No heat after Plex install

tks1800

I’m located in Toronto, ON. I have a 2 storey house with a boiler and rads. I did a kitchen Reno and had to move the 2 pipes, 3/4 in metal pipes and replaced them with 3/4 in Plex. The original routing was straight down from the rads in the second storey to the basement. The new routing introduced 2, 90 degrees. I ran the boiler and now do not have heat in the rad as well as any of the other ones located on the same side of the house. The rads on the other side are working as well as the basement ones. I have bled the system for air.

My contractor is telling me that I can get them warm by balancing the water flow to all rads. Meaning controlling the flow of water by the valve to each rad in the house. I have to fix this before the pipes get covered by drywall. Any ideas?

GroundUp

PEX

And did you actually purge the system, or just open some vents? It's almost certainly airlocked and needs to be purged. If "your contractor" did this work, he needs to come back and make it right.

Ironman

Water takes the path of least resistance. 3/4” pex has about 60% of the capacity of 3/4” black iron. If yours is a Monoflo system, then the additional resistance you’ve added may have been too much.

Also: if you do have a Monoflo system, they can be very difficult to purge of air.

More info and some pics would be helpful.

Did you use O2 barrier pex? If not, it all needs to be re-done.

HomerJSmith

Pics, Pics, Pics, Please. I always take the customer's analysis with a 'grain of salt'. As Reagan said, "Trust but verify."

Heat Transfer depends upon three things. Supply Water Temperature, FLOW,FLOW, FLOW which is the conveyor belt that moves heat energy from the boiler to the heat emitters, and a temperature differential between the heat emitter and the environment. Water flows more thru the least restrictive piping. Maybe you need balancing valves if you have one pump and multiple zones that operate at the same time.

I think that "GroundUp" is correct. The pump which is a circulator cannot move water thru a air bubble. How did you purge air from the sys? To move air down a vertical pipe you need a flow of at least 2 feet/sec. What kind of Rads do you have? I want to know whether there is trapped air somewhere, the pump make and size, and the boiler SWT.

tks1800

Pictures are posted in first chat.
I purged the system this way.
1.Boiler was off for 24 hours.

2. Open air valve at each rad until water comes out.
I put boiler on and ran it for 1/2 hour. Every rad is warm except this one and one more on the same side on the second floor. Ironically the washroom rad is warm and it is between the 2 rooms that are cold.

psb75

You need to "force purge" i.e. run the boiler pump and/or lift the fill lever on the fill valve to PUSH water into the system with the air exits (bleeder caps, valves etc.) open. Isolate any other circuits by shutting them off with valves.

HomerJSmith

Well, strange, your pics showed up. I would like you to draw out the circuit from the boiler to each radiator as it is piped. So, you removed a bearing wall and put in a steel W beam and only changed the pipe to the radiator in your pic that was in the bearing wall to the basement with pex and everything worked fine before that change?

Are there any valves near the boiler or else where that might be closed off to this circuit? No, mix up between the hot and cold supply and return piping? Does the pex connections only go the one radiator that your pic shows? How does that circuit connect at the boiler or any other rads (pics)?

There is more pressure loss in the pex fittings that you used. If your pex is type A an expanded pipe connection and type of fitting would have been better with lower pressure loss.

How about taking a cheap laser thermometer and measure the temperatures from the boiler to the radiator all along the circuit.

I wouldn't close anything up until you solve your problem.

GroundUp

Again, it needs to be purged. Opening the bleeders isn't going to do the job.

tks1800

I’m going to have to purge properly by “Ironman “ thanks for the question on the O2 Barrier per. It is not. Potable water only. I contacted the supplier of the pex and they confirmed it is not O2 . It should be green colour which is O2 B. I’m going to notify the contractor to replace it.

I’m still going to try to purge it before the contractor comes to see if I can get water flowing to the rad. It’s probably a waste of time because I then have to drain the system again when the pipes are replaced but then I guess I’ll be more knowledgeable.

It is very strange because these are the only pipes I removed because of eliminating the wall. Nothing else in the system has changed. The inside diameter of the steel pipe was 3/4 in. The inside of the pen is 5/8. At the transition it is smaller. Maybe this has something to do with it. Perhaps I should install a 1 in Plex. Anyways I have to solve this before closing it up.

hot_rod

You should get enough flow through the 5/8 for that radiator. Pex does flow better than steel pipe, smoother inside.

Back where those pex lines connect at the boiler piping, add a purge valve there to get a good flush and purge.

A valve like this.

If you are trying to get some bounce out of the floor, a full depth joist lagged to the existing one would be best. Those 2X6 may not do much other than more sheetrock nailing surface :)

Screenshot 2024-06-20 at 10.06.43 AM.png

GroundUp

Again it is PEX, not plex- and 3/4" is more than adequate for what you're feeding. The new piping has air in it and that air needs to be purged out regardless of what happened in the rest of the system. Opening a bleeder or vent is not the same as purging. When the contractor returns, make sure he/she has the system operational before he/she leaves the building. The fact that they used potable PEX is a good indication that they also will not know how to purge the system, but you are undoubtedly paying for a professional installation that works when it's done. Anything less is unacceptable.

tks1800

My contractor admitted his junior person installed the wrong pex. He will remove and do it properly. He suggested going back and doing it with steel pipe and just use pex for the final small run.
He assured me he will also purge and get it running before the wall and floor is closed. Will keep this post updated.

Alan (California Radiant) Forbes

Whatever materials gets used, try to insulate the piping if possible. And where you cannot insulate the pipes, they should not be strapped too tightly against the framing as you will get expansion/contraction tick, tick, ticking.