hydronic loop issues off a steam system

Joe C._3

Thanks for that Dan, I read it earlier; but now reading it closer a second time I have realized some things:

1. Looks like whoever set up this loop branched it off of the lower sight glass tap => is this a major problem? The cutoff valve is right next to the circulator, not leaving any room to bring in a bypass line.

2. Am I right to assume all of the noise I am hearing in the line is air caused by water vaporizing in the line?

3. I am still pretty sure the Flow control valve needs replacing, and is clogged up with rusty sediment from the boiler. When I bleed the line, the water pressure coming out of the relief valve is much lower than it used to be.

Again, any advice or info greatly appreciated, thank you

Joe C._3

hydronic loop issues off a steam system

Hi There, I am fairly new to this site but have got some great info here that helped me get my steam radiators all balanced.

I have a closed loop steam system, with a hot water heat loop as well. The hot water loop heats our master bedroom, bathroom and pantry. Two issues:

1. it has been making noise lately when the furnace is cranking, otherwise the circulator and loop are fairly quiet. I think there might be sediment build the flow control valve (it's 20 years old) the loop takes a good while to heat up. It is on the return side just befor the furnace - should there be one on the outgoing side? I plan on replacing this valve this weekend. I replaced the circulator (007) a few years ago.

2. The (hot water) thermostat isn't wired in to the furnace properly, when the hot water loop calls for heat, the furnace will keep cranking and make the rest of the house too hot through the steam rads. Is there a way to wire this smartly?

Thanks for any and all help. The search engine is a bit tricky on this site, I've tried digging around without much luck on this subject.

DanHolohan

Take a look

HERE

Long Beach Ed

Could be...

If this is an older installation, you are really limited in how much you want to beat things up taking them apart.

The noise, especially if it only happens when the boiler is firing is probably from steam in the line. The water is too hot and it flashes to steam when the pump reduces its pressure. This can also eat up pumps.

You can try putting the pump on the feed side, which would pump water into the loop rather than suck it out. That would create less of a pressure drop. You can still have a problem with "cavitating" inside the pump, because pressure is reduced in parts of the impeller.

The real solution is to install a bypass pipe with a valve that can add cooler water to the loop.

The loop's connection at the sight glass can be problematic. Fist of all, it will undoubtedly distort the indication of the sight glass, making it appear that more or less water is in the boiler when it is running. In a worse case it can suck the front section's water level too low and reveal the crown sheet causing the boiler to dry fire and crack. This also isn't the most tranquil part of the boiler, so if you are sucking water at this point you will be getting steam bubbles sucked right into the pipe.

Beat that flow control valve with a hammer or take it apart and clean it out. It's possible that there is so much restriction in it that it is increasing the pressure drop in the loop causing this cavitating or flashing hot water to steam.

You may also open up a pipe somewhere and reverse flush the loop with a hose.

Good luck.

Joe C._3

Thanks Ed

Thanks Ed, lots of good advice.

The water in the sight glass does bounce around a bit when it's firing, but not terribly so. I keep a close eye on it every week, and add water if necessary.

I am thinking of maybe relocating the circulator a little higher (it's already a little higher than the sight glass) in order to make way for a bypass.

I didn't realize that flo valve came apart, might try to clean it, but pretty intent on replacing it. I should mention there is a hot water line piped in for adding water from the hot water tank, with a gate valve control.

There is a temperatue control on the feed side, is this gadget smart enough to shut down the boiler only when the hydronic thermostat is calling for heat? Because it seems to shut down the boiler when it's trying to make steam if I have it set too low.

Thanks again,
Joe

Long Beach Ed

Wiring

Joe, most steam boilers have no high-limit control. They only have a pressure control and a low water cut-off. The pressure control shuts down the steam system after it fills the system with steam. The low water control shuts it if the water gets dangerously low.

When you add a hydronic loop, you need a way to get the water hot if that loop calls for heat, but the thermostat isn't calling for steam heating.

There are many ways of wiring this.

In the old days, installers just used a "low limit," that would keep the boiler hot all the time, just in case the loop's thermostat called for heat and turned on the circulator.

This arrangement is also needed when the boiler has a domestic hot water coil in it.

Without the coil it is a bit wasteful, because on mild days the boiler is kept hot.

Another way we've seen them arranged was with a "high limit," wired so that the loop's thermostat would turn on the circulator and fire the boiler. But the high limit aquastat would let the boiler fire only until the boiler reached a certain temperature (the high limit setting) -- whatever was needed for the loop. If the loop wasn't calling for heat the boiler could cool down to room temperature.

Of course there are other ways of wiring to lock the water zone when the boiler's steaming or lock out the steam while the water zone is heating.

I've showed you the two most common ways of wiring this thing. How yours is actually set up is anyone's guess. You've got to figure it out, or send a wiring diagram.

Also, be careful about raising the height of the pump. Pumps don't "suck," they circulate. If you expect the pump to suck water up above the boiler's water line it isn't going to happen. It will push water up. Depends on if that high tapping at the sight glass is the inlet or outlet of your loop.