Questions about my boiler piping

Roylee

Hello, I live in a 2100 sq ft rancher with an oil fired Crown TWZ 090 boiler. The home is divided into three zones using Taco zone valves. The entire system uses monoflo tees and 10" high baseray cast iron radiators. Zone one has 40' of radiation, zone two 62' and zone three 20'. My question is - I've been here a few years and the heat seems to work well, but if the system has been off for a while, I will get a lot of rushing water/air noise on the first call for heat, regardless of which zone is calling. When the water is hot, it's pretty quiet. Looking at how my system has been piped, I saw there is a system bypass with a ball valve (i read you should never throttle flow with a ball valve) which was part way open. When I close it, there is much less noise, but still some. That led to cold water coming back to the boiler, although it does have an aquastat relay that shuts the circulator of at 140 degrees. I've bled the system and no air comes out - all the radiators get hot. I'm posting pictures of my system and if anyone has suggestions on whether I should leave it be, or if I could make it better by relocating components, changing the bypass, etc, I'm all ears. Thank you in advance for your help

Zman

I think the tank hanging in the joists and the green air separator with the silver air vent is the key to your problem. With that type of tank,there should be a gauge on one end, could you take a picture? The cap on the silver air vent should be closed. What is your system pressure?

smithfan

If possible, you want to isolate the zones and purge one at a time. Also, on your make up water line, do you have a fast fill valve? I've chased air around my system a few times, you sometimes don't win on the 1st or even 2nd try! I like to purge one zone at at time. I hook up a hose to the purging station and open up your fast fill valve.

What works for me is letting the pressure build a bit, but not too much or you'll blow the relief valve, but just enough that when you open the spigot you've built up enough pressure in the lines to dislodge the stubborn air pockets. Also if you have those old cast iron radiators, they should have air bleeders on them, I'm assuming you've already tried that though.

Zman

One common issue with that kind of system is that the expansion tank has no bladder. If there is an active air eliminator in place it will remove the air from the tank causing the relief valve to burp which in turn causes the aerated water to be added and the cycle continues. If the system has too much air it will circulate around making noise.
It can be a little tricky to get it set up correctly, once it is, it should work just fine.
Hopefully @Roylee will post some follow up info.

Dave H_2

Is the tank that is in the ceiling connected to anything? Or was it left from an older heating plant. As @Zman was saying, you should not have both an air seperator system and an expansion tank.
Two courses of action;
1. Disconnect the ceiling tank and add a bladder style tank. The Air scoop vent should be open the system charged to 12 psi.

2. Close off the vent to air scoop and add and air-trol system to the expansion tank in the ceiling.

The difference between the two systems is one is air management (air-trol and tank) and the other is air elimination (scoop and bladder tank). They shouldn't be mixed in a system.

Dave H.

Bob_72

Sorry wrong post

Roylee

Thank you all for your replies. Yes, the ceiling tank is presently connected to the boiler. I don't have an auto fill valve, so I have to let water in manually. I repeat this process until the ceiling tank is waterlogged, (usually once per heating season) then drain it and start over. I did pick up a bladder type expansion tank, and can re pipe the system if that would be better. I have a concern about the circulator being at the boiler outlet, and the ball valve in the system bypass - are those things I should deal with? Thanks

HVACNUT

Like the others have said, you have an air control system so you should remove the auto vent (and any others not in view) and plug the top of the scoop, 1/8". I would leave the expansion tank, as opposed to diaphragm extrol because of the circulator location. The boiler bypass should be regulated to prevent too much temp drop mostly because you have the tankless coil. The last zone Looks MONOFLO. Are you sure the first 2 zones aren't loop? I don't see a pressure reducing valve and can't believe the system doesn't have one.
When you purge, do one zone at a time, turning up the thermostat to call for heat. The zone valves open and close slowly so wait a few before starting the next zone.CLOSE the valves to the expansion tank and bypass while purging. Be careful as you don't have a PRV. Maybe install one first. Don't forget to open the valve to the expansion tank when done.
Play around with the bypass valve. On cold days (dont know what climate your in) if the bypass is closed, you might run out of domestic hot, even though the low on the triple is set to 140. Which is low for the northeast.
Typical settings are 180 high, 160 low for domestic and prevent condensing if flue gas. Adjust bypass for 20 degree TD with all zones calling.

rbeck

Move the circulator after the expansion tank connection. That will make the system bypass a boiler bypass. Open the valve in the bypass wide open. Slow flow through boiler and all will be fine.

HVACNUT

> @rbeck said:
> Move the circulator after the expansion tank connection. That will make the system bypass a boiler bypass. Open the valve in the bypass wide open. Slow flow through boiler and all will be fine.

Exactly right. I missed that.

Roylee

Thank you all for your insight. I will move the circulator as suggested

Zman

HVACNUT said:

> @rbeck said:

> Move the circulator after the expansion tank connection. That will make the system bypass a boiler bypass. Open the valve in the bypass wide open. Slow flow through boiler and all will be fine.



Exactly right. I missed that.

