Boiler & domestic hot water problems/questions.

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Old 01-30-10, 12:49 PM
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Boiler & domestic hot water problems/questions.

Greetings,
I've lived in my home for 5 years, and the boiler has never been able to provide enough domestic hot water to take a hot bath or even a decent hot shower. I had the boiler serviced when I bought the house, including having the domestic hot water coil descaled - no change. I've had the boiler checked out a number of times over the years; they usually make a little adjustment to the aquastatic control and say "fixed". Well I've had it with warm showers at best, and I am going to install an electric water heater (the boiler is oil fired, we do not have natural gas). My questions are; can I run the domestic hot water from my boiler into the new electric water heater as kind of a preheat system to cut down on the work the electric water heater will have to do to heat the water? Or should I cut out the domestic hot water from the boiler completely and hook up the electric water heater in the conventional way, and finally, if I must remove the domestic hot water provided by the boiler in order to hook up the electric water heater, can I simply shut off the valve from the domestic hot water and cut and cap the pipe?

Any help would be appreciated. Thanks
 
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Old 01-30-10, 01:39 PM
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Big Chief, are you familiar with indirect water heaters? If not, before you set your sights on an electric, perhaps you should check them out... google "indirect water heater" and see what you think. Pricier than throwing an electric in, but with the price of electricity... might be something to consider.

By the way, if you do abandon the coil in the boiler, you should NOT cap the pipes coming out. You don't want pressure building in the coil... also, keep in mind that unless you do something with the aquastat control, the boiler will still continue to fire and keep itself warm.
 
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Old 01-30-10, 01:56 PM
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Just to support the idea of an indirect hot water heater; I switched from a 50 gallon direct fired gas water heater to a 35 gallon indirect water heater and I have never run out of hot water with just the shower going. It runs off the boiler as another zone. I have mine set up as priority so when the hot water tank needs to be reheated, it dedicates the boiler to just that and will not heat the house until the water tank is satisfied. I am quite happy with it.
 
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Old 01-30-10, 02:23 PM
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yes, I have considered an indirect water heater, the last tech who checked out my boiler suggested one - very expensive to have it installed. It would be a far better solution I'm sure, but we need hot water now, and cost is a factor. What I am planning is to instal the electric heater after the tankless coil, so the water entering the heater would already be hot (from the tankless coil) in the winter months while the boiler is fired up. I would shut down the boiler in the summer, and the water would flow through the tankless coil into the electric heater unheated of course. This is an installation that I could do easily myself - I'm sure the indirect heater is beyond my abilities.
 
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Old 01-30-10, 02:29 PM
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I think you will save more money if you take the boiler out of the loop altogether. The way it is set up now, the boiler will always maintain a min. temperature because of the hot water coil. If you stop using the coil, you can modify the boiler for a cold start so it will only fire when there is a call for heat.
 
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Old 01-30-10, 02:35 PM
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Any suggestions on taking the boiler out of the loop altogether?
 
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Old 01-30-10, 09:33 PM
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"What I am planning is to instal the electric heater after the tankless coil, so the water entering the heater would already be hot (from the tankless coil) in the winter months while the boiler is fired up. I would shut down the boiler in the summer, and the water would flow through the tankless coil into the electric heater unheated of course."

Not meaning to sound rude, but- WRONG!

Inefficient, and code violation.

Take a look at this:
http://i790.photobucket.com/albums/y...tem2000DHW.jpg

Instead of plumbing to the plate exchanger as described, you
would plumb to your coil. Relatively cheap, efficient TEMPERED
hot water, and you still have the electric option. Local code
may require you to install a tempering valve. I've installed or
replumbed MANY water heaters in this manner, and I have
MANY smiley faced customers with virtually unlimited hot H2O.
 
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Old 01-31-10, 08:35 AM
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YES! Thank you SuperSteve. I thought there had to be some way to do this - I obviousely didn't know the proper way. The 2 plumbers, and the heating oil provider tech that have come and checked out my boiler did not mention such a system, they all just suggested an indirect system. Thanks again!
 
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Old 01-31-10, 09:58 AM
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That is a good idea if you like higher fuel bills than you already have. It is a terrible way to make hot water. Instead of not having enough hot water now you will have enough hot water at a cost of the same oil bill and add the electric bill to run the hot water heater. This was a better idea when oil was much cheaper. We must taylor our thoughts as conditions change.
Take the coil completely out of the picture, cut the pipes but don't cap them, cold start the boiler and get an oil savings, add the electric hot water heater and use your fuel savings and pay the electric bill.
This would not be my first choice as electric is an expensive way to make hot water. The indirect is better. I understand the $$$ issue.
Before you jump the gun let's review what you have now rather than spend the money when the time is not right.
What are the aquastat settings? What is the flow rate. Get a 5 gallon bucket and put it in the tub. Adjust the water to the temperature you want. Turn off the cold, stick the bucket under the faucet for one minute. How much water is in the bucket? Did it stay hot? You may just be overdrawing the coil. Is there a manual blending valve between the hot and cold pipes above the coil? Is it closed? Is there a good washer in it? When the water runs cool is it cool right out of the coil.
?
Believe me I am not a proponent of boilers with coils at all. But the electric water heater is not much better in my book. It will supply more hot water if you are having coil problems.
 
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Old 01-31-10, 10:50 AM
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Hi rbeck,

Thank you for your post.

I am running a solid 2gal/min

the highest temp I can achieve running the tub is 94 degrees (temp of water in the bucket), and that will not last for more than 90 seconds before it gets cool - not ice cold - but too cold to draw a tub. With the tub running on full hot, the water is scalding for the first 10 sec, then it cools down rapidly. We also get scalding water from the kitchen and bath faucets with full hot, but we can draw enough hot water for dishes and shaving, etc. I can get about a 10 min shower that is OK, but not nearly as hot as I would like.

There are no blending valves at all in our system.


Aquastat settings: HI 190, LO 170, DIF 15

Thanks
 
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Old 02-03-10, 10:03 AM
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What make/model is your boiler?
 
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Old 02-03-10, 12:16 PM
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Big C
When you check your coil is the water coming right out of the coil before the mixing valve hot, or does it start hot and then run cold. You said your coil had been cleaned but was it done right. I once went on a job where they thought they were cleaning the coil but the way they had it set up they were short circuiting through the mixing valve and not the coil. If it is staying hot continuously out of the boiler and getting cold after the mixing valve that may be your problem. Depending of what kind you have you can remove the element and try that to see if it helps before you do anything as drastic as installing an electric tank and save for an indirect. You can also raise you aquastat setting to 180/200 to surround the coil with higher temp. water. The designed rated output of these coils are at 180deg. anyway.
 
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Old 02-09-10, 04:01 AM
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lukewarm shower

hi, just moved into this place and it has steam ( hated my other place with forced hot air) one thing i have noticed is water in the kitchen on the 1st floor is hot, very hot, water in tub/shower on 2nd floor is ok then turns lukewarm? the pipes have been banging all around the house and i need to bleed the system, any ideas as to why 2nd floor water cooler vs 1st floor? thanks
 
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Old 02-09-10, 06:29 AM
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More Hot Water

As the kids got older, my old oil-fired
Burnham tankless coil could not keep up with their endless showers. I fed the output into an electric water heater and ended the problem. Because I couldn't lay it up for the summer w/o leaks, I just set the Aquastat way back in the summer and then simply left it there. Worked great.
Since we lose power here with hurricanes, I fed the output into an H shaped system, with valve on crosspiece normally closed. That way, I could shut off valves on the heater, open