Built in Domestic Hot Water Coil?

Pacowy wrote:We used a DHW coil in an EFM 900 and it was awesome. In your case, I agree you're not going to get 6 gpm out of it in real time. The actual number depends on the inlet water temp and the rise needed. Using typical values you probably could get a max of 4.0-4.5 gpm; more than a modern showerhead and less than many older ones. You also start with the BTU's in 42 gallons of hot boiler water; between that inventory and the real-time capability it seems like a good producer for most normal DHW needs.

To prevent the heating load from giving you a cold shower (and stressing the boiler), my limited understanding of controls would be that it is important that the heating circulator shuts off when the boiler temp goes below the low limit setting. To ensure satisfactory DHW under those circumstances, you might need to adjust the low limit. For us 160 was a good setting but "your results may vary".

Agree that a tempering valve of some type is essential.

Mike

I think I may plumb it like hotblast did, going from the boiler to the electric hot water heater that way I will never have any issue? I will put a boiler bypass in though just incase.

I have a boiler bypass, along with all the correct shut offs and what not for servicing, and your going to want drains on each side so you can flush the coil if you ever have to.. the only thing I don't like about this Setup like previously stated was that you always have COLD in-coming water to your coil, unlike if you where to circulate the water through it with a bronze or stainless steel circulator, then you would be only pumping say 100-120 degree water into the coil, but your boiler may not have an issue, mine being 90,000 BTU when its 20 below zero and the garage and house are calling for heat, you don't want to use to much DHW because it will flip my boiler over lol

What don't you like about the side arm?

lsayre wrote:Rev. Larry, I fully agree that coils can work well, but the OP made mention of infinite DHW!

My Father once filled a small swimming pool for his Grandkids with hot water in early May.... because he could. LOL When I say small it was like 2.5 feet high and about 10 foot across. The coil we have is bigger than 6 but I'm not sure what it is. The boiler had no problems with it, about half way through he did turn off the boiler because it was too fired up.

swyman wrote:
I think I may plumb it like hotblast did, going from the boiler to the electric hot water heater that way I will never have any issue? I will put a boiler bypass in though just incase.

That's the way ours is setup but the electric hot water heater is not on. The only reason it's there is in case something happens to the boiler so you still have hot water. As long as you have 2 or 3 people taking a shower every day and other normal usage you should have plenty of hot water without it on. Setting up a bypass is simple though so plumb it in.

The boiler should be piped with a bypass to keep the temperature uniform when it sits idle.

You should also pipe a bypass around the coil, that way when the boiler is not is use you are not running cold water through it.

Lastly, as I mentioned before if you have hard water the coil will become less and less effective over time, until it plugs.

Always best to plumb your system the last way first.

hotblast1357 wrote: What don't you like about the side arm?

Side has been great, just seemed to have dropped off in efficiency last year. I would imagine there could be some scale or something inside that is effecting heat transfer. I just thought with this boiler I could get rid of some plumbing and that monster 70 gallon tank but from some of the replies I have on this it just confuses me more on what is the best route to go? I could just add another side arm on that water heater?

Rob R. wrote:The boiler should be piped with a bypass to keep the temperature uniform when it sits idle.

You should also pipe a bypass around the coil, that way when the boiler is not is use you are not running cold water through it.

Lastly, as I mentioned before if you have hard water the coil will become less and less effective over time, until it plugs.

The coil is bolted in and can be replaced but not sure what they charge for a replacement?

swyman wrote: but from some of the replies I have on this it just confuses me more on what is the best route to go?

Chevy Ford or Dodge?

it all depends what your boiler can handle, your DHW demand, and your budget.

i would say a coil can be the most demanding, and if your boiler is running flat out with calls for heat, and you take a shower or something, then your also hitting your boiler with COLD water from the well (city water) which really drags it down, but if you have a lot of boiler then it might not be an issue, we don't know how well your boiler is going to do with this design.. hopefully it does well...

i think for the most part everyone can agree that your best performance is from a indirect tank, with its own zone off your boiler, you can also have it as a priority zone so that it gets taken care of before your heat calls do.. but this is the most expensive also...

you already have a side arm, and a domestic coil, so I guess its whatever is easier for you to install, and what you want from it.. you could leave your side arm installed the way it is, and run your dishwasher and whatever else you have that people do not come in contact with off your coil, so that it gets HOT water for better performance, but that is getting into complicated piping...

it all depends...

You gotten recommendations to ditch the current setup and go with the coil in the boiler, replace the side arm, put in bypass piping and leave it there but valved out. My self I would go with the coil in the boiler and eliminate all the extra piping and valves.

But like everyone has said it depends on what YOU want to do.

The bad part here is ALL the ideas work. Which one do you want to do?

hotblast1357 wrote:i think for the most part everyone can agree that your best performance is from a indirect tank, with its own zone off your boiler, you can also have it as a priority zone so that it gets taken care of before your heat calls do.. but this is the most expensive also...

I don't think I agree with that. If you have a boiler with a big real-time output capacity (or in some cases a big reservoir of hot boiler water even if the real-time output capacity is limited) an indirect to me is an expensive middleman that adds a bunch of superfluous installation and operation requirements with no tangible performance advantage. If the boiler is up for it, a coil provides a simple, passive and generally economical way to satisfy DHW needs.

Mike

We have had some interesting discussions about this over the years...I should start bookmarking the threads so save me the trouble of trying to find them again.

My $0.02 is that tankless coils work very well in the right application. What is the right application you ask? Well that depends...on your water chemistry, water usage patterns, and boiler capacity.

If I had an EFM 900 like Mike used to or a Van Wert 1200 like Richard I would probably be using a tankless coil. I have a very nice water treatment system that nearly eliminates the problems with calcium deposits, and those boilers would have plenty of capacity to meet our domestic water needs. In reality I have an EFM 520, and it did not have enough capacity to power the coil correctly unless I cranked the feed rate up...which lead to the boiler overheating after a long heat call. I also had to keep the boiler at a higher temperature all the time, which made the basement pretty warm. Not a big deal in the winter, but it wasn't much fun in the warmer months.

Pacowy wrote:an indirect to me is an expensive middleman that adds a bunch of superfluous installation and operation requirements with no tangible performance advantage.

.

Compared to the price of a coil and mixing valve, my indirect water heater was about $500 more (little more than double the total cost). The installation is very simple on most hot water systems. Steam systems are a whole different story.

Pacowy wrote:

hotblast1357 wrote:i think for the most part everyone can agree that your best performance is from a indirect tank, with its own zone off your boiler, you can also have it as a priority zone so that it gets taken care of before your heat calls do.. but this is the most expensive also...

I don't think I agree with that. If you have a boiler with a big real-time output capacity (or in some cases a big reservoir of hot boiler water even if the real-time output capacity is limited) an indirect to me is an expensive middleman that adds a bunch of superfluous installation and operation requirements with no tangible performance advantage. If the boiler is up for it, a coil provides a simple, passive and generally economical way to satisfy DHW needs.

Mike

"but if you have a lot of boiler then it might not be an issue, we don't know how well your boiler is going to do with this design.. hopefully it does well..."

That's why I said this also..

In that part I thought the "issue" you were discussing was the coil dragging down the boiler, and not specifically comparing the performance of the coil vs. indirect. No worries, I think we're saying the same thing.

Mike

Pretty much lol