Waaay OT: Home Heating System Question

[newbert]

Would anyone here know whether a hot-water baseboard (gas-fired in this case) home heating system be able to continue operating if the water supply to the home gets shut off?

Thanks!

[Fatcycledaddy]

Normally those are independent systems with no connections to your water supply. Those pipes are filled with some type of corrosion inhibitor and anti freeze so they cant blend or mingle with the water supply. There is normaly a water makeup supply line to add water to the system if there are any leaks and it runs low, but there is a check valve in line so water can only go one way.
So water supply shut off should not affect the heat in any way unless there is a leak somewhere and makeup water is needed.

[Bob Denman]

[ARtraveler]

Good question...but I have to watch this one. I have radiant heated floors--with water and powered by gas.

[canamjhb]

I know the gas-fired water heater in our house will not fire up without the water flowing. We can turn the water main off when we leave for a week or two and the water heater will not keep trying to heat the water. I suspect your system is the same.....? No water flowing = no fire.

[R FUN]

CANAMJHB, NEWBERT I am sure was talking about his home heating system. I agree with FATCYCLEDADDY that the heating system is definately a closed system and his advice is correct. That is the same as my system.
Roger

[Fatcycledaddy]

I know the gas-fired water heater in our house will not fire up without the water flowing. We can turn the water main off when we leave for a week or two and the water heater will not keep trying to heat the water. I suspect your system is the same.....? No water flowing = no fire.

Two totally different things, or systems. Your gas water heater is heating your potable water for your home and yes water flow must be there.
Water for heating such as baseboard heat, (radiators) as the OP said, is not part of the potable water system.
Water flow provided by an inline pump that supplies all the radiators with hot water is required to fire the heater, but no water flow from the line is required unless a low water alarm goes off and makeup water is required.

There are several safety checks on the system.
1. No water flowing through the system will cause the heater to build up steam by heating the same water too long. So a pump pushing water through the system must work.
2. There is a high temp or overheat sensor that will shut down the gas valve if it over heats.
3. There is a low water shut off that will shuts the boiler down if a low water situation is detected.
4. There is a pressure relief valve that will relieve the pressure created by any steam from overheating.
5. There is an expansion tank that has a air bladder in it to absorb the expatiation and contraction of the heated and cooled water.
6. There is an anti corrosion additive and antifreeze added to keep the pumps and lines free of corrosion, and from freezing and bursting if system shuts down in cold weather.
Because of this being a "closed" system, makeup water would only be required if water was leaking out somewhere within the system.
Our system here works with the NO water flow from the makeup line for years because there is no leaks.
So if the system is not working after water is shut off, it is low on water due to a leak, or one of the other safety system systems could be activated.

[bscrive]

Yep, fatcycledaddy is correct. I have helped put in a couple systems over the years.

[BLUEKNIGHT911]

Two totally different things, or systems. Your gas water heater is heating your potable water for your home and yes water flow must be there.
Water for heating such as baseboard heat, (radiators) as the OP said, is not part of the potable water system.
Water flow provided by an inline pump that supplies all the radiators with hot water is required to fire the heater, but no water flow from the line is required unless a low water alarm goes off and makeup water is required.

There are several safety checks on the system.
1. No water flowing through the system will cause the heater to build up steam by heating the same water too long. So a pump pushing water through the system must work.… This doesn't make sense to me ….. your water heater ( gas , elec. or oil sourced ) has a thermostat to regulate the Temperature - it doesn't matter if the water is used or not, there will be hot water made ….. On the other hand if your potable water has individual heaters at the faucet or washing machine or shower ….. then it is a heat-on-demand system …..jmho …..Mike
2. There is a high temp or overheat sensor that will shut down the gas valve if it over heats.
3. There is a low water shut off that will shuts the boiler down if a low water situation is detected.
4. There is a pressure relief valve that will relieve the pressure created by any steam from overheating.
5. There is an expansion tank that has a air bladder in it to absorb the expatiation and contraction of the heated and cooled water.
6. There is an anti corrosion additive and antifreeze added to keep the pumps and lines free of corrosion, and from freezing and bursting if system shuts down in cold weather.
Because of this being a "closed" system, makeup water would only be required if water was leaking out somewhere within the system.
Our system here works with the NO water flow from the makeup line for years because there is no leaks.
So if the system is not working after water is shut off, it is low on water due to a leak, or one of the other safety system systems could be activated.

