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December 14, 2008
Using the main boiler for Heating Water or can we add a second stage
Our Coop uses the main boiler to heat water year round.
We have a large Steam boiler. With a relatively modern burner. I believe the this boiler type is called and indirect boiler. Meaning the (chemically treated) boiler water is never mixed in with the water supply.
My question is: is it really necessary to heat up the huge amount of water in the boiler to get hot running water? Also it usually takes a while before that hot water gets to where it's needed, would having a small boiler ready to go improve the situation?
Is it possible to connect a small boiler in sequence to the big one? Meaning if the large boiler already made heat and heated water, then use that water for the hotwater supply, and If the water coming from the big boiler is not hot then heat it in the small boiler.
Or if for example it's is the peak of hot water usage and the small boiler is not keeping up with the hot water demand could it signal the Big boiler controller to make hot water and then mix that with the water from the smaller boiler.
Comments
do you have a heating coil in the steam boiler or do you have an indirect hot water heater, meaning an additional holding tank heated by a separate zone from the boiler...if your heating bill is large during the off season you might consider a separate hot water heater rather than a separate boiler..simplification of systems usually saves money
Posted by: eman1234 at December 14, 2008 9:15 PM
It's a coil in the boiler.
Posted by: Gosha at December 15, 2008 8:11 AM
Then you've got a tankless coil which is the lest efficient way to make hot water.
Consider adding a holding tank and a pump to your current arrangement to make better use of your energy dollars.
Me:
http://www.GatewayPlumbing.com
Posted by: Master Plvmber at December 15, 2008 9:03 AM
MP, do you have a preference for Indirect Water Heaters. I'm looking at Weil Mclein 60, Burnham al70sl, and Smart 60.
I have a 250K oil burner with DHW coil. I really like the continuous HOT water that my current setup provides, but also realize the inefficiencies.
My 1 hour max load is a little over 250 gallons and prefer 140 degree to 115.
Posted by: la di da di at December 15, 2008 10:45 AM
We do not have a separate holding tank.
The boiler is about the size of a steam locomotive and as I was saying it boils it's own chemically treated water.
The supply water then goes through a coil in the boiler absorbing the heat from the boiler water. The very hot water then comes out of the boiler and is mixed with cooler water from the water supply via a mixing valve (which happens to not be working well at this time, as the temperature is very inconsistent).
So are you saying that we could add a separate water Heater with a holding tank ? Could we still use the main boiler for hot water during the heating season? How would that work ?
Posted by: Gosha at December 15, 2008 11:43 AM
Phripley, that's not the device we're talking about.
The old set up the OP has is called a tankless coil. The new gas-fired devices are called tankless water heaters. Unfortunately, the terminology is similar but the equipment is very different.
La di da di, as much as I am a fan of Burnham, it seems their indirect water heaters are best suited for areas of the country where the water has a high mineral content. That's the best way to justify the cost and weight of the stone-lined Alliance tank.
I most often install Burnham boilers partnered with Weil-McLain or Super-Stor indirect water heaters.
Gosha, the water moving through the tankless coil in the boiler can be stored in an insulated tank which will allow the boiler to run at a much lower temperature and increase efficiency greatly. This arrangement also goes a long way in stabilizing domestic hot water temperatures.
This type of system can be used every day of the year effectively. There is no need to install a back up or parallel water heater.
Me:
http://www.GatewayPlumbing.com
Posted by: Master Plvmber at December 15, 2008 3:22 PM
Thank you, MP. You're my hero. I knew there was something extremely odd about this whole setup. I do have one more concern though, is there a way to electronically ensure that the water in the storage tank does not go bellow a certain temperature, and what can be done when it does.
Currently the boiler is so massive that the top of the burn chamber stores enough water for a considerable amount of time. When you combine that with what mixing this water with cold water gets us, the boiler only fires about once an hour. How long would an insulated tank keep the water hot?
