Installed a Boiler and Have Questions

[Reicherb]

I installed a Weil McLain CGA2 and created 1 challenge and have a couple of other questions.

1. I created a "manifold" of sorts to distribute to the zone valves. If either of the bottom 2 zones are open, the top gets no heat... Why? Do I need to add balancing valves?

2. I didn't think about a low water cutoff. Is there a unit that you would recommend?

3. I want to set the water temp as low as possible but don't want to damage the heat exchanger. The manual says 130 degree return water minimum. Is that an absolute or is it more related to the temperature difference between the output and the return? I've currently got the boiler at 150 degrees. I'm sure that will be too low when winter arrives.

Attached are pictures.

Thanks,

Brad

 

[Sylvan]

GET THAT GALVANIZED OUT OF THE SYSTEM

Why would you have the back flow preventor discharge over electrical

Gas connection YIKES

Call a real heating contractor

 

[Sponsor]

 

[Reicherb]

Thanks for your constructive assistance.

The galvanized is there because it game with the boiler. There was galvanized on the previous 50 year old boiler as well. What issue will it cause?

I've got parts in route to plumb the backflow preventer discharge elsewhere.

The gas is a mess and will be replaced next weekend. It was that way when I bought the house. The boiler took me longer than I expected.

 

[Reicherb]

Everything I read online seems to indicate that galvanized connected to copper is fine because it's a closed system which will become depleted of oxygen.

 

[Dana]

I installed a Weil McLain CGA2 and created 1 challenge and have a couple of other questions.

1. I created a "manifold" of sorts to distribute to the zone valves. If either of the bottom 2 zones are open, the top gets no heat... Why? Do I need to add balancing valves?

Maybe, probably. It looks like some pretty fat low-head plumbing (big fat radiators?) , and the 007e can only push so much water. If the zone on the top zone valve has significantly more pumping head than the other zones the other zones could hog the flow enough to limit the flow/output of the high-head zone. You can test that thesis by throttling back the flow on the lower two zones with either of the ball valves at the zone valve.

Alternatively, if the top zone's radiation is 28' vertical feet or more above the boiler and the system pressure is only 12 psi at the boiler it could create this sort of symptom, since it would be prone to collecting air and vapor locking with air. It may still get enough flow with the pump's pressure making up the difference when it's the only zone running, but not if the other zones are taking flow, reducing the pump induced pressure.

The static pressure of water grows by 0.433 psi per foot. The minimum operating pressure on the system needs to be about 3 psi + 0.433 x the vertical distance between the pressure gauge and the top of the system. The additional 3 psi is necessary to cover negative pressures induced on the return side of the highest radiators in the system when the pump is running.

3. I want to set the water temp as low as possible but don't want to damage the heat exchanger. The manual says 130 degree return water minimum. Is that an absolute or is it more related to the temperature difference between the output and the return?

Condensation is all about the entering water temperature at the boiler, which determines the temperature at the coolest part of the heat exhchanger plates. The dew point of natural gas exhaust at sea level at typical air/fuel mixture levels is about 125-127F, so the 130F gives it just a few degrees of safety margin.

If you have high volume cast-iron radiators you may need to add a system bypass branch or other protection to avoid excessive condensation during the shoulder seasons when loads are low, since the rads may not reach 130F before the thermostat is satisfied.

Most cast iron boilers can handle 50F temperature differences in-to out (say, 130F in, 180F out), but I don't recall if it's any different for the CGa series.

I've currently got the boiler at 150 degrees. I'm sure that will be too low when winter arrives.

Why?

How much radiation (and of what type) do you have on this system? (Break it down zone by zone.)

What is the design heat load?

 

[Dana]

From one of your other threads I see we estimated a design load of about 35-37K, and :

Zone 1 has 24' of baseboard

Zone 2 has 52' or baseboard

Zone 3 has 80' of baseboard (is the top valve zone 3? If yes the additional pipe adds more pumping head.)

At an average water temp of 140F (150F out, 130F return) the 152' of baseboard will deliver about 45,600 BTU/hr. If that's a CGa 25 it's DOE output is only 44K, so 150F out is about where you'd max out. If it is a CGa 3 (as indicated in the other thread) it's good for 59K , and you'd be able to hit output temps higher than 150F.

Before the winter arrives it's worth insulating all of that plumbing with 1" or thicker fiberglass pipe insulation.

 

[Reicherb]

The whole system is radiant baseboard headers. Zone 3 is the top floor of the house. the one not getting water when other zones are open.

Can I simply partially close the ball valves on the other zones?

Thanks for your help!

 

[Reicherb]

When is the appropriate time to evaluate the return temperature? When the boiler cycles back on or mid cycle?

 

[Reicherb]

I set back the bottom 2 floors overnight and left the top floor o. It did not keep up. It must be air locked. how do get the air out? I haven't found a bleeder anywhere.

 

[Dana]

The whole system is radiant baseboard headers. Zone 3 is the top floor of the house. the one not getting water when other zones are open.

Can I simply partially close the ball valves on the other zones?

Thanks for your help!

I'm not sure what "...radiant baseboard headers..." means. I was assuming fin-tube baseboard:

Is it cast-iron baseboard?

Or is it something else?

If it's a story house above a basement boiler room you probably need more than 12psi pressure on the system. Measure the vertical distance fairly carefully. If increasing system pressure, be sure to pre-charge the expansion tank to the new pressure.

