Steam with Added Hot Water Zones

NickZ

We recently bought an older home that was added onto in 1994. The original part of the home (built in 1893) is heated with steam and the new addition (1994) is heated with two separate hot water zones, one for the new first floor and one for the new second floor. Additionally our hot water is also heated from the boiler. The boiler is a Weil-McLain and the two hot water heating zones utilize the same Everhot heat exchanger, but each has their own circulator (Bell & Gosset). We have had issues with regulating the heat in the house since we moved in. There seem to be two separate issues:

1. When it is cold out (below 20F) and the new first floor hot water zone calls for heat the boiler overworks to the point where it starts creating steam which results in heating the steam portion of the house even if the steam portion of the house is already hot.

2. When the circulator is on for the new first floor zone and the new second floor zone has NOT called for heat, hot water is actually flowing up to the second floor on the return feed.

The net result of this is we have no ability to regulate heat in the house because whenever the new first floor zone calls for heat all other zones are heating up, even if they are already warm enough.

We have had many tech guys come out and look at this over the past two years and seem to get a variety of answers as to how to fix this. One reason we have gotten for the first problem seems to be that the Everhot heat exchanger has gotten dirty on the inside and needs to be replaced. Would this cause the boiler to overwork while trying to get the hot water temp up high enough and is replacement the best option? The heat exchanger is only 11 years old. Is it reasonable that it would go bad that fast? The second problem seems to be caused by a bad valve that is supposed to close off and prevent water from entering the second hot water zone. Is this a common problem and does it make sense?

I am hesitant to act based on this reasoning only because we have been dealing with this problem for almost 2 years now and have gotten many different opinions and solutions. This is our first house that does not have forced air heat and I have tried to do some reading on steam and hot water systems, but will be the first to admit that my knowledge is very limited, so any help would be greatly appreciated.

Tom M.

a couple possibilities

Without actually seeing the instalation, it is hard to say for sure, but here are some thoughts. From your first problem, it souns like there is some device to call the burner on when the fhw zones call. This is usually accomplished by a set of contacts in the circulator relay connected in parallel with the steam thermostat. This circuit should be broken by a limit control in the boiler set at 180*F. If this is a Weil McLain SGO boiler, there is a tapping for this control on the left side in the rear section. If there is a control installed, it may be set too high, reading improperly, or in a poor location.
For the second problem, if the flow in the second floor zone is actually pumped around by the first floor circ, then there is a problem with the flow control as you mentioned. However if the hot water goes up the return by gravity, only one or two rooms are over heated, and the hot water never actually comes back down in the supply pipe, then you only have a gravity situation. This could be corrected by adding a flow control on the return side of the loop or by using an "underslung" return manifold where the returns enter the bottom of the manifold so that the hot water will be trapped.