Triple Aquastat

Alan (California Radiant) Forbes

Construction workers had to remove and replace the wiring to this boiler, but now, it only heats the indirect and not the radiators. The indirect is controlled by a separate transformer relay and I think this triple aquastat is toast.
There are two pumps and I want to add a pump control and have the end switch fire the boiler. Is there any reason why I can’t replace this triple aquastat with just a simple L4006A aquastat?

HydronicMike

You could, but why not use a hydrostat, take advantage of the zr & zc terminals, get lwco and circulator hold off, plus some other energy saving features?

HVACNUT

It probably has a triple aquastat because the boiler once had a tankless coil. Now that there's an indirect, yes, an L4006A would work but the boiler will still maintain limit minus the differential. No TT or end switch to start the burner on a heat demand. An L8148E is a cold start aquastat, or the Hydrostat 3200 Plus like @HydronicMike mentioned offers more and is probably cheaper.

109A_5

Would it help if all the wires were connected properly ?

mattmia2

why are there 3 transformers (and probably a 4th for the indirect that we can't see)? it is probably time to pull all the wires out and start over before you condemn any controls. it looks like someone added the indirect with as little effort as possible so there is now wiring going everywhere. figure out what goes to the t-stat and the aquastat in the indirect and piece it together from there.

109A_5

I would put the wires back the way they should be even if it goes to the extent of what @mattmia2 suggests. and prove the triple aquastat has failed. Although since the wiring was touched last I would bet on the wiring is not correct or simply not completely hooked up.

Another way is rip it all out, since there is an indirect just a high limit aquastat is needed for the boiler and maybe a ZR503 which may have benefits of wiring simplicity, DHW priority, and without the warm start it may save fuel over time. However this would probably cost a lot more in the short term.

EBEBRATT-Ed

Zone relays to start the pumps, L4006A for the boiler limit. Lockout the heat when the indirect calls to give you priority

Alan (California Radiant) Forbes

What's curious is that the boiler never had a tankless coil. You hardly ever see them out West here. I have only one customer that has one. Curious also is that the control is meant for a millivolt system, but the gas valve is 24 volt. Hydrotherm never made a boiler with a millivolt gas valve. The wiring from terminals B1 and B2 to the gas valve have been modified to add the 24 volts from the transformer.

@HydronicMike Thanks for the suggestion, but I really don't need all those features.

EBEBRATT-Ed

@Alan (California Radiant) Forbes maybe the original aqustat failed and someone had that one on his truck.

Big bucks for something they didn't need. Well, maybe not so many bucks back in the day. Hydrotherms were very popular around here in the 80s when the world went modular boiler crazy. Never saw to many installed as single boilers.

Alan (California Radiant) Forbes

It took me awhile to figure the damn thing out, sitting there on the basement concrete floor between the stinky cat litter box and the stinky cat food bowl. Two technicians had preceded me, telling the owner they needed a new boiler.

I'm picking up a new aquastat relay and 2-pump control and will install it tomorrow morning. Thanks for everyone's thoughts. Out of confusion comes clarity.

mattmia2

the "2 pump control" is a 2 zone zone panel? it will make it all neater although I don't think you need it it be warm start so a plain aquasatat relay or even just an aquastat would do.

at least it isn't the aquastat relay somehow filled with rat crap.

EBEBRATT-Ed

I hate cats. I am so allergic to them if I go in a house with cats I can only stay an hour at the most. When the hour is up I can't breathe so I am out of there.

My Nephews girlfriend has 8 cats

Both my girlfriend's daughters have 2 cats each.

So I am outnumbered. I have had allergy shots or drops my whole life, well at least 50 years.

Dogs,not as bad.

Alan (California Radiant) Forbes

I got so focused on the wiring, that I missed the capped tankless coil and the reason why there was a triple aquastat. They should have changed out the control when they capped the HX and saved a lot of fuel.

I installed the 2-pump control and a simple L6006 aquastat this morning and all is good.

EBEBRATT-Ed

@Alan (California Radiant) Forbes

I got called in to start up an oil boiler once where the plumber installed a boiler for heat but it had an unused tankless coil in it so it was hot all the time.

Instead of replacing an expensive aqustat I installed a relay in front of the aquastat breaking the 120 to the aquastat with a relay pulled in from the thermostat and jumping T & T in the aqustat.