Hello,

I have an indirect water heater, a Vaughn Boiler Mate (Top Performer Plus Series), which is hooked up to an oil boiler.

The aquastat on the Boiler Mate is a Honeywell L4080B, which is turned all the way up to the 150 degree stop set point.

Though the water in the boiler comes on at 185 degrees and off at 207 degrees, not much of the heat is transferred to the Boiler Mate, as the Boiler Mate is never higher than 130 degrees and I'd like it higher. The Honeywell aquastat must be cutting out at 130 degrees or so, rather than the 150 it is set on.

Is there a way to override the stop on the aquastat from the 150 degree set point to set it higher at 200 or less?

Looking forward to someone being able to help me.

 

The Boiler Mate unit could be clogged with sediment, either facing the boiler interior preventing heat transfer from the boiler water, or on the inside preventing the domestic water from picking up enough heat.

Does the Boiler Mate have a tempering valve or anti-scald valve just outside, between the cold inlet and the hot outlet, possibly commingling too much cold water with the hot?

 

Hello AllanJ,

Thank you for your response.

First, I can find no tempering valve anywhere on this system.

Here's the layout.

Domestic well water enters the heat pump heater (to the left in foto 1) and warms it before it feeds into the Boiler Mate. It then enters the Boiler Mate through the bottom of the tank.

This tank seems to be an older version with only 3 pipes coming out its top (foto 2). The left pipe with the red valve feeds the house with domestic water. The 2 center pipes circulate water from the boiler which runs on oil. The pipe at the right, although it looks like it goes into the top of the tank, actually is the pipe that feeds domestic water into the Mate. You can see its full length and location in foto 1.

Foto 3 shows the Honeywell L4080B 1360 aquastat and connection where warmed domestic water enters the Mate.

I emptied and flushed the Mate, which the builder installed in 2000, when I installed the heat pump water heater, in the summer of 2010. At that time, the water emptied from the Mate ran clean. The system has a large filter which precedes the heat pump. Though I believe the tanks to be pretty clean inside, I will flush them this weekend: January 28 or 29.

I think the aquastat I have maxes out at 150 degrees. I've thought of replacing it with an aquastat that can be set higher than 150 degrees. The boiler turns off at 200, so I'd need a setting lower than 200 degrees on the aquastat to keep the boiler from running non-stop. Wonder if that would work?

Any other suggestions are appreciated.

 

How are the pipes connected to the boiler? Does this have a dedicated circulator pump? Any strainers in the boiler piping?

 

Hello Furd,

3/4 inch copper all the way with a dedicated circulator pump which runs fine. No strainers anywhere.

The system ran fine until about mid-November 2010, so the setup with the heat pump water heater was fine. Even if it fed cold domestic water into the Mate, it should work, no?

The aquastat is cranked all the way to its highest setting. Should I try to defeat the stop?

Thank you.

 

I think that stop is adjustable, if you could post an in-focus close up I might be able to tell you how.

Try jumpering the connections on the L4080B and see if the circulator runs. If it does, let it run for a while and see if the temperature in the tank rises. If it does, then the problem is likely in the L4080 calibration.

 

Hi Furd,

I jumpered the connections and after wahile, the domestic water wen fro 147 to 154 degrees.

The included photos are as good as I can make. The stamped writing on the dial is very crude.

























So, you think this aquastat can be set to turn off at approximately 165 degrees? Or do I replace this aquastat with one that can be set at 165 or higher off temperature, and if so, what model?

 

I suspect that the aquastat is badly out of calibration for some reason. You could bend the stop and adjust higher in small increments, testing the water temperature periodically until achieving the desired temperature or you could replace the aquastat. Any model that "opens on rise" will work.

 

I'll bend the stop and see if I can get a higher temp out of it.

Many thanks for your help.