Do I leave the my hydronic heating make-up water supply line open or closed?

oak

My installer piped the make-up water run to my hydronics through a B&G pressure reducing valve (installed vertically, by the way) , a back flow preventer, and isolating ball valves. This supply is T'ed into with a port for adding glycol. When finished and operating, he left the make-up line open. The other day the boiler service technician shut off this supply (closing both isolating valves), saying it was unnecessary and risky (i.e. the boiler will tell me when it needs make-up water; and, he didn't favor leaving any opportunity for the 50-50 mix to move backwards (defeat the backflow preventer).

I guess P-glycol is sold over the counter as a laxative these days; but if you don't need it. Seriously though, what is the best default condition for the hydronic heating system: open or closed make-up water supply?

hot_rod

Does it have glycol in it now? If so I don't like to see a fill valve attached at all. A better choice is a fill system, like Axiom, or glycol pig.

All new systems, or systems that have been opened for service and repair will attempt to de-aerate for days, maybe weeks. If you have a micro bubble type air purger, which you should, those take time to scrub all the micro bubbles. Also the system should be run up to operating temperatures to drive every bit of air out, all zones opened. Including high temperature for indirect tank, if applicable.

So I would highly recommend leaving the valve open for several days, maybe a week depending on the system size and capacity. You need to replace evacuated air with fluid or you will get noise, and possibly cavitate circs, or go into burner lockout if pressure drops enough.

After that, it's a ongoing debate. I prefer open for all the above reasons. Systems can reabsorb air if they are shutdown for periods of time, the fill will assure that purged air will be replaced.

I've never had a system or building flood due to frozen hydronic lines and fill valve flowing, some have and prefer to leave the valve off. But you still have domestic water lines under constant pressure under the same condition.

With the Caleffi Autofill the knob on the bottom allows you to regulate the flow volume. Closing it down avoids having a 5 gpm flow through an opened pipe, but a small flow to replace and purged air, another option to consider.

I like the compromise above. If the valve is left off from day one, save the money and don't even install a fill and BFD

oak

Bob ... the glycol mix is 50/50 now. We already have the type of valve in the photo (is it adjustable?) . In fact, the Triangle Tube tech has recommended I use a cable tie just like the photo.

Inspectipedia says its (i.e the cable tie) a bad idea:
http://inspectapedia.com/heat/Water_Feeder_Valves.php

SlamDunk

I operate a 10,000 gallon HHW loop and I leave my make up water valve closed.

Every couple weeks I open it for a few hours just to make sure it is full but it rarely takes a gallon. It has a back flow preventer but it can fail between inspections. Our system is chemically treated so I don't take chances.

Another reason I keep it closed is we operate at 170F and if there is a power outage, or failure with the heat exchanger, the loop gets cold, the water shrinks and make up water enters. Then when turned back on, there is too much water in the loop for the expansion tank to handle and the pressure relief valve dumps about fifty gallons or more. My guess is the expansion tank is too small but I'm not an engineer.

hot_rod

The zip tie is to disable the fast fill lever function, from what I can see.

I'd still rather not see a fill on a glycol system. Every, or any time it adds water you glycol % drops. You may not even know that is happening.

You could shut off the ball valve and remove the handle. A zip tie to hang the handle nearby is a better use of a tie.

Hopefully the system has a low water cutoff or low pressure lockout on the boiler if you leave the fill valve off and do not have another glycol fill system.

Depends on how much "insurance" you want on the system. In any event, keeping an eye on working and accurate pressure gauges is always a good idea.

oak

I have a house performance routine that includes checking the water pressure on the boiler. It has remained stable for with the make-up water supply valves open.

Its a TT boiler with a low-water display code; it can disable itself. I know this because when we first commissioned the boiler we were losing pressure and getting a hard lockout as a result. I believe that pressure loss was due to the new system start-up adjustments, purging of air, etc ( I have Stelrad, wall hung radiators). That was when we opened the refill valve as a default.

I have a well and a 40 gal bladder tank supplying the maniblock. The hydronics are buffered by a 3 gal pressure tank. The well pump's pressure is set for an 80psi refill cut off. I suspect from what you say that I am getting some thinning of my glycol mix already so I will check this. Its been two seasons since glycol was installed. Supply temp is set for 140*.

In the meantime I have closed the refill valve's access and I am curious if there will be any affect on boiler pressure. Listening to you gents makes me realize there are more downsides and risks than upsides to keeping the refill valve open.

RobG

I agree with leaving it closed. As well, either buy a refractometer and a PH test kit or ensure that your service company tests the water annually.

plumbgod

You should leave the make up water closed. If the system is install correctly then you should not need any make up water at all. If you do that means that something is leaking and should find where it is leaking from. Most new boilers have a low water cut off and that is a safety feature. If you have more question feel free to ask.

SWEI

On new systems and major retrofits, we don't install fill valves. We have a couple that are rigged with hose thread adapters. Leave them on the job for a couple weeks and then move to the next one.

For existing systems that we service, we valve off the autofill and ask the owners to check system pressure daily for one week, then weekly for a month. We frequently learn things from this, and the owners start to get a sense of how their system works.

oak

I have valved-off the autofill.

So I need to test/read of my water/glycol miture. Is that an annual routine? Which is basically suitable: the refractometer or the PH test kit or do I need to do both?

hot_rod

On a closed, sealed system the glycol % should not change. Check it now, record it on a tag near the boiler, check every few years. Also put a note or label Do Not to Add Water to this System

Then ph should be listed on the glycol you put into the system, usually around 10- 11. Same applies here, if the system is sealed and never opened the ph should remain stable for many years. record the number now, it may drop from the number on the bucket depending on how well the system was cleaned before the fluid was added.

Ph drops when the fluid is stressed, often from continuous overheating. You will see that in solar thermal system that go into stagnation often, no so much on glycol in hydronics.

Here is a tag example, put it in a sandwich bag to protect it from errant , rogue conditions