KA6 and DHW?

I don't want to reinvent the wheel here. I know a number of you are and have been successfully supplying your DHW using your boiler for some time and would really like to learn from your experiences

Concerning using my newly installed Keystoker KA-6 with DHW coil to supply our DHW, I've been considering replumbing most of our house with PEX at the same time, using homeruns and manifolds.

I was considering a main mixing valve near the boiler to limit water temps to 140F, for washing machine, dishwasher, and utility sinks.

Then adding one of those new thermo controlled fixture for the tub/shower to prevent scalding.

I want to have our electric hot water heater available as backup. I'm okay with 3 way valves on this if necessary.

The other big piece I have, but not sure we'll use is an indirect hot water heater I added several years ago for the oil boiler to make DHW. I understand now that was a mistake, installing the new electric DHW (worked out okay as we took the hydronic offline for a couple of seasons while remodeling the house, long story).

I don't know if it makes sense, or is feasible, to use the electric hot water to boost water as needed?

Is it wise or foolish to plumb boiler DHW coil hot water through the electric water heater, supplying it at 140F and setting it at 120F? If so, do I need some sort of circulator between them for tank standby losses?

We have spring water that supplies about 15-20 psi gravity and boost it with a pump and expansion tank to 30-40psi. Part of our consideration for water supply includes the ability to get basic low pressure water when the power is out.

Not sure if that is a problem/risk with the DHW coil in the boiler or not? Don't know if that will interfere with the mixing valves or not?

Any tips or suggestions? Gotchas to watch out for?

Thanks, all!

Don't everyone post all at once

Lacking any advice to the contrary, I think I'll reactivate the indirect hot water heater on its priority zone, shut off the electric hot water heater and turn off its valves, and see what happens.

The gist of what I've been reading is that indirect HWH is superior in performance and efficiency but more expensive to install.

Before our coal boiler the oil boiler running in the summer for hot water when prices of oil skyrocketed and our remodel started prompted a reinstall of an electric HWH.

I had hoped for some advice and opinions on which way was better and maybe some suggestions, but I know everyone is busy with the cold and snow, too.

Icy roads cancelled my trip to the capitol today, so maybe I'll do this instead.

I think of the indirect as being a "middleman" that may be needed in some circumstances, but also adds constraints to DHW production relative to using the coil in the boiler. If you already have that coil and if it's not a big deal to pipe in a tempering valve, you might want to try that and see how it works for you. That option was available in our old house and we were very happy with it.

Mike

The indirect is plumbed before the electric, so I'll just have to add a couple of Tees and valves for a bypass of the electric and try using the indirect first.

Thanks, guys.

Pacowy wrote:I think of the indirect as being a "middleman" that may be needed in some circumstances, but also adds constraints to DHW production relative to using the coil in the boiler.

Mike, what kind of constraints would the indirect have? I've read some about the coil?

Thanks.

BTW, decided to cook up some channel catfish from the freezer tonight instead of working on the hot water. It's going down to 2F here tonight. I'd like to drain and flush both tanks before making the full change, so probably tomorrow as it will be in the mid to upper 20's.

Hope everyone else is warm inside, too! A very welcome change for us

CoalisCoolxWarm wrote:

Pacowy wrote:I think of the indirect as being a "middleman" that may be needed in some circumstances, but also adds constraints to DHW production relative to using the coil in the boiler.

Mike, what kind of constraints would the indirect have? I've read some about the coil?

Thanks.

Initially, the coil in a KA-6 can supply its rated capacity of 5 gpm by drawing from the BTU's in the 55 gallons of boiler water. After that, the coil can extract BTU's as fast as the stoker makes them, up to the throughput capacity of the coil. In a KA-6, the stoker running flat out produces a gross boiler output of 144k btu/hr, which equates to about 3.5 gpm of DHW that the boiler could produce all day long in real time.

An indirect starts with an initial reserve, but after that extracts BTU's based on the flow of boiler water through its heat exchanger. By definition an indirect can't extract more than the stoker produces; as a practical matter it sometimes produces less than that.

Mike

All that is fine if one is running a car wash.
But for a residence it is a non issue.

Using our electric HWH, my teenage daughter gets a hot shower. If my wife waits 45 mins, she runs out near the end of hers. She like very hot water. I have to wait an hour or two, which often means I take a shower in the am. Not bad, except during these cold days.

We would be thrilled if the new setup would allow us all to shower in an evening, almost back to back, and each have plenty of hot water. Or at least a much faster recovery. Is this a reasonable expectation?

Other loads are one or two laundry per week using hot water, others are cold or warm washes, and nightly dishwasher, then hand washing and utility sink for daughter's chickens (hot water to thaw everything out). Maybe a hand wash of a special pot or two throughout the week.

Right now the zone to the indirect HWH is 1" copper, off the 1-1/4" main loop, fed by the coal 1-1/2" parallel boiler (other boiler is oil 1-1/4" for backup use).

Does an indirect HWH have "recovery times" like an electric, or is it "bulk btus from stored water, then based on capacity" ?

I did look this stuff up and work something out, but it was before my last big medical problem and I seem to have lost those memories. Somewhere I had a notebook with it in, too, but can't find it either. I can usually recover most memories, but not successful so far. Sometimes it feels like a "stranger" did the earlier work

Anyways, I really appreciate the help figuring this out. Family really likes the KA-6 so far and I don't want to disappoint them by doing the DHW "wrong" (not that there is a right and wrong, but which way meets our expectations)

1" pipe and a circ. pump of sufficent flow will recover to do those back to back showers and such.

We can go back and forth on this all day, but the answer already exists.

Look up your indirect's specs and it is all spelled out for you there.

I'm not an expert on this, but this is how I have my setup. I use my coal stove coil to heat my electric water heater. I have a circulating pump between the stove and hot water tank. I keep the electric heater ON just in case my stove does not provide enough heat during idle. When the stove is at high burn, the water lasts for 2 to 3 showers because of the tempering valve adding cold water to the mix. Hope this helps

McGiever wrote:1" pipe and a circ. pump of sufficent flow will recover to do those back to back showers and such.

We can go back and forth on this all day, but the answer already exists.

Look up your indirect's specs and it is all spelled out for you there.

That was my next step, to clear things out of the way and take some pics of the indirect HWH. I did want to be sure the 1" with 007-F5-IFC Taco was enough to fully supply the indirect, too.

I'm sure it can get boring to go over the same ground. The searches I've done here and other places didn't quite answer the questions in my situation. Besides, I trust the experience and advice from the collective brain trust on this board more than most manufacturer's installation suggestions

One thing I am trying to do on my end is post lots of pics. Figured not only can that help the next fellow with questions, I know we all enjoy a little "boiler p*rn" once in a while LOL.

Thanks for your patience. Look for pics when I get back later today.

Rob R. wrote:An electric water heater relies on storage since most of the elements are only 5000 watts, and operate one at a time. 5000 watts is about 17,000 BTU's per hour. An indirect of equivalent storage capacity will often have 4-5 times the recovery rate depending on how it is piped and what size the boiler is.

Another item to consider is water hardness. Any type of water heater will collect mineral deposits if fed hard water, but a tankless coil will be the first to have a noticeable drop in performance.

Great answer, thanks!

We have spring water, not hard at all. We filter for limestone sediment, which occasionally can get through as it regens or power outage, etc.