Hi low limits and DHW

pmarinello489

Good afternoon I currently have an oil fed boiler with 2 zone heat, and an indirect water heater on a third circulator.  Currently aquastat set at 160lo/180hi. I have recently noticed everytime the water heater calls for heat my boiler will kick on and my zone control turns off thereby turning the circulators off until boiler reaches hi limit again. Only reason I ask if this is correct is because technically I am not making any hot water for another 5 minutes as the boiler gets to temp. I have a 40 gallon water tank and a Bainultra AirTub which is all in spec. I am trying to comfortably use, trying to make sure everything is correct.  

Thanks 

mattmia2

Are you sure the dhw circulator is off? Most zone controls can be set up with dhw priority so the turn off the heating zones and turn on the dhw zone when there is a dhw call.

STEVEusaPA

Doesn't sound right. Is the indirect piped off the existing coil in the boiler or a separate zone? If it's a separate zone you don't need the low limit.
Which aquastat?
Pictures of boiler piping and controls.
Circulators shouldn't turn off at high limit, just the burner.

EdTheHeaterMan

STEVEusaPA said:

Doesn't sound right. Is the indirect piped off the existing coil in the boiler or a separate zone? If it's a separate zone you don't need the low limit.
Which aquastat?
Pictures of boiler piping and controls.
Circulators shouldn't turn off at high limit, just the burner.

Agree with Steve. My guess is the original boiler was equipped with a triple acting aquastat relay like the L8124 or L7224. The Indirect was added to the boiler and the aquastat ws never replaced, adjusted or rewired to make the boiler a "Cold Start" boiler.

With the info previously asked for, we can guide you to a more efficient operation. Cold start is almost always better that maintaining boiler temperature.

Of course if @pmarinello489 is mistaken a tankless coil with a recirc pump for a indirect... that seems unlikely... Picture of the boiler and the indirect and the near boiler piping, with the model number of the aquastat relay (cover off to see the wiring) will help.

EBEBRATT-Ed

Your installer may have installed the indirect in place of a tankless coil. The controls and the wiring for the indirect are a little different from a tankless operation

pmarinello489

here are some images not sure if I attached them correctly. Anyhow the indirect is piped off of a circulator. At one point before I moved into this home there was a direct fired oil burner water heater, at some point it was switched out for this indirect and the circulator was added. I can tell from different color Teflon tapes and fittings etc. 
thanks again 

mattmia2

Where does the power for the dhw circulator connect? it looks like it goes in to the top of a box on right side of the boiler.

pmarinello489

All the circulators including the DHW one go into the electrical box next to the zone control and my on/off switch. Pictures are attached if you need to see the wiring I’ll pull it all out when I get home from work later. 

HVACNUT

That aquastat always maintains the High setting, now 185°. 
The Lo side should drop power to the circulators if the temperature reaches that setting. But the way its wired, I don't think the Lo is doing anything. Where does the Red wire go after it leaves the Lo side?
ZR,ZC aren't being used for circulator control, and only 2 out of 3 zones are in the zone panel so the water heater is just wired line volt through the water heater aquastat to its corresponding circulator. 
Look into replacing the boiler aquastat with a Hydrostat 3250 Plus or similar. Wired and set correctly itll provide DHW priority, thermal targeting, and condensate protection. 
And Green is NEVER used as line volt power. Green is ground.

pmarinello489

I think the low limit is def working only because the boiler does drop zone control if that temp is hit. (160F)
The red wire from the low side of the aquastat from the boiler goes to the image i uploaded. Turns to a black wire and is connected to "120V in H" in the zone control panel.
I need a new gasket where the boiler aquastat sits anyway I may just call a local guy to see how much to do everything (aquastat, rewire, and new gasket). What you think I am looking at for labor? I have an understanding of all this but I heard that gasket could get tricky, and yes I have some background in electric I have no idea who decided to use a green wire on line voltage.. just like everything else in this house. lol

Thanks again

mattmia2

What's leaking? That blank off plate for the tankless coil that you don't have? The round plate that the aquastat is mounted to.

pmarinello489

Yes where the coil would go, where the aquastat screws in. 

MikeAmann

You mean the well that the sensing bulb on the back of the aquastat goes into?

pmarinello489

This gasket lol

MikeAmann

It looks like the gasket is fine. Sealant should have been used on the threads of those 6 bolts.

pmarinello489

When the boiler cools down it starts to leak. I need a new temp/pressure gauge so if the boiler is drained I figured I do everything needed at one time. Aquastat, gasket, and gauge 

HVACNUT

pmarinello489 said:

When the boiler cools down it starts to leak. I need a new temp/pressure gauge so if the boiler is drained I figured I do everything needed at one time. Aquastat, gasket, and gauge 

Coil plate bolts in cast iron like to snap. Use a good 6 point socket. Spray with penetrating oil first. If any seem seized, try tapping the sides of the bolt with a flat chisel and lump hammer. 

pmarinello489

I’ve been spraying them for the past year. This has been an issue that I’ve been putting off, like I said it doesn’t leak on the regular but when it cools down it starts to drip. I called a local boiler mechanic he said $$$ for service (normal) and $$$ and up for the gasket noting the same concerns you guys have. I need him to do the gauge while the boiler is down and might as well do the aquastat too. 

EdTheHeaterMan

I would be surprised if at least one of them didn't break off.
my sure fire, go-to, always works fix for this is to use acetylene torch to heat up the bolts cherry red, then let them cool, then heat again, several times. On each cooling I would spray with rust buster or liquid wrench. then try to move the bolt about 3° to 5° loosen and tighten. As the process progresses, the bolts get to turn about 5° more than the previous cooling cycle. It can be time consuming but I have had great success

I also own a set of "
Easy-Out" stud extractors

mattmia2

A T handle socket wrench for the socket helps a lot so you can put a pure twisting force on the bolt and work it back and forth, try both tightening and loosening gently but firmly using both ends of the T so your force is rotation only. Might try a hand impact driver too, the type you hit with a hammer. If you can heat the whole bolt enough to dehydrate the oxides that is a pretty reliable way to loosen it.