Need some recomendations for boiler hook up

I just got my kaa-2 and its sitting next to my oil boiler. I would like to keep the oil for back- up, and have been told it is better to keep it heated than to shut it down and keep full of water and cool. So I need to hook the two together. Here is what I have (I do not have this MAC sketch program figured out so I sketched it on paper by hand and took a picture) A Trianco boiler with a Becket burner, I have three zones with a circulator for each controlled by an Erie boiler boss relay (controller). Three flow check and one expansion tank. The circulators are on the return to the boiler, pumping into the boiler, on a 1 1/4" manifold. The boiler output (top of boiler) is 1" and goes up about 1 foot to a safeguard low water cut off. after that it is reduced to 3/4" pipe up and over to the expansion tank then the flow checks branch out to feed each zone. All this was done with copper pipe. I do have lots of valves, couplers and flanges installed throughout. I have been reading on here how to pipe this in and to be honest the more I read the more confused I get as to the easiest and best way to do this with my system. I am on a budget (low) as I just had to pay for the boiler. I have attached the hand drawn sketch of my oil fired system as it stands now. It has ben working fine for almost 20 years now even though my living area has almost doubled in size. Should I just let the DHW remain as is from the oil or maybe go through the coal DHW coil first then into the oil DHW coil. Im not sure yet if I will run the coal in the summer or go back to oil for DHW needs. So what do you think for boiler hook up to my system ? series ???? parallel ??? I have pictures of my oil boiler as is now if needed. I also promise to take and post lots of pics of the install as and when finished. Thanks in advance for any and all help

This is what I was thinking just to run it by you guys. The output from the coal boiler with a circulator (runs when coal up to temp) pumping into oil boilers return (Teed into manifold between system circulators and frt of boiler) done with the same 1 1/4" copper as the current manifold. Then the return of the coal boiler will Tee into the output of the oil boiler (top of boiler) either above or below the safe guard LWCO, this will be with 1" copper (the same as the output pipe on the oil boiler). The circulator between the two boilers will pump hot water from the coal boiler into the oil boiler then back to the coal boiler as long as the coal boiler temp is up to temp. if the coal goes out or I go away the oil boiler (with lower aquastat setting) will take over when the oil boiler temps gets low enough. I think that if the oil boiler takes over that the coal boiler will not be heated from it but this should be ok for temporary oil boiler operations. does this make sense or am I missing something ?

autoguru wrote:I think that if the oil boiler takes over that the coal boiler will not be heated from it but this should be ok for temporary oil boiler operations. does this make sense or am I missing something ?

There are several ways to plumb your system, the choice will be yours depending on how you want it to work. What I see that you are missing is a pair of lift check valves, these will isolate them thermally if you want to separate the two when one is not operational when plumbed parallel.

Autoguru,

What you describe is how I have my boilers connected. I have the circulator in the return line between the two boilers and controled by an aquastat on the coal boiler that is set to turn off the circ. if the coal boiler water falls below 130*(which would mean the coal fire is out) the aquastat powers a relay cutting out the circ. and also closes the end switch circuit for the oil boiler allowing the oil boiler to come back on line.

Good luck with your install and have fun doing it.

I piped the hot water out from my coal boiler to the hot water out of the oil boiler. I connected into the return of the oil boiler and connected this to the return of the coal boiler. There is a circulator in the system between the two boilers--I put the circulator at the return of the oil boiler and it pumps to the coal boiler. I used a check valve in this return line to prevent back flow when I am not using the coal boiler.

This arrangement allowed me to basically operate the coal boiler independently of the oil boiler. All existing controls and pipeing for the oil boiler continue to operate as before installation of the coal boiler.

I put a temperature sensor on the coal boiler and when it senses the coal boiler is up to temperature it activates a relay that shuts off the oil burner and applies power to the circulator between the coal and oil boiler.