Replacing furnace, but before I do...

margaretp

I need to replace our furnace. It was an oil steam unit that was converted to gas when we took the oil tank out due to construction. It constantly turns off (and thermostat goes blank/off). If I empty a bit of water, it will turn back on (whether it needs to be emptied or not). This can happen at least 1x per day. Usually does the trick, but this will be a disaster if I am away in the dead of winter and can't do this trick. I have had many parts replaced over the years in the hope of helping this problem. It usually buys me a few months, but the problem returns. So I have decided to replace the unit.
The house is over 100 years old. The cast iron radiators are difficult to regulate - some rooms cold, others too hot. I have had valves replaced and balanced... There is also the problem of noisy water-hammer sounds, whistling radiator vents and radiators only getting half heated.
Before I buy the new furnace, do I have another problem to deal with in the existing system. Who do I call to "blow out" the system. If the pipes are old and possibly clogged, how can I correct that without tearing down the house and the plaster walls?
Finally, I have quotes on Weil McClean and Lennox - any opinions on either?
Thanks!

KC_Jones

First it sounds like you have probably been dealing with the wrong contractors. What you need is a steam expert. Some of the things you are saying don't make sense. And honestly unless the boiler is leaking it might not be worth it to replace the whole boiler. Where are you located? We may be able to recommend a good steam person in your area. Second post some pictures of what you currently have and we can give you some amount of system evaluation. Do you know if you have a one pipe or 2 pipe system (how many pipes run to each radiator?). Oh and just to keep terminology straight you have a boiler NOT a furnace. A furnace makes hot air for forced air systems. Welcome to the forum!

Jamie Hall

You have multiple problems here! Throwing parts at them won't -- usually -- solve them.

Start with the simplest one: chances are, if you are hearing whistling sounds from the radiator vents (sounds like you have one pipe steam? One pipe going to each radiator, and a vent part way up the other end?) the odds are very good indeed that you are running at too high a pressure. The place to start, then, is to make sure that the pressurestat on the boiler is set to as low a pressure as it can be -- usually about 1.5 psi -- and that it actually turns the boiler off and lets it turn back on when the pressure drops again, as it will.

Now this is one occasion where it is possible that throwing a part at the problem may help: it is quite possible that the pigtail -- the looped pipe which connects the pressurestat to the boiler -- is plugged, or that the pressurestat itself is faulty. If whoever you have working on your system doesn't know what I'm talking about, find someone who does! In any event, get that attended to.

Second, the water hammer sounds may also be caused, in part, by too high a pressure. However, they may also be caused by some pipes somewhere not being pitched correctly to drain, allowing condensate to collect in the pipe. It then gets pushed along by the steam, and bangs. So someone needs to check the pitch of all the pipes in the system.

Third, it is quite likely that there isn't enough -- or any -- main venting; that is to say, big vents at the ends of the steam mains. That needs to be addressed.

You really can't address the problem of some radiators not heating properly until, at the very least, the three items above are addressed and corrected. As KC said just above, if whoever you have looking at your system hasn't thought of these things, or doesn't know what we are talking about here, then let us know where you are and we may be able to find a good steam man in your area.

I might add that replacing the boiler does NOT appear on that list above, does it? It might be needed, it might not --but doing that alone isn't going to fix any of your problems.

unclejohn

Your thermostat goes blank because a safety switch is breaking power to the transformer. You need to find out which switch is causing it. How letting water out of the system resets the switch i'm not sure.

KC_Jones

Pressuretrol possibly? Pressure builds up cuts out, pigtail is mostly plugged up so it doesn't react. Let water out of boiler causing a slight bit of vacuum to develop in pigtail and the pressutrol let's burner fire again. That is all a real STRETCH for sure. Could it also be a float LWCO that is all hogged up and she is letting the water out there which then frees up the float just enough to work? It's all theories and guessing at this point.