Controls Upgrade (1960's AmStan GPM boiler)

Yellowlab

Looking to upgrade controls on subject unit:

-Single zone gas fired boiler supplying cast iron radiators (no domestic HW);

Goal: replace existing transformer and basic aquastat with a reliable unit that will allow proper thermostatic (2-wire) and circulator control.

Thanks in advance for your time to search memory banks ;)

Steamhead

Post a few pics of what's there now.

EBEBRATT-Ed

What is wrong with the way it is now?

mattmia2

What is unreliable about it now? If it is a pre total shut off system there could be some upgrades that are possible, if it is already a total shut off system it should be about what a modern system would be.

Yellowlab

mattmia2 - I am sure there is good information in your post, however I am not clear with terminology: Total shut of vs Pre-total shut off?

Looking forward to better understanding…

mattmia2

total shut off: the pilot is controlled by a combination gas valve or a separate thermocouple controlled valve so if the pilot goes out the pilot gas is shut off.

pre total shut off or "wild pilot": The pilot gas is only controlled by a manual valve, if the pilot goes out the pilot gas stays on but there is some sort of safety to keep the main valve from opening. Since the amount of pilot gas is small and methane is lighter than air the pilot gas just dissipates if the pilot goes out.

Yellowlab

great insight…thanks.

I lifted this pic from the web. Gas valve, transformer, relay all the same with the exception of the aquastat. The aquastat was changed out with a similar type only with 3 terminals…R W B (common, circulator and burner). I am not savy enough to troubleshoot but can't help to think that an upgrade to a self contained unit might geve a fresh start.

mattmia2

That's a modern system with a combination valve, the main valve, regulator and pilot control and safety are all bult in to that one valve.

Yellowlab

Incredibly good of you to share your knowledge mattmia2.

With the gas feed defined; do you think the unit would benefit from more modern controls.

The controls interface (fan center to aquastat to thermostat) were modified from original. Terminal definition is not clear and do not necessarily follow convention, even though Honeywell components. No "clear" identifiers for thermostat (T) or circulator (C). I am not good enough to troubleshoot, but however can grasp concepts and wire to defined terminals. This would give me a fresh start so to speak ?

mattmia2

Because they use a fan center to isolate the boiler controls from the thermostat, g is the control wire to the relay because g is the fan terminal on a furnace. That is pretty common with boilers. If the fan center was original there is usually a schematic inside of one of the covers showing where the thermostat should connect. C is usually common, the side of the transformer connected to the unswitched side of the devices being controlled.

hot_rod

an outdoor reset control might be what you are thinking? It changes/ regulates the boiler supply temperature based on out door temperature it can save fuel dollars and increase comfort.

Yellowlab

TY hot_rod. Funny you reference outdoor temp control. Before any awareness of such, I thought these systems should have some outside temp interface; little did I know that such existed. My situation is such that my home was build in the 40's, very little insulation and in a time when coal was common. I am certain that the piping and associated hardware is not properly matched, sized, etc. Trying to make the best of what I have. My guess that outside interface is likely not an option with such. Trying to nail the basics by making sure that the existing control is at least at baseline. Thanks again!

hot_rod

This NORA video does a nice job of explaining boiler control and ODR add-on

https://www.google.com/search?q=outdoor+reset+control+foroil+boiler&oq=outdoor+reset+control+foroil++boiler&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRirAtIBCTE3MTE2ajBqNKgCALACAQ&sourceid=chrome&ie=UTF-8#fpstate=ive&vld=cid:f06797e0,vid:lmZD5gBG1WI,st:0

mattmia2

if the system is cast iron radiators it very likely will do well with outdoor rest, however that boiler must heat to a minimum temp to keep from condensing so it isn't as well suited to outdoor reset.

hot_rod

A 4 way with actuator, properly installed and configured will protect the boiler from extended cold return..That is the beauty of a 4 way with actuator. The valve has two mixing points so it can do both tasks.

If the system was designed for, or needs to run 180 on design days, you could get 30 degree of temperature reduction with the ODR. That is well worth chasing for comfort and fuel efficiency

Yellowlab

mattmia2, steamhead, hot_rod, and EBEBRATT.

Thank you all for your generous sharing of knowledge. I treat this as a special gift and remain very grateful.

I was able to restore the boiler control to baseline function by removing the three terminal aquastat and replace with a simple high limit aquastat. I was able to gain enough knowledge from your posts to wire all components: thermostat, aqua, pump and burner. As we all acknowledge…the unit is quite old. For now I need to be satisfied that it remains functional !

Thanks to all !!!