View Full Version : indirect on old steam boiler

04-15-2010, 06:52 PM
can an indirect hot water tank be installed on this old boiler?

the only taps that I can see are from the hw coil?

can I remove this coil?

can I get a new coil?

Is it possible to replace the coil with an empty box that would supply the indirect?

04-15-2010, 07:33 PM
Installing an indirect tank on a massive vapor steam system would be a complete waste of money. For about the same cost of components, you could get a gas tankless that would operate 60% - 70% more in annual efficiency

Wally Hays
04-16-2010, 12:48 PM
Does that beast still have the origional burner in it? It is a lovely example of an old school cabinet boiler. Efficiency is probably in the low 70's with the original burner. If you have a newer retention head burner, somewhere closer to 80% Because it is a high mass boiler, system efficiency is pretty low, but believe it or not, not all that far off new steam boiler efficiency. Steam is a pretty poor use of your energy dollar because you need to get the water to 212 before anything happens. That said, you can indeed pipe an indirect off the system. forget about the old tankless coil, you will have to tap a feed and return below the water line of the boiler. Usually there are tappings somewhere that can be used for that purpose but getting the plugs out may be a challenge. Of course, by the time you buy the indirect, a circulator, valves, an aquastat and all the piping it will cost about 6 times what the original boiler cost. Better off with either an oil fired water heater, gas or even an electric for the cost. If you have the cash though I would seriously look into converting the system to forced hot water and changing out the boiler. In the end the conversion will probably pay itself back in fuel savings in under 10 years.

04-16-2010, 05:42 PM
The old beast has a new burner. oil fired Becket. I would never consider changing from steam to hot water. The old steam system works great. Very comfortable. I have no idea if there are additional taps on this boiler because the cabinet has never been off. the only ones that are visible are the in and out on the old coil. I have plenty of hot water now but the pressure and volume are much lower than the cold water. That is my problem. I want more pressure and more volume on the hot water. I have been told that the old coil is restricting volume. Even though I have 3/4 copper feed into that coil the coil itself is 1/2" and cruded up to boot. That coil is 65 years old. I would love to change it out for a new one but I have no idea where to get one. I was told on this forum that the holding tank can be piped differently. I was told I could increase the volume of hot water if I make a few changes to the piping. Thank you Wally for your reply. Could you take a look at the attached picture and tell me how you would pipe the holding tank/coil/pump/loop, differently to increase the volume on the hot water?

Wally Hays
04-17-2010, 07:48 AM
Wally, I do see two tappings that you could use. One is where the water feed enters down by the the drain. You could change out that tee and use that tap for the return and the other one is where the aquastat mounts in the tankless coil. Since you won't be using the coil, you won't need the aquastat.

04-17-2010, 08:57 AM
Cap off the cold water going into the coil, but leave the line from the pump intact. Connect the cold water into a "T" on the cold inlet to the tank, (the right hand one where the water is returning from the coil). The coil will heat the water, but you will draw the heated water directly from the tank. As far as the tank is concerned, it will think it has become an electric water heater, but it will use the hot water from the boiler instead of electricity.

04-17-2010, 08:04 PM
Thank you very much HJ for the reply. your suggestion sounds very much like the previous suggestion that I received on this same topic. Could you tell me if it is the same thing that you are suggesting?
Quote from John:
The re-pipe is not that much of a change. I'm just not sure of how the circulator is wired. For it to work it should be controlled by the lower thermostat on the heater. What needs to be done is to remove the cold water feed from the coil and feed the top right taping on the heater. This line should be 3/4". Put a 3/4" x 1/2" tee in that line and connect the existing 1/2' line that is coming from the top of the coil to it. Above that tee on the cold water feed you will need a check valve with the arrow on it pointing to the heater. Piping it this way eliminates the water going through the coil before going to the fixtures. The circulator will circulate the water between the coil and the tank to heat your water. The lower thermostat should control the circulator if that is how it's wired. I recommend that you get a professional to do this re-pipe.
There also should be a thermal expansion tank installed on the heater. It also looks like the relief valve is piped with 1/2" and it must be 3/4".

It sounds like the same thing to me but I just want to be sure.
Also Can you tell me if you think this will increase the volume and pressure off the hot water? That is my goal.

Wally Hays
04-18-2010, 09:01 AM
That is what the tank is doing now. It circulates through the coil into the tank. There is a checkvalve on the line that keeps it from back feeding. Piping it that way will make no difference in the amount or the cost of hot water. what you could do is get hold of a plate exchanger and use the tank for storage.

04-18-2010, 07:11 PM
Hello Wally. What is a plate exchanger? Why wont HJ`s idea for the repipe work?

Wally Hays
04-20-2010, 03:33 PM
It will work, it just won't make much difference. google plate exchangers. There are several companies that make them. System 2000 boilers use them to make hot water.

04-23-2010, 12:09 PM
What do you think of wally hays comment: "It will work, it just won't make much difference"

He is referring to your re-pipe suggestion. Do you agree with him?