View Full Version : Aqua Booster vs Indirect Water Heater Tank

02-06-2007, 09:43 AM
i am looking at buying a house in CT with a 1990 New Yorker oil fired boiler (dry based - 133000btu) that has baseboard heat (2 zones)and a tankless coil for domestic hot water. serviced yearly by the oil company since they installed it. it looks in good shape but the dometic hot water is inadequate for me.

i tested the sytem and if you turn on two hot water faucets at once, the pressure drops and the water flows much slower than when only one hot faucet is open.

would an indirect water heater (50gal) be better than using the old coil with a booster? i want to be able to use two showers at once or at least one and run the dishwasher without running out of hot water.

02-06-2007, 09:51 AM
So the problem is not inadequate flow, but a shortage of hot water? If that is the case I would feed the new 50 gal WH from the existing tankless coil, it seems to me that's the way it should have been done from the very begining.


02-06-2007, 10:19 AM
there is no tank at this time so i'm not sure what you mean by "that's the way it should have been done from the very begining."

why would i need to use the old coil if i install an indirect?

02-06-2007, 03:44 PM
The tankless coil likley has a flow restrictor to help ensure you can get hot water out of it (think moving your hand over a candle - move it slow enough, and you get hot - move fast and you hardly notice it - same idea with the water).

Yes, an indirect would work fine for this. If you really want two showers running at the same time, you may want to control the boiler zones with the indirect as a priority zone (when it calls for heat, it won't let the other zones run). That's basically what I just had installed.

Depending on the temperature you set the indirect to, its design, and the size of the boiler, you can figure out the first hour draw from your system with the different tanks available.

02-07-2007, 07:34 AM
Yes, an indirect would work fine for this. If you really want two showers running at the same time, you may want to control the boiler zones with the indirect as a priority zone (when it calls for heat, it won't let the other zones run). That's basically what I just had installed..

could you be more specific on parts and controls, brands and ballpark costs for what you installed?

Depending on the temperature you set the indirect to, its design, and the size of the boiler, you can figure out the first hour draw from your system with the different tanks available.

example please?

i guess the flow restrictor is might be the problem with the pressure drop along with only luke warm comming out while the two faucets are open?

02-07-2007, 05:30 PM
A priority zone is one that gets heat - typically all of it, when it asks for it. You need a boiler that has it built-in, or an add on control that can do that. One place you can read a little about it is probably www.taco-hvac.com (http://www.taco-hvac.com). I'm sure Honeywell also makes controllers, and others as well.

Go to the website of any of the brands of indirect water heaters and first hour draw is one of the specs listed. I opted for a SuperStor Ultra - SS tank and coils, good insulation. It depends on the size of the tank, the temp setting, and the capacity of the boiler how much hot water and at what temp you can get from a tank. One thing to also look at are standby losses - i.e., how much the temperature drops/hour. This is a good indication of the quality of the construction and insulation. Some are as low as 1/4-degree per hour. Course, if it is sitting in an unheated, cold garage, the delta-T will be higher, and you'll lose more energy than you would in a warmer place.

I had a tear-out of the existing system done, and a new boiler, controls, and indirect installed. Cost an arm and a leg, but I opted for a super high-tech boiler and a larger tank than I probably needed. The system was moderately complicated, since it had to reconnect to existing radiant floor heating, and a hydro-air system - plus, it needed a new vent run. Actual costs will vary by the local conditions. I'll probably never see a payback for the increased efficieny, but I'll guess I will continue to be able to fill the 6' tub quickly whenever and as often as I want while doing laundry, dishes, or whatever else happens to be going on at th esame time. Is it an indulgence? Yes. So far, I'm happy.

02-08-2007, 05:06 AM
what size tank did you use and what type of high tech boiler?

what do you think about installing a plate heat exchanger and a storage tank from energy kinetics. this would eliminate any questions i may have about my coil and if the boiler goes, i could get a high tech type boiler from them as well. any experience with energy kinetics?

or maybe you have other brand recommendations...

thanks for all the input.

Bob NH
02-08-2007, 06:51 AM
I had a similar problem and solved it by installing a 40 gallon electric after the tankless coil. Size should be based on your needs.

An indirect heater is much more expensive and it doesn't make your boiler produce any more hot water.

The symptoms of my situation were that the hot water was limited and erratic in the winter when the water supply was about 35 F. A defective tempering valve was contributing to the problem. Tempering valves also tend to restrict flow.

I also found that I was using a lot of $2+ per gallon oil to keep the boiler hot in the summer. The cost of oil was about twice what it cost to heat the required water with electricity in the summer.

The temperature of the electric heater is set so it never/rarely comes on when the boiler is operating. When I shut off the boiler after the heating season, the electric heater takes over. If you have a capacity problem in the summer, such as a lot of guests taking showers, you can turn on the boiler.

The occasional hot/warm/off cycling of the boiler has not been a problem.

02-09-2007, 08:29 AM
here are a couple of pics of the current setup just for clarity.

