Hi everyone,

I am looking at going from a tankless coil in my DHW system to an electric hot water heater. I have no interest in an indirect system. Electric is cheaper here and I want to use oil as little as possible.

Currently, I run an oil fired boiler.

Beckett AFG Model Oil Burner
Honeywell 206625a (this is the number printed on it) Aquastat

The aquastat settings are 200 Hi and 180 Lo.

As I said, I want to install an electric hot water heater. I am unsure how to do this with the tankless coil, however. I am toying with the idea of not doing anything with the tankless coil and just running the hot water output of that coil right in to the cold water input of the electric water heater. Then, in the summer, I would just flip the power switch on the furnace to off. I am not overly fond on this method tho, as even in the dead of winter I try to use the oil furnace as little as possible. The thermostat in the house is set to a chilly 46 just to keep the unused parts of the house from freezing. I then space heat whatever room I'm in (I live alone) with an electric space heater (ONLY 1 room at a time is heated--saved me a TON of money last winter doing this). I am afraid then, that the furnace may still kick on to heat water in the coil even tho there is also a hot water heater running therefore causing me to pay for TWO methods of hot water heating.

I was also thinking that I should just disconnect the input and output of the tankless coil completely and leave them totally empty. I am afraid this method will do damage to my furnace in some way, though?

Suggestions are welcome.

 

The very first thing I recommend is that you change the settings on the aquastat to a high of 180 and a low of 150. That alone will save you oil. You could then experiment with even lower settings and possibly be able to go down to a high of 160 and a low of 140.

As for installing the electric heater...I would suggest totally disconnecting the water inlet and outlet from the tankless coil. I don't know what your electricity rates are but a tankless coil is the second worst way to heat domestic water, the first being a kettle on a wood-burning kitchen range. You can leave the coil connections open or closed. Some people will try to tell you that closing them (putting on caps) will allow an unsafe pressure build up in the coil but that is not true.

The number you cited for the aquastat is unfamiliar to me but perhaps one of the people more familiar with residential equipment will recognize it. You may be able to simply move a wire to convert your boiler to "cold start" or it may require a different aquastat. Understand that some cast iron sectional boilers don't like wide temperature swings and may leak if converted to cold start.

 

yea, i've done some reading and I am afraid of converting my boiler to a "cold start" willy nilly. This is another reason I've considered leaving the new water connected to the outlet of the tankless coil.

I believe you when you say they are terrible for water heating. I hate this piece of crap... using my heating method of space heating 1 room at a time I purchased 150 gallons of oil back in February. I had over a quater tank when the summer began and I ran out on Sunday. So from the beginning of summer to two days ago over a quarter tank of oil was consumed just heating water. I was disgusted.

That said, I still do not want to damage my furnace.

 

You won't damage anything, it will just leak slightly when cold. When it warms up again it will stop leaking. It may not leak at all, some do and others don't.

Definitely turn down the aquastat settings as soon as possible, tonight (this morning?) is not too soon. If you can go without hot water for a day turn off the power to the boiler and see what happens. Be sure to also turn off the make-up water (water to the boiler itself) and note both the temperature and pressure readings. After the boiler has been off for several hours again note the pressure and temperature readings. Do this until the temperature is approximately the same as the room temperature if you can stand to be without hot water this long. Look all around the boiler for any wet spots on the floor, it is highly unlikely that it will be a major leak, just some dribbles.

Post back with the results of this testing.

 

I'll tell you this:

The boiler was turned off from late saturday night until 7pm just this evening as it was completely out of oil. LOL. I did not see any leaking at all. Same as a year ago when I let it run dry then too and it was out of oil for a few days.

Aquastat has already been turned down.

No damage will occur from disconnecting the tankless coils? Is there a setting I should flip on the aquastat when I do this?

 

No, no damage will result from disconnecting the tankless coil. No special settings when disconnecting the tankless coil, just turn off the supply water to the coil and re-route it to he new electric water heater. Disconnect the coil outlet and re-route to the outlet of the electric heater. Yes, it really is that simple.

It also sounds as if you will have no trouble going to a cold start system.

 

Disconnect the coil outlet and re-route to the outlet of the electric heater.

That sentence has me a little confused...? LOL

Thank you for your help so far.

 

Disconnect the domestic water supply from the tankless coil and re-route this supply to the electric water heater. When you get done the domestic water cold will go to the electric water heater and the outlet of the electric water heater will go to the house piping that previously came from the tankless coil outlet. Nothing will be connected to the tankless coil.

Oh, one new setting for the aquastat. Turn the low limit down as far as possible. Posting some pictures of the aquastat with the cover removed might help to identify if you can disable the warm start feature.

 

Ask and you shall receive!

Clickable link:


Also, I just noticed that I have an anti-scald valve on this hookup. Should this affect anything?

