Radiant slab mechanicals questions

[slackdaddy1]

Finally getting ready to finish my slab heat in time for winter and have a few questions.
22x32 garage, 1" blue board under 4" slab, R19 walls, R40 ceilings, premium insulated doors ( 2- 8'H x 10'W)
2 - 300' 1/2" pex loops.
It will be a closed system with no connection to domestic water.
EMB-S-5 electric boiler.

I do want to run antifreeze, can Propylene glycol RV antifreeve be used?

Does a closed system run under pressure? if so what pressure range is desired and how to achieve?

A 4.4 gal bladder tank is being used, I assume the only way it will do any good is if the system is under pressure to push the bladder down?

Should the Elec boiler be mount below all the other components so as to not allow it to run "dry", I see most of the elec boilers mounted on the wall above everything else.

Has anyone added a low water cut off? is it needed, or do new boilers have this built in?

Thanks,
Slack

 

[HoosierBuddy]

Not an expert, by any means...but answering based on my setup:

I would say...yes on RV antifreeze...I don't run it as it will cut down on efficiency slightly.

My system runs at 10 to 12 PSI.

You're correct on the bladder. Once you pressurize the system it will hold pressure with the bladder.

On the boiler, if you do this right, it shouldn't matter....however my system has makeup water and your evidently skipping that step.

I do think you need a safety to shut off your system if water pressure drops due to a leak. Again, my system has makeup water...so not really sure there.

Phil

 

[Northislander]

I would recommend an Axiom system feeder with a (50/50 depending where you are) mix of propylene glycol formulated for hydronic. RV antifreeze does not have the inhibitors in it that Propylene Glycol formulated for heating systems does and will prove to be unstable under heat. Unstable glycol has a very low Ph and will accelerate corrosions issues and tend to burn, (caramelize), and sludge up the boiler.
On a small system such as yours you could skip the system feeder i wouldn't recommend it but it can be done. Fill system to about 18 to 20 psi and use the expansion tank as a pressure tank as the entrained air in the system water vents you should end up with about 12 to 15 psi. with absolutely no leaks the system should hold pressure for approx 5 years. then with evaporation and micro leaks at threaded joints and valve stems you will have to recharge. Attached pic. shows the system feeder on a system i finished on Saturday
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[yeldogt]

I would recommend an Axiom system feeder with a (50/50 depending where you are) mix of propylene glycol formulated for hydronic. RV antifreeze does not have the inhibitors in it that Propylene Glycol formulated for heating systems does and will prove to be unstable under heat. Unstable glycol has a very low Ph and will accelerate corrosions issues and tend to burn, (caramelize), and sludge up the boiler.
On a small system such as yours you could skip the system feeder i wouldn't recommend it but it can be done. Fill system to about 18 to 20 psi and use the expansion tank as a pressure tank as the entrained air in the system water vents you should end up with about 12 to 15 psi. with absolutely no leaks the system should hold pressure for approx 5 years. then with evaporation and micro leaks at threaded joints and valve stems you will have to recharge. Attached pic. shows the system feeder on a system i finished on Saturday
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Interesting setup -- I like the two pump cozy

 

[slackdaddy1]

Thanks for the responses.
I will go with the kryo-tec antifreeze
I will forgo a system feeder (for now) and fill it to 18-20#
Can I remove the air from the bladder, fill the system with a utility pump in the pail of solution, then pressurize the bladder to get my system pressure?

Slack