Lochinvar KN155 pressures

CraigCO

I have a Lochinvar KN155. It is operating an in-floor radiant system and a side arm. The radiant is 2600 square feet under 4 zones. The inlet pressure sensor, expansion tank, TP valve and pressure reducing valve have been recently replaced. The pressure reducing valve is set at 15lbs. The system has been purged multiple times to confirm no air in the lines. However, the system keeps increasing to around 30lbs. The distance from the boiler to the furthest faucet is approximately 25 feet. Once the system is purged it takes about 2 days for the pressure to creep back up to around 30lbs. Not sure if this could be a factor but the home is located at an elevation of 9000'. The boiler is a high elevation unit and is to be acceptable up to 9600'.

Any thought to a possible solution would be greatly appreciated.

EBEBRATT-Ed

I take it that you have some type of side arm heater for domestic hot water? It could be possible that that heat exchanger is leaking internally.

CraigCO

Yes, there is a side arm for domestic.

hot_rod

Try it with the fill valve turned off. It could be slowly raising the pressure.

Your relief should be a 30 psi, not 15?

If a DHW tank or side arm leaks across pressure would go well beyond 30 and the relief would stay open, I think.

CraigCO

hot_rod said:

Try it with the fill valve turned off. It could be slowly raising the pressure.

Your relief should be a 30 psi, not 15?

If a DHW tank or side arm leaks across pressure would go well beyond 30 and the relief would stay open, I think.

I miss spoke. The pressure reducing valve is at 15 and the pressure relieve valve is a 30 PSI valve.

At rest the reducing valve is not on other than any water that would normally flow through it if a request for water is sent to the boiler.

hot_rod

Yes, but any air that vents out gets replaced with water if the fill is left open. Glycol takes a long time to give up all its air, so you could add a gallon of water to your mix and dilute it at a new fill and start up.

Save both money and potential problems by not installing one.

Best option with glycol systems is a fill tank. It give you some spare fluid, a visual, and alarm circuit if pressure falls off.

CraigCO

hot_rod said:

Yes, but any air that vents out gets replaced with water if the fill is left open. Glycol takes a long time to give up all its air, so you could add a gallon of water to your mix and dilute it at a new fill and start up.

Save both money and potential problems by not installing one.

Best option with glycol systems is a fill tank. It give you some spare fluid, a visual, and alarm circuit if pressure falls off.

Thank you so much. I shut off the valve that feeds the house water to the through the pressure reducing valve to the radiant side. So, far pressures are holding and no relieve valve drips.

Ill consider the glycol feeder. I have approximately 2500-3000 linear feet of 1/2" radiant pex piping. I have read that for Glycol that 1/2-1 gal per 1000' of run is sufficient.

Karl Reynolds

1/2" pex has a water capacity of .92 gallons per linear foot. So your installed pex has a capacity somewhere between 23-28 gallons. You also need to take into account system piping and boiler capacity. Here in the Colorado high country, it is common practice to have a concentration of propylene glycol of 25-30%. So you would need about ten gallons of 95% concentration of inhibited P.G. The feeder is a nice touch and the residential units that Bob recommended come in two capacities, 6-gallon and 17 gallon.

GGross

Karl Reynolds said:

1/2" pex has a water capacity of .92 gallons per linear foot. So your installed pex has a capacity somewhere between 23-28 gallons. You also need to take into account system piping and boiler capacity. Here in the Colorado high country, it is common practice to have a concentration of propylene glycol of 25-30%. So you would need about ten gallons of 95% concentration of inhibited P.G. The feeder is a nice touch and the residential units that Bob recommended come in two capacities, 6-gallon and 17 gallon.

1/2" pex is 0.92 gallons per 100 feet not per linear foot, that would be some massive systems out there

CraigCO

Karl Reynolds said:

1/2" pex has a water capacity of .92 gallons per linear foot. So your installed pex has a capacity somewhere between 23-28 gallons. You also need to take into account system piping and boiler capacity. Here in the Colorado high country, it is common practice to have a concentration of propylene glycol of 25-30%. So you would need about ten gallons of 95% concentration of inhibited P.G. The feeder is a nice touch and the residential units that Bob recommended come in two capacities, 6-gallon and 17 gallon.

Thanks. I am also in Colorado. Pikes Peak region. We rarely lose power but considering the glycol as a possibility.

CraigCO

UGH, I was hoping that shutting off the ball valve to the radiant side would stop the pressure increase. Seems after watching it wants to stay between 25-30lbs PSI which unfortunately causes the TP relief valve to release some pressure.

HomerJSmith

It seems to me that there are two reasons that the pressure rises to 30 psi is: 1) the fill valve has failed and is allowing pressure creep from 15 psi setting. 2) the expansion tank has no acceptance. No acceptance, either the air charge is too high or it's water logged. Shake the tank, if it is sluggish it maybe water logged.
If the Pressure Relief Valve has been leaking for a long period of time, I would replace it, although that's not the problem. Just preventive action.
If you lower the pressure to under 20 psi by opening the PRV with the boiler not running, does the boiler pressure increase to 30 psi with the boiler off? If so, then I would suspect the pressure reducing valve or if the Ex tank is a fill-trol 110, the fill-trol valve. If the pressure increases when the boiler is running and producing hot water then I would expect a problem with the EX tank.
The air charge on the Ex Tank should equal the PRV pressure setting (15 psi).

hot_rod

If you rule out the fill valve, and the expansion tank is not waterlogged, you are down to the side arm as @EBEBRATT-Ed suggested. Valve that off from the boiler piping if possible.