The return water temp doesn't stabilize until all the stagnant water that had been sitting in the zone plumbing has been purged with hot water from the boiler. At 2 gpm it takes a full minute to replace the water in 100' of 3/4" plumbing, so give it a minute or even two before taking the return water temperature measurement.

 

[Dana]

I set back the bottom 2 floors overnight and left the top floor o. It did not keep up. It must be air locked. how do get the air out? I haven't found a bleeder anywhere.

Turn the system off, turn the ball valves off a the other zone valves, then manually open the zone valve to the top floor. Crack open a drain valve (not all the way), and manually open the fill valve to force flow through the zone. It's not clear if you have a main ball valve on the return to turn off or check valves to, to force the flow in one direction or the other, but the potable water pressure is what you're using to force the flow- it can be either the pumping direction or opposite direction of the pump flow. Keep an eye on the pressure while doing this- the pressure relief valve will open up if it gets to 30psi, but it probably has to stay above 15psi to deliver much flow to the top floor.

Let the water flow through the zone for at least a minute to purge any trapped air, then turn off the drain valve before letting up on the fill valve. From your pictures it looks like the fill valve is near the ceiling, with maybe a boiler drain valve near the floor by the pump(?) and a system drain valve near the floor on the other side of the boiler, which means this probably has to be a two-person job. It may be possible to fill through one drain port while draining through the other to get the flow going, but that isn't obvious from your pictures.

Of course installing a bleeder on the return side of the top floor radiation could make the air purging job a lot easier.

 

[Reicherb]

I've got fin tube baseboard. I did as you suggested and it seems to be working now. We'll see what the next few hours bring. Thanks for all of your help.

 

[Dana]

I've got fin tube baseboard. I did as you suggested and it seems to be working now. We'll see what the next few hours bring. Thanks for all of your help.

Any air in the system might still migrate to the top and lock it out again over time. The air-scoop and vent above the expansion tank should be able to take out tiny bubbles flowing by over then next week or so, if there is a sufficient length to the straight section of pipe between the last ell and the intake side of the air scoop to quell the turbulence induced by the ell. (It looks like you have about a foot or so? If yes, it should be OK.)

 

[Reicherb]

Yep about a foot. The 2nd floor is nice and warm like the others as the water temp is back down to 150.

 

[Reicherb]

How am I doing for boiler return temp? This is after not being on for quite a while and then the furthest zone calling for heat:
time input temp output temp
0 min 100 125
30 sec 100 110
1 min 100 110
2 min 90 110
3 min 100 115
4 min 110 120
5 min 110 125
6 min 115 130
7 min 120 140
8 min 125 145
9 min 130 150
10 min 135 155
11 min 140 155 boiler turned off

Am I ok?

Thanks,

Brad

 

[Dana]

For the record, how are you measuring the return water temp & output temp? If it's an IR thermometer pointed at bare copper or shiny-gavlanized it's going to be reading WAY low.

If those numbers are real, in terms of burn time you're doing great, but at those temperatures there is quite a bit of condensation going on inside the boiler, which would be GREAT if it were intended to be a condensing boiler, but it's not. To raise the entering water temps it needs a system bypass branch so that the EWT is above 130F by the second or third minute of a burn it or that boiler will be toast by the end of the season:

Note the position of the branch tee relative to the pump- the pump is driving toward the tee. If it tees off between the boiler & pump it's a "boiler bypass", which isn't quite as protective of the boiler.

A thermostatic mixing valve to mix the bypass output with the return water temp can shorten the time it takes for the entering water temp at the boiler to rise above 130F by delivering 100% bypass flow until the boiler has achieved a high enough temperature. That approach delays and initially reduces the flow going to the radiation, only delivering full flow to the radiation once the return water is above where you've set it (130F- 135F is fine for gas-burners), but that's OK.

Hook up the cold input the return from radiation, the hot to the bypass branch, and the middle to the boiler return.

 

[Reicherb]

Thanks.

I put a gauge on both the output and the return side of the boiler so I'd have accurate numbers?

How soon do I need to get the bypass installed? Do I have a couple of weeks or is it urgent?

The pump I have is on the return side of the boiler. Does that create an issue?

 

[Reicherb]

I'd like to add a low water cutoff as well. The boiler doesn't have a spot to add one. Is there a model you would recommend?

Thanks.

 

[Dana]

Thanks.

I put a gauge on both the output and the return side of the boiler so I'd have accurate numbers?

How soon do I need to get the bypass installed? Do I have a couple of weeks or is it urgent?

The pump I have is on the return side of the boiler. Does that create an issue?

You're not going to destroy the boiler in a couple of weeks, but don't let it go a couple of months.

It's fine to be pumping on the return side- just be sure the pump is between the bypass tee (or mixing valve) and the boiler.

Some "smart" heat purging boiler controllers such as the HydroStat 3250 Plus can be set up to inhibit the circulation pump until the boiler is above some specified temperature if desired, which is another way to manage the return water temperature issue, but the system bypass with a thermostatic mixer is a pretty rock solid approach. It also has a low water cutoff feature.

 

[Reicherb]

Thanks. I'll go ahead and remove the galvanized pipe at the same time. Is blank pipe ok or should I be threading copper into the boiler?