Kinda excited to rip my old oil boiler and piping out soon.

Dave Carpentier · 2:21AM

[Ok, Im only reaching for second base (the bank), but will be running home from there.]

25 years with a CI oil boiler running always-hot (from Oct-Apr) is a decent life.

IBC has a new(ish) controller in the units that is amazing. Im going with a VX-110. And a proper feeder tank, a dirtmag, even uponor stainless rack with flowmeters !

(sidenote- is getting excited about a heating system a sign of aging ? )

I have a nearly-retired good-people guy that Ive known for a long while doing the piping (copper, soldered) and venting (wall), otherwise a team effort. He's always been fair in the hourly work, and I think it's good to have a pro in the mix.

A couple of things Im debating on..

How large of a "large pipe" would I need ? I was thinking 2" brass tees ? Should the nipples be long to create more vol in the pipe ?

Will I be able to maintain ~7gpm in the primary loop while going through the 3/4" ports of the buffer tank ? The tank will be near the boiler.

I would appreciate any comments, suggestions, etc.

Kaos · 2:42AM

You can put the air handler on the DHW input on the boiler and program that to supply the 130F. You can probably get about the same amount of heat out of the air handler by running at at 2GPM. This would reduce the flow through your pipes, so well within the range 1" pipe and 1"NPT port on a standard tank. No need for 2" Ts for ~70k of heat.

Still keep the mix valve on the floor heat loop but it should now only run when the boiler is making the 130F for the air handler.

This will let you set the reset curve for your main heat source which is the floor heat and get that boiler into deep condensing range for most of the time.

hot_rod · 3:00AM

take a look at the Zilmet buffers, the oruce is very reasonably for a nicely insulated/ jacketed tank. I used the 7 gallon on my heat pump, the wall hanger is a nice feature.

The small one is 1”” connections I think the 14 and 21 gallon are 1-1/4

With all pumps running the header would like to be flowing a 2 fps or less. But it is not a dealbreaker if you are not spot on.

A 3 pipe buffer is possible with the Zilmet tanks, they have 4 connections

hot_rod · 3:06AM

example of 3 pipe buffer

Basically the return crosses the bottom of the tank so it engages the lower, coolest part of the tank

Which assures the tank is always engaged and the boiler efficiency will be driven by the cool return.
Ideal for heat pumps, but also a nice method for mod cons

Dave Carpentier · 4:12AM

@Kaos - The boiler's controller will take up to 4 tsats and control up to 4 circs (plus the primary), and you can set profiles for each 'load', and each load gets a priority value (1-100 kinda thing) where it time slices (or runs multiple if the temp desired is in overlapping ranges).

I would run the slabs at low as I can, but if the AH calls for heat it will bump the primary loop up to 130 or more and the mixer (MixCal) should do its job.

Im thinking of leaving some tees at the boiler in/out to potentially serve an indirect. That 'load' profile could hold the main primary loop circ off and use its own circ thru the boiler while cranking the temp way up. Not sure if I could manage DHW with a 110k boiler though ? I dont think I would step up the boiler size for this model as it's only a 6.5:1 turndown and I do have a few small zones.

@hot_rod - I should ask what small buffer tanks they have. I just assumed a water heater would be the more affordable option.

mattmia2 · 4:39AM

unless you have some insane dhw load, you can trade boiler capacity for tank size to get more capacity with a smaller boiler.

Kinda excited to rip my old oil boiler and piping out soon.

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