boiler bypass

Dale

The best info on the topic I've heard was a a free Crown boiler class sponsored by the local wholesaler, If you have a Crown supplier near you stop by and get one of their boiler booklets or call Crown, very nice people. Best is to spend a few hours some evening when the Crown trainers come by. What I remember from that was to keep the outlet at 140 degrees by the use of inlet and bypass valves or a pump controller on the outlet that won't let the pump run unless the outlet temp is high enough.

hvacman1028

boiler bypass

Can anyone tell me how to determine when you need to install system or boiler bypass? Just got back in the field after 15 yrs inside and started MOB...(back hurts!)Have a lot of catch up. Been trying to research on the net and cant find anything definite one way or the other. I have a 4 sect Dunkirk going in Monday and reading the IOM it says install bypass if DESIRED water temp is to be lower than 140 degrees. I assume for radiant. This house has 12 cast iron rads and not very big. 2" mains with S/R -3/4". Probably gravity system years ago. Do you install them anyway needed or not or is there some calc to figure first?

frank_25

bypasses

The return needs to be above 135-140 as it enters the boiler or the boiler will start condensing and/or make a noise that tells you the iron just cracked. Sopme blr mfgs do it differently, but if Dunkirk doesn't give a layout, pull water from the supply, before the system circ, and into the return at the boiler,and install a thermometer into the mixed water. Use a throttling valve on the bypass to keep the return above 135-140 and you should be OK.

hvacman1028

thats about what I figured for this one, but I came across a few articles that recommended to pull some water from the return and mix in the circ inlet and let the boiler see less return to increase DT at the boiler....due to the cast radiation. whats better?

Unknown

ur best bet is

Your best bet is installing a Danfoss TV and piped after the boiler pump, that way, u don't have to be messing around the bypass valve as the TV will do it automatic and better protected....

Phil_20

just checking

As experience has shown me the piping for a bypass is usually not installed ar applied properly and has shortened many boilers lifespan. The bypass should be equall in size to the suppply pipe and be piped as to "inject" hot supply into cold return.
Therefore bypass should be on outlet of supply pump to return OR piped to return on inlet of return pump from supply. For cast and in floor radiant these are crucial for long life of the boiler. Also long life for the chimney.

Servicemonkey

Where I work, we usually pipe the bypass before the circ, giving 100% flow to the radiators with tempered water thus providing even temperatures throughout. We carry cast iron boilers by Weil Mc Lain. Are you saying the bypass piping should go after the circulator, boiler gets 100% of the flow and system gets supply water at boiler temperature at reduced gpm?
Howard
(Chicago near-west-burbs, gas no oil houses 100 yrs old)

Dave_4

boiler bypassing

Here is a link that will answer your question regarding boiler, and also system bypassing techniques.

Pete

http://www.bellgossett.com/Press/BG-insand.asp

Dan Keirns

Agree with Danfoss TV

In setting a manual bypass, the temps you set it for are only good for that exact scenario. As the load increases on the system, the water coming back to the boiler will drop. Possibly into sustained condensing. The manual bypass will work fine if you set it up on a minus 10 day.
By using the TV valve, your boiler is protected no matter what is going on in the system.