Circulator pump limit setting

Redcdr

I have a very small single story home with a very old gas boiler in the basement with 5 cast iron radiators on a single zone. 

Earlier three radiators were only getting luke warm. I discovered that the neutral on the circulator pump was loose so the pump wasn’t running.  I got it fixed and now everything is getting hot. 

My question is regarding when the pump should run. The pump is on the return side of the loop feeding right into the boiler. It is switched with a very old strap on style AQUASTAT (White and Rodgers #11B09). It’s strapped to a supply pipe. When the pipe reaches a certain temperature the switch closes and sends power to the pump (Taco 1/4HP pump). What temperature should the Aquastat be set at?  Right now it’s at 130. It kicks on after the boiler runs for a few minutes and continues to run for a few minutes after the call for heat is satisfied. Any help or advice is appreciated. 

Jamie Hall

Sounds about right to me...

EdTheHeaterMan

Not the most efficient design, Sounds like something I might do to a very old boiler if I didn't have a circulator relay with me when I installed the circulator, a long time ago.

Are you interested in comfort, or efficiency? Perhaps both? How much time do you want to spend on this? And is this the best time of year to do a redesign?

Redcdr

EdTheHeaterMan said:

Not the most efficient design, Sounds like something I might do to a very old boiler if I didn't have a circulator relay with me when I installed the circulator, a long time ago. Are you interested in comfort, or efficiency? Perhaps both? How much time do you want to spend on this? And is this the best time of year to do a redesign?

Right now, comfort and safety are my main concerns. I have no desire to do any work on the system right now. I just wanted to make sure it’s a relatively rational setting. Since hooking up the pump I’ve got a few additional concerns which I’ll include in a new post. Thanks for your help. 

hot_rod

It seems like that aquastat was added for boiler return temperature protection. Are there zone valves on the system? Typically the pump would fire whenever there was a heat call. Using whatever temperature is in the boiler. If the boiler is inside, never dropping below 65f, it will deliver heat within minutes of firing.

Redcdr

hot_rod said:

It seems like that aquastat was added for boiler return temperature protection. Are there zone valves on the system? Typically the pump would fire whenever there was a heat call. Using whatever temperature is in the boiler. If the boiler is inside, never dropping below 65f, it will deliver heat within minutes of firing.

No zone valves.  This is a very old system. I believe the boiler is from the early 50s. No isolation valves, old steel expansion tank in the ceiling. The boiler is inside, but it’s in an unheated basement so it gets chilly down there, definitely below 65. 

hot_rod

I would leave it 130F if you want to keep that control logic, unusual but bit must work.

That being said, I've run cast radiators as low as 100- 110 F and they still emit some heat.

If the iron is warmer then air or skin temperature you feel the heat