New boiler: tankless coil or separate hot water tank?

Dhertz

We are replacing our boiler and are trying to decide between these two options. Currently we have a boiler with tankless coil that is about 35 years old. We've never had a problem running out of water, as it's just three of us (me and wife and young child). We usually use cold water in the washing machine, and each take a normal shower in the morning, daughter takes bath at night. I understand one benefit of the separate hot water tank is that you don't run out of hot water, but that doesn't seem to really matter to us. The main question is about the potential savings. We've been told that simply replacing our existing boiler with a newer, more efficient one of the same type will save us a lot on energy cost (we are on oil heat), but what I really want to know is, what percentage of the cost of our hot water usage will be offset by savings from increased efficiency due to a separate hot water tank. I estimated that about 20% of our current oil cost (average over the year is about $250/month total) is hot water, so that's about $50/month average. The cost of the additional hot water tank is $2500, so I figure if it cuts our hot water cost in half, we'd pay about $25/month, and it would take 100 months or about 8 years to recoup our initial $2500 investment.

In reading about this online, it seems there is general agreement (although not by everyone) that tankless coils are outdated and inefficient, and separate hot water tanks are much more efficient. But this only matters to me if it will actually save me money in the long run. I'm hoping someone here can shed some light on this given the numbers I laid out.

One additional item he recommended is to increase efficiency is a Beckett Heat Manager - I read about this but I don't really understand what it does. Also hoping someone can recommend whether or not this is worth it for $275.

Thanks in advance!

John Ruhnke

A separate hot water tank will save you a lot in fuel. You can pipe from the coil in the boiler to the tank. Or get a tank with the coil in it. The savings wont happen unless you use the right control strategy. You need to have the controls set up for a cold start boiler. To save even more money you could use outdoor reset and do a post purge to the tank to remove the energy from the boiler after the burner shuts off.

Not only will this save you huge money in the summer months but you will have huge savings in the winter months too. Avoid a separate stand alone hot water heater.

Dhertz

Hi John,

Thanks for your reply. I want to make sure I'm describing this correctly, so I'm just copying and pasting the proposal from the HVAC guy here. Given all this, and the fact that we seem to average about $50/month in oil during the summer (when we're only using oil to make hot water as opposed to heat), how soon would you expect us to recoup our initial $2500 investment?

***************
Option 1- Install new boiler with tankless coil and all new controls as indicated above.
Total cost complete $7400

Option 2- Install new boiler without tankless coil, instead adding a heating zone to the boiler to connect to a 60 Gallon hot water maker. This is a tank that will sit to the left of the boiler. The tank is manufactured by HTP. The model# is SSU-60.
The total cost for a new boiler with a 60 gallon tank as described above $10100

**************
(About the Beckett Heat Manager)
If we were to install an additional time for $275.00 called a Beckett Heat Manager, that device claims to save up to 15% on your bills as it prevents the boiler from operating as it would without the control. Specifically, it holds off the boiler for longer, behind the scenes, and the occupants are unaware, but by holding it off longer, the run cycle will be longer and more efficient. It is very inefficient to have short starts and stops (short run time/ shot cycling). This creates a definite efficiency increase.

I recommend you install this device as it boasts a guarantee that it will save you fuel savings.

Dhertz

Also, can you explain what a "cold start" means? Also "outdoor reset" and "post purge"? Thanks!

John Ruhnke

Option Two is a good option. HTP is a good company. The Becket Heat manager will save you money in fuel. A Tekmar outdoor reset control with post purge to the hot water heater will cost more money but save a lot more in fuel.

To save energy, the goal is to run as low a water temp as possible in the boiler. Also after the burner shuts off you want to pull the extra energy out of it. In the summer the boiler should stay cold unless a call for hot water. Boiler manufacturers have min return temps so you cant exceed that.


Tell the heating guy to make sure the flue gas is high enough not to condense. Have a Combustion Analysis done. They need a meter for this. It costs around a $1000. The lower the o2 reading the more money you save in fuel. The lower the stack temp the more you save in fuel. First you lower the o2. The stack temp automatically goes up when that happens. Then you work on lowering the stack temp.

