Ask Experts Questions for FREE Help !
Ask
    rrekih's Avatar
    rrekih Posts: 19, Reputation: 1
    New Member
     
    #1

    Nov 28, 2009, 08:45 PM
    Pressure and hydronic radiant heat
    From what I understand the pressure for hydronic radiant systems is about 12psi.
    What is the reason for this being so low?
    The pex pipe is rated much higher even at high temp.
    Does it have anything to do with the supply to the boiler?

    I have a tank less hot water heater system that is going to go into a heating box that supply's domestic hot water and the heating system, it is closed loop system with heat exchangers.
    I plan to install a pressure regulator on the supply to the heating manifold after the heating box so the domestic hot water will still run at about 60psi while I can drop the pressure to the heating system.
    massplumber2008's Avatar
    massplumber2008 Posts: 12,832, Reputation: 1212
    Senior Plumbing Expert
     
    #2

    Nov 29, 2009, 05:58 AM
    Hi Rrekih:

    Pressure, volume and temperature are all related to each other (I'll spare you the equations). Here, in a boiler system, if you have 20 PSI and then you heat the water to 190F the pressure could increase to say 25 PSI. With a pressure relief valve (all boilers have them) set to relieve pressure at 30 PSI you can see where a pressure exceeding 15-20 PSI would be a problem for the boiler system.

    Further, boiler systems, radiators, etc. are simply not made to operate at pressures that exceed the 30PSI rating. Inevitably, if overpressurized these systems will fail at the boiler or the radiator sections.

    Boilers are just big boxes of water and fire... low pressure is just another way to protect the homes from flooding or the boilers from failing.

    Let us know if you want to discuss more...

    MARK

    PS: Don't forget to install a backflow preventer (see image) with that pressure regulator... keeps boiler water out of your drinking water... ;) They also sell a combination pressure regulator/backflow preventer (see other image).

    .
    Attached Images
      
    rrekih's Avatar
    rrekih Posts: 19, Reputation: 1
    New Member
     
    #3

    Nov 30, 2009, 09:44 AM

    The check valve is installed in the heating box.
    I am not using a boiler so that takes that out of the equation.
    But the part about radiators etc. is a good point.
    Heating the water to 190deg. Seems excessive, I will only being going to 140deg. Give or take.

Not your question? Ask your question View similar questions

 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

Radiant Heat addition [ 3 Answers ]

I am trying to add radiant floor heat to a old room that had electric baseboard heater. I currently heat the rest of my house with a pump driven boiler with radiant heat. I would like to tap into this existing system. But because of the allowable space in the new room. I am only going to be...

Hydronic/Radiant Heat Problems [ 1 Answers ]

In the townhome I am renting the furnace is hooked up to the water heater & I have been told it is a hydronic or radiant heat system. I don't know anything about this type of system, but once the weather turned cold & I began using the furnace to heat the home, the water in my facets became...

Hydronic heat system [ 5 Answers ]

I have a 21 unit builiding with a hydronic heat system with zone valves in each unit. Hot water flows slowly in the unit I am in but does not respond to thermostat. Old low voltage thermostat had three wires green red and yellow. Old thermostat was connected with green to the R terminal Red to...

Pex tubing for hydronic heat [ 1 Answers ]

I have cast iron radiators. I am replacing the pipe in the basement with pex tubing. What size pex tubing should I use? I am going to have 5 runs with two radiators to a run. One large 30" by 10" with 17 to 19 sections and a smaller 30" by 10" radiator with 7 to 9 sections on it. I was thinking...


View more questions Search