Pressure relief valve and propylene glycol

HAB

Is using a higher btu rated pr valve with same psi rating ok? The original was rated at 535k and the new one is 790k.
Is "cyro-tek-100" a good brand of propylene glycol? I have a cast iron boiler with 2 zones.
THANKS

Empire_2

The blow off must equal and or exceed the MFG relief in any case. Pressure is pressure, but since the pressure rating in youQ;? higher is always better to exceed the MFG rating. Hope that makes sense.

HAB

The boiler specs shows max. Working pressure of 30 psi and min relief valve cap. Of 72 m.b.h. or lbs. Per hr. What would that eguate to on the pressure relief valve btu rate per hour?
Thanks

SWEI

That's 72,000 BTU/hr -- lower than the rating on any PRV I have seen.

Note that the relief pressure must be equal to or less than the boiler vessel rating -- generally 30 PSI for small hot water boilers.

lchmb

and cryo-tek is a good antifreeze. Do you have a need for antifreeze? If so, make sure you dont add to much. Odds are it will never get to -100 in your house..I hope..

HAB

I am going to use the the prv that I bought. What I have read is that btu per hour is importent in that it meets or exceeds the min capacity listed on the boiler and the psi does not exceed the max. Listed on the boiler. So in this case it would be 72,000 btu. Hr. and 30psi. The prv I am using is 790,000 btu. hr. and 30 psi.
Now, should I use tap water to adjust the glycol freeze temperature or distilled water?
Thanks

lchmb

Unless you have serious water issue's tap water is fine (imho). Just make sure to test the PH yearly as well as the set temp.

Empire_2

SWIE, do you mean equal to or greater than??? On the market usually starts out at about 300M and up......@30lb. HW...


Peace;
Mike T.

Empire_2

M=1,000 roman....

kcopp

HAB said:

I am going to use the the prv that I bought. What I have read is that btu per hour is importent in that it meets or exceeds the min capacity listed on the boiler and the psi does not exceed the max. Listed on the boiler. So in this case it would be 72,000 btu. Hr. and 30psi. The prv I am using is 790,000 btu. hr. and 30 psi.
Now, should I use tap water to adjust the glycol freeze temperature or distilled water?
Thanks

You are best to clean and flush the system first. A dirty system will kill the O2 inhibitors in the glycol and shorten its life. Do you REALLY need the glycol in the system.???
I as a rule don't like it.
As a rule 95% of all hot water heating systems don't need it.

SWEI

Empire said:

SWEI, do you mean equal to or greater than??? On the market usually starts out at about 300M and up......@30lb. HW...

Sorry if I wasn't clear, but just for the record:

PSI rating on relief valve must be no larger than than the pressure rating shown on the boiler nameplate.

BTU/hr rating on relief valve must be at least as high as the firing rate.

delta T

Yes that relief valve will work.

I will ask it again. Are you absolutely 100% sure you NEED antifreeze? have you ever had a problem with freezes? If so, you are usually money ahead by fixing the cause of the freeze (hole in the siding, short length of pipe exposed to a draft from outside, etc) than you are adding glycol. glycol does more than just lower the freezing temperature of the fluid. It also significantly lowers the specific heat of the fluid, and it increases the viscosity of the fluid. Lowering the specific heat will lower your system's efficency by lowering the capacity of the fluid to carry heat (if that makes sense) . Increasing the viscosity will make your pumps have to work harder. You will also have to keep up on the Ph of the fluid every year and add glycol and inhibitor as needed to prevent damage to system components. Add to that the fact that if you ever need to make a repair to the system that involves draining it or any portion therof, you will have to either capture and re-inject the glycol or purchase more glycol to bring the concentration back up. Either way the repair will take more time and money to complete. As I said, you are usually better off fixing the cause of the freeze in the long run.

I am not a fan of glycol unless absolutely necessary, and even then I very rarely go over a 20% concentration. Most of the time I keep it at 15%.

HAB

The way the pipes are run I have to use glycol. I may have to rethink this setup one of these days.

delta T

keep in mind that the freeze point of your glycol mix is not really the freeze point. The solution will be pumpable down to a lower temperature than the stated freezing point and will be burst proof even lower than that. I have never had even my worst problem system freeze at 20%. I will second that Cryotek is good stuff. Make sure you use the correct Glycol if you have an aluminum boiler, they require different additives to prevent the glycol from eating the aluminum.

Best of luck!