BYPASS PIPING

jim f

i would like to incorporate bypass piping in this
reverse return scenario. looking for ideas and inputs?? would you have two seperate bypass lines to each boiler or one common bypass off the headers??
searching for diagrams with no luck.
thanks in advance!!
jim f.
milford, ct.

jim f

real life

heres a real life picture of the diagram i drew

Gary Fereday

\" ? \"

How do you intend to run the boilers, together, & or seperately, say as demand increases? That is perhaps where to start.

Steve Q.

By-pass piping

The best approach to piping 2 boilers is to icorporate primary-secondary piping with pumps for each boiler and a staging control.(Tekmar can provide you with the one best suited for your needs. This drawing comes right out of one of Dan's books. He has a great book called primary secondary piping. Get it for future jobs.

Unknown

Parallel Piping with Bypasses

Jim,

Here is a drawing of individual boiler bypasses with parallel piping. Hope this helps.

Glenn Stanton

Burnham Corp.

Mark J Strawcutter

thermal shock

Doesn't this run the risk of thermal shock and short cycling on the secondary boiler?

Mark

jim f

thermal shock.

thats why i would like to put bypass piping to each boiler.

Mark J Strawcutter

two kinds of thermal shock

bypass piping protects against thermal shock from cold return water hitting a hot boiler.

The diagram posted showing each boiler as a separate secondary loop off a primary can have another kind of thermal shock - hot return water hitting a cold boiler.

Mark

jim f

what if?

what if both boilers were maintainer temp for indirect??

Mark J Strawcutter

indirect or tankless?

with indirect I don't think you'd be maintaining temp so shock would still be an issue

if tankless coil in boiler, then you would probably be maintaining a min temp so this "reverse shock" would be less of a concern.

Mark

Steve Q.

Control Scheme?

I'm not quite sure about Glen's piping diagram? It looks like your bypassing the boiler and lowering supply side temperature? Is this true? Glen could you explain?(No disrespect intended.) Do you intend to reset boiler temperature? Are there indirect water heaters?

Unknown

Steve

That is exactly what is happening with the piping. The flow from the return of the system is bypassing the boilers. This will reduce the amount of cooler return water the boilers may encounter. Jim's request was for bypassing piping for tandem boilers when piped in parallel. He is not stage firing the boilers in this case so there is no concern about reverse thermal shock or hot water hitting a cold boiler. The better way to pipe tandems is primary secondary injection, preferably with a way to monitor the return water temperature.

Glenn

Steve Q.

No stage firing?

Why wouldn't he stage fire these boilers. With all those zones the heating demand has to be varied by quite a bit. Does it not pay to do this in this situation?

Howard

May I jump in?

> i would like to incorporate bypass piping in

> this reverse return scenario. looking for ideas

> and inputs?? would you have two seperate bypass

> lines to each boiler or one common bypass off the

> headers?? searching for diagrams with no

> luck. thanks in advance!! jim f. milford, ct.



Based on your photo, let me propose a bypass pipe. It would look like a 7th zone just like the other 6 but would consist of a pump and a short circuit of pipe from supply to return. Run the circulator whenever the boilers fire. Comments??

I'd be concerned about overheating a satisfied zone if water can run backwards through it when other pumps are running.

I'm a service tech. I's a good day if I can help. I's a better day if I can learn.

Howard

May I jump in?

Based on your photo, let me propose a bypass pipe. It would look like a 7th zone just like the other 6 but would consist of a pump and a short circuit of pipe from supply to return. Run the circulator whenever the boilers fire. Comments??

I'm a service tech. I's a good day if I can help. I's a better day if I can learn.

Ward

BYPASS PIPING

REFER TO WEIL MCLAIN MULTIPLE BOILER SYSTEMS. IT'S IN THERE COMMERCIAL BOILERS REFERENCE MANUAL. DIAGRAMS WILL GIVE ALL YOU NEED, AIR ELIMINATION, PRIMARY / SECONDARY PIPING AND CONTROLS FOR STAGING BASE ON LOAD. SOME REPIPING WILL BE REQUIRED BUT YOU'LL END UP WITH A VERY EFFICIENT SYSTEM WITH MINIMUM STANDBY LOSS. CHECK IT OUT.

jim f

any suggestions or input on howards post?

Unknown

What you are describing

is what we refer to as a shunt pump. It is an acceptable practice in the industry and is used quite often on larger jobs and boilers. The best strategy would involve an injection piping system with return water sensors to vary flow or divert flow with a variable speed pump or a 3 or 4 way diverter valve.

Glenn Stanton

Burnham Corp.

Mark Eatherton1

Answers and Questions...

In that order, attached is a drawing showing the ultimate primary secondary sytem with a thermostatic bypass incorporated to avoid cold shocking the boiler. Not quite how is would work for reverse thermo shocking, and not even sure that's a real issue.

Now for the question, Why do boiler and water heater manufacturers still show "bull headed" tees in their hydronic piping configurations?

One of the very first articles that the Grand Master of hydronic education, John Siegenthaler penned had to do with bull headed tees and why you SHOULDN'T use them.

Here it is, many years later and numerous hydrponic heating equipment manufacturers are still showing their drawings with bull headed tees incorporated. Not that Siggy needs any more work, but it would be wise for these errant manufacturers to hire Master Siegenthaler and have him
"update and upgrade" their mechancial drawings.

The Munchkin folks hired him to do the design drawings for their newest installation manual on the Vision series boilers, and it looks great. Not that Brian French needed any help really, I've always been impressed with Brians parallel reverse return characteristics. Brian "gets it". Just like Siggy does.

Come on guys, catch up. Yer giving us a bad name:-)

NO MORE BULL HEADED TEES PLEASE!!!

Happy Gobble Gobble day!

ME

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