K8 Tstat Wiring Question

g1625s · Post by **g1625s** » Tue. Nov. 11, 2014 2:42 pm

Ok, so my boiler has been up and running for a couple weeks now and so far I love it! I have it tied into my forced air duct work with a heat exchanger. Everything works excellent as far as I can see, but there is one issue that has been plaguing me. The tstat is tied into the triple aquastat, the safety controller and the fuel oil furnace, with the burner on the furnace disabled. Taco pump is wired to the triple aquastat. Tstat calls for heat, everything turns on and all is well with the world. (oh, the fuel oil furnace is on its own separate circuit, fwiw.) By manually turning the safety controller down, I verified that it was indeed working and only the blower and pump cycled on that call. My concern is that when the tstat calls for heat, the stoker runs no matter what the boiler temp. I'm set for 175 and it holds perfectly there at idle. I would assume the stoker should only start up once the return water from the exchanger drops the boiler temp, no? I have a single zone relay sitting here and was thinking of wiring the pump to it and removing tstat wires from aquastat. In my mind, the boiler would then just do its own thing to maintain temp as opposed to stoking on every heat call. Thoughts? Comments? Swear words?

Assuming this is a good idea for the moment, Do the tstat terminals in the aquastat then need to be bridged together? Thanks in advance for any and all advice! Should have got one of these things a looong time ago!

Heres a pic for grins.

greg

Post by **Rob R.** » Tue. Nov. 11, 2014 3:12 pm

If the TT terminals in the triple aquastat are shorted, the stoker will run until the high limit setting is reached. At that point the stoker will shut off, and stay off until the boiler temperature reaches the high limit setting minus 10 degrees...or until the TT terminals are no longer shorted, whichever comes first.

What do you have the low and high limit set at in the triple aquastat?

g1625s · Post by **g1625s** » Tue. Nov. 11, 2014 5:13 pm

I am at 175/155 presently.

g1625s · Post by **g1625s** » Sun. Nov. 16, 2014 5:37 am

Bumping this to the top on a sunday morning. I guess my main question is weather or not changing how I wire the tstat will ultimately lead to greater efficiency or not.

Post by **Rob R.** » Sun. Nov. 16, 2014 7:40 am

g1625s wrote:I guess my main question is weather or not changing how I wire the tstat will ultimately lead to greater efficiency or not.

I doubt it will make a measurable difference, but if you want to switch things so the boiler just maintains the low limit setting go ahead. The stoker will run less often, and longer when it does. The problems start when the weather gets colder...keeping the boiler at 155 probably won't get enough heat out of your heat exchanger, so you will have to raise the low limit setting. At that point the boiler will just be hot all the time, and that will likely require more coal than bringing it to the high limit only on heat calls.

McGiever · Post by **McGiever** » Sun. Nov. 16, 2014 7:57 am

A Keystoker KB-8 appears excessively large for your application. Efficency will be difficult to reach if it is indeed large.

g1625s · Post by **g1625s** » Sun. Nov. 16, 2014 5:47 pm

It is a big boiler, but the house is close to 5k square feet and I will be implementing the dhw loop soon. Also, I will be slowly converting much of the house to radiant floor heat...and if I'm still not working the ol girl hard enough, there is a chicken coop to heat and a hot tub in the works, haha!