BeGreen said:
Looks promising. They've got a nice guarantee attached to it. I say go for it. The priciple is sound. It just holds off firing the boiler if there is enough residual heat from the last firing of the boiler until the water temp drops. Anything that increases efficiency with a 1-3 yr. payback is a good plan in my book.
here's a direct link:
http://www.becketthm.com/
I also looked into this at one point - however, we will be using so little oil now between wood heat last year and solar HW going in next week that it wouldn't make economic sense for us.
The technical principle is very sound - reduce the number of firing cycles, and let each cycle run longer for better overall efficiency. Much like pushing the limit settings apart a bit on your aquastat to accomplish the same goal all summer if you are using your boiler for domestic hot water. So from that perspective, it's a very honest claim. However, I wonder if there is a simpler way to get comparable benefit.
Our boiler can kick on one of two ways. First, if the boiler temperature as measured by the aquastat drops below the lower setpoint, it will fire and run until the upper setpoint is reached. This is for domestic hot water generation. However, if any thermostat calls for heat, this is bypassed as the thermostat immediately sends a signal to fire the central boiler and it will fire unless the aquastat is already above the upper setpoint temperature. I think this is fairly typical.
I suspect the reason systems are wired this way is to proactively get the burner fired up and going ahead of the rush of cold baseboard water that is about to enter the boiler, helping to prevent the boiler being cooled down too quickly and having a hard time recovering. However, particularly in multi-zoned setups, many of these heat cycles are relatively short and wasteful because there was ample heat in the boiler to supply that demand without ever firing, and it could have waited a while until a later call for heat to recover.
I have considered simply disconnecting the thermostat signal and relying on the aquastat to decide when the boiler is cool enough to require firing. In doing so, you would perform a similar function to the Beckett Heat Manager - the only thing the Beckett really seems to add is an anticipatory sensor to help avoiding the temperature in the boiler drop quite as low, which would be important if you have an undersized boiler and are having trouble keeping the house warm with it. I don't think that would apply for many folks - I think the worst thing you would see is that on really cold days, it may spend another minute circulating slightly cooler than normal water before getting hot water at peak temperature up to the baseboards. But if that happened, the thermostat would just call for the circulator to run another minute or so to meet the demand, so no real issue.
Perhaps an experiment for a cold day this winter...
-Colin
