Sounds like you have a Weil McLain Ultra Boiler. Assuming it is not grossly oversized for heat loss of home, the piping isnÂt undersized at the near boiler piping and the circulation to zones and boiler is also proper, there are only a few things you can do.

First to quickly explain, assuming they installed the outdoor sensor, your boiler is programmed to vary the output water temp based on outdoor temp conditions. When a heating zone calls for heat the boiler is designed to start at a medium fire, and then read all the thermisters on the supply, return, vent and outdoors and decide what firing rate to go with. This could be anywhere from 35% to full potential. On a call for domestic hot water from the water heater you mentioned, you must have an indirect water heater. If wired properly, this should take priority over heating and override outdoor temp signal and heat up to a maximum setting programmed into the MB module on the boiler.

Unless someone has played with the programming on the MB module, the factory has the normal settings as a default. It is possible to massage these setting if one understands what they are doing and as one example you could change the differential which could keep boiler on longer with fewer cycles per hour.
As a last step, when a large boiler is required to supply small zones or perform under less demanding conditions such as spring and fall, many times a buffer tank is added. This is just an insulated storage tank installed in the primary circuit of the near boiler piping that serves as an additional mass of water to heat that is available to heat the house. The more mass or water, the longer the burner stays on and longer intervals that it is off.

Many things should be checked before living with the ssyetm, such as temp difference of boiler, boiler piping and circulation, zone piping and circulation and control settings to be assured that you are getting the heat out to the home versus having it be stifled back at the boiler with a bad design and install.

Wow - thanks for the detailed info. I'm glad to have it before talking with the heating company.

We don't have the outdoor thermostat, I just happened to see it on This Old House last week and it sparked my curiosity relative to our system.

Sometimes, things like this are hard to find on the net and this is when people on this board really shine. Thanks.

The cycling in the summer is OK. In most cases. teh differential temperature in the tank is about 10 degrees which means that the boiler is on until the high temperature is satisfied and doesn't go back on until it reaches about 10 degrees below that . For example, say you are using 2gal/min of hot water then the rate of energy usage is 2*8*100=1600BTU/minute. If your tank is say 30 gallons then when its temperature goes down 10 degrees, its change of energy is 30*8*10=2400 BTU . Then the time it should take to call for more heat is 2400/1600=1-1/2 minutes, which about what you say and the 20-30 seconds off on time has to do with the boiler capacity and is not unreasonable for a large boiler.
What is problematical is the on/off cycling of the heating which should be much better controlled by proper modulation and perhaps a thermostat. In a normal situation,with a single firing rate, the length of the off time is controlled by the heat load which depends on the outdoor temperature and cannot be in the range of seconds, more in the order of many minutes and for a given load the ratio of off/on times would be fixed, so the cycling would inherently lower. However, with the programmed unit, the system figures out what the load is by monitoring flow rate and return temperature, it knows what the firing rate should be to increase the "on" time and thus minimize the cycling. So it looks like the control is the problem and you would be well advised to seek professional help.

The outdoor sensor is shipped and packed with the boiler and there is no reason not to install it and connect it to the proper terminals. Once connected this inacts the outdoor reset option, without being connected the boiler just runs up to hi-limit and you are not realizing the full potential of the boiler.

Nifty info. We'll see what the heating company can do for us. I'm curious if our model (Well McClain Gold) had that outdoor sensor option and it just wasn't installed.

The on-cycling can definitely be on the order of tens of seconds when it does happen.

Gas is going up 22% for us on Jan 1 and we don't want to be making the baseboard water any hotter than it really has to be.

Hey, another Anchorage visitor to the site. :-)

I also had a Weil-McLain GV boiler installed recently. (Mine was just over a year ago.) The link below shows the model.

My boiler was not equipped with an Outdoor Reset module 'out of the box', but Klebs installed it with one and it works beautifully. (Taco controller set.) My cycle times are around 1 ~ 2 minutes with a 15° differential. (If I remember correctly, the size is 70k BTU, which is half the size of the original boiler and still a touch large for my home.) The Taco module really took over almost all the functionality of the boiler's own controller.

My system runs a lot, but that's because it's running at a low water temperature right now. (Around 145°.) You should pop the top cover off your boiler and watch the lights on the controller when you expect it to do a short cycle. Maybe it will give you a clue as to why it stops. Perhaps the flame didn't ignite on time or the air pressure switch didn't give the right reading?

The Outdoor Reset module is definitely an add-on for this boiler, but it works well. My gas bill arrived today and came in at $85.00. Last month was $42. A co-worker of mine had Klebs install the Lochinvar-Knight (most expensive boiler offered) and her gas bill this month was over $100, so I'm not feeling to shabby about my GV!

Side note: When was the last time you placed oil in the cups on the blower motor?

Send me a message through the web site! I could Email you a picture of the Taco controller and explain how it works.

Here is a link that might be useful: Weil-McLain GV

mrehberg,

Do you have a Weil McLain Ultra or GV boiler model boiler?

Bray, the GV is 87%, yet a knight is 95%+, however if run at high temps will never achieve that. If yours is doing the same, you probably made the right choice.

Weil-McClain Gold CTs, sealed combustion, installed autumn 2001 (seems like yesterday...). Back in the days when Alaskans paid their *own* money for home energy improvements!

Only reference to an outside sensor in the manuals has to do with cool-temperature water for radiant heating systems. Outdoor sensor not listed as an option. Taco circulator on top for what it matters.

We'll be quizzing our furnace guy about this during the maintenance visit soon.

I'll spend some time watching the little LED lights on the controller panel like you suggest. Sometimes I sit and stare at the clothes going around and around in the front-loading washer too so I should be pretty well prepared for that task.

Sorry when you said sealed combustion and living in Alaska with 11.5 months of heating I guessed it was an Ultra. No your boiler does not have a factory outdoor reset, but an aftermarket could be added, such as a Tekmar 256.

Go back to my original post regarding proper piping, circulators and a buffer tank if your system warrants it.

Ah, the Tekmar name. They must work closely with Taco or re-badge their products as other names. The Taco controller installation manual was very vague in places. I discovered the Tekmar model online and downloaded its installation guide, instead. Other than a few additional menu options, they're the same. But the Tekmar manual is so much easier to understand. It helped me double-check and understand the settings that were in it.

Yes Taco adopted the Tekmar controls years ago. In fact they made it simpler by putting harnesses to plug directly into their panels.

However Taco is vague in explaining the functions and logarithms, thus referring back to Tekmar helps to explain things.

Thanks everyone. My suspicion is that our Armitrol domestic hot water thermos simply calls for brief shots from the boiler to maintain temps. Seven years and the boiler runs well with no failures. We'll see what our furnace guy says. Thanks again!