I have an old American Standard A-5 Oil Boiler. No. A504, Series 2BJ2. There are two thermostats on it. I assumed one was for hot water and the other was for heating (Baseboard Heat). One thermostat is set at 120, the other at 160. I've had it serviced many times and one guy upped it to 160 from 150 (The hotter the water, the less it takes to heat a room). What I found out is the water temperature at my faucet is 160. Since I've had this boiler serviced by many 'experts', I assumed what they are doing is correct. Is it possible they are setting the wrong thermostat. Or are they correct and I have to live with very, very hot water at my tap. What would the other thermostat be for. I have searched online for manuals for this boiler and have not found anything. The cold season is approaching and any help would be appreciated. Thank You.

 

These "thermostats" since they measure water temperature are actually aquastats. So much for the terminology lesson.

The best way to control the temperature of the water at the tap is with a mixing or tempering valve. This is a device, simplified as at variable tee, which mixes some cold in with the hot to give you a reduced temperature at the tap.

http://www.taco-hvac.com/en/products/5000+Series+Mixing+Valve/products.html?current_category=116

 

The thermostat/aquastat that is set at 120 degrees may be a "circulator low-limit control" that prevents the circulator pump from operating until the the boiler water temperature reaches a minimum setting, in this case, 120 degrees.

 

Thanks for the help. The mixing valve looks like just what I need. Thanks again.

 

In my neck of the woods, there are 2 aquastats. One for the heat and one for the hot water. It sounds like the service guy confused them. Hot water at 120 and boiler at 180 are the local settings. A mixing valve is a good idea in any event.

Lou
Just a home owner, not an expert

 

I too have a 1950's American Standard Boiler. I also have two aquastats. The one inserted into your domestic hot water coil is the low limit circulator control which should be set at 160 deg. The other aquastat that is probobly located on the opposite side of the boiler is your high limit which should be set at 180 deg. There should always be at least 20 degrees difference. Yours was probably set to the lower temps of 120 and 140 for the summer months when heat was not needed but high enough to produce enough domestic hot water in an attempt to increase efficiency. I have done this myself. Just do not forget to bring the settings back up for winter or it will take forever to bring the heat up in your home. I have recently removed both aquastats and installed one new triple aquastat into the hot water coil. This new aquastat (L8124A) automatically keeps the boiler between 140 deg and 160 deg when there is no call for heat to maintain domestic hot water temp. It then climbs to 180 deg only on a call for heat. Hope this helps.