How many circulators?

ALH_4

What is the piping strategy? Any chance of a schematic? Why get rid of the heat exchanger?

Eric Johnson

How many circulators?

I have a wood-fired boiler connected to a Weil McLain gas boiler through a 250-foot loop of one-inch copper connected to a flat plate heat exchanger and driven by a Grundfos 24-96 circulator. On the gas boiler side, I have four zones, each with its own circulator (Grunfos 15-42s and Taco 007s). Cast iron rads.

I'm planning to get rid of the glycol and htx and pipe the wood side directly into the gas boiler.

I'd also like to replace the circulators with zone valves, if possible.

If I put one big pump on this system and run it continuously, will I have sufficient flow to get the job done? I believe the 24-96 is sized correctly for the 250-foot loop. Is it big enough to take on the rest of the system as well?

Brad White_9

What is

the flow rate and BTU load?

What are the characteristics of the worst-case zone? (Head, flow, load?)

hr

Is it an open system wood boiler?

that is typically why the high head circs.And the reason for the HX separation.

I install Aquatherms (pressurized type)and rarely use glycol. The only glycoled systems are the ones where the owners leave them un-attended for a week or more mid winter.

Other than that glycol brings too much cost and baggage for large capacity OWF applications.

We need the info Brad requested to size the circs. Typically a small 15-42 or 007 will run that entire package with zone valves. Not sure about your wood burner type and size.

hot rod

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hr

Is it an open system wood boiler?

...

Eric Johnson

Bear with me here.



I run either wood or gas, never both at the same time, and generally wood during the bulk of the heating season.

The current wood boiler is rated at 150K btu/hr of output and it runs between 15 and 20 psi. I'm not sure what the flow rate is, but somewhere between 10 and 20 gpm.

The gas side has 192K btu of output and the system pressure generally sits on 15 psi. No idea of the flow rate there either, but the main zone is 1.25-inch copper and it has 11 of the 15 ci rads on it. The other three zones serve additions to the original house, and have about 2 rads per.

What I plan to do is replace the wood boiler with a 205K btu/hour wood gasifier and connect it directly to the gas unit. I'm going to add a 3/4-inch pex line to the existing 1-inch copper line to handle the increased output of the new boiler.

I'm going to put a four-way mixing valve on the big zone, which means I need continuous circulation anyway.

Seems like I have more circulators than I need.

Eric Johnson

to clarify

It's a closed system, hot rod.

The reason for the glycol and the htx is that the wood boiler and piping are insulated, but run through unheated spaces. I think I can get around that with more insulation and continuous circulation. That way when I'm on vacation or otherwise not around to feed the wood gasifier, I can run the gas boiler and circulate hot water to the wood unit. A power failure is a concern, but I think I can run the circulator with a battery backup.

On the question of why I want to get rid of the htx and glycol, after using it that way for 3 years, I think it's probably more trouble than it's worth. My current flat-plate heat exchanger can't handle the additional heat output, and I think it's not as efficient (or responsiver) as piping direct.

Eric Johnson

picture

I don't know how much this helps, but here's a pic of the current connection between the two systems. Out of the frame are the 24-96 and the other three zones. What you see here is the htx and the circulator that gets the heat into the gas boiler, plus the one that serves the main zone with the 11 ci rads. That's a Grundfos 20-42.

Eric Johnson

bump