Hydronic pump always running—is this working properly?

bobthebuilderbob · December 11

Hi All,

I recently purchased a townhome in Seattle and I’m puzzled about if/how hydronic heating system is working properly. There is a tankless water heater that heats the water to 120F. The house is warm and the pump is constantly running despite all thermostats being set to zero. There are wall units with switches indicating “I 0 II” but I’m not sure if these switches do anything. The wall units are warm when the heat pump is running. The only way I’ve found to turn the heat off is with the circuit breaker that kills the pump. Is this how this should work? The house gets warm and we either need to open a window or go down and switch off the breaker. It begs the question: what do these thermostats do? And if this is how this system should work, is there any an affordable way to improve it? Any help or advice would be much appreciated!

bjohnhy · December 11

Where does the flexible metal conduit come from that feeds the Grundfos circulator? Can you track that down? Maybe through that wooden hatch?

The I O II switches, I believe those are to control that fan in that particular wall unit (I presume it's a small hydronic coil with built in fan, but cannot tell from the zoomed in photo). Low, Off, and High

Can you ask previous owner?

Maybe thermostat is stuck closed. Or that King thermostat controls something else other than your hydronic system.

bjohnhy · December 11

hot_rod · December 11

That looks like a combined DHW/ heating system? Tankless heater and a bronze pump on them radiant are indicators also.

That King stat looks a bit like a line voltage 120V stat the could switch the pump.

I agree, with @bjohnhy trace the wire, call the previous owner or Greenwood, the company on the sticker.

GroundUp · December 11

Most likely a constant circ system with the thermostat only controlling the fans in each unit. Pretty common but not always ideal

HVACNUT · December 11

Can you pull back the insulation on the vertical pipes to the left of the boiler/water heater? Are they tee'd in. I can't figure it out. It doesn't look like a combi.

EdTheHeaterMan · December 12

Just so you know, someone did you no favor using a water heater to heat your home. We find a lot of this problematic design with many variations here on heatinghelp.com. A water heater is designed to heat potable water in what is known as an open system. An open system takes water from the source like the water meter at your house and heats that water to use for things like showers and cooking and washing, the water then goes down the drain. The end use of the hot water is OPEN.

Most standard heating systems are what is known as a CLOSED system. That is where you fill the boiler and the supply and return water pipes to the radiators with water and that same water is heated over and over again as it leaves the boiler by means of a pump. That hot water moves thru the pipes to the radiators where the hot water can warm the room. Then the now cooler water returns to the boiler thru a separate pipe to to be reheated. This closed circulating system normally uses a different water heating device called a boiler (not a water heater). The water temperatures in a boiler can get much hotter that a water heater is designed to make.

Boilers are usually more expensive compared to water heaters and that is why some penny pinchers try to reinvent the heating industry by using the wrong, lower cost appliance for space heating. This ends up with homeowners like you coming hear for help to get comfortable heat in your home. You problem is a little different; too much heat. That is an easy fix usually. Just add a thermostat to turn off the thing that is making too much heat. That may be the purpose of that King thermostat. Perhaps it is broken or disconnected for some reason. You will need to take it off the wall to see it the wires are connected to the thermostat or not.

Hydronic pump always running—is this working properly?

Comments

Categories