Nat. Gas Boiler Selection

[Indigo]

Looking to replace a ~30 year old boiler with a new one with domestic hot water. Caveat: has to be a direct vent unit as I would otherwise need to reline the chimney.

I've gotten bids on the following units -- the pricing for all has come in around the same +/-

1) Weil-McLain ECO with a 45 gallon Weil-McLain AquaPlus Indirect Tank
2) Weil-McLain Ultra with a 45 gallon Weil-McLain AquaPlus Indirect Tank
3) Weil-McLain WM97+ with Integrated AquaLogic Tank
4) Laars Neotherm with an Indirect Tank - model not specified as of yet

Overall, I can't imagine a 45 gallon indirect tank is needed -- we have yet to exhaust our older 40 gallon standalone unit and that's with no mixing valve in use, which there would be with an indirect.

I prefer the contractor that suggested Options 2 and 3 and I feel they did a more accurate sizing (though that's a discussion for another thread). They are also an authorized Buderus installer -- is it worth examining any of that manufacturer's units?

Weil-McLain seems to have their foot in the door in this market -- which I figure will make long-term support easier, but there seem to be some horror stories out there - especially with the aluminum heat exchanger in the Ultra.

Appreciate any thoughts! Thanks.

 

[Jadnashua]

It's more the quality of the installation verses the exact unit you select. Sizing is critical. Oversizing is a travesty, but quite common. When the Weil-McLain Ultra first came out, they had issues with the heat exchanger, enough so that the dealer I used (sold both brands) would not install the Weil-McLain, and offered the Buderus (which he indicated that he had in his own home). I'd expect they've resolved their original teething issues on the Ultra, but have no direct experience.

As to the size of the indirect, the cost to go a bit larger isn't all that much, and it's nice to not run out. Depending on your use patterns, a smaller one may work out. I have a 6' air tub, and have an even bigger one...probably didn't need it, but I'm dumping a lot of water fast into it, and I didn't want other users in the house to be inconvenienced. It really costs no more to heat the bigger tank. The good ones have a very low standby loss, and it's there if you need it.

 

[Sponsor]

 

[Dana]

The question is whether the 18 gallon AquaLogic is going to be enough for your hot water use patterns. Filling tubs at 3-4 gpm doesn't cut it for a lot of people, but the continuous flow rates are fine for folks who usually shower.

On the boiler sizing issue: The vast majority of homes in the US would be best served with the smallest of the WM97+ line (WM97+ 70CT ). Any proposals for bigger should be accompanied by a Manual-J heat load report where you can look over the input parameters and verify that it was done at least half-correctly.

 

[Indigo]

Thanks for the info. I'm pretty confident that the AquaLogic will cut it -- we have 1 shower and 1 tub/shower -- the latter of which has been used a handful of times. That said, the AquaLogic is capable of filling a tub, right?

 

[Dana]

The AquaLogic' s capacity is about 18 gallons, your tub is more than that, but you can keep it a 160F or something to improve capacity when mixed down to ~110F for a tub-fill. The size of the tub matters, as does the size of the boiler. When the stored heat in the tank is pretty much depleted., it's the size of the boiler that determines the maximum flow rate. Filling a big soaker tub may be annoyingly slow since you'll be finishing up on boiler firing-rate alone and may have to throttle back on the fill-rate to maintain a sufficiently high temperature, but an average tub is probably going to have reasonable fill-times.