Opinions on a Weil Mclain WM97+ CT Wall Mount Gas Boiler

Xmytruck

Hello
Wondering what your opinion is on a WM97+ CT Wall Mount Gas Boiler for a single family house, two floors, 2.5 bathrooms with baseboard heat? Is this a good, reliable unit and how is customer service?

Thank you
Xmytruck

Danscrew

My unit has been running fine so far no problems. Happy with it the biggest thing with a Mod/Con is sizing it correctly. Do your homework and your heat loss calculation . Dan

Rich_49

70 , 110 , or 155 ? 2 1/2 baths can be pretty demanding . Make sure whatever you use will stand up to max DHW demand .

Robert O'Brien

I agree with both Dan and Rich,size the boiler to the heat loss but be conscious of DHW load. There are much better ways to meet DHW demands than oversizing the boiler. Figure out how much DHW you will need and satisfy that without an oversized boiler by using a mixing valve (Code in most places) on the indirect and maintaining a higher temp than the usual 120. Use a larger indirect or if that still won't do it,go with a tankless.

bob eck

When installing any condensing gas boiler the return water temp needs to be below 135 - 130 F Deg to make the boiler condense. If the boiler is not condensing the boiler will only be 82% - 85% efficient. if you have to run high water temps like 170 - 180 Deg F you will be paying a higher cost for a boiler that will not condense most of the heating season. Also look at the Weil Mclain GV 90+ boiler. This boiler has a special SS secondary heat exchanger on the side of the boiler recouping heat energy exhaust normally wasted when venting from the building. This boiler vents with PVC pipe and fittings. Use a 40 - 60 - 80 gallon indirect water heater to make sure you have enough domestic hot water.

SWEI

bob eck said:

When installing any condensing gas boiler the return water temp needs to be below 135 - 130 F Deg to make the boiler condense. If the boiler is not condensing the boiler will only be 82% - 85% efficient.

With return temps are in that range, most mod/cons will fire around 87-89% IIRC.

if you have to run high water temps like 170 - 180 Deg F you will be paying a higher cost for a boiler that will not condense most of the heating season.

Even 170°F supply temps on a design day leave you condensing well over 50% of the season. The effective AFUE will still be north of 90%. The increase in comfort from properly implemented modulation is significant.

There is no magic leap in efficiency that happens when condensing starts. Lower return temps = higher efficiencies.

Xmytruck

How can you tell or measure the return temp?

SWEI

Mod/cons and many other modern boilers have internal sensors you can read using their onboard displays.

Xmytruck

Thank you

Jean-David Beyer

It seems to me that unless people are running a commercial laundry, or have so many teen-age daughters that the hot showers run for hours at a time, that you need not worry very much about the domestic hot water load.

I am at the opposite extreme, just me, and I rarely take over one shower per day. I have run three loads of laundry and the diswasher in a single day. I have a W-M Ultra 3 80,000 BTU/hour input boiler and one of their indirects that has about 36 gallon domestic tank. It runs two or three times a day for 10 to 15 minutes each time.

It is set right now to supply 190F water to the indirect, 145F maximum to a baseboard zone, and 128F maximum to a radiant slab at grade zone. These maximum temperatures would be supplied only if the outdoor temperature goes to 14F below design temperature.

My washing machine runs either cold (i.e., minimum of 60F) or warm, so it does not use as much hot water as one might think. My dishwasher runs full temperature (120F delivered) but does not use all that much water either.

The W-M WM97 is similar to my boiler in many ways (though probably a slightly better design). Its controls are quite similar.

Normally, the indirect runs at highest priority, but for a relatively brief time, so it would not matter much if it condenses or not. Actually, mine sometimes activates the condensate pump when producing domestic hot water. The boiler is cold-start, and it takes some time to warm up. So during the run-up interval, it condenses too. Until the return water from the indirect warms up. In my system, there is about a 20 degree temperature drop through the indirect until the domestic water gets pretty near the set point.

Since my boiler, at least, but I imagine this applies to most, spends most of its time heating my house, not heating domestic hot water, I believe one should size for the home heating load, not the domestic hot water load. As others have said, perhaps heat your hot water to a higher temperature, such as 150F, and mix it down to 120F. And get a bigger indirect if you have one of those high volume rainwater type shower heads, or have way too many teenage daughters. You do not want to oversize your mod-con boiler.

Gordy

A 40 gallon gas water heater has over 30k burner. You won't do worse even with a 50k input boiler. Just don't expect some of the indirect data claims. More storage, and, or higher storage temps to compensat for most short falls if any.

Jean-David Beyer

My W-M Ultra Plus indirect claims that if I supply 6.6 Gal/min of 190F water to the indirect from my Ultra 3 80 boiler, and run the indirect at 140F, the first hour rating is 124 Gal/Hr. The heating surface is 16 square feet. This is a tank within a tank design. The domestic side is 36 gallons and the boiler side holds 6 gallons.

icesailor

How big is the indirect tank? That is part of how they get the first hour rating. Its complicated and deceiving. Hardly ever achieved. Like the MPG on your new car. It never gets as good as they claim on the window sticker hype. Expect for my 2001 BMW 325IX wagon. That did better than advertised for 153,000 miles.

SWEI

It's a re-branded SMART 40. TT actually publishes useful data on the larger models.

Xmytruck

Really? Interesting