Hot Water Coil as Emergency Dump Zone

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Joe in NH
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Post by Joe in NH » Mon. Jan. 05, 2009 9:59 pm

I have a Harman SF 260 hand fired wood/coal boiler that is connected to my oil fired hot water boiler. The water heated by the Harman is circulated through the oil-fired boiler that then feeds the four zone hot water heating system throughout the house. I purchased a hot water coil for the Harman that I plan to install in tandem with the hot water coil in the oil boiler to increase the water coil area available for heating our hot water. There is no hot water storage tank. At the same time I am wondering if the water coil in the Harman might also be used to create an emergency dump zone for that hopefully rare occasion where the electricity fails and I am not home to hook up and start the generator. We have municipal water (very cold in mid winter) that continues to be available during an electric outage. The key to this arrangement is some kind of water valve that will stay shut when the electricity is on and will open when the electricity is off. This valve could be included in a line that is teed off the hot water line from the Harman and run into the basement sink. Does such a valve exist and, if so, where might I find one? Also, does this idea make any sense or should I just forget about it? Any advice would be greatly appreciated.

 
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Post by CapeCoaler » Mon. Jan. 05, 2009 11:08 pm

80-120 gallon tank on thermosiphon loop, valve opens on electric failure and backed up by some baseboard radiator for additional heat dump.
Keeps you heating water while the power is out.
What happens if city water fails also, though it may be a rare event?

 
Joe in NH
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Post by Joe in NH » Tue. Jan. 06, 2009 9:08 pm

Thanks for the reply. My house is built on a ledge and I am somewhat limited in available space in the basement. I will have to look into a water tank that could fit in a limited space. Did not think about the possibility of the local water stopping during an electric outage but I should check that out too. Thanks again. Joe

 
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Post by U235a4 » Tue. Jan. 06, 2009 9:27 pm

I have a question on your question.... are you looking for a way to heat hot water without power or are you looking for a heat dump if the coal boiler gets two hot?

if your just using this for dhw then I have these question
#1 are you going to run the coal boiler in the summer aka year round except cleaning time
-my answer if your is "yes" then why not just use the coal boiler as your sole hot water coil and forget the oil boiler.

#2 are you worried about water being two hot and thats why you want a tank?
-my answer if yours is "yes" I would just install a watts mixing valve to adjust hot water temp.

 
Joe in NH
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Post by Joe in NH » Wed. Jan. 07, 2009 9:05 pm

U235a4 – I am looking for a way to cool the boiler if the there is an electric outage. I do not plan to run the boiler in the summer. I was wondering if there was a way to use the domestic hot water coil to cool the boiler should there be a power outage and there was no one at home to connect and start the generator. In that we have municipal water, there should (still need to make sure) be cold water available during a power outage. I have since discovered that there is an ASCO solenoid valve for hot water that would be closed when the power is on and open when the power is off. It costs nearly $300, which is more than I want to spend. Thanks for your questions. Joe


 
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Post by Plumbit » Thu. Jan. 08, 2009 1:17 am

A loss of power in a wood or coal fired boiler should have a normally open zone valve that is close when power is on and opens on loss of power it would be hooked up to a gravity heating zone that would be able to disapate 15/20% of capacity

 
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Post by efo141 » Thu. Jan. 08, 2009 1:43 am

What do you do if your coal boiler is higher than the oil boiler and the baseboard? I have been looking at inverters with auto transfer switch. Is there a cheep way to do this? I have a 400 watt inverter it is a mod. sine I need to power 1 Grundfos 3 speed circ. I think it draws about 60 watts on low speed.

 
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Post by JB Sparks » Thu. Jan. 08, 2009 6:11 am

Joe in NH,

Well since this is a discussion that I am concerned with, I thought i'd chime in and put in my two cents.
I have an SF160 boiler tied in parallel with my oil boiler. I hold the oil boiler off electricaly as long as the coal boiler temp. stays above 130* and have a circulator running between them 24/7. When the power went down in the ice storm, I had to shut the coal boiler down as I didn't have enough gas to keep the generator running continuously. So having said all that, this is what i'm going to do. Somewhere on this forum there is a post about a 750 watt inverter which would be big enough to run the boiler circulator as well as the four zone cirulators. That will take care of power outages. It will transfer automaticly. One of the zone circulators is for the DHW superstor water tank. I am going to install a preheat tank to warm up the water before it goes into the superstor as we have very cold water in the winter time here too. also going to cut in a bypass that Freddy suggested to keep the boiler water temp. more even. I have a relay that will kick in on over shoot of boiler temp. and it will turn on three zones at the same time which will pull the water temp. down in about 4 or 5 minutes. That keeps the BTU's in the house.
If a DHW coil in the coal fired boiler is used, you have to have a circulator running 24/7 to keep the water flowing. That to me is a circulator that could be eliminated with a storage tank and a circulator that only runs on demand.

