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[RSI]

Is the unit heater in series? How large is it and how much extra pipe did you have to add for it?
What are the dimensions of the 40 plate?
Is there any chance there could be any trapped air anywhere in the system?

I have never tried putting another pump in series with an alpha but it might be worth a try to put in the 007 and see what happens. If you have room, just bolt them together.

[tawilson1152]

I just put 2 tees in the return line and put a pump in the loop. I did have the pump running all the time and controlled the fan with a tsat, but I've shut the pump off and still get enough flow through the heater to keep it hot. Probably because I put the tees on either side of a 90.
The only place I could have any trapped air would be in the heat exchanger, it's all  level or uphill from there to the owb. I've got temperature gauges on all four pipes to the hx, so I could do something there for a vent. Good point, thanks.
I thought about adding another pump. I can always take it out. From what I've read, the more powerful pump should be first.

[tawilson1152]

Ok, I pulled out the thermometer well and stuck in a boiler drain for a vent. It did have some air in it and after bleeding I gained a gpm to get to 6gpm. Then I stuck a new 007 in front of the Alpha, and it is now bouncing between 7 and 8gpm. Funny thing is, it stays right there no matter where I set the Alpha at. Thank you RSI. I just temp wired it with a lamp cord, I'll do it permanent if I'm leaving it. I'm still debating putting the 007 right at the boiler to get better circulation through it.

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[RSI]

That is really interesting, especially not making a difference where you set the alpha. If you set it to constant head it will run full speed because the pump in front of it will pull the water away and keeping it from building pressure. a Grundfos 15-58 would work even better but since you already have that pump, you might as well use it. Let us know how it keeps working.
If you do want to cut your power usage down a lot, you could run a wire out to the boiler and put a strap on aquastat on the pipe and set it up so the taco only comes on when the boiler is running or there is a big temperature drop. Then you could run at 20 watts or so on the alpha all day and use probably less power overall than the alpha on high was using.

[tawilson1152]

The gpm on the Alpha seems to vary. Can't figure why. This morning it said 9gpm, still at 43 watts. Last night it was at 6. This is with the 007 still running in front of it.
I've got a leak I'm going fix next weekend. As I've got to drain the boiler to fix it, I'm streamlining the piping in the basement. I figure I can eliminate 5 of the 90's I have now. I'll let the pex do the offsetting to the floor where it enters the basement. Didn't give it much thought when I originally piped it. I'll also flush some water through all parts of the system to make sure I don't have any obstructions.
This is a pic of the piping into the boiler. I am considering crossing the connections to get better flow through the boiler. I can hear boiling water inside the boiler towards the end of it's normal cycle to 180. I would welcome input/experience with that.
No matter what, I'm putting valves on all the ports so I can play with it, maybe even putting a pump right at the boiler to circulate through the boiler only.

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[RSI]

Does the GPM change happen to coincide with boiler temperature or when a lot of heat is being drawn off the water? Hotter water flows better so if it is colder you might see a drop in flow.

Going to opposite corners for the boiler supply and return isn't a bad idea.

[tawilson1152]

9 gpm is more like I expected when I put in the Alpha and it's stayed there for 12 hours now. I'm wondering if I did have some air in my underground lines that finally worked it's way out. I did do a little burping and flushing last night at the new vent I added at the hx. Didn't hear any air, but who knows.
The boiler manual doesn't say about crossing them. I'll give it a whirl, see what happens.

[RSI]

Do you still have the taco pump running too? Have you tried turning it off to see how many GPM you lose? It doesn't hurt anything leaving it in there turned off. It will make a little restriction but not that much.

[tawilson1152]

Yep, it's still there and I've turned it off and on a dozen times in the last week to see, and no matter where the Alpha is at, it loses 1 gpm of flow. Tonight it's at 7, and unplugging the Taco dropped it to 6.
I'm gearing up for my boiler repair and repiping job this weekend. I've played with this now enough to feel confident the nineties I'm eliminating will give me all the flow into the house I need with just the Alpha. I am doing the crossover at the boiler too. If I still hear water boiling during the course of a normal cycle, I'll stick the Taco on the back of the boiler on the 2 open bungs to see what it does.

[tawilson1152]

I did my repair and repipe project this week. The Alpha pump is stll at 6 GPM, but I'm ok with that now because changing the return piping connection on the owb seems to have made a difference. I used my infrared heat gun and I have consistent temperatures, where before I had stratification and I could hear water boiling during the course of a normal cycle. I just fired it up, so time will tell.

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