View Full Version : How to CHange Water Temp on an Indirect Water Heater

01-31-2010, 05:20 PM
I have a Munchkin Boiler with a Vision controller. It has an Indirect Bradford White Water heater. The hot water temp coming from the hot water heater is 127 degrees. I would like to lower it to around 120 degress. I'm comfortable working with the controller. How do I lower the hot water temp?

02-01-2010, 08:24 AM
Somewhere on the side of the thing tyically 1/3-1/2 the distance up from the floor is an adjustable aquastat that is wired to your zone controller. You may have to pull the cover to adjust it, but most have a cutout in the housing to be able to read the setting. Wiith oil or gas cast iron boilers it's common to set them to 130-140F to avoid condensation in the boiler, but with the condensing Munchkin setting it lower results in higher combustion efficiency.

02-01-2010, 08:32 AM
On my indirect, the setting is all done on the controller, there is no adjustable aquastat on the indirect, only a sensor that feeds into the boiler telling it what the temperature currently is. So, you'd have to read the Vision controller card's instructions to vary it, if that is even possible (I'd expect it is). If you have an adjustable aquastat in the indirect, it should be straightforward, otherwise, it may not be.

02-01-2010, 11:46 AM
In a quick scan of manuals online, most Vision controllers have the option of using either the indirect's aquatstat or a seperate sensor, but it shouldn't be too tough to re-configure it if it's otherwise not programmable. All Bradford White indirects are fitted with aquastats. The default DHW temps on the Vision 2 (which was purpose-designed to work with Munchkin boilers, and thus the most likely version in use here ) if utilizing it's thermistor sensor is 119F, with 8 F of hysteresis.

The instructions fro programming it to a different temp are on p.13:


See notes 8 & 9 p. 24 if you prefer aquastat control instead.

02-01-2010, 01:45 PM
Thanks for trhe info!! .. I checked the settings the de DHW setpoint is set at 106 (Default is suppose to be 119), The dh DHW Differential is set at 10 (Default is 8). I'm getting 127 degree water with a meter at the hot water heater (Attaching to the pipe). Should I lower the 106 setting? I changed the differential setting to 8.

02-01-2010, 02:51 PM
It sounds like either thermistor sensor or the control board is way out of calibration if you're getting 127F water with a 106F setpoint. You can lower the programmed setpoint to where the tanks output is at the temp you like, but check for bad connections on the sensor wiring first. If it's a simple mis-calibration issue it may still control it fine. If it doesn't do the trick you may need to do a deeper diagnostic.

02-01-2010, 04:40 PM
Next tune up I'll have them lower the temp . The tech said 130 was a good temp. Next time I will have them lower it to what I want. I remember when they 1st installed the unit the HW was coming out at 140. After they adjusted would take forever for HW. Last time is at 127 and the water heats up faster. I've had the unit for 10 months and it is great. My gas usage has dropped dramtically. I just hope it lasts. See alot of bad stories about Munchkins but from what I hear most are due to improper installations.

02-01-2010, 04:53 PM
Make sure that the sensor is fully inserted into the well of the indirect. On mine, it is just held in place with a spring clip and, if you pull on the wire, it is fairly easy to move it in and out. Also, the clip may not be around the sensor properly, holding it back from bottoming in the well.

02-02-2010, 04:19 AM
I'll check on the sensor. I lowered the setting from 106 to 101 yesterday. When we took our showers this AM you could see that the water was at a lower temp. Right where I want it. When I hit the S3 key I also get a 30 for come reson with no corresponding letter(s) which was strange. Thank you all very much. I posted this on another forum and they refused to help saying no how to repairs