Posted by: Gosha at December 15, 2008 3:36 PM
The tank would have an electronic thermostat installed that will allow the water to recirculate through the boiler when it cools down.
A well-insulated tank will loose less than one degree per hour as opposed to the 10-20 lost through the flue of a conventional water heater.
It's a good purchase and a great way to recapture some of the standby losses of a heating boiler in its off cycle.
Posted by: Master Plvmber at December 15, 2008 4:08 PM
MP, why don't w/h have flue traps like boilers to limit the standby loss?
Posted by: cmu at December 15, 2008 4:35 PM
As in automatic vent dampers?
Because most residential water heaters use a non electric uni-trol gas valve and most vent dampers work as an interlock, switching power on and off to the boiler's gas valve, to be effective.
We do see them on commercial water heaters, though. Those heaters need to be hard-wired to get 120 volts and have all the safety and efficiency controls of any space-heating boiler.
Posted by: Master Plvmber at December 15, 2008 4:59 PM
MP I just wanted to clarify that the setup is in a 48 unit coop. As I understand it, the electronic thermostat would measure the temperature of the water in the tank and if needed would signal the Boiler controller for a burn cycle. Currently it is done by a mechanical water level gizmo that is Quite old. It would then pump the water through the coil again and then wait again.
Would this tank store the superheated water that is to be mixed with city-water, or is this ready for distribution throughout the building?
How would this work in a high demand scenario ?
Everything would still go through the boiler, and be electrically pumped into the tank. Then from the tank would it be mixed in with cold water directly from city like it is today.
Posted by: Gosha at December 16, 2008 1:04 PM
Gosha -
Following up on an earlier thread: Why did you go with the MPC Platinum and not the EPU? Do you have any additional sensors in the buildings?
Also, why don't you just let Ari figure all of this stuff out for you?
Posted by: Pipecock at December 16, 2008 1:53 PM
The reason we went with the MPC Platinum unit is because we eventually want to be able to monitor the system's operation over time. Meaning once the return water temperature sensor is installed properly, we will hopefully also add ambient temperature overrides as recommended by MP.
That will effectively create a way for us to see what the temperatures throughout the buildings do during and after each boiler burn. That will point out if and how we could optimize the operation of the existing boiler with the current one pipe steam system. Perhaps see how much heat we loose by not having insulated pipes and how long does it take for the radiators to cool after a burn.
We have rebalanced the TRVs during the last season. That helped quite a bit. However the current configuration still does not respond to weather changes correctly without human intervention. Meaning we are constantly over/under-heated every time the weather changes significantly. Someone needs to adjust that every time.
While I realize that the current system is very primitive and that we can not do much with what we have I believe we can prevent the boiler from running when the buildings have already been heated sufficiently. That will conserve some oil, save us money (I doubt oil prices will stay where they are right now, after what we have seen over the summer) , and hopefully prevent any more crud from being released into the air for no reason.
With regards to Ari, he's pretty useless as far as managing managing projects is concerned! For ex. it took him 3 months to make me a nametag. We've been fighting with him to manage projects for us for years, many were not even acknowledged with a phone call. The ones that were, quickly turned into disasters. The only reason we're still with him is the fact that he's honest, which I can not say about other management companies we've been with, over the years.
Posted by: Gosha at December 16, 2008 5:54 PM
mp's idea of a storage tank connected to the coil with a circulator pump is a great idea....btw gateway is a great outfit, honest, a little pricey , but that is because they are a union shop that respects its employees....
Posted by: eman1234 at December 16, 2008 7:16 PM
Gosha,
At 48 units and considering what I have been reading, I think it may be worth having a discussion about your heating situation. You are probably running a boiler between 150 and 200 HP. Perhaps more. This is my field. Let's talk.
sfontas@moltenmechanical.com.
Best regards.
Posted by: SteamMan at December 19, 2008 6:16 PM
I prefer to make this sort of information public domain. What do you have in mind? Is it something that was not mentioned on here yet?
Posted by: Gosha at December 19, 2008 6:54 PM
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