High delta T losing hot water

If your supply is 185 and the return only 110 you have nowhere near enough flow. The most likely culprit is still air — but bleeders won't help much. You will need to purge each zone of air individually.

1000 sq ft of heated space with a 90,000 btu/hr load doesn't seem correct?? Even for both units, 2000 sq ft that is 45 btu/sq ft.

Those look like Honeywell ZVs? Typically an 8 Cv valve, so no problem moving 4 gpm, even 8 gpm through them. I think the Amtrol tanks have a 3/4" coil, so 4 gpm is about all you will flow through them.

It looks like an older system, has it work properly in the past?

The ∆ you measures depends on the point in time that you measured it. Expect a high delta at first start up, as the system warms the ∆ could close to 20 or less. So you need to observe and measure that over a period of time.

Those Amtrol have a habit of liming up the finned coils inside, so performance drops off as that happens

This coil came out of an Amtrol with only 1 years of service. Granted the building had some pretty hard water. But performance dropped considerable.

The most common, on the shelf HW 8043 is an 8cv., in a 3/4 or 1”.

They do offer a 3.5 in a 3/4”

We mainly sell low Cv valves to OEM. I don’t think many wholesalers know about low Cv, nor do their purchasing agents. If they call in to order ZVs from us they get 7.5 unless they specify otherwise.

Even a 3.5 Cv flows 4 gpm with a tiny, maybe 1.5 psi pressure drop if that was installed by mistake.

The ZVs in the pic look like 3/4”

8’ of head he still gets 8 gpm from an 007, that should cover an indirect, and all 3 zones even if that is a 45,000 btu/hr load?

Something else is going in.

8’ of head he still gets 8 gpm from an 007, that should cover an indirect, and all 3 zones even if that is a 45,000 btu/hr load?

Something else is going in.

What is going on is the fact that the 007 will never put out anything close to 8 GPM when the resistance of the zone valve is added to the resistance of the piping to and from the pump which is then added to the resistance of the coil in the indirect. The coil resistance is HUGE by your chart and the current flow rate through the indirect is not more than 4 GPM under any condition. This is why the DT is huge.

In order to get a decent flow rate, a larger pump is required together with 1" piping to and from the pump.

@Staddy said:

"3 gpm x 6 zones is 18 GPM @ 6 feet of head. Using this data a pump chart indicates my Taco 007 is not enough pump."

Seems to me you answered your question right there. A 007 can flow 18 gpm only if head is 3.5 feet or less. You have about twice that head across your indirects and shortest 100' heating loop, and closer to 8 ft head across your longest 130' heating loop. So if all zones are calling for heat at the same time, including indirects, you won't get 3 gpm through any of them.

If you do as @LRCCBJ says and add another 007 to each of the indirects, that means your existing 007 now only has 4 heating loops to feed, so the flow rate through that pump only needs to be about 12 gpm at a bit over 6 ft head, which the 007 can do. Now each of those loops is getting about 3 gpm.

Then your indirects have plenty of pump and can get the needed 4 gpm each at heads up to 9 ft, assuming one 007 per indirect.

He claims to have this much boiler to work with 118K, so why even talk about 18 gpm flows? Although a 206 should be more like 145 out? If it is in fact 116K out maybe it is a 205?

Even if both indirects get prioritized he barely has enough boiler to give them 4-5 gpm each, if 118K is the boilers output. The piping and ZV he has could move that amount of btu/hr to the tanks

We really don't have enough info to suggest the fix if he has purged properly as suggested.

My suggestion is more data collecting and actual observation and onsite trouble shooting.

I think you have a similar type of building, does a heat load of 90,000 btu/ hr sound reasonable for a 2000 sq ft duplex? 45 btu/sq. ft

These are one bathroom units, how much DHW is needed, expected, required?

What is the boilers actual output? Is it a 205 or a 206?

How many feet of fin tube in each unit?

Have the tenants been in the units for some time? Are these new problems, or have they always existed?

If the indirects are not on priority, that could be a simple, good upgrade if you want to maximize DHW production. From the pic we have, it looks like each zone has a good purge point.

I'm not convinced repiping or pump and copper upsizing is the next step with so many unknowns?

They amount of heat emitter would indicate how many BTU can be moved into the space. Any boiler output beyond that is always available for DHW recovery. If the units maintain temperature with the heat emitters installed, you could work the numbers backward. 60' of fin tube could be adding 30,000 btu/hr for example.

So maybe two units = 60,000 at design condition, 58K available for DHW.

118K boiler output operating at a 20∆ would need about an 11 gpm flow.

If there was a design done, ever, the boiler could be sized to cover a heat and DHW load at the same time?

I'm not sure what the Amana ERGW0012 is? A furnace and AC unit?

And that would be the ideal operating condition on a design day. The heat emitter output perfectly matched to the boiler output.

The report of a delta T of 75 across the boiler, with 185 supply and 110 return, is consistent with 118,000 BTU/hr output into 3 gpm through one of the indirects.

And 3 gpm through the indirect seems consistent with the 007 pumping through the indirect only. (Indirect manual says 6 ft head through the indirect, and then if there's 3 ft head through the zone valve, that's 9 feet total, at which point the 007 is pumping 3 gpm.)

if it is dumping 118,000 btu/hr in to the indirect it would take about 15 minutes for that zone to satisfy assuming 90f rise

the delta t would fall if it weren't dumping the heat, assuming the heat exists in the first place.

that Amana model number shows up as a furnace?