Heat flow HF 40 vs Pure Pro 40ss

wnelsoniii · April 2

Im looking to add a indirect water heater to my 2 year old pure pro boiler. So far I've had two contractors quote me two different heaters. Which brand has the better indirect water heater?

thanks for your help!

kcopp · April 3

I have used a few of the new Pure pro SS. Appear to be pretty solid. Its an Amtrol rebadged.

Another option would be a Bradford White SS. Lifetime warranty.

Kaos · April 5

People tend to overestimate the efficiency of an indirect. In the best case, they run about the same efficiency as a decent power vented stand alone gas water heater but cost about 2x to install. Around me the combination of boiler and power vent is the most common.

If you want cheap hot water and don't have a big tub to fill, heat pump water heaters are the cheapest to run and tend to be the least expensive to install especially in places with utility incentives. There are now versions that can be connected to a 120V circuit as well.

pedmec · April 5

I don't think anybody overestimates an indirect. It's a fact. The numbers don't lie. A power vent water heater can never give you recovery of an indirect. its not even close. A superstor SS45 with an a properly sized boiler and circulator can recover a gallon of water with a 100 degree temperature rise in 18 seconds. Showed me a ny direct fired water heater can match that. And while your at it find a direct Direct with a lifetime warranty.

Ill state it again as i have multiple times. I have an SS60 with a taco 0010 circulator and had 5 people showering back to back and at the same time over 2 bathrooms in a 45 minute window. Show me a any direct fired water heater that could do that. (2) 2.5 gallon showers heads. And that is without any mixing valve to aid. 130 degree tank setpoint.

Your indirect is as efficient as the boiler its tied too. I don't know any direct fired water heater other than the on demands that are that efficient as an indirect.

hot_rod · April 5

https://forum.heatinghelp.com/discussion/comment/1893753#Comment_1893753

Efficiency and recovery are different

The efficiency of an indirect cannot be greater than the boilers efficiency, a bit less as every heat exchange costs some efficiency loss. So I’d say low to mid 80% maybe?

Recovery is about the btus you can deliver to the coils of the indirect. If you have an 80,000 boiler you generate quicker than a 37,000 water heater

My though is a tank with a 4” hole through the center would be a bit less efficient than a good cast boiler

A power vent WH would have less standby loss compared to a standard wh, but I think the heat exchange in the tank would be similar efficiency

I’m sure someone has tested the various tank fuel-water efficiency, Larry may have some data?

I think a condensing tankless wh would be in the running for performance and efficiency.

Kaos · April 6

This has most of the water heater options:

https://web.archive.org/web/20130828221141/http%3A//www.nora-oilheat.org/site20/uploads/FullReportBrookhavenEfficiencyTest.pdf

Look at Table 2 summer efficiency. Not only does efficiency tank since all the heat bringing the boiler up to temp is lost, but now that lost heat becomes part of your cooling load.

As for recovery for indirect, lot also depends on water quality. The coil on mine scaled up over time and recovery time significantly increased. It got to the point that I would have to wait for the tank to recover before I could fully fill a tub as it could no longer keep up.

pedmec · April 6

I never said that an indirect is more efficient than the boiler. I stated that the indirect is as efficient as the boiler it is tied too. Losses are from the supplies and return outside of the tank exposed to the ambient air. The heat transfer in the coil is 100% because water to water heat transfer is 100%. There is no loss in energy transfer between the water in the coil to the water in the tank. The losses would be in the boiler and piping.

hot_rod · April 6

the heat transfer in an indirect involves the tube also. The type of metal, speed of the fluid, surface area of the coil, condition of both the inside and outside of the tube. The transfer, even at best of conditions can never be 100%.

The coil is generally in still water in the tank, so the heat exchange drops as the water around the coil warms.

The finned copper type indirect coils are about the best transfer, but can suffer from fouling and scale build up between the tight fins. Great the first few days, but performance and efficiency drops as the surfaces foul.

A flat plate HX can get into the high 90% efficiency as you have two moving, counterflow and turbulent flows, a lot of surface area and a thin metal wall thickness.Properly pumped the high velocity turbulent flow condition helps keep the surfaces clean compared to an indirect coil. But in all cases the minerals in the fluids will attract to the hot metal surfaces and reduce transfer efficiency over time. Demineralized water on both sides would be the only way to avoid this.

Tank type water heaters suffer from the same scaling, in a tank with low flow velocity the minerals layer up at the bottom, directly over the burner, so the tank heat transfer suffers the same conditions. Eventually a thick layer of scale leads to percolation, wher the flame heats the water via the mineral layer. With hard water conditions several inches of sediment in the bottom of tank type water heaters is not uncommon. This caused heat transfer to drop like a rock, pun intended😉

Kaos · April 6

Lets not mix things up. What @hot_rod and @pedmec are talking about is temperature efficiency. This is how close the tank temperature is to the heating loop, something hydronics nerds care about. This does not have any effect on thermal efficiency, 100% of BTU from heating loop is transferred to the tank.

When folks talk about efficiency is about BTU in to gallons of hot water out.

hot_rod · April 6

Heat flow HF 40 vs Pure Pro 40ss

Comments

Categories