John Ruhnke

Post purge is pulling the energy out of the boiler after the burner shuts off. Outdoor reset is measuring the outdoor temps and adjusting the boiler water temps as low as possible based on outdoor conditions. Cold start is eliminating the minimum boiler water temp setting on the boiler control so when the boiler shuts off it stays cold until another call for heat or hot water.

Dhertz

Thank you for all that info, I really appreciate it. Can I just ask simply, based on my numbers, how many years would you expect it to take to recoup the extra $2500 in savings with a separate hot water maker vs the tankless coil? I get that it’s more efficient as a general rule but if it will take a very long time to recoup that investment then it may not be worth it for us.

John Ruhnke

it depends on how good a job the installer does and the equipment he chooses.

John Ruhnke

It also depends on how bad the existing equipment is operating.

Dhertz

I appreciate all that, but I'm trying to get some idea of best case scenario, as I have no idea what's even possible in terms of increased efficiency with a separate hot water maker. Could it be 50% more efficient than the tankless coil? That seems like a lot, but it would take that much of an increase to recoup my initial cost in about 8 years.

So, is it possible to have some idea of how much more efficient the separate hot water maker could be? I asked the HVAC guy this same question and he could not give me an answer, which is why I came here to ask. Maybe what I'm asking is just not possible to answer, and I just have to decide whether or not it's worth taking the chance that it will pay for itself in a reasonable amount of time. I'd prefer to have an idea going in, though.

Again, thanks so much John for all your help with this!

John Ruhnke

When I ran my business I would examine the old equipment and compare that to the new equipment design I had in mind. I would then give the client a % saving range. I would guarantee that in writing with a certain amount of cash back if they didn't hit said savings. Nobody ever asked for the money back or claimed the savings were not hit.

I can't do that for you because I don't know the condition and design of the existing equipment or the knowledge and quality level of your installer.

John Ruhnke

P.S. Most didn't measure. But some did. Most of the time they could tell they were saving but didn't know how much it actually was.

Dhertz

I understand what you're saying. But shouldn't I be comparing the two options that he is presenting me, both of which would involve new systems? If so then what does it matter what my current system is?

I've already been told that a new boiler should pay for itself within 5 years. So what I'm trying to figure out is, given best case scenario like the best installation and best equipment and best everything, is it possible to recoup my $2500 (that is in addition to the $7500 I'm already committing to for a new boiler) in a reasonable amount of time?

Sorry if I'm asking the same thing a dozen different ways - you obviously know what you're talking about so I'm hoping you can help inform my decision here. So far I'm still not clear on whether it's worth it to spend an extra $2500 without knowing whether I will recoup my investment.

HVACNUT

No pricing is discussed here guys.

Dhertz

Ok sorry about that...first time posting here, didn't know the rules. Without discussing specific costs, I guess I'm still hoping to get some idea of even a percentage increase in efficiency between these two options. My HVAC person said a new tankless coil boiler could be 12% more efficient than my current boiler. I was hoping to get that kind of info about having a separate hot water tank, but maybe it's just not possible to even hazard a guess.

John Ruhnke

Dr Tom Butcher did a study at Brookhaven labs a doe lab and found the worst oil boiler performer to be the boiler with a coil in it. The system 2000 by energy kinetics was the best performer.

The buderus boiler with its controller was found to save around 40% over the boiler with coil in it.

Dr Tom Butcher did not do everything I did.

John Ruhnke

I visited Tom Butcher at his lab and we discussed his results. I have taken many classes and read many studies involving energy efficiency. I learned many rules of rules of thumb over the years. As an example. For every 2 degrees you drop the water temp you save 1% in fuel. I can look at the old equipment, how dirty the fire chamber is, stack temp, water temp, control strategy and more and tell how efficiently it runs. I then can add up the all the little things to be improved or changed. Compare with past studies and past real world results. That is how I come up with the saving range. I dont guess.

John Ruhnke

Dont get the boiler with the coil. But if the installer gets you a seperate tank like in option 2 and installs a control that maintains temp all year round by bouncing off a low limit on the aquastat it wont matter. Its not the boiler and coil that caused the bad fuel costs. It was the aquastat control that cycled between a low and high limit all year long. A boiler with a coil is set up that way. Otherwise you would get cold water in the first 10 minutes you used the hot water as you waited for the boiler to recover.

So it is important to hire a good hydronics guy that understands all this. Option 2 if set up properly with the right boiler, should be able to save you around 40% in fuel according to the doe study.

