Boiler Corrosion Protection

Josh_S

I'm still in the process of making my fhw system more efficient. This was a gravity converted system, there's a 3" main and 2" main that run off the 1 1/4" copper from the boiler. Now with a system that large it takes AGES for the water to heat up. It'll run for about two hours getting up to 170° from cold start. It has a system bypass (not ideal but I'm not changing it at this point) that is throttled to 1/3 of the way open. I have a Grundfos 20-42 circ pump set on III. Now with a system that large if I throttle down the bypass a tad bit can I turn the circ to the II setting without compromising too much on the flow through the system?
With the current setup on a cold start it takes 15 minutes to reach Crowns specified point of 120°. Is that acceptable? I'd like to try to get it down to between 5-10.

SWEI

You really want constant circ for a gravity system. Is the system direct pumped, or primary-secondary?

The 120°F number is a bit for returning water on a conventional boiler. If that's the supply temp, you are going to have issues.

Josh_S

Here are some pictures. Basic setup, no primary/secondary.

Josh_S

Boiler is a 195K Crown cast iron boiler. The only thing I know is that the boiler temp gauge (about 5° off below actual temp) states 120° about 15 minutes after running.

SWEI

Assuming the boiler is in good shape and burning cleanly, I would install a Taco iSeries-R mixing valve and set up the system for constant circulation.

Josh_S

At some point funds will allow for that, I'm pretty handy but copper pipe is not something I deal with. In the meantime what can I do to maximize system heat while allowing enough to cycle back to the boiler? Also have these pictures of the heat exchanger granted they aren't very good but it seems to be in pretty good condition. Boiler was installed in 08'.

Josh_S

Like, will turning back the circulator speed reduce system flow by a huge amount?

Paul48

Look at an ESBE thermic valve. You're going to have to spend some money, that is probably your cheapest option. While you're at it, replace that scoop, that's useless plumbed that way, with something like a spirovent.

SWEI

A 3-way thermic boiler protection valve (ESBE, Caleffi, LK, etc.) will require some pipe work and the addition of a second pump.

A properly piped 4-way iSeries-R will work with a single pump on most gravity conversions. I would probably install a VT2218 while I was at it.

Paul48

The diagrams I have seen show a single circ, with the alternate position on the return ( not ideal). I believe I was looking at Danfoss?