Cast iron boiler turned off for summer?

[Klutch9]

We recently moved into a house with baseboard hydronic (hot water) heat. Boiler is original with the house from 1953, and actually works pretty well. They’re hard to kill from what I hear. To save money, I want to turn the boiler completely off for the warmer months. Some on the internet suggest keeping the pilot on, to keep the boiler warm, but any combustion produces water also, which can cause condensation and rust. The unit is in a dry basement, and the basement is a walk-out, so not as damp as most. FWIW, the aquastat has a low-limit adjustment only with a non-adjustable differential, about 15 degrees. I only bring this up because some people leave their boiler on, just turn the water temp down. Domestic hot water comes from a stand-alone hot water heater, so that’s not an issue.

 

[Wolf359]

Shouldn't be an issue. Lots of new boilers are electronic ignition so there's no pilot normally anyway.

 

[The_Jeff]

The theory I heard was you kept it on to keep condensation and rust out.

 

[stang5]

our house was built in 1965 and still have the original boiler. In Summer time I always turned it off by unplugging the unit and shutting off the pilot light as did the previous owner. never had any issues with it and fires right up in the winter. I also flush and bleed the system yearly.

 

[caravanmike]

Some boilers will leak when cold. If yours doesn't I would turn it off. I have two old Pennco boilers. I flip the 110v switch off but leave the pilots on. The pilots keeps the core around 80 degrees.

 

[carviewsonic]

I leave the pilot on, but turn off power so boiler won't light. Ours is 1985 vintage, no sign of trouble yet.

 

[philipp10]

Originally Posted By: stang5
our house was built in 1965 and still have the original boiler. In Summer time I always turned it off by unplugging the unit and shutting off the pilot light as did the previous owner. never had any issues with it and fires right up in the winter. I also flush and bleed the system yearly.


You flush the system yearly? Can I ask why? I suppose next your going to tell me you only use distilled water too....lol

 

[benjy]

i have been doing that for many years, at first i got a little seepage but no more. for the last 10 yrs i burn a Harman coal stove when it gets very cold about $300 yearly + since its install i use a stiebel eltron on demand water heater that i piped thru the furnace as it has a temp sensor that turns on when needed. in moderate temps the furnace in on very low + the 220 on demand heater picks up the slack. you can only burn ONE type of fuel safely in a chimney at a time!!

 

[Wolf359]

Originally Posted By: caravanmike
Some boilers will leak when cold. If yours doesn't I would turn it off. I have two old Pennco boilers. I flip the 110v switch off but leave the pilots on. The pilots keeps the core around 80 degrees.


If they leak, you can add boiler liquid which is basically a stop leak for boilers.

 

[Donald]

My guess leaving it on will cost a few dollars. Cast iron expands when its hot so it jambs itself even tighter. Your boiler is probably made of a few sections. I doubt any harm would come from leaving it on, but I doubt there will be a big savings either.

 

[Klutch9]

Originally Posted By: Donald
My guess leaving it on will cost a few dollars. Cast iron expands when its hot so it jambs itself even tighter. Your boiler is probably made of a few sections. I doubt any harm would come from leaving it on, but I doubt there will be a big savings either.


I dunno Donald, my gas bill is pretty high. The boiler is stout, but also old, oversized, and not as efficient as a modern one. If I left it running, what should I set the low limit at? Normally it’s set around 160 degrees in the heart of winter. High end is around 175, set differential.

 

[Wolf359]

Originally Posted By: Klutch9
Originally Posted By: Donald
My guess leaving it on will cost a few dollars. Cast iron expands when its hot so it jambs itself even tighter. Your boiler is probably made of a few sections. I doubt any harm would come from leaving it on, but I doubt there will be a big savings either.


I dunno Donald, my gas bill is pretty high. The boiler is stout, but also old, oversized, and not as efficient as a modern one. If I left it running, what should I set the low limit at? Normally it’s set around 160 degrees in the heart of winter. High end is around 175, set differential.


Well if it's that old an inefficient you might consider replacing it. Around here there was some state program that offered decent sized rebates when you replaced heating equipment that was between 15-25 years old depending on the type. Old boilers were probably in the 70-80% efficient range when new and the efficiency drops as they age. Some of the newer direct vent boilers go up to 96 percent (Buderus). You should have a manual J calculation done, you'd also save money going to a properly sized boiler and with a higher efficiency one, you could also get a smaller boiler.

 

[ecotourist]

Originally Posted By: philipp10
Originally Posted By: stang5
our house was built in 1965 and still have the original boiler. In Summer time I always turned it off by unplugging the unit and shutting off the pilot light as did the previous owner. never had any issues with it and fires right up in the winter. I also flush and bleed the system yearly.


You flush the system yearly? Can I ask why? I suppose next your going to tell me you only use distilled water too....lol

We had an ancient hot water system when we lived in Winnipeg. The house was built between 1928 and 1931 and the boiler was apparently original.

We were told to leave the water in the system alone. The theory was that all corrosion would eventually stop and the water and the system would remain in balance. That was the theory anyway.

