Blowby coming on after working on system, cant stop pressure from rising

cwilliams2000

Hi I just had an indirect plumbed in by to my system and the pressure kept risijng to about 30. He mentioned my fill valve might be bad so I ended up directly replacing the fill and backflow preventer how it was originally installed. The pressure is still doing the same thing and now the blowby keeps opening. What I dont understand is that the pressure valve on the boiler is obviously right since at about 30 the valve starts dripping, but I dont understand why the new valve is defiitely hissing and letting water in even when thepressure is over the 12-15psi it says its set too.



I dont have a coil and definitely have some air in the pipes that si mostly worked out, but I am not sure what else to try, I thought the expansion tank could be it since it definitely gets worse after a night or so.

jim s_2

Indirect?

Possible that the indirect is defective?

Timco

indirect

Really sounds like the indirect has a small leak and the city pressure is over pressurizing the system. You would need to isolate the indirect or take it off the system and check for leaks in the coil. You can also fill to 12-15 and close the fill valve and see if it stops filling. If it was x-tank, you would fill to 12 cold, then it would shoot up to  30 as soon as the system was at operating temp and it would be worse as you get the air out.



Tim

cwilliams2000

Even odder

The other thing that changed was that my main circulator was changed to a 3 speed TACO unit.



The reason this matters is that I noticed that I can set the pressure to say 15psi, and as soon as the main circ runs the boiler fill valve starts hissing. It is mounted on a T about 5 inches away from the main lines, and I think what is happening is that the new pump is set to the highest speed and it may be cause a pressure drop when it first goes on or off, so that it makes the valve think it needs to add a little water, then it keeps doing this every time it turns on, so add it up and it keeps going over 30.



Not sure if the valve is in the right place, but my installer told me to try switching the pump to the middle setting to see if it helps, I will do this when I am home



Any other ides or if you think this makes sense would be great

cwilliams2000

More interesting

I spoke with TACO this morning to discuss what is happening. He thinks there is a chance that since the fill valve is within 6 inches of the return line on a T that perhaps the Taco is creating enough differential presure across the line to make the valve think the pressure has dropped. I am probably going to have the line connecting to the T extended about 5 inches to see if that helps since this seems like a pretty unusual problem. Any thoughts?

cwilliams2000

Solution, I think

It looks like after a discussion with Watts that the T for my fill valve is before the circulator on the return so there is some suction being created there, and they felt quite strongly that more than likely this lower pressure is causing the valve to open slightly whenever the circulator is running. Their solution is to put this valve after the circulatory, or to tape it into the air separator area.



This does make sense to me since the valve is opening very slightly every time the cir runs, so hopefully I will be able to simply put a T between the expansion tank and the separator and plumb the valves in there.

Timco

Pictures!

It would really help to see near-boiler piping pictures. All angles, showing the pumps location and the fill location. Then folks will weigh in. Remember, pump away from the expansion tank, and no bull-head tees!



Tim

Mark Eatherton

Taking bets....

I am betting that the pump is on the return, pumping towards the boiler, and the expansion tank...and the make up is on the inlet side of the new high head pump.



ME

Charlie from wmass

Mark

you could not have a better bet

cwilliams2000

Pics

Please let me know what you think or what might be wrong



thanks

bill_105

Explain

Are you the whole thing isn't hooked up backwards. Now, I know those pictures are sometimes hard to decipher. And I know you can rotate the cartridge on the pump. But it appears the water is being sucked through the lower tapping. That and a few other things.

cwilliams2000

I dont think so

I dont think its backwards, I checked the flow on the pumps and the flow is going down from the zones above into the return. The boiler valve is positioned just before the circ pumps, so i would think the suction there would be quite strong.

Mark Eatherton

Where is the expansion tank connected?

ME