See above in BLUE

[Fatcycledaddy]

"This doesn't make sense to me ….. your water heater ( gas , elec. or oil sourced ) has a thermostat to regulate the Temperature - it doesn't matter if the water is used or not, there will be hot water made ….. On the other hand if your potable water has individual heaters at the faucet or washing machine or shower ….. then it is a heat-on-demand system …..jmho …..Mike"

You are not thinking boiler, you are thinking water heater. A boiler is used for hot water heat, it has a very little water in the water jacket that heats up VERY quickly so you will have heat faster. The Thermostat does not control the water temp, it controls the room temp and if it demands heat, hot water is made. If the thermostat does not demand heat then nothing happens.
Because there is so little water in the water jacket and it heats up so quickly, steam could be made and pressures build up very quickly if there was no water flow through the water jacket.

There is one other safety feature I forgot to mention. On some boiler systems there is a damper that shuts off the exhaust pipe or stack keeping it from drawing the colder air over the water jacket cooling it off after the flame shuts down. This system must open the damper and be verified by the boiler before the gas valve will open.

I have maintained apartments for years with hot water heat, the current office I am in had hot water heat, and the home I built and currently live in has hot water heat. You do learn a thing or two about it after being exposed to it for over 30 years.

By the way, a licensed expert I am not, but with the years of experience working with them, I can troubleshoot them with the best of them, and have to quite often.

[canamjhb]

Fatcycledaddy, I know the systems are different. The point I was trying to make is that if the circulation/water system in not operating, then there are safety features to insure that fire doesn't burn up the system. Both a HW heating system and a potable water system have their individual safety features. Guess my original comment was not very clear.....

[newbert]

Thanks for all the comments, guys. Especially FatCycleDaddy - Now, I'm edjumakated!

[C. Lee]

For the most part the guys so far are correct however in my area 98% of residential hot water boilers use a connection to the domestic water line for water supply and generally maintain a pressure of 10-15PSI in the system. they don't use any kind of antifreeze or rust inhibitor. That being said the question was "does the boiler need the water turned on to operate" and the short answer is no. As long as the system doesn't spring a leak or loose pressure, It should operate with main water valve turned off. I would turn the valve on the boiler which supplies the water off before I turn off the water main to prevent pressure from bleeding back into the house water system.

Normal boiler operation is as follows;
1. Thermostat calls for heat
2. Pump comes on and begins to move water through system
3. Once flow is verified and assuming the water in the system is cool, the damper opens, main burner comes on and water is heated to a preset temperature, the boiler then maintains that water temperature while the water is circulating until the thermostat is satisfied.
4. Boiler shuts down and damper closes.

The flue damper is designed for standing pilot or intermittent pilot systems and it's primary purpose is to keep any heat generated by the pilot inside the heat exchanger for efficiency reasons. There are other safeties in the system as well and all are designed to regulate water pressure and temperature. If a hot water boiler begins to make steam, something has gone terribly wrong as the relief valve should have opened well before it reached the 212 degree point. Temperatures in most hot water heating systems range from 120-180 degree depending on application whether radiator, base board heaters or radiant floor heat (which has the lowest temperature). Chris

[C. Lee]

In addition, of the water in the boiler is already hot, then when the thermostat calls for heat the pump will come on circulate water until it has lost its heat, then the boiler will come on.

[Easy Rider]

Normally those are independent systems with no connections to your water supply.

But then you go on to say that there IS a connection.

Most systems also have a pressure release safety that tends to release a bit of steam occasionally.

It will NOT cease to function immediately upon the loss of outside water pressure.

You would need to contact the manufacturer to find out exactly how YOURS works and how long you might expect it to work without any outside water pressure.

Generally right answers are not guaranteed to be right in every case.

[Bob Denman]

The two systems connect only because the heating system uses water...

… so you can open a valve, and "top things off" (so to speak...)

[Fatcycledaddy]

In addition, of the water in the boiler is already hot, then when the thermostat calls for heat the pump will come on circulate water until it has lost its heat, then the boiler will come on.

I think you meant "if" not of the water in the boiler is already hot.
The boiler heats the water up to a designated temp and the burner shuts off, the water continues to circulate if the thermostat is demanding heat.
Unless your house is VERY poorly insulated, the water in the system will cool off before the thermostat demands heat again meaning there is no residual heat when it is called for.

Some people think that the boiler kicks on and off to maintain a certain temp of the water at all times, like a water heater does, and that is not true. The boiler only heats water when the thermostat is demanding it, at least in every system I have worked on.