 

Who, me? Yeah, I think so! True or not, manufacturers recommend to NOT cap the tankless coil stubs. While they don't give any reason, one can surmise that they fear a pressure buildup and resultant lawsuit. It's this litigious world we live in, ya know?

Chances are that it won't cause a problem. So, if you want to cap it off, go ahead, but just don't solder the caps on... best of both worlds!

Rewd, check your private messages...

 

If the anti-scald valve is a decent one, with thermostatic control, and it is still in good shape and re-usable, it should be installed on the new electric heater. If it's in so-so shape, discard it, but buy a new one to install on the new water heater. Set it for 120° and adjust the thermostats on the water heater to 135-140.

The higher setting on the water heater will minimize the risk of legionella bacteria colonizing your water heater and causing illness or death... (Legionnaires disease) and the 120 setting on the anti-scald valve will prevent burn injuries in the home from too hot water.

Google these things for more info...

 

Thanks guys, I really appreciate all of your help.

 

Trooper, (and others) do you recognize that aquastat and if so, can he remove a wire to make it a cold start?

 

It appears to be an L8124A from what we can see in the photo. Yes, there is a way to convert them, but pulling a wire is only half the job.

Then, there's the old liability angle again... so I don't choose to post the info on the forum.

BTW Rewd, nice Dobies!

 

Are you say'in the boiler may leak?

It would be up to the OP if he wanted to cold start it right? Same as if he installed just a high limit aquastat. At least with that aquastat he could put the wire back if it starts drip, drip, drip.......

Right?......

Maybe its a different liability. ( Just thinking out loud )


Mike NJ

 

Thanks for the dobe comment. They are wonderful dogs.

I'm open to all pros and cons of doing this so don't hold anything back guys! If you know something keep the ideas coming!

 

With the help of this forum I did the exact same thing your are about to do and I couldn't be happier. I have the same aquastat that you have and all I did was turn the LO as low as it will go and was done with it. It shows on my gauge (that is probably wrong, I know) it maintains water temp at about 100 which is not much. In the summer when I don't need the boiler any more I just turn it off completely.

 

That's great to hear. Did you completely disconnect your tankless coil from all water supplies?

I am thinking now that I should leave the tankless coil connected, turn the aquastat down as low as it will go, and then plumb the outlet from the tankless coil to the inlet of the electric hot water heater. This way, if the electric heater ever goes down I'll have the tankless coil as a backup.

I am afraid that if I do it this way the furnace will still kick on in the winter months to heat water passing through it to the water heater, though.

 

Put a ball valve on the inlet of the coil. That will give you the option to use the coil or not. Having the outlet with no valve allows the water in the pipe to expand when it gets hot. You will save the most money if you convert to a cold start boiler.

 

Originally I had tankless only. I never hadenough hot water and i hated the operation. Then I pumped the tankless into a 40 gallon electric hot water tank thinking I would preheat the water. It was better and I did this for quite area years when I had the idea of why am I running my cold water throughou the boiler at all? So I dumped the 40 gallon tank and got an 80 gallon and disconnected the tankless (uncapped). The water temp is much more stable and I have more the enough. I don't notice that my electric bill is much higher either. What I have noticed is my oil consumption is less. I was able to go from a .70 nozzle to a .60 and this year I am trying a .50. Now all I need to worry about is balancing my burner/boiler to heat my house and not having to heat hot water at the same time as I am trying to heat the house.

 

Thank you bidaci. Well, I've just completed installation of the new water heater. I ended up just plumbing it from the outlet of the tankless coil.

If I want to completely disable use of the tankless coil I can still just use the instructions I was given on adjusting the aquastat so the boiler becomes a "cold start" boiler without having to do more plumbing so that no water runs through the tankless coil, right?

Basically, I want to modify the aquastat so that the tankless coil never causes the boiler to fire and heat water. Not even to "preheat" the water going in to the new electric water heater while still having water running through the plumbing in the boiler, right?

I'd still like to keep the plumbing in tact in the event something bad happens to the new water heater so I'll always have hot water.

 

I just got my new furnace installed after our house had all the basement contents damaged from flooding. We relied solely on the tankless coil from the old furnace for dhw before. After 4 days of cold showers I installed an electric water heater until we could get our furnace replaced. My plumber, who is also a friend of my family, my old scoutmaster, and the one that taught me the little bit I know about plumbing suggested I keep the wh and use the coil on the new furnace to heat the water up to 120 and the let the wh take it the rest of the way to 150. Between my wife, 2 kids, and myself, hot water was an issue. Well after using it this way for the last 4 days since our furnace has been up and running, I don't have to be the one taking a barely warm shower before bed, or waiting for the furnace or water heater to recover. I still have a thermostatic mixing valve to install at the shower/tub that should cut down on the hot water usage, but I like this system compared to what we had before. The 50 gal water heater alone just wasn't enough for the demand after our old furnace failed My other concern for using the tankless coil is power outages, my generator will run my furnace, but not my water heater.