I left the heat off until the days stopped being sunny. During that time the house temperature didn’t go below 64 degrees. Even when it got down to 20 degrees outside at night. We woke up to a steady 64 degrees every day even when the outside temp was warmer than 20. I supposed that means the house loses heat at a constant rate no matter what the outside temperature is? As long as it is below the inside temperature anyway. During the sunny days the inside easily heated up to 70 or 72 within an hour or so of the sun shining into the house. And it did not get warmer than that.
But this weekend the sun stopped shining and we got some snow. So I turned on the heat with the new pump installed. I had confirmed that it worked with most of the valves–at least two of the valves are not turning on the boiler so there seems to be a problem with their wiring. But enough zones are working so that I have three turned on and the nighttime temperature in the house is staying at the daytime temperature of about 70. I have the thermostats set for 65.
The pump is not reading 6 GPM though. With only one zone open it reads between 1 and 2 GPM and with all zones open between 3 and 4 GPM. With those numbers and my calculations we should not be feeling warm when the temperature outside gets cold. Obviously the programs that I used to figure the Manual J stuff were a bit on the generous side for BTU requirements. But we can’t complain! We seem to have good system in place, despite the issues with the valves. I rebuilt them this summer and maybe some of the old wires should have been replaced too.
After I installed the pump, I tried all the pump settings with various numbers of valves open. I could get it to pump a little faster on a high setting both at the fixed high speed and at the high variable speed but it uses a lot more watts to do it, while the Auto uses the least watts for the same speeds, it just doesn’t pump at the highest possible GPM. Not sure how it determines the flow rate, but it must be the head from the piping is high enough to result in the lower variable speeds.
Here are the control settings. Number 3 is the variable setting within a section of the performance curve. Auto is variable within the entire performance curve.
Grundfos Alpha Control Display
This is the pump in action with one valve calling for heat. It is on Auto Control and shows the watt and flow measurements. This is a great feature.
Grundfos Alpha 15-55 at 14 Watts
You might notice that the pump is installed with the existing flanges. I worried about whether it would fit. Grundfos does not offer stainless flanges for their pumps. Since I was not sure I could use the existing Taco flanges, I ordered an expensive set of Grundfos brass flanges from Amazon. But the Taco stainless flanges worked great. So the return of the brass flanges will cost me $8. However, I thought the insurance that I could put in the pump before it got very cold and cloudy was worth it.
At 14 watts of power the pump flow is 2 GPM. That seems slow but it also seems to be heating the house at that flow rate.
Grundfos Alpha 15-55 at 2 GPM
If the 6 GPM calculated flow rate was a too high estimate, perhaps the Taco 011 pump was too large for the system? I will just have to see how the Grundfos performs and lasts.