OWB not transfering heat into oil burner

[maple1]

Pics of the OWB setup?

Can you describe your OWB line purging method, exactly? Those 90s above the HX are prime air trapping spots.

 

[warno]

@Mahoney86 could I see a picture of your OWB plumbing at the boiler itself?

Also how long exactly is your underground run, 1 way, to the home and how many feet of pex are in the home before the FPHX?

I think the 0011 circ would be better but there might still be a better option. Are you dead set on buying a Taco circ?

 

[Mahoney86]

Back of OWB photo

I have 75’ of 1” thermopex prior to going through my foundation wall. Then I have another 8’ of 1” pex line before the HX. Same amount on the return line.

Circulator brand doesn’t matter to me, just stayed with taco as it’s the most commonly found and fastest delivery

 

[warno]

I went with 200 total feet of 1" pex to cover underground, in home, in boiler cabinet, and elbows. I found that elbows add about 10 feet each of head loss. So I just rounded back to 200 feet total. I went with 8 gpm for the math. Here's the site I used to get it.

200 feet at 8 gpm
3.68(per 100ft 1" pex) x 2 = 7.36 psi loss
7.36 x 2.3 = 16.92 head loss

1 psi = 2.3 ft of head

With more flow your head loss goes up. so be sure to size a circ that work for your desired gpm. If you go with that 0011, it can run about 16 gpm at 17 ft of head. But remember your head goes up with flow and I did that math based on 8 gpm.

Anybody want to double check my math. I don't want to steer anyone wrong.

 

[maple1]

There would also be pressure drop from the HX. Not sure how much that would amount to. I think I'm now thinking that the 009 should be doing better than it seems to be.

It might work better if it was mounted lower - there isn't much water above it to give it good inlet pressure. Does it make any noise when it is running?

I am still suspicious about some air in the lines. Maybe even in the HX itself. The way that HX is oriented & plumbed, and the location of all the valves there, is making for real good air trap potential.

 

[TCaldwell]

I agree with maple on the air, how much trouble would it be to disconnect the return at the owb , energize the circ and fill a 5 gal bucket till it runs air free? That could also help determine flow rate. If the air is back at the hx, it could take 5 gal before you’d see/hear it come out. If that is successful then put your efforts to the pressurized side

 

[Woodman1]

Your math looks ok but 8 gpm would be the upper limit for 1" pex. Anything beyond that would push head loss and water velocity to the point of causing other issues

 

[Mahoney86]

Just unhooked my return side and ran a
Little over 5 gallons out. Didn’t see anything crazy indicating air but maybe it did the trick

 

[Eureka]

It’s a pain in the butt, but if you could do that again and time exactly how long it takes to fill 5 gals, it’ll help your diagnosis greatly. If you have water treatment in the OWB just use a nice clean bucket and dump it back in.

 

[stee6043]

Just unhooked my return side and ran a
Little over 5 gallons out. Didn’t see anything crazy indicating air but maybe it did the trick

Was the water hot (within a few degrees of supply)?

 

[maple1]

Just unhooked my return side and ran a
Little over 5 gallons out. Didn’t see anything crazy indicating air but maybe it did the trick

Little details can get lost in internet talks.

Where did you unhook it exactly? Boiler circ was running when you did it? No other sources of water or water flow at play when you did that? Should top the OWB up with water before you do it so it won't get too low while doing it.

And as suggested above - when you do that, time the flow or bucket filling to get a GPM idea. And watch & report on temps - the water coming into the bucket should be almost as hot as the water leaving the boiler. After you get a couple gallons through. Well, no, that's not quite right. If starting when there has been no flow for a while, it will likely take a couple buckets running through it before all the water in the pipe gets purged and things get close to heat soaked.

 

[TCaldwell]

Anything figured out yet?

 

[maple1]

Anything figured out yet?

I think he was going away for the weekend.

 

[Mahoney86]

I think he was going away for the weekend.

Correct I was away for the weekend and of course it was the coldest days of the year! I hoped to get the boiler going last evening but I lots and lots of vacation traffic made my ride home much longer than anticipated. Hoping I can fire it up tonight after work, but its not looking so good.

Good news is I am working from home on Thursday so that will give me some time to really keep an eye on the boiler. Unfortunately I am expecting temperatures over 50* for Thursday.

 

[TCaldwell]

My bad,

 

[maple1]

My bad,

Pfft, that wasn't bad...

 

[Mahoney86]

Waiting for the down pouring rain to stop before I disconnect my return line to see how long it takes to fill 5 gallons. In the meantime I took a sample of water out of the drain valve on my supply line right before the heat exchanger and the water temp is 174* where the OWB display is showing 203*

 

[TCaldwell]

Just to complicate things a little more, if there hasn’t been flow through the owb lines for awhile, they get cold and takes more time than you’d think to get them warmed up to get the actual water temp

 

[Mahoney86]

Just to complicate things a little more, if there hasn’t been flow through the owb lines for awhile, they get cold and takes more time than you’d think to get them warmed up to get the actual water temp

Agreed. I actually didn’t close any of the bypass valves while I was gone for the weekend so the water in the OWB and the lines remained at 140-150

 

[Mahoney86]

Ok the monsoon rains have stopped so I went out and disconnected the supply line at the wood boiler. Its amazing how much water gets pushed out just due to head pressure from the OWB being above the basement level.

Anyways with the pump plugged in I was able to fill a 5 gallon bucket in 33 seconds. So with my math that is 6.6gpm I am pushing through my HX.

 

[maple1]

The supply line? Or the return line?

 

[Mahoney86]

The water was taken from the return line right where it would connect to the OWB

 

[TCaldwell]

Have you bypassed or removed the expansion tank?

 

[maple1]

Ok the monsoon rains have stopped so I went out and disconnected the supply line at the wood boiler. Its amazing how much water gets pushed out just due to head pressure from the OWB being above the basement level.

Anyways with the pump plugged in I was able to fill a 5 gallon bucket in 33 seconds. So with my math that is 6.6gpm I am pushing through my HX.

The only head pressure would be from the height of the OWB water above the fitting you unhooked. If that is 3', it would only be 1.2 psi. An isolation valve at the OWB outlet would make it less messy.

And actually I think that is 9gpm by the math.

There is something strange going on here that I don't think we can help sort out any more, without actually being there. 9gpm should be moving all kinds of heat to the HX. Something is not jiving, in the info or how things are being done.

Why do you have that bypass leg in front of the HX? Are you sure nothing is going through that? It was closed when you did the bucket thing?

EDIT: There could be inaccuracies in the temp measuring too depending on how its being done. I see shiny fittings & surfaces & no flat black spray paint.

 

[Dutchie84]

Ok the monsoon rains have stopped so I went out and disconnected the supply line at the wood boiler. Its amazing how much water gets pushed out just due to head pressure from the OWB being above the basement level.

Anyways with the pump plugged in I was able to fill a 5 gallon bucket in 33 seconds. So with my math that is 6.6gpm I am pushing through my HX.

I would check you math again. It more like 9 gpm.


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