[img=http://img131.imageshack.us/img131/4426/dscn0134mo6.th.jpg] (http://img131.imageshack.us/my.php?image=dscn0134mo6.jpg)


[img=http://img131.imageshack.us/img131/1858/dscn0133tg8.th.jpg] (http://img131.imageshack.us/my.php?image=dscn0133tg8.jpg)


02-09-2007, 11:38 AM
The system I had installed was expensive (at least to my non-pro view), but in their defense, it was complicated and space constrained.

I chose the products because of the rep of the installer, personal review, and the fact the US distributor is within 10-miles of my house (parts availability).

My system has an indirect (Super Stor Ultra), a hydro-air system, and 4-zone radiant floor heating. The WH is on a priority zone, and the whole system is controlled by an outdoor reset which feeds into the boiler control to modulate the boiler supply temperature. The goal is to run it as low as you can so it runs close to full time, and condenses as much as possible of the heat out of the flame and exhaust as possible.

The unit is made by Buderus. Other companies make similar systems. They each have their plusses and minuses. The Buderus is rated at 94% AFUE, but since I'm running it with the outside reset controller, it is often as much as 98% (predicted). I won't have my first bill for another week or so, and you'd want several to get a good picture.

THe local utility company will be sending me $1100 in rebates for the boiler and indirect.

There are very few boilers thatmeet the federal requirments to get the tax credit (requires AFUE of >=95%).

02-10-2007, 07:14 PM
sounds like a great system. nice to get some $ back for a change.

which buderus boiler did you use and what part of the country are you in?

it would be helpfull to me if you might list the other brands/models of boilers and indirect tanks you considered. price is of course important since i don't have an unlimited budget but would like to get the most for my $.

i like what you chose, but i recently looked at few different products like the thermo 2000 turbomax and crown megastor as indirects after speaking to some people at a local trade show this weekend. Weil Mclain also came up for both boilers and indirects.

it's looking more and more like i should just do a complete new system instead of tying to work around the current boiler. i may get better pricing to pipe in everything at once but i still need to talk to more competent local installers that are not just trying to sell me the next latest great thing.

any comments are always apreciated. thanks.

02-10-2007, 07:25 PM
It's a GB142-24. I'm in New Hampshire.

02-10-2007, 08:49 PM
oh, you are able to use gas. i don't have that option. i am working with oil.

03-07-2007, 12:07 PM
I recently installed a Buderus GB142-30 with a SuperStor 36gl indirect tank. The dhw has priority and on cold days this is causing a problem because the heat shuts off to accomodate the dhw and the house temp drops considerably.

My question: Is it possible to set it up so the heat & hot water can both be satisfied at the same time?

The house was a recent gut job and has some air leaks no doubt, but I didn't expect this to be that much of a problem. It's a big house with high ceilings and my gas bill last month was $535! I almost fell over when I saw it.

I'm really hoping that by buttoning up the house a little better this spring will make a difference next winter.

03-07-2007, 01:40 PM
Depends on how they wired and plumbed the system as to whether it would be easy to make the indirect a "normal" zone. Be aware, though, that that will decrease the quantity and recovery rate considerably. You must tighten up the house if you want to save some on energy costs - sounds like it leaks like a sieve. I would have preferred even a smaller unit than I have, but it was the smallest they have. I'd guess the only time it runs at full output is when it is heating the indirect. Luckily, my bills are much less than yours, but my condo townhouse only has two outside walls and is moderately well insulated. Sounds like you could save a bunch with some weatherstripping and insulation - probably pay for it in the first seaon easily.

04-09-2007, 10:46 AM
By far the largest range of very high efficiency boilers are gas/propane. Propane can cost more than oil. You can probably get propane if you have room for a tank.

But with gas you can get a modulating condensing boiler. Many of these have almost no water retained in the boiler itself.

What does this mean?

Modulating - the boiler can fire at a variable rate depending on multiple factors such as heating/DHW demand, outside air temp. This means that a boiler may run at 20K BTU for light heating and with relatively low temp water. Cranks up to max rate of the boiler (e.g., 100K BTU) when demand is high (e.g., DHW).

Condensing - boiler condenses the exhaust gasses to recover latent heat. Water comes out a drain and much less goes out the vent (which can be PVC). When this is happening the boiler can do about 98% or so efficiency. The higher the water temp the less effective this recovery is, but it will still be quite good. I think the magic number is around 135 or 140 degrees but don't quote me. When my boiler (WeilMclien) is doing the house heating the water temp is seems to be running from about 90 degrees to about 115. I store DHW in the SuperStor at 140 degrees. Less temp runs the risk of Ligeonella developing in the tank. A tempering valve is necessary for DHW either at the tank or at each fixture. Each fixture is best in my mind because it gets the pipes hot. But it costs more and has more pieces to break. Some fixtures have this built in. The temp of water used for heating is a function of the design of the system emitters (in-floor, radiators, air exchangers). In floor should use the lowest temps, followed by radiators.

Little water stored in the boiler jacket and heat exchanger - you don't have the problem of keeping that water hot in the summer. I believe my boiler is less than 2 gallons plus some piping to the DHW tank.

Maximum advantage accrues with smart controls. The boiler can do some of this by itself but an external control system is much smarter and adapts to conditions better. My feeling is that Techmar is the gold standard for these controls.

It ain't cheap up front. But it may pay for itself rather quickly depending on existing system performance.