Bleeding my radiant heat system and some basic questions

johnsmith303

Hello:

I think there's some air trapped in my radiant heating system because I hear a lot of gargling and bubbling when the system is running. The picture below is how I think my system works, but I have no experience in this. I basically started from the water heater (on the upper right), because I know what the pipes are from the manual. Then I worked backwards. However, I can't tell where the system gets input water from, and where it dispenses hot water to the house, so I'm not confident in my understanding. If anyone can figure it out based on the picture, that would be helpful.

In order to bleed the system, I think I have to:
1) Close the two yellow valves next to the pump in order to bypass it
2) Connect a source hose to outlet 2 to supply water
3) Connect an exit hose to outlet 1 to let water out.

Is this correct?

Also, the heater is providing hot water to the rest of my house. So does that mean I have use potable water to bleed my system?

Thanks in advance.

Edit 1: Add better pictures

STEVEusaPA

Can you also post a pic that isn’t marked up?

EdTheHeaterMan

Your description of the filling/purging process may be right... tough to tell.

Does the pressure reducing valve pictured serve the whole house, or is that the automatic feed valve for the closed loop boiler system? It appears to be for the whole house.

I do not see a feed pipe to fill the boiler system or the other side of the heat exchanger. Are there both low temperature zone(s) and higher temperature zone(s)?


In most cases (at least it's how I design a system) there is a feed pipe that has a pressure reducing valve (Auto feed) that will supply a constant low pressure (~12 PSI) to the boiler during the filling and purging process. If you leave that valve pressurized for a few weeks, and the piping is designed properly, once the initial purge is done, the rest of the air will leave the system automatically as the system operates, over time. Most professionals will leave that fill valve open, however after a few weeks, you may decide to close the feed valve. If the closed system is truly sealed, then you may never need to purge the system for several years. (until you need to replace a part that requires draining the water from the system)

Your photo is difficult to see where all the pipes go!

Perhaps another photo from farther back, a different angle, or at least without all those squiggly lines.

johnsmith303

Sorry for the delayed response, it's been a busy week.

I thought annotating the picture would help, but apparently not. I've replaced it with a non-annotated one. I've also uploaded one taken from the left of the system, and one of the other side of the heat exchanger.

EdTheHeaterMan said:

Does the pressure reducing valve pictured serve the whole house, or is that the automatic feed valve for the closed loop boiler system? It appears to be for the whole house.

I'm not sure. It's not connected to the heating system, as far as I can see. The valve is part of a pipe that just goes into the wall at either end.

EdTheHeaterMan said:

I do not see a feed pipe to fill the boiler system or the other side of the heat exchanger. Are there both low temperature zone(s) and higher temperature zone(s)?

• I'm also confused about this, because I don't see any inputs to the boiler (i.e., where is it getting the water)? And I'm pretty sure this is also heating my water, so water must be coming in somewhere.
  
• I believe there is only one temperature zone.
  

hot_rod

Looks like a tankless water heater connected to a plate heat exchanger? So it could be suppling heat via the HX and hot water

leonz

Turn the thermostat way up and wait your bubbles should be gone in an hour or two.

EdTheHeaterMan

@johnsmith303 Your original purging description is correct, however there may be a problem isolating one of the loops.

After close observation of your photos, This is a diagram of what I believe you have. I see three changes that I would make. Most important is to install a 30# relief valve on the closed system. There is no relief valve on the closed system and if some day the expansion tank were to become waterlogged there may be a condition where water were to expand and build up significant pressure that can cause a rupture of the weakest point in the closed system. That weakest point may be located in the living space near a radiator or connection, close enough to cause injury, death, or property damage.

The other two items...

Install valve(s) in order to purge the large tube on the manifold and isolate it when purging other loops



Install a fill valve with automatic feed set at 12PSI on the system to facilitate filling and venting of the closed system.

EdTheHeaterMan

Since this is already existing. I would not change it, if it is working. However it is never a good idea to use a tankless DHW for space heating. They are not designed for this function. That is also why they are less expensive than Closed System Boilers and Combi units that ARE designed for space heating. When it comes time to replace this Tankless DHW appliance, you should STRONGLY consider a Boiler designed for the purpose you are using it for.

It is Important to add the 30# Relief valve. You won't need it today... You will need it many years from now when other parts start to fail. Hate to be you if that pressure causes a catastrophic failure on a pipe or fitting connection next to your bed when you are sleeping there... Just sayin'... Because there are heat emitters or tubing in your bedroom that are connected to the closed loop system.

johnsmith303

Thanks for the detailed response. I had some follow-up questions.

| Install valve(s) in order to purge the large tube on the manifold and isolate it when purging other loops
What is a loop? Is it the same as the manifolds you labelled in the diagram? Does each tube represent a loop (i.e., 4 loops = 3 thin tubes and 1 large tube)?
Do I need to purge the system loop by loop, or can I do it all at once?
For the record, the whole house is one heating zone (I'm not sure if loop is the same as heating zone).

| Install a fill valve with automatic feed set at 12PSI on the system to facilitate filling and venting of the closed system.
Is this necessary, or is it something which would make my life easier? I was just planning to hook up two hoses to the outlets with the green knobs. I would feed the system using the hose outlet from my yard.

Also, some additional questions I forgot to mention last time:
1. I'm pretty sure the reason the reason there is air in the system is because I opened the air eliminator valve above the expansion tank (i.e., this action caused the problem I'm trying to solve). I thought the point of that valve was to get rid of air. Did I misunderstand its purpose?
2. The pressure gauge beside the air eliminator valve is showing 0. Does that likely mean the gauge is broken, or there is another issue with my system?

EdTheHeaterMan

What is a loop. This photo shows 4 loops. 3 small loops and one larger loop. The larger loop has no isolation valves.


I have illustrate one of the loops to be radiant floor heat. I have illustrated one of the loops to be a Standard Copper tube w/Alum Fin Baseboard series loop.

It is not necessary to install an auto fill. You can manually fill the loops. But after you leave the system operating and some leftover air finds its way to a point that will cause an air-lock, you will end up with no heat in a loop. or the whole zone. The auto feed with the proper air vent location will make that almost impossible. It's up to you. Trouble free automatic or constant maintenance. Personally, I'm lazy and don't want to get up to fix the heat when it decides to fail.

I see the brazed plate heat exchanger. Is that separating the new PEX loops from the rest of the system? Since that is a separate system in itself... Is it a closed system? If it is a closed system, when the water heats up and expands, where will it go? I do not see an expansion tank or a relief valve for that closed system. You may have a dangerous situation if that is a closed loop with no expansion tank or relief valve. Hard to follow those pipes.

EdTheHeaterMan

Looking at the diagram I posted earlier, it appears the one side of the BPHX is on the open system that feeds your domestic hot water to the home. The other side of the BPHX has a closed system. I am thinking the exantion tank is on the closed loop side of the BPHX but you do not have a relief valve. Should be a 30PSI valve like this one https://www.supplyhouse.com/Zurn-P1000AXL-30C-Wilkins-30-PSI-Relief-Valve-Lead-Free.

johnsmith303

Yeah, I looked at the open loop and there is no relief valve. There is one (or something which looks like it) on the hot water outlet of the DHW tankless heater.

Agreed, auto-fill would be nicer. But I called around and all the contractors are backlogged in my area. So manually filling the loops will have to do for now.