boiler bypass

Adam_16

Boiler bypass is great added protection but saying that it still can be compromised .Ideally you want 100% protection that a properly selected control can offer .For about 1/3 the price of your boiler you can rest assured that your boiler has the maximum protection .This is even more important now that we are getting into shoulder season where heating systems wil only be fired for more short periods . This increases the amout of cold starts which could mean more chances of flue gas condensation .The control system helps modulating challenged boilers maximize there firing cycles and improve there efficiency .

Jeff Price_2

Boiler bypass

I have a burnham v73 with three circulator zones, the controls are setup for cold start. It is plumbed without a boiler bypass.
My question: Is it worth it to have the boiler configured with a bypass and if so what is the preferred configuration, using a valve or circulator?

Paul Pollets

Full port bypass

a bypass should be the same size as the supply and return piping. A glode valve is used with the bypass being at least 12" long. A thermometer is located and installed on the return after the bypass, to indicate correct return temps. The boiler should reach 140 degree temps on the return within 5 minutes of boiler operation. The bypass is always installed before any takeoff tees, and is never reduced in sizing from the mains.

If the system water content is greater than the boiler water content by a factor of 3 (this will depend on the boiler and manufacturer's guidelines, a bypass is required.

If a 4 way valve is being used, a "system bypass" is installed connecting the system supply and return of the 4 way with a 12" bypass and globe valve.

Glenn Stanton may have some further comments, regarding Burnham boilers and bypass requirements.

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Timco

My WM CGA6 Gold offered many piping options...one of which was a bypass setup. Just how desireable is this? Does it have to do with a zone being at temp and a cold zone starting up, somewhat shocking the boiler? Will a bypass extend the boiler life? (on a 3-zone system) With one zone...would you still need a bypass?

T

hr

No easy answwer

it depends on the system. How closely the boiler matched the load, what type of emitters, high or low mass, etc.

HW baseboard systems have been installed for decades without any bypass piping.

If I had a choice I would install a boiler control that could both watch and adjust for return temperature, and reset your system around outdoor, and indoor conditions. tekmar comes to mind

Now you are assured of protection regardless of the load conditions, and have a more efficient system to boot. It may take some repiping to make it all happen.

A manually adjusted ball, or globe valve is just a guess. Better than nothing, no doubt. But it lacks the "brain" needed to do the job properly.

hot rod

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Unknown

I heard Danfoss has a good product for that.

Unknown

Jeff

Since you stated that you have a V73, it can be assumed that it has been installed for some time now. If has not had a boiler bypass installed and has been been operating with a minimal temperature drop across the zones, then it is probably OK. The person that has been servicing the boiler would have a much better idea of whether you need a bypass added because they would have either seen or not seen indications within the flue passageways of condensation occuring due to cool return water.

A bypass is not 100% protection for any boiler. It is simply a way of allowing the boiler to handle the possibility of cool return water by diverting a portion of it back to the supply in an effort to reduce the amount of cool return flow the boiler actually encounters, thus allowing it to ramp up in temperature quicker. Hope this helps.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Jeff Price_2

Reason for my concern

My boiler was recently replaced due to a crack in the casting, the unit was only 6 years old. I was told that my unit had a defect in the casting and that it was a known problem area for that particular boiler. The replacement unit looks exactly the same as the previous one, so I am trying to determine if I should change the installed layout. When the contractor was giving the estimate for replacing the bloier I mention a bypass is recomended in the V73 manual. His take was don't worry, but I am concerned that in six years I might be back in this situation again.

ChasMan

Don't worry, be happy... Ill drop this behemoth in your basement and walk away.. Just pay me on the way out. Don't you just love it?

Unknown

Replacement

Although from the outside it looks the same, the internal design is somewhat different now. If this is a replacement block, then I would also advise installing the bypass as well Jeff. There are too many unknowns on field installations that can contribute to the failure you encountered. Return water temperatures, flow rates or lack of flow rates as well as the type of system (large mass) the boiler is connected to are some of these things. A bypass can only help the boiler from encountering it again. Although there are certainly better and more bulletproof methods of boiler protection, at the very least a boiler bypass can be effective.

Someone asked this past week on this site what the desired temperature difference should be through a residential oil-fired boiler. As I recall an answer was given of a 20°F difference with an acceptable difference of 40°F. The best answer would be 20°F. Although I have seen plenty of systems piped with a 40°F temperature difference, you can be assured that that kind of temperature rise is going to cause more thermal stresses to occur within the iron than a 20°F rise.


Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Holycack

What firing time is considered short cycling? Mine will sometimes run for only 3 minitues is this too short?

Jeff Price_2

Temp Difference

How is the difference measured? Is it difference once the zone has pushed hot water around to the boiler return, i.e. how much heat is lost due to the radiators. For my system the water comes ~25 degrees cooler.

Unknown

25°F Difference

Is that temperature difference at startup only, the same for each zone and does it lessen after a short running period for each zone? You should see the temperature differential lessen as the zone runs a couple of minutes as the water in the zone is no longer sitting at room temperature. What type of radiation do you have this installed with? If you have cast iron radiators then you have what is considered to be a large mass type system and a bypass or other method of protection should have been installed from the get go!

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Jeff Price_2

25 degree difference???

I guess I am a little confused about the temperature differential..... lets start at night when the house is 70 degrees and the boiler is ~170 degrees, at 11pm the night setback kicks in to 64 degrees. As the house cools the water in the radiators does also, the next call for heat will return the room temperature water (64 degrees) from the radiators to the boiler which I am assuming is still above 100 to 140 degrees. Is this the diff. temp. I should be concerned with??? because, I can not see away around this unless you had some form of bypass setup isolating the system loop from the radiator loop.