We recently had the MPO IQ installed. The contractor acknowledged then that even the smallest MPO was too big for our 900 square foot home. He said adjustments could be made to lower the out put. I assumed this meant he'd do the adjusting at installation. We've used it a few times. It heats fast and very well, almost too well. The thermostat is set for 65, we're getting 73. The heat lasts a long time. I contacted the installer and asked if this is efficient. He again acknowledged that the unit is too big for our house and started talking about either an aquastat or some sort of device that would heat based on the outside temp. I'm disappointed that we now have to purchase another part for the brand new system, but I want it to operate as efficiently as possible with the oil prices being what they are. Not unhappy with the MPO, just want to be able to control the heat and be comfortable while maintaining efficiency. Thoughts or suggestions appreciated. I have no knowledge of these systems. Thanks.

 

Ask the contractor to install the smallest oil nozzle that can be installed with that boiler. And, what nozzle is installed and what boiler is actually installed (complete model number and size)

 

What happens to the heating system when running and the temp reaches t'stat setting? An 8 degree over setting seems there is a possibility of adjustment in the t'stat and/or the furnace water temp control. If the t'stat is analog, maybe a digital type would control in a narrower range.

 

If we turn the thermostat down lower so that it won't get so hot, then we have to wait for it to get that cold again before the boiler runs again. The thermostat is digital and worked fine with the old unit. We got whatever temp we set for. I heard him say we got the MPO "84". I'll check the unit after work for specific model info. I don't believe he put a smaller nozel in, just left what came factory.

 

Installer said he has smallest nozzle on it and he will install a "strap on" unit that will allow us to manually adjust water temp. Does this make sense? I'm really struggling to understand this stuff. I can't find model or serial numbers on the unit or on paperwork.

 

The big question is why did you install an oversized boiler in the first place?

 

S,
An oversize boiler will not by itself give you an 8 deg. override. The boiler simply heats the water to be delivered to the emitters(baseboard or rads) which in turn heat the house.

The stat controls when the pump stops delivering hot water to the emitters. If your stat is overriding by that much you have another problem.

The only problem that you will have with an oversize boiler is short cycling which is wear and tear on the burner components.

The aquastat settings will determine the temp of the water delivered to the emitters. Your boiler's aquastat has temp water temp adjustments on it that can be lowered to send lower water temp to the emitters giving you a more gradual heat.

Do you have baseboard heaters or cast iron rads. If you have rads and the water temp is too high going to them the residual heat after the boiler shuts down might be causing your room temps to continue to rise, overshooting the stat which will cause a long down time before the stat calls again.

This becomes a problem with people with drafty houses. People tend to feel the cold before the stat does.

I don't see the need for added equipment as you should be able to lower your water temp from the aquastat on the boiler.

Your boiler is rated at 64,000 BTU'S and you have a .50 gal. nozzle which means for every hour that boiler runs you are burning a half gal. an hr which is very little. It's a 3 pass boiler which is very efficient at 87% efficiency if set up right.

Just my thought. Hope this helps a little.

 

If the original house was not insulated and has now been made more efficient by adding insulation and energy efficient windows, then the heating radiation will be way too big for the heating requirements of the rooms. Also, make sure that the heat anticipator in the thermostat is set correctly. An indoor/outdoor control such as the ones made by Tekmar, Aprilaire< or Honeywell may correct your overheating problem. I was familiar with the Honeywell device model T991B and similar models. These units will reset (change ) the allowed water temperature of the heating system based on the outdoor temperature and change it up or down based on those temperatures. AS SPOTT said, the size of the boiler is not causing the room temperature to exceed the temperature setting of the thermostat. The problem is in the type of control system in play. You can regain comfort in your with the right control system.

 

Our house it is heated with radiators. It's a plank house so it's not super well-insulated. We got several estimates on boilers before purchasing this one . Each contractor told us that there would be an issue with it being too big for the house because our house is so small , but each contractor also told us that they could adjust settings to make the boiler they were suggesting fit the size of our house. There were several different boilers that we got estimates on. This particular contractor was the only one to suggest the mpo. We liked the sounds of that unit, it was the lowest estimate, and he assured us it would work good for our home. What we have found now that it has gotten colder outside (since my original post on this forum) , is that it is heating closer to the temperature on the thermostat. However it does seem to rise after the boiler shuts off- only a few degrees above the thermostat though now that it is cooler outside. I talked to the contractor that installed it, he seemed to get frustrated with the questions I had and got kind of short with answers. It just seems like he did not want to have any follow-up conversations with us after installation and is frustrated that we are asking questions. He did state that he can install a strap-on aquastat to help us adjust the temperature of the water. Oh and he also said he has the smallest nozzle available in the unit already. I'm thinking this won't be a problem so much through the very cold months but maybe only in the fall and spring when it's warmer outside but we still need to run the unit. I truly appreciate all of your comments and suggestions as it's helping me to understand this a little more, but I'm not sure that the contractor I'm dealing with understands how to adjust the water temperature as you have described. Otherwise why would he be suggesting that I buy a strap-on aquastat? So I'm thinking I may need to call in someone else just to be safe and see if they can make those adjustments to the water temperature via the built-in aquastat before I buy another aquastat to strap on a pipe. I still believe the mpo was the right unit for us and I will be glad that I purchased it once we get this minor issue resolved. Thank you so much for all of your help.

 

This is something that you can try; have a contractor install a control similar to the White Rodgers 1127-2 or the 11B02-1 or a Honeywell pump controlL4006B-1163 or a similar control to run the circulating pump. Add 1 of these strap-on controls to the boiler's supply piping .Allow the pump to come on with the boiler controls and also be controlled by this new device. Set the control to run the pump anytime the water temp is above 100 degrees. This may or may not help but it is worth a try. Back in the early days of my entry into boiler service, the late 1960'S that is how it was done. The water gets circulated any time there is even luke warm water in the system. Give it a try. You may be surprised by the results.

 

S,
It sounds like your boiler is shutting off by the stat which is correct but the cast iron rads retain the heat for so long, which is ordinarily a good thing, that it overshoots your set stat temp and the house being drafty, you get chilly before the temp drops enough for the stat to turn the boiler back on.

With CI rads you do not need the same boiler temp as finned baseboard. They heat at different rates, and baseboards cool almost instantly where rads cool at a much slower rate.

If it's possible to post pics of your boiler and controls it is not rocket science to change the operating temps.

What is your running temp now. With the rads you can run at about 150deg. and get the same output as baseboards running at 180.

All you have to is lower the aquastat so the rads don't get so hot an overshoot so much.

You'll get a more even heat and avoid those highs and lows. Another aquastat just means more wiring to deal with and if they can't figure out what to do now any more would be a nightmare for them. They may not even take your calls then.

Hope this helps a little.

 

What is the make and model of the thermostat you have installed? There could be a problem with the "heat anticipator" setting if the thermostat has one.