Taco VT2218 Rattling Sound

SeaTurtle

Hey everyone! For context, I am a DIY homeowner, not a professional plumber, and my hydronic heating system has frankly turned into a favorite hobby of mine. I recently repiped most of my house to replace the polybutylene with orange oxygen barrier PEX using expansion fittings (the pipe is PEX-B, but F1960 compliant). I also repiped the main boiler manifold using cast iron, and it includes a nice Spirocombi air and dirt separator to prevent rust. I am learning a lot as I go and having a lot of fun.

I just installed a new Taco VT2218 (Delta-T) into my boiler system. It is the main pump, and all the zones use zone valves. The goal was to ensure that the return temperature is with 20F of the supply temperature as required by my boiler. However, this pump often makes a rattling sound as if there's plastic inside of it hitting against something. I've taken the motor apart and the impeller looks totally fine. The sound can be heard throughout the entire house. I've read in various places that this sound can be a sign of cavitation. I've noticed that the sound fades away as the GPM increases. On some zones, as you'll see in the video, the pump runs at around 58 watts while pushing only ~6GPM. Does this mean that the pump is undersized?

Note I've also had some trouble getting the sensors to correctly read the water temperature, I think because of the iron pipes. I moved the supply sensor onto the brass fill/purge valve since recording the video, with some CPU thermal paste, and that has helped a lot.

Here's a video:

https://imgur.com/a/RDbntlv

And some photos of the system:

Thanks for the help.

hot_rod

Can you get enough flow through that copper tube boiler with just one zone open? You may need a primary secondary piping to assure the boiler gets adequate flow

Looks like a good size boiler, what is the heat load of the building?

bjohnhy

My initial thought is you have air in the pipes that hasn't been purged out. How long has it been doing this?

Try taking out the ifc from the circulator if it's in place. Integral flow check valve. That could be vibrating causing the noise.

" On some zones, as you'll see in the video, the pump runs at around 58 watts while pushing only ~6GPM. Does this mean that the pump is undersized?" Not necessarily undersized. Is 6gpm enough to heat that zone. My experience with this 2218 is it runs full power 58 -65 watts until the delta is satisfied and then it backs off significantly to 7-11 watts until Delta exceeds parameters then it goes back to full power. There is not much for middle ground.