Basement has a heated concrete floor with radiant heating. Electro Industries Mini Boiler model EMB-S-7 and a Taco ZVC404 zone valve control with 3 heating zones installed. Turned the system on for the first time this winter and all appears to be operating properly. PSI is just above 30 with boiler temp slowly rising & currently at 95F. The floor appears to be heating adequately. The zone valve control shows yellow leds illuminated for the 3 zones thermostat lights and shows red leds illuminated for the 3 zones zone valve lights with the green power LED illuminated. The mini boiler has 3 LEDs lit, green Boiler Power, yellow Utility Off Peak and red Mini Boiler Heat ON. My question is whether the Utility Off Peak LED being illuminated is normal or something to be concerned about because I don't have the knowledge of knowing that Utility Off Peak is.

See page 8 Operational Tips of the installation and operations manual for the LED indication status. The utility Off Peak LED is illuminated when the boiler is not being load controlled. 30 PSI is too high. Maximum pressure is about 18 PSI. Does your system have an expansion tank and a pressure relief valve?

Appreciate your response! So, to be that guy, what does it mean if the boiler isn't being load controlled?

Yes, my system does have a tank.

I know that the upper right valve handle is the water inlet. I don't know what the upper left valve handle is.

I'm guessing that one of the lower valves is the pressure relief valve, my best guess would be that it's the red twist handle

It means the boiler isn’t setup to take advantage of off peak time utility rates. So this isn’t a problem per se.

The pressure relief valve doesn’t have any handles. It is just a component that will get triggered and dump the system if the pressure in the system exceeds the maximum design value, usually 30-35 psi. It usually has a copper pipe that is routed to floor level or outside. There is usually a label on it indicating the relief pressure value.

If your system is heating the building ok, I think you are ok. My only concern is that your boiler installation manual states that maximum pressure is 18 psi and you indicated it was 30 psi. Maybe bad pressure gauge or maybe this system has operated at this higher pressure since initial installation? So this might be something for you to investigate further.

Your large photos are making this thread very difficult to read. I can't view the photos because I am on the road and only have my cell phone. Perhaps edit/delete them and just post links instead.

Thank you again! I really appreciate your insight.

Not sure how closely you looked at the pics, if you looked at all, and, sorry for posting such large photos (my bad!).

But, the larger copper down pipe leading to that clear 5 gallon bucket is the pressure relief. If the water inlet is turned on after a few seconds that pipe expell water until the inlet valve is shut off and it will stop expelling water shortley thereafter.

All appears to be operating as it should and this 3 zone system is heating my basement very very well with no forced air heating help.

I will be looking into the PSI further to make sure, but I suspect that it might very well lbe a case where the system was set up for 30ish to be the norm.

Please just know that just because it was setup at 30 psi, doesn’t mean you should continue to allow your HR system to operate at this high a pressure. Typically, HR systems are setup to operate around 10-15 psi and they have a pressure relief valve set to relieve pressure if it exceeds 30 psi. The reason HR systems are pressurized is to prevent pump cavitation by satisfying the pump minimum required pressure at the inlet port which is called Net Positive Suction Head (NPSH). Pump cavitation occurs when the pressure at the inlet port drops below the vapor pressure of the liquid. Vapor bubbles form at the inlet port and are moved to the outlet port where they collapse creating a grinding sounding noise and often damaging the pump in the process. Only about 5 psi is required to avoid pump cavitation for the typical pumps used in HR systems.

When you open the inlet ball valve you introduce the system to the amount of pressure that your domestic water supply has.

Your 30psi relief valve opens to not exceed 30psi. The brass item that says inlet and vent should be a pressure reducing valve, it is suppose to keep the HR system pressure down to 12-15psi.

I don't see where yours is adjustable, it may need replacement.

Yes, that’s very likely what happened. Someone opened the inlet ball valve causing the HR system pressure to attempt to rise to the domestic water system pressure (usually about 60-70 psi) and the pressure relief valve dumped the HR system pressure down to 30 psi. You should get the HR system pressure down to about 10-15 psi.

Just using only a ball valve between the domestic water system and the HR system is bad practice. It would be better use something that allows setting the desired HR system pressure directly and prevents any chance of backflow into the domestic water system. Something like the Taco 3450-2 Combination Boiler and Backflow Valve:

Taco 3450-2 Combination Boiler and Backflow Valve

Is there any manual way for me to reduce the pressure in the meantime before I would purchase and install a backflow valve?

I currently can't view your big photos very well. It looks like your manifold has purging valves. There is usually a cover over the hose bib that must first be removed and then the valve is open/closed by turning the nut above and on top of manifold. First make sure the inlet ball valve is fully closed so as to fully isolate the domestic water and HR systems. Then attach a hose to one of the manifold purging valves. Slowly open the valve while watching the pressure gauge. Letting out a very small amount water will quickly reduce the pressure. Target about 10-15 psi and close the valve. If you let out too much water and the pressure gets too low, you can just crack open the inlet ball valve a very little bit and slowly bring the pressure back up. Good luck and please keep us posted.

Right click on image and click "Open image in new tab" He has two images there so you have to do it on both.

Posted By luthor on 23 Jan 2018 01:54 AM
Is there any manual way for me to reduce the pressure in the meantime before I would purchase and install a backflow valve?

Shut off the water supply to your house at the meter or some other convenient point.  Open a faucet somewhere in the house near your heating system to bleed down the water pressure.  Now crack open the supply valve to your heating system while monitoring the pressure. This will bleed down water pressure from your heating system unless there is a check valve in the water supply line.

I have just lifted the lever on top of the pressure relief valve or open a hose bib very slightly to let out some water.

Newbostonconst, thank you. Is there a way to right click on a cell phone? Right now all I can do is scroll across a massive image. It’s like viewing a house plan with a microscope...

Arkie, your approach will backflow the HR system water into the domestic water system. I wouldn’t recommend doing that unless you also fully flush the domestic water system afterward. There could be glycol or water biologically unsuitable for drinking in the HR system.

ChrisJ, that would work well, but I haven’t spotted a PRV with a release lever in the photos.

Thank you very very much for everyones' help! I figured it out. There is a small pressure release lever on the line that leads just above the boiler itself and then down to the floor to the release pipe. It's kind of hidden behind the air exchange system.

I have the PSI down to just below 20 now. The gauge is kind of hard to read what the exact PSI level is, but I am pretty confident it's very near the 15-18 range right now.

Nicely done and congratulations! I can even see the PRV in your latest photo!

I neglected to mention previously, but the other benefit of that Taco Combination Boiler and Backflow Valve is that you just set the desired HR system pressure and it then supplies makeup water to ensure that the system always stays at this pressure. Sometimes HR systems have minor leakage (e.g., pump seal packing, etc.) that can cause them to slowly lose water over time. It doesn’t take too much water loss to cause the system to become under-pressurized which can then result in pump cavitation and associated pump damage.

I will definitely be checking out that Taco backflow valve when I have the extra time and cash. I'd be lying if I said that I didn't like the thought of just setting it to a desired pressure & then it just takes over from there!

Sounds good. The only other thing that comes to mind is to perhaps flush, fill and purge your HR system sometime down the road too. When you do so, you should also check and set the expansion tank air-side pre-pressurization before filling your HR system. We have software that can help you with this:

Borst Expansion Tank Design Software

Please read the instructions for details on how to accomplish this.