Do I need a bypass valve?

CTGuy

I tried to post this question before, but had problems with the drawing file, so here it is again.  I did the drawing with Taco's software, which is really easy, even for a DIYer like me.



I am adding an old wood "water jacket" boiler to

my existing system.  My oil boiler is an old American Standard which has a

domestic hot water coil. A layout is attached.  As you can see, I have

plumbed the boilers in series.  I did so because I need to keep the coil

hot at all times.  The idea, obviously, is to allow me to burn wood and

run the heat through the oil boiler, and when the wood burns down, the oil will

kick in.  The wood boiler's circulation pump will kick in once the water

in the wood boiler reaches the desired temp. The question is: Do I need to use

a bypass valve on the wood boiler?  Normally, I would say, yes, but when I

think about it, I have my doubts.  Since the boilers are plumbed in series,

and the oil boiler will always be hot, the water returning to the wood boiler

should also always be hot, right?  If the purpose for the bypass valve is

to prevent cold return water entering the hot wood boiler, do I need one? 

I have included one on the layout plan (just above the wood boiler) to show

what I had originally had in mind.



Since I have a separate circ pump and flo check on the wood

boiler circuit, do you think I will get much back flow through the wood boiler

when it is cold?



The wood boiler is old.  I don't have an

owner's manual, and can't even find a model or manufacturers' name

anywhere on it.

Big Ed_4

Bypass

A system bypass to prevent thermal shock could not hurt . What ever can happen will happen......



One problem I see is with the lower right two loop ,(I cant read what they are) and the wood stove , The flows from stove / loops will intermingle ... For sure if the wood burner circulator is on the flow would run though those loops even without them calling for heat .. not sure if they , (supply , supply and wood return) share a union or a single check . But each loop needs its own check... The expansion tank / air scoop should be relocated back to the supply out of the boiler for a more even pressure drop. across the loops.

icesailor

Bypass?

That might work for you. There are easier and less costly ways to do this but it might work for you.

I don't see how you will protect yourself from the wood boiler if it overheats. If there are no tags with information, if you do have a problem and there is an issue of damage, will your HO's insurance cover you?