Added VRV to solar, now hear some water hammer

[jjslinger]

Originally my solar heating system did not have a VRV, so I added one, it's at the low end of the panels near where the cold water feeds in. I'm now hearing a little bit of water hammer when the solar valve comes on. Is this an issue? It's not too bad, just a few mild thumps.

Does it have something to do with this check valve where the solar returns:


I've always thought that valve was installed wrong, it's vertical when it should be horizontal, so the flapper doesn't close the way it should.

Thanks,
Don

 

[mas985]

The check valve is installed correctly. Do you see it closing at the same time you hear the thumps? Do the thumps stop when the valve is fully on or do they stop only when the panels are fully primed.

 

[jjslinger]

The check valve is installed correctly. Do you see it closing at the same time you hear the thumps? Do the thumps stop when the valve is fully on or do they stop only when the panels are fully primed.

The flapper in the check valve flaps when I hear the thumps. I'm not sure exactly when the thumps stop, I will check into that. I THINK the thumps stop when the flap stops flapping, but I need to investigate.

Thanks,
Don

 

[mas985]

There are a lot of dynamics going on when priming solar panels so it isn't exactly a quiet event nor should you expect it to be. When you didn't have the VRV, the panels were always full of water so there was no priming. As long as it is isn't rattling the pipes too hard, you should be ok.

 

[jjslinger]

There are a lot of dynamics going on when priming solar panels so it isn't exactly a quiet event nor should you expect it to be. When you didn't have the VRV, the panels were always full of water so there was no priming. As long as it is isn't rattling the pipes too hard, you should be ok.

Thanks. I just went out there and activated the system manually. It worked fine, no thumping. I guess I have to be out there when it comes on by itself. The only thing I find a little strange is that after the solar valve shuts off, I would expect the flapper in that vertical check valve to close, but it doesn't, it just hangs there.

Don

 

[mas985]

The check valve is there so that the solar panels do not fill up when the solar valve is off. It is suppose to be open when the solar is on or when the pump shuts off so the panels can drain.

 

[jjslinger]

The check valve is there so that the solar panels do not fill up when the solar valve is off. It is suppose to be open when the solar is on or when the pump shuts off so the panels can drain.

How about when the solar shuts off but the pump is still on? My pumps runs faster with the solar on, but it still runs at a lower RPM when the solar turns off. That's when I see the flapper open.

Anyway, thanks for your answers. It sounds like everything is okay, I just get a little occasional mild hammer. Maybe it happens when the panels are partially drained or draining, and the solar "decides" to come on again because it's gotten warmer outside again.

Don

 

[mas985]

The controller may be increasing the pump speed when solar is turned on.

Sometimes if you turn off the pump and the panels start to drain and then turn on the pump again, the return side check valve will slam shut causing a very large bang.

 

[jjslinger]

The controller may be increasing the pump speed when solar is turned on.

Sometimes if you turn off the pump and the panels start to drain and then turn on the pump again, the return side check valve will slam shut causing a very large bang.

My controller does set the RPM higher when the solar comes on.

I think that "bang" you mention may be what I'm hearing. With a couple "echos" perhaps, that make the flapper do a couple flaps. I think this does only happen when the solar goes on and off a couple times in a relatively short timeframe, if the system is deciding to call for heat or not when it's right on the edge.

Thanks again for all the help.

Don