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

Dave Carpentier

[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

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

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

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

@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

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

hot_rod

https://forum.heatinghelp.com/discussion/comment/1903490#Comment_1903490

You can use the formula for sizing a buffer. With a modulating boiler the buffer will be much smaller than a normal modulating type buffer/ boiler or heat pump.

Once you start looking at maybe 20 gallons or more, the electric water heaters prices look good. Just because millions are manufactured a year.

Those Zilmet at those prices will be close or less than a small 6-20 gallon electric tank. Plus you get the larger connections, wall bracket, etc.

A 110, evennan 80k boiler should be plenty of DHW for most residential use. That is 2 to 3 times the btu of a basic fired, tank water heater.

Dave Carpentier

@hot_rod - my system works out to 14g buffer, with an oem 10min run time, my smallest zone, the unit fully turned down and filling the tank to a 20f differential. The 12g water heater was a close fit, keeping some savings.

Im not sure what affect increasing the delta in the tank has, as anything higher than the mixer set temp isn't drawn at the same rate while the mixer blends in it's own return water. Confusing..

hot_rod

If you change the delta when you plug into the formula you see the result. The wider ∆ increases the drawdown from the tank. Or decreases tank size.

However when the tank is pulled down to that lower temperature you need to be sure it can adequately supply heat to zones that are calling.

So the high tempeature zones, how low of a SWT can you send them? You don't want to run lower than that. The ODR will handle how and how much the SWT can lower on lower heat load conditions..

You could also raise the high temperature end, so run the buffer to 180 or 190.

But if you don't need that high temperature, no good reason to do that with a mod con.

If you had a wood fired or pellet fired boiler you might run the tank up to 190 to get a long hot burn cycle, maybe 140- 190 for a 50°∆. And you get more draw down from a hotter tank, more energy is stored.

20∆ is just a number someone came up with for hydronic design. It could be 14, 24, 31, really any ∆ can be used for design.

Panel radiators are commonly designed around a wide 30- 35°∆. They give off much of their heat as radiation, and the low end helps increase a modcon efficiency.

The boiler and tank piping is important!

Your most valuable hydronic water is the water you just paid to heat. Or cool. Send it directly to the emitters.

If you are heating with fuel oil currently, that is precious. You want to avoid any piping or tank configuration that blends that down before it hits the emitters. That is why the direct to load tank piping, and parallel P/S loop piping is so important.

Dave Carpentier

Re- High temperature zones. When the air handler (2nd floor) calls, the Supply Temp (buffer tank sensor) target will change from ODR low temps (In floor (main floor) heat) to a set temp of ~140. At the end of the AH call (or if it's a long call that gets time-sliced back to In-Floor) the buffer will be at 140.

However. its fairly rare that the AH calls for heat. We have returns in all the In-Floor rooms (keeps the air circulating, which I think is the bane of in-floor), so the house mixes pretty good. When it's -20f or so the AH calls for heat.

The old oil boiler runs 130-160 with the TT strapped "always hot" for 25 years. The in-floor mixes down to about 105 and the AH draws directly. Im fairly convinced that the lower heating bills with this new setup is going to shock me about how much Ive been paying for heat.

Heat stranded in the utility room didnt really bother me much. It's still inside the structure and in my case the util room is open to a drop ceiling so it warms the 2nd level floor a bit. What does make me wince is the loss up the flue from an always-hot boiler.

hot_rod

It look like that boiler has a good zone control, temperature control for multi temperature systems. That seems common on all the higher models these days.

It’s possible 130 or so is as high as you need to ever run the boiler. Yes that will save some fuel costs over the old boiler with the fixed 160 setpoint

Is the AH in a freeze prone area of the home?

Dave Carpentier

@hot_rod - The AH is in the util room on the main floor, hanging from the joists above, so it stays at house temp. It will be interesting to see how much cooler my util room become with the new setup. Maybe I'll hold off insulated any of the new copper until I live with it for a while.

If I do go with the water heater buffer (3/4" ports) , could I get away with 1.5" tees as the Large Pipe ? If I ever add a heat pump (wife wants a/c) I would insert the heat side at the Large Pipe junctions, if that might affect the rule of thumb for Large Pipe ??

hot_rod

what I have done is increase as close to the tank as possible

You can get a 3/4 male dlip adapter, solder it into a 3/4 x 1-1/2 copper bell reducer

But that is a big step up. A tank with larger ports would be better

So the heat pump just tees into the header next to the boiler

Most of the a2whp have a function in their controller to call on a boiler when the hp doesn’t keep up, or the cop drops