Always air-bound after vacation

dpschuste

Hi everyone, I have a forced air unico mini-duct system heated by an oil-fired boiler. Every time we leave for a few days, the system becomes air bound & blows cold air. Otherwise it runs fine—it’s only when we go away. This is annoying when we come home & have to bleed the system, but especially concerning b/c pipes could freeze if heat is off while we’re away.  Any idea why this is happening and suggestions for a permanent fix? Thanks! 

Grallert

When you get a chance show us the boiler and its related piping. Air's getting in and pictures could very well tell the story.

EdTheHeaterMan

The obvious answer is to not go on vacation!

If that is not an option, then we need more information.
First is the location of the Unico air handler in reference to the boiler location. If the air handler is located several stories above the boiler, for instance, the static pressure of the water in the system may need to be increased.

Another possibility is that air from the expansion tank is finding its way to the air handler heat exchanger. Pictures of the boiler piping from ceiling to floor and from at least 2 different angles (more is better). And maybe some of the air handler piping.

Finally, what is your procedure for bleeding the air? that may also give a clue as to what is happening.

Looking forward to hearing from you.

Yours truly,
Mr.Ed

Jon_blaney

When you go away, what do you do to the system that is different than normal?

STEVEusaPA

When you say air bound, you mean the oil line that needs to be bled, correct?

EdTheHeaterMan

STEVEusaPA said:

When you say air bound, you mean the oil line that needs to be bled, correct?

I assumed the hydronic coil needed to be bled. I should have thought of that oil thing.
I guess if you are a hammer, everything looks like a nail. I glossed over the Oil-fired statement and went for the air in the Hydronic System.

Grallert

I made the same assumption about the hydronic side of the thing.

EdTheHeaterMan

Grallert said:

I made the same assumption about the hydronic side of the thing.

I, Betting on the Hydronic side too, but @STEVEusaPA has been correct once or twice before.

Jamie Hall

So did I...

EdTheHeaterMan

3 votes for Water... 1 for Oil.

I hope the OP returns to let us know who is right!

HVACNUT

I assumed the hydro loop as well.
If it is the oil line, a Tiger Loop wont fix it. It might act liked it's fixed, but we all know it's not. 

EdTheHeaterMan

If it looks fixed, and it acts like it's fixed, and it walks like it's fixed. Then it must be a Duck in a Tiger costume.

And you know that your comment is the only reason I posted that @HVACNUT. Now I can edit that out LOL

5 Hydro to 1 OIL

STEVEusaPA

It's probably on the heat side, but I like to ask questions before providing answers.

ethicalpaul

Jon_blaney said:

When you go away, what do you do to the system that is different than normal?

Here's my favorite question! The system doesn't know you're on vacation--there must be some other change.

EdTheHeaterMan

ethicalpaul said:

Jon_blaney said:

When you go away, what do you do to the system that is different than normal?

Here's my favorite question! The system doesn't know you're on vacation--there must be some other change.

You never know... there may be a smart thermostat!

ethicalpaul

That's a great point, Ed, I totally missed that possibility

EdTheHeaterMan

Still think @dpschuste just needs to stop all winter vacations, Paul

ethicalpaul said:

That's a great point, Ed, I totally missed that possibility