I believe that the expansion tank is piped via 1/2" copper to the boiler inlet which would be correct.
As for the bipass, keep an eye on it and see if boiler return temp is dipping below 140.

Roylee said:

Thank you all for your replies. Yes, the ceiling tank is presently connected to the boiler. I don't have an auto fill valve, so I have to let water in manually. I repeat this process until the ceiling tank is waterlogged, (usually once per heating season) then drain it and start over. I did pick up a bladder type expansion tank, and can re pipe the system if that would be better. I have a concern about the circulator being at the boiler outlet, and the ball valve in the system bypass - are those things I should deal with? Thanks

I think the simplest thing would be to install the bladder tank, less fussing.

HVACNUT

Move the circ to where? Just above the bypass?
Are you sure those first 2 zones are monoflo? Looks like they were add-ons, that's why the zone valves.
Send the wife and kids to Grandma's for the weekend, repipe from the supply out of the boiler to the first zone branch. In order to fit everything, you might have to pipe towards the back and then swing it back around. I'm sure you can find a piping diagram somewhere on HH.
Air scoop, PRV teed in from that 1/2" plug and #30 extrol below that. Circ pumping away down line from the scoop, motor on the horizontal. Look into combo circ flanges/isolation valves with new nuts and bolts for ease of future circ replacement, or you'll be bleeding a lot of rads.
Oh, and 2 new circ flange gaskets.
Done yet?

Zman

Just take out the old expansion tank and install the new one on the boiler return, problem solved. The boiler has almost no head loss so you will be pumping away. Who cares where the air eliminator is?
It just sweating a few 1/2" fittings and the problem is solved.

HVACNUT

I guess there are numerous options.
Not really a fan of hanging an extrol off a vertical copper pipe. If he could support it somehow...
And install that PRV.

Roylee

The home used to be a single zone monoflow system. At some point it was divided into two zones, both still paralleled piped and joined together at the vertical return pipe near the boiler (it's obvious where pipes were cut and rerouted). An addition was added and the third zone is piped the same way - all monoflo tees joined at the same return near the boiler. I can take more pictures or draw a diagram if I'm not clear. The current expansion tank is piped directly off the rear top of the boiler, no water fill tied into it, no valves. The boiler water fill is presently teed into the bottom of the boiler at the return inlet down by the burner. My plan was to start over, re pipe towards the back, as was mentioned, boiler bypass, install a bladder tank, air scoop, and then the circulator. HVACNUT, I'm not sure of this PRV, can you please explain more about it? thanks

HVACNUT

> @Roylee said:
> The home used to be a single zone monoflow system. At some point it was divided into two zones, both still paralleled piped and joined together at the vertical return pipe near the boiler (it's obvious where pipes were cut and rerouted). An addition was added and the third zone is piped the same way - all monoflo tees joined at the same return near the boiler. I can take more pictures or draw a diagram if I'm not clear. The current expansion tank is piped directly off the rear top of the boiler, no water fill tied into it, no valves. The boiler water fill is presently teed into the bottom of the boiler at the return inlet down by the burner. My plan was to start over, re pipe towards the back, as was mentioned, boiler bypass, install a bladder tank, air scoop, and then the circulator. HVACNUT, I'm not sure of this PRV, can you please explain more about it? thanks

You mentioned you don't have an auto fill valve. That's the PRV, pressure reducing valve, to keep the boiler at about 12 psi. Pipe it to feed between the scoop and extrol with a 1/2" tee.
If your replacing the air scoop, think about a Spirovent which has a superior means of air elimination. I see Caleffi mentioned a lot on HH but have never used.

If your going in balls deep, check the condition of the vents on the rads and replace if needed.

TrueDat

Also maybe rethink that zone 3. At only 20' if it's the only zone calling for heat, you'll likely get short cycling.

Roylee

Thanks Hvacnut, I will install a new PRV. Trudat, regarding the small 3rd zone, it's in a 400 sq ft addition that has a wood stove in it. I'm thinking the way the zones were split had something to do with that. When the wood stove is burning, the addition and main living area zone thermostats are overcome by the heat, which leaves only the bedrooms needing boiler heat

Roylee

I am considering removing the small third zone as trudat pointed out. Looking at the layout of my house, it really isn't needed, and I do get a lot of short cycling. I've drawn a diagram, best I could, of the current piping (minus all the near boiler stuff) and am showing the change I would like to make in the dashed box near the bottom. Can you folks tell from this information if that would work? Thanks for all of your help.

Roylee

I don't know why the drawing is so small in the post

Gordy

Why are we recommending anything other than adding an airtrol fitting to the tank?

At present the complaint is some air noise. The xtank is piped so you are pumping away.

Add the airtrol tank fitting as Dave mentioned to keep the air from migrating out of the compression tank, and into the system, and make sure the valve is closed on the air separator.

Nothing wrong with air management systems. So long as the installer understands how they work. So long as you are pumping away, and do not actively remove air from the system.

Zman

I agree with Gordy. Either his approach or replacing it with the bladder tank you have will solve your problem.
Why are you trying to fix something that is not broken?