Zone not heating up

ChrisUNY

I have recently had a new boiler installed and prep work to split my 4 Zone home into a 7 zone home.
Due to the weather the zoning part was delayed (for now), however one of the existing zones has quite a few large (3") black iron pipes that run supply and returns for the majority of a 3 story home (44' bottom of boiler to top rad). Other zones run garage/additions.

After the work was completed we bled all the radiators to where the system was working. When the heat shuts off to the "main zone" it will not come back on with the thermostat. Its getting the call and that in turn activates the pump, however one side of the manifold where the pump is, is cold while the other hot. This happens every cycle.

My contractor says this is likely due to air bubbles in the system. That's fine, as I've been bleeding the system (opening air valves on rads) for 4 days now to no resolve. I've also tried draining from the return. We also isolated the boiler and increased the pressure to 40PSI trying to force out the air.

Since we recently spray foamed and remodeled the 2nd floor that area gets hot very fast which causes us to turn off the heat prematurely. The contractor said this could be part of the problem so yesterday we spent 8Hr of the day in 90 degree heat (working from home) trying to get the air out.

This may be nothing but I'm curious: As I have seen the calculations for pressure and the height requires about (44/2.31) 19PSI. Some of the calculations I've seen have said to add 4 which would bring it to 23PSI. My water makeup valve was installed at 15PSI from the factory, if I'm bleeding the system consistently it can never stay at that pressure and I constantly have this back and forth game.

Last night we shut the heat off as our children were going to bed and didn't want them sleeping in that heat. This morning we wake up to cold again. (don't worry I have electric radiators for now)

I'm stumped and I just need some suggestions and my patience has worn thin with the contractor. The original reason we didn't zone as he said we would be out heat a few days (not sure what the difference is now). I have to remove some walls to shoot thermostats to the floors as well but I'm not going to let that stop me if I spend an hour in the basement everyone morning/night getting the heat on.

Jamie Hall

The joys of hot water heat in a tall building.

First, that 23 psi isn't optional. That is your required, cold, static pressure. Since there is very little margin between that and the pressure relief valve setting, and a lot of water volume, you will need to be certain that the expansion tank is amply large. It must be precharged to that pressure, and the pressure reducing feed valve set to that. Hopefully the tank is connected before, but very near, the intake to the circulating pump.

Simply bleeding, as you are doing, may get the air out -- but only if you keep the pressure up. If the pressure at the inlet to the pump drops much below that 19 psi you mention, it will suck air in and you'll have gained nothing.

Second, the size of the pipes tells me that this was, at one time, a gravity hot water system. They can be rather difficult to balance, and you will find it necessary to have balancing valves for the radiators on the lower floors and close them down until you get even heat on all floors.

Alan (California Radiant) Forbes

Second, the size of the pipes tells me that this was, at one time, a gravity hot water system.

I agree with Jamie. Was it a gravity system before your contractor installed the new boiler or had it been converted before?

Some pictures of the new boiler, boiler piping, pump and manifold would help.

clammy

Issues w tall homes and bleeding been there done that and what I have found is use a prv that you can set like a califee . I have found them the easiest to set and then go bleed with out blowing the safety valve off .then lower to the fill pressure you need . I would hope your pumps are on the supply and that you have a good micro bubble air elimator . Your heating contractor should be able to straighten it out if not then he s not your go to guy . If he did the boiler repipe and installation new boiler then he should be the one to straighten it out not you that’s what you paided him for right ? If not get a new heating contractor . From the sounds of it you now have a micro zones system with each one having different flow and btu outputs . You may need some circuit setters to straighten out flow and possibly some flow checks to stop ghost flow if there’s issues with that occurring . Just some food for thought has anyone check your make up water and water hardness ,it would be wise to do so if you know u have hard water . As I stated if you paid for all this work and the contractor does not follow through w straighten it out don’t waste your time or any more money find a new contractor no sense living in discomfort peace and good luck clammy

ChrisUNY

Yes this was likely gravity fed at one point.  However, when i bought the home it was already in this configuration.  Basically just a boiler replacement and prep for zones. 
The air lock appears between the taco pump and the elbow on the supply.  Im thinking adding a baseboard tee to the tops of these would get me moving in the right direction.
In regards to Jamie's comment i've attached the tank, which was the same tank on my old system, which may or may not be right.  If 23psi is minimum do I need a new water makeup?  And where can i find one with the right pressure or an adjustable one?
Side question: after all this i think we are going to go ahead with the zoning in about 2 weeks.  We are going by floor.  I want to do pex so i can bury the lines in the wall during the remodel.  Do i need a second manifold after these pumps to hit the radiators?  https://www.supplyhouse.com/Bluefin-CM5-75PXZ-PXV-3-4-PEX-Crimp-x-Closed-Copper-Manifold-w-1-2-PEX-Crimp-Ball-Valves-Lead-Free-5-Outlets?gclid=Cj0KCQiA5vb-BRCRARIsAJBKc6Is1L_cGUhHzrtWgUJhvDA_4E6yRJioOJJUrXYsUq5WRSqB4QkPLQsaAuwnEALw_wcB

I'm thinking i need something like this for each floor(one return one supply)
Lastly: we arent exactly flush with experienced and knowledgeable contractors in my area and this was my last one after 2 told me i cant put a high efficiency boiler in a cast iron system.

ty 

Jamie Hall

On the tank. There's a simple test: start with the system at the required cold pressure. Fire the boiler and get everything you can nice and toasty. Check the pressure. If it's less than about 27 psi you have a big enough tank. Otherwise, you don't.

You have a very narrow window between the minimum acceptable static cold pressure (23 psi) and the maximum acceptable hot pressure (28 psi).

This should have been taken into account in the initial planning and design of the system, but... one of the things that dropped between the cracks on that.

Even SharkBite has an adjustable pressure regulating valve. There are many much better ones... if the one you have isn't adjustable, it should have been -- and there should have been an accurate pressure gauge fitted downstream of it as well, with isolation valves and unions... sigh... get it right.

ChrisUNY

I do have one upstream and downstream, and isolation valves to each zone supply and return.  Ill check the tank.  And get a makeup valve that allows adjustment.  Thanks for all the pointers so far!

ChrisUNY

The pressure tank seems to hold up.  Talked to the contractor he said he agreed with the information gathered here.  So I owe you guys!  I bought a few baseboard tees to bleed more of this system that he will install tomorrow.  We will get and adjustable prv and put another gauge on there.