I hope this well help, sorry for the long rambling.

JB

 
Joe in NH
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Post by Joe in NH » Thu. Jan. 08, 2009 8:59 pm

J.B. – Thanks for joining in. I look for your posts because of my obvious interest in your SF160. Although my hobby is the repair and restoration of antique pendulum clocks, I am not very skilled with electricity and plumbing. Not much need for either when working on a mechanical clock but very important when setting up a coal boiler. We live in an area where there is very good electrical service and through a combination of that and luck, we have not had an extended power outage in the time we have lived here. I bought a gas generator about seven years ago and have never had to use it for an emergency.
I love my Harman but at the same time I have the uneasy feeling that we are sitting on a volcano and could come home to a power outage and a boiler that is producing more heat than the non-energized system can handle. A friend of mine says to not worry, the worst thing that can happen is that the pressure valve on the boiler will open and dump the hot water and it will be replaced with cold and everything will be fine. He is probably right but I am still trying to come up with a simple way of automatically controlling the heat in the boiler should the electricity fail and no one is home. I do not see me heating the house with the Harman during a prolonged power outage. I would probably use the faster responding and more controllable oil boiler during that time. The fact that we will be installing a hot water coil in the Harman to help produce more hot water got me thinking that I could use the same hot water coil without electricity to cool the boiler. I talked to one of the maintenance guys where I work and he thinks that a “normally open” solenoid valve for hot water would do the trick. They can be expensive so I will certainly test the coil’s cooling ability prior to installing the valve. I will let you know what happens. Joe

 
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JB Sparks
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Post by JB Sparks » Sat. Jan. 10, 2009 6:25 am

Hi Joe, Sorry I didn't get back to right away,been busy installing emergency generators for people. Nothing like a big ice storm to drum up new business.

Don't need electrical and plumbing in making clocks.....what about a nice big water operated clock like the Greeks or somebody way back then used to make.... That aught to be a fun project!!!! :lol:

As to a solenoid valve, the valve has to be either powered on or powered off. If you want the valve to be opened when the power is down then that means you have to keep it energized 24/7 in the opposite state when the power is on, I don't like to keep an electrical coil energized 24/7 just cause you never know when it's going to quit, like maybe when your not home.This is just my opinion. I would rather opt for the inverter that will keep a battery charged up when power is on so as to be ready when the power goes down. The only thing that has to be figured is how many hours of run time you would get out of a 12 volt battery. I would want at least 8 hours or at least enough run time for the fire to go out on it's own if nobody is around to tend it, so that means I hook up more than one battery in parallel to meet the need. Having said all this, I haven't bought the inverter for myself yet, but it is diffenately on the list for spring modifcations of my setup.

These are just my thoughts on the subject Joe, Let me know how you make out on what ever you decide to do.

If i'm not mistaken I think you mentioned that you live somewhere around Littleton NH, My wife and I love driving around up in your neck of the woods, maybe the next time we are up that way we could stop by and see your setup and just say hello.

Hope this helps Joe.

JB
PS: don't ever get rid of the generator, you never know when you'll need it. If nothing else it's peace-of-mind having it.


 
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Post by stoker-man » Sat. Jan. 10, 2009 8:41 am

Danfoss Valve for Stoker Safety

check that possibility.

 
Joe in NH
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Post by Joe in NH » Sat. Jan. 10, 2009 9:24 pm

J.B. – I see where you are getting some snow (no ice) down there tonight. It is +4 degrees here and not a sign of a flake. I would very much enjoy meeting you. PM me when you are thinking about coming north of the notch. At this point I have decided to have the hot water coil installed in the Harman to increase the amount of domestic hot water that is available. At the same time, I will run a line over to the basement sink. I am still researching the solenoid valve idea.

Stoker-man has posted a link to a thread where a non-electric valve is discussed and I would be interested in knowing if anyone has tried it. If it works and the price fits within the budget, it sounds like it would be the ideal valve.

 
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Post by journeyman » Sat. Jan. 10, 2009 11:04 pm

the nonelectric valve you need is your presssure relief valve, install dhw stroage tank within 10ft and no circ pump is needed, even with a circ pump hot water will turn the impeller of the pump with a storage tank you have a bit of time before the water would flash over to steam thats the reason for the prv.
no need whatsoever for a elaborate "rube goldberg" system

 
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JB Sparks
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Post by JB Sparks » Sun. Jan. 11, 2009 6:09 am

Joe,

Thanks, don't know when we'll be taking our next ride up country, but i'll be sure to let you know ahead of time.

I looked at that nonelectric valve the other day myself. Didn't know that type of valve excited, It looks very interesting, should fit right in with what you want to do, hope it's not too pricey. As Journeyman says you probably don't need it, but I like having a good back-up system in place for those just-in-case situations.

Got about 2" on the ground right now, this should be an easy one.

JB

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