zoned hot water system problem

[RayV]

My BIL has a problem with his system, here's the current setup: Boiler in basement

Split level house with all zone loops higher than basement

Three zones - all thermostats working properly

Circulator pump on the cold/return side of boiler mounted just above boiler inlet comes on with furnace (zone independent)

Flo-control valve on the hot/supply side of boiler mounted near ceiling

Air separater right after main flo-control valve with bladder expansion tank

Three additional zone circulator pumps connected to the thermostat relays

Three zone flo-control valves, one right after each zone pump

The problem is that whenever any zone calls for heat there is flow thru all three zones. I verified that each of the zone pumps are working independently and correctly. He told me that the system has always operated this way and he just sets the thermostat on the upper level to

50 so it never kicks on because he always gets heat up there. There are no zone valves on any of the zones, only the flo-control valves. The zone pumps, flo-control valves and thermostats appear to be add-ons to the original system.

I would like to hear ideas on possible repairs or system changes that would get the system to only heat the zone(s) that is calling for heat.

[dd]

Shut off the circulator mounted at the boiler return bet the problem will go away

[Steve Scott]

Flow checks are open or failed if the pumps are operating properly.

Is the supply and return manifold piped completely separate or are they connected at some point other than through the loops?

What is used for heat emitters? Baseboard?

[RayV]

I cranked the flo-controls to the full open position and ran all of the pumps to flush out any sediment that might be on the seats then closed them. I did just change one of the zone pumps for him and the flo-control for that zone held the water in the pipes while I changed the pump.

The supply pipes are teed right after the air separator and the returns don't come back together until right before they go to the inlet circulator pump.

Yes, standard baseboard around the perimeter of each level.

[RayV]

Doesn't having the pump(s) only on the outlet side of the boiler increase the chance of a boiler overtemp?

I suppose I could just disconnect it and run each zone for 20 minutes and see what happens.

[Steve Scott]

The purpose of the flow check isn't to hold the water when you pull the valve, it's to keep other circs from moving water through a loop that isn't calling.

That said, if the system worked pr>

You most likely don't need a return pump then.

[Steve Scott]

Generally speaking, a typical residential system that's properly piped and is in a standard series loop configuration w/o primary/secondary piping will only have circs on the supply side after the expansion tank.

What makes you th>

[RayV]

This is the third house I've seen in this area (Eastern PA and NJ) with a pump on the return side of the boiler. One was a ranch with no zoning, the other had one pump with three zones with zone valves after the boiler (worked fine), and this crazy system with four pumps!

Of course most of the houses in this area have the shingles overhanging the sheathing by 1.5" so they hang in the gutter but that isn't right.

[RayV]

The system hasn't worked properly in the 8 years since he has been there. It may have never worked properly.

Could have been the previous owner had it 'zoned' because it was colder in some parts and was sold all these extra circulator pumps and relays when all he needed were a few zone valves.

[Steve Scott]

Manufacturers have for years installed circs on the return side which is wrong. They should be on the supply side after the expansion tank.

Pumps >

[DIMwit]

Many ways to skin a cat. The older Weil McClain's came with the circulator flange mounted on a chrome pipe from the boilers return port, bottom left corner. This one shows the circulator(s) or zone valves in the outlet port. My own boiler (P-468) is using the return port. I use one motor and 5! zone valves. One is the Super store tank circuit.Works super.

Bob

[dd]

[AKS]

If I understanding you right you have 4 pumps running in parallel on return side without zoning valves or check valves on supply side (discharge) but just the flow valves no wonder you customer is having problem PUT CHECK VALVE ON EACH PUMP DISCHARGE you problem will be eliminated Dido say that

[Steve Scott]

Many ways to do it wrong. Proper circ placement isn't arbitrary. There are better places and worse places. Any location will move the water around. Some location will cause problems like excessive air into the system or premature expansion tank failure.

The first system shown >Many ways to skin a cat. The older Weil McClain's came with the circulator

[Steve Scott]

Where are the fill valves located on the systems you see?

You're right about less air problems with the circ on the supply side. Do you know why that is?

Where should the fill valve be? Why?

[RayV]

At the same level as the boiler inlet or lower.

Higher pressure from the hotter water raising the boiling point?

Close to the boiler inlet.

Because it is easier to run the piping?

[RayV]

One pump on the return side at boiler inlet

Three pumps parallel on the outlet side after air separator/expansion tank

Three flo-control valves after each pump on the outlet side

No zone valves but the flo-control valves are also check valves

How would a 'check valve' on each pump discharge solve what seems to be an unneeded pump on the inlet side that is pushing hard enough to lift the flo-control valves in the two zones not calling?

[Steve Scott]

On the boiler return side? Same side as a lot of circs you're seeing? Is the fill valve before the circ? Replace many expansion tanks?

The expansion tank is the point of no pressure change in the system. The circ causes pressure differential. So, the expansion tank is the point of no pressure change and the suction side of the circ is close to the tank the circ adds to the static system pressure. That causes the pressure to be as high as possible at the highest point in the system.

If the circ is on the return side and the expansion tank is on the supply side the highest points of the loops can be under negative pressure causing air to migrate into the water...even from water tight solder joints.

The fill valve should be near the expansion tank because it's the point of no pressure change.

What we all commonly see is the expansion tank of the supply side, the circ on the return side (cause the boiler manufacturer stuck it there) and the fill on the suction side of the circ. This is a guaranteed revenue stream as you will be replacing the expansion tanks regularly and maybe the relief and fill valves trying to figure out what the heck is going on.

The problem is this: Fill valve and tank factory set at 12psi. Who changes them? Virtually no one.

So the circ is off and the system is full there's 12psi at the fill and at the expansion tank.

Let's assume the circ creates 6psi differential. The expansion tank is the point of no pressure change so that stays at 12psi. There's maybe 1psi loss through the boiler so the outlet side of the circ is at 13psi (12psi at the tank + 1psi through the boiler). The circ creates 6 psi differential so the suction side is 7psi. Which is what the fill valve is seeing cause it's on the suction side of the circ.

Wait a minute. The fill valve is set at 12psi and now it's seeing

7psi? What's it gonna do?

Add water?

Yep.

Where's the water go?

The only place it can go is the expansion tank. The rest of the system is already full.

What happens when the expansion tank has too much water in it?

The diaphragm ruptures.

And that's the short version of why in a correctly piped system the expansion tank goes in the supply near the boiler with the feed near the expansion tank and the circ right after the tank. With very few exceptions.

If you're in the trade and want lots of good info on this buy this book.

Best $25 you'll spend.

[RayV]

Thanks for the explanation. Easy to understand and makes perfect sense the way you explained it. A welcome difference from the way most posts are written.

I'm going to disconnect the pump on the return side of his system and run the zones to see if that cures the problem of non-calling zones always getting hot.

Thanks again.

[AKS]

I see what are you saying check and examain valves see that valve is doing what it it should be doing Dido