET FEEDING INTO THE THERMIC VALVE.

YOU MUST, REPEAT MUST, INSTALL THE PUMP BETWEEN THE BOILER AND THE THERMIC VALVE, WITH THE BY-PASS LINE TAKEOFF AFTER THE PUMP. THIS WILL INSURE THAT BOILER FLOW IS NOT STARVED. YOU CAN GO WITH ONE PUMP, BUT I PREFER PRIMARY-SECONDARY PUMPING. A KEY HERE IS TO HAVE A PUMP WITH ENOUGH HEAD CAPACITY TO OVERCOME THE ADDED PRESSURE DROP OF THE THERMIC VALVE.

THE THERMIC VALVE WILL KEEP WATER CIRCULATING IN THE BOILER LOOP UNTIL THE TEMPERATURE GETS UP TO 140F, THEN WILL ALLOW WATER TO GO TO & FROM THE SYSTEM, MODULATING AS NECESSARY TO INSURE 140F MINIMUM WATER TO THE BOILER. IT IS A GREAT SYSTEM THAT SELF REGULATES ITSELF. NO ELECTRIC OR PNEUMATIC CONTROL NEEDED. A FIXED BY-PASS DOES NOT WORK AS WELL AS IT IS ONLY GOOD FOR A SPECIFIC CONDITION, WHERE THE THERMIC VALVE WILL ADJUST THERMOSTICALLY TO ANY CONDITION.

THESE VALVES WORK WILL FOR HIGH THERMAL MASS BOILERS LIKE CAST IRON AND STEEL. WITH LOW THERMAL MASS BOILERS, SUCH AS COPPER FIN, YOU HAVE TO BE CAREFUL TO AVOID SHORT CYCLING.

I LIKE TO USE A THERMIC VALVE WITH A CV (GPM FLOW WITH 1 PSI PRESSURE DROP)AT ABOUT THE FLOW FOR A 20F DIFFERENTIAL TEMPERATURE ACROSS THE BOILER. THERMIC VALVES ARE AVAILABLE FROM SMALL TO VERY LARGE. IF YOU NEED A MORE ON THIS CONCEPT, CALL ME ON 816-252-4005.

GOOD LUCK. THERE IS AN EASY SOLUTION TO THIS HUGE PROBLEM.

DAVE

Biged

Condensation in cast iron boiler

Here is my problem, I started my tuneups for the winter already. I am finding a lot af condensation in about 85% of the boilers I do(none are piped properly)The agency I do work for is State and Federal Funded so not a lot in the budget for repiping these boilers and the guys doing theses installation are doing swap outs on old gravity or steam conversion. What is the easiest and or cheapest way to fix this problem?

Al Letellier

condensation

Why are they condensing? Is it piping or is the boiler on demand start with no low limit. Keeping the boiler above 130* in most cases, will help the problem. It may be as easy as adding a low limit, but make sure you know why the boiler is condensing...

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Biged

Condensation in cast iron boilers

they are condensing because of the high volume of water returning from these gravity conversion system making the return water below 130*F. I thought about installing a triple aquastat after reading some info sometime ago but Burnham would have none of it.

A.J.

Big Ed boiler by pass is the only correct band aid

a low limit would waste fuel.If the powers a be will not spring for the fix at least have them sing off on a notice so they cann't come back at you in the future when the boilers die prematurly.

Kupetz's Plb & Htg

hr

Primary secondary

with a boiler control that provides return protection. The most basic of tekmar boiler controls offer 100% return protection.

A VS pump on the boiler loop of the PS piping would accomplish this also.

Those large volume, high mass systems are not at all unlike a radiant slab. It is very possible that they could keep the boiler in "unhealthy" condensing temperatures for extended periods.

A boiler control or VS arrangment would basically pulse the BTUs to the system at a rate the boiler could safely keep up.

I used a VS pump on a wood gasification boiler last winter. Works very nicely.

It will not reduce the amount of heat going into the system, a common rumor

3 way thermostatics are another good method, but they have a bit of pressure drop to work around, watch the Cv.

This link shows some options

http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,128051,00.html

Better yet, a condensing boiler

hot rod

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Biged

I kinda knew that the only fix is the bypass but wanted to know if they were any other way to fix. I was just lookinkg at the Taco 00vs circulator which might just be close to perfect for protecting the boiler.

clammy

triple aquastat

Hey big ed the cheapo fix would probably be a triple aquastat with a low limit circ .It would waste some money on stand by loses but would cycle the circ on low limit but all aside a by pass or better yet a simple primary secondary with a low limit but as you know it there ain't time or money to do it right the first time they'll never be money to do it again .Peace and the best of luck clammy

Unknown

Ed

As many others have stated here, there are various levels of guarding against prolonged quantities of cool return water through the boiler. The standard "Boiler Bypass" that we show is not neccessarily protection against cool return water. It is simply a way of reducing the quantity of return water that the boiler encounters. A "System Bypass" will blend heated boiler water with the cooler return water to aid in keeping it above 140°F but is a preset condition. A 3-way diverter valve on the boiler supply is another way to protect against condensation but is also a preset condition unless an electric actuator and return water sensor is utilized.

As Dave has stated here, a 3-way valve with a thermostatic actator to maintain 140°F or above on the return to the boiler may be the simplest and most dependable way out. Variable speed pumping utilizing a return side sensor and Primary-Secondary piping into the system is effectiove but is only reducing the quantity of return water the boiler is seeing by modulating return flow, but not warming up the return water. Utilizing a low limit control will only increase the temperature difference through the boiler and increase the risk of thermal stress unless a shunt or blend pump is utilized. Hope this helps.

Glenn Stanton

Manager of Training

Burnham Hydronics

Jed_2

BigEd

I believe that is exactly ONE of the scenarios Taco had in mind when developing the 00vs circs and i-series valves. Call Mark Chaffee.

Jed