Indirect Water Heater Install on Steam Boiler

mikeg2015

I’m preparing to install a Weil McClain Aquaplus 45 on my very basic Hydrotherm VGA-200 Steam boiler. Going to follow the indirect manual, but had a few questions it doesn’t answer.

1) I’m using the 2nd 2” return taping on the right side of the boiler for the supply, the left side has the condensate return,equalizer, LWCO, and supply header. Return will feed after the Hartford loop, also where the fill connection is, so filling and flushing the indirect coil will be easy. This also allow my to use a long 9” immersion well for the DHW aquastat. Assuming I flow 8-10 GPM can I pull the maximum boiler capacity on longer DHW draws (indirect rating slightly exceeds boiler) or will too much water bypass pass right through the bottom of the boiler?

2) I had planned on taking advantage of my 2 stage gas valve and downfiring it when it exceed 180F, max limit 190F. (Will adjust if it overshoots and starts steaming, drop header will help trap the heat. Goal was to prevent stop short cycling with the pre-post purge losses. Any concern with doing this.

3) Any issue with the Y strainer being vertical? I’m short on space to fit the strainer and pump before I’m up to the water heater, and leaving enough room for the return pipe in the same plane, so I can avoid a a bunch of extra elbows and cleaner look.

Any other tips? I’ve put a boiler drain on about every low point elbow. Actually below the water line I think I only used Tee’s everywhere except the Wye on the Hartford loop

JohnNY

Don't use the 2" return tapping to supply the indirect. You won't get hot water to the coil. You'll skate return water across the bottom of the boiler and never get the full potential of your heated boiler water.

mikeg2015

I don’t have any other spare tapping over 1/2”. I was worried about that. I can live without full output. Might short cycle a little is all.

What if I rolled the Tee upward so it pulled more from the top of the pipe?

Suppose I could drill and tap a 3/4” tapping just a little higher than bottom of sight glass in the same forward location on the side opposite the return. Will that work? Should be able to squeeze 7-8 gpm at least through there a get another 1-2 on the bypass with a higher delta t.

mikeg2015

Only other crazy solution is to use 1-1/4” brass bushing then use. 1”x 1-1/4” internal reducer so you can sleeve a piece of 1” copper that’s bent upward and mounted so it creates a pickup point that higher and more forward inside the boiler closer to the ideal
Location.

Also, 7/8” soft refrigerant line copper I could bend cleanly with a tube bender then it just inserts right in to 1”.

This is my own boiler at home so it’s a good place to experiment on my own time. Not a paying customer.

mikeg2015

Better idea. I clean up the old float LWCO I have and install that. Worked ok for low water trip but not for auto fill. Probably just needs new switch assembly. Then use that 3/4” tapping that my electronic is in now for supply. Put the return on the opposite 2” tapping.

mikeg2015

JohnNY said:

Don't use the 2" return tapping to supply the indirect. You won't get hot water to the coil. You'll skate return water across the bottom of the boiler and never get the full potential of your heated boiler water.

There weren’t any other tappings below the water line. I ended up sleeving a 1” copper pipe through a 1-1/4” fitting to a 1-1/2” brass bush to a 2x1/2” CI bushing. Fitting the end with a sweep elbow and the longest stub that I could slip in to elevate the pick up point. Only able ot get a 20-25 degree “approach”. SO 160F water with 180-185F boiler water temp. Probe location isn’t ideal either and probably getting some of the cooler water.

I thought about reversing the flow so the 1” pipe acts like a nozzle, but then I’d be pulling from the condensate return side, but still after the mud leg.

The other challenge is the sections are only connected at the bottom at the minimum water line and just connect together at the normal water line.

On the positive, as it’s setup now, I’m still getting about 75,000 BTU with 120F tank temp and 60F incoming water. SHould get maybe 90k BTU when it’s 45F water mid winter and 115F during long draws and more when it’s steaming. At 140F tank temps, it’s down to about 25-30k BTU.

I think I’ll leave it and just monitor performance before spending a couple hours un-sweating joints and cutting to reverse the piping. My previous 50 gallon electric tank is only 30,000 BTU, so it exceeds that all the time.

mikeg2015

Update. Brought boiler up to steaming. Got 195f supply 170f return and had to open the bypass to mix the temp down a little to be safe. So I was getting 100k BTU. Raised tank 10f in about 1 minute. I’ll take that.

I theorize when steaming there’s more convective current and violent movement of the water.

So in summer I’ll just over fill the boiler a little and live with less capacity.

JohnNY

That's great. Good results you've got there. Nice to be able to play around a little on your own equipment.