John Ruhnke

save you 40% in fuel compared to the Boiler with coil in it. Not compared to the existing equipment.

Dhertz

Thanks so much!

Dhertz

John, when you wrote this...

John Ruhnke said:

Dont get the boiler with the coil. But if the installer gets you a seperate tank like in option 2 and installs a control that maintains temp all year round by bouncing off a low limit on the aquastat it wont matter. Its not the boiler and coil that caused the bad fuel costs. It was the aquastat control that cycled between a low and high limit all year long.

...are you referring to something like the Beckett Heat Manager? That was part of his proposal.

HVACNUT

> @John Ruhnke said:
> Dr Tom Butcher did a study at Brookhaven labs a doe lab and found the worst oil boiler performer to be the boiler with a coil in it. The system 2000 by energy kinetics.
>
> The buderus boiler with its controller was found to save around 40% over the boiler with coil in it.
>
> Dr Tom Butcher did not do everything I did.

The System 2000 by Energy Kinetics does not have a tankless coil and as far as I recollect, took the BNL first place trophy for actual efficiency. I like Buderus oil boilers but the EK is the Ali of the BNL tests.

@DHertz dont be so concerned with the recoup as much as reliability and efficiency. No tankless coil. Not if you want it right. What boiler and burner are being proposed? The Beckett Energy Manager is obsolete compared to the aquastat controls you get automatically with most boilers. Like the Hydrostat 3250 Plus or the Beckett Aquasmart. These controls offer ODR when used with an indirect water heater, cold start, and other cool stuff.
I would suggest you take a look at the Energy Kinetics EK-1 Frontier, but the contractor must be a certified dealer. Maybe get some other estimates, then pick the one that actually does a heat loss calculation.

Dhertz

HVACNUT, he is proposing "Weil Mclain Oil Fired Hot Water Boiler with or without internal tankless coil for domestic hot water" - WGO5 or WTGO5. The water heater is HTP SSU-60. Are these going to give me as much increased efficiency as possible? Do I not need the Beckett Heat Manager with these? Sorry if my questions seem ignorant or naive...I'm trying my best to understand all this stuff! I so appreciate your help!

STEVEusaPA

First of all you need a proper heat loss performed before selecting a boiler.

Unless you have some very extenuating circumstances, I’ve never seen a 5 section boiler in any house in the Philadelphia area under 10000 sq ft.

Proper sized boiler will save you money.
An Energy Kinetics boiler with a flat plate heat exchanger and a separate small 30 gallon storage tank (if you deem necessary) will be the most efficient operating boiler, period.

Take the Heat Manager out of your brain.

Select a new installer, one who understands modern hydronics, modern controls, modern components, proper sizing, and modern (correct) methods of piping.
Or better yet, call Energy Kinetics, have them locate an approved installer in your area to give you a quote.

John Ruhnke

According to Tom Butcher the boiler with the coil is the worst performer by far, big margin. That is because it runs all the time. Even in the summer it bounces off the low limit. You can have a boiler with a coil in it if you pipe it to a separate storage tank and turn the boiler into cold start. In fact I have done that upgrade to existing boilers with coils and saved the client a lot of money. Energy Kinetics was the number one boiler. The Buderus was number 2. But the difference was real tiny 1 or 2 percent. Also Dr Tom Butcher could not simulate outdoor reset very well in his test. I feel in the field the Buderus using outdoor reset would win. Also the Buderus lasts longer and is more reliable. For me it is just a choice. I think the Energy Kinetics boiler is a very good option too.

John Ruhnke

@Hvacnut. You are right. It was a misprint on my end and I corrected it in the next post. I stopped typing too early when writing about the system 2000. Brain fade. My brain had already moved on to the next sentence with out finishing.

The sentence said "The system 2000 by energy kinetics."
I meant to say "The system 2000 by Energy Kinetics was the best performer."

I did not see a way to edit the post.

ratio

@John Ruhnke, on the grey title bar of your post, hover over on the right side, a tractor tire will appear. That's the edit button.

John Ruhnke

Thankyou Ratio. I found the edit button and went back to correct a few things. Things will be better in the future now.

Erin Holohan Haskell

Thanks, guys. Here are some more tips for making post edits, etc in the forum: https://heatinghelp.com/forum-user-manual