Our boiler has an asbestos cover. You can bet that we had the asbestos cover professionally encapsulated and the basement HEPA vacuumed before we moved in. While asbestos on your ancient boiler doesn't sound like an attractive situation, apparently the way they used to replace these boilers was to push them over so they would break into sections for easier removal. I don't imagine the asbestos was removed beforehand either. So an intact asbestos covered boiler in an old house might actually be the best situation.

 

[Wolf359]

Originally Posted By: ecotourist
Originally Posted By: philipp10
Originally Posted By: stang5
our house was built in 1965 and still have the original boiler. In Summer time I always turned it off by unplugging the unit and shutting off the pilot light as did the previous owner. never had any issues with it and fires right up in the winter. I also flush and bleed the system yearly.


You flush the system yearly? Can I ask why? I suppose next your going to tell me you only use distilled water too....lol

We had an ancient hot water system when we lived in Winnipeg. The house was built between 1928 and 1931 and the boiler was apparently original.

We were told to leave the water in the system alone. The theory was that all corrosion would eventually stop and the water and the system would remain in balance. That was the theory anyway.

Our boiler has an asbestos cover. You can bet that we had the asbestos cover professionally encapsulated and the basement HEPA vacuumed before we moved in. While asbestos on your ancient boiler doesn't sound like an attractive situation, apparently the way they used to replace these boilers was to push them over so they would break into sections for easier removal. I don't imagine the asbestos was removed beforehand either. So an intact asbestos covered boiler in an old house might actually be the best situation.


Around here, we would call those snowman boilers because of all the white asbestos. But it's not that expensive to remove asbestos here, around $1000-$2000 for a licensed guy to remove it all before you get rid of the boiler.

 

[Donald]

Newer gas boilers are condensing and modulating. Modulating means they come on at a low flame and go to a high flame if the call for he heat is not satisfied in a few minutes. You will help resale if you get a new boiler

 

[Andrew1972]

Originally Posted By: Wolf359
Originally Posted By: ecotourist
Originally Posted By: philipp10
Originally Posted By: stang5
our house was built in 1965 and still have the original boiler. In Summer time I always turned it off by unplugging the unit and shutting off the pilot light as did the previous owner. never had any issues with it and fires right up in the winter. I also flush and bleed the system yearly.


You flush the system yearly? Can I ask why? I suppose next your going to tell me you only use distilled water too....lol

We had an ancient hot water system when we lived in Winnipeg. The house was built between 1928 and 1931 and the boiler was apparently original.

We were told to leave the water in the system alone. The theory was that all corrosion would eventually stop and the water and the system would remain in balance. That was the theory anyway.

Our boiler has an asbestos cover. You can bet that we had the asbestos cover professionally encapsulated and the basement HEPA vacuumed before we moved in. While asbestos on your ancient boiler doesn't sound like an attractive situation, apparently the way they used to replace these boilers was to push them over so they would break into sections for easier removal. I don't imagine the asbestos was removed beforehand either. So an intact asbestos covered boiler in an old house might actually be the best situation.


Around here, we would call those snowman boilers because of all the white asbestos. But it's not that expensive to remove asbestos here, around $1000-$2000 for a licensed guy to remove it all before you get rid of the boiler.


Asbestos is quite painful to deal with. One method is just leaving in your basement. The other is finding someone who will mix loads of legit paperwork asbestos and add your small amounts in for a "fee".

 

[ecotourist]

Originally Posted By: Wolf359
Around here, we would call those snowman boilers because of all the white asbestos. But it's not that expensive to remove asbestos here, around $1000-$2000 for a licensed guy to remove it all before you get rid of the boiler.

It's important that asbestos be properly enclosed or properly removed.

When you're dealing with a 1930s house there's been a lot of time for someone to not properly remove the asbestos. So there may be all sorts of unanticipated environmental contamination in an old house that no longer has its old boiler. Asbestos was treated fairly casually right up to the mid '70s.

When we bought the house in Winnnipeg we knew about the boiler and presumed the cover was asbestos. When we were talking to the owner and looking at the boiler, her little boy started to pick at the covering. Although we warned her about the dangers of asbestos, by the time we took possession of the house the cover had been picked at quite a bit. I assume the little boy did it. That little boy now has his whole life ahead of him carrying a load of inhaled asbestos. So a latency of even 20 - 40 years gets right into the prime of his life.

 

[bmwpowere36m3]

Odd to have a separate direct hot water tank... usually older boiler systems had a domestic coil and they were kept hot year-round. Then people starting adding indirect tanks on a priority loop which meant the boiler only needed to come on in the warmer months to produce hot water (much more efficient). Now we have modulating and/or condensing boilers.

The only downside I see to turning off the boiler is potential leaks... However if the boiler is truly that old I consider replacing it at some point. A new modulating boiler and indirect tank would be a very efficient setup. Condensing gains you a bit more, but you must have enough radiation to allow lower water temps and generally are run on an outdoor temperature (ODT) schedule (lower outside temp = higher boiler temps, higher outside temp = lower boiler temps).