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What are the Pros and Cons of switching from tankless to Indirect hot water and other questions?

I'm looking to upgrade my standard contractors special domestic oil fired boiler which provides my baseboard hot water and domestic hot water, my house is 1800 sqft.  We live in the Massachusetts where winter temperatures get down into the teens and occasionally dip into the single digits and below.

I've had the local oil company come out and spec what I would need and offered the good, better, best options.  I won't mention prices, but the Weil-McLain's seem to be in my price range.

Two of the options I'm milling over:

Better: Weil-McLain P-WTGO-3 Gold Boiler, tankless with Carlin oil burner

Best: Weil-McLain PUO-3 Ultra Boiler with Weil-McLain Ultra Plus 40 Indirect hot water with Becket NX oil burner.

As I grew up in a home with a hot water heater I remember getting the last shower and not having any hot water, something I don't want to repeat.

The safest bet would be to go with the 2nd option and keep things in my home as status quo, but the oil guy recommended the indirect domestic hot water (option 3) as a more fuel efficient system as my boiler would not be kicking on as often in the summer.

Currently the house has only my wife and myself, but we plan on having a couple of children in the near future and I would like to plan accordingly.  We have 2.5 baths, laundry and a dishwasher.

I'm looking for the pros and cons of having an indirect hot water system installed vs tankless. 

Is the indirect 40 large enough?

Will I be running out of hot water after the 3rd shower?

(currently I don't)

Can two people use different showers at the same time? (currently we can)

Please let me know your pros and cons especially if you've switched from the tankless to indirect with similar capacity.


  • scott markle_2
    scott markle_2 Member Posts: 611

    Most oil boiler indirect configurations can provide continuous hot water provided the demand is reasonable 2.5 gpm and the incoming water is not frigid, provided the indirect has priority over heating.

    If the load exceeds the output of the boiler it's helpful to have some buffer from a larger storage tank.

    If your boiler can put out 100kbtu and the control has DHW priority you should be fine with the 40 gallon, provided you don't expect to run multiple showers and tubs simultaneously.

    Personally I don't love the oil indirect pairing in the summer when significant amounts of heat get stranded in the mass of the boiler.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    I agree

    wit Scott.  Set up with a proper control strategy, you won't run out of hot water.  With almost the same set up, the boiler doesn't even fire until I'm just about done with my shower, with plenty of hot water.  You just have to be practical about it--meaning you're not taking a shower, running the dishwasher, doing a hot load in the washing machine, and filling up a 4X6 jacuzzi.   It'll keep up just fine with 2 showers.  And the dishwasher, depending on the model, won't use that much.  Remember to install the mixing valve on the domestic side, so you can get the indirect up to 140 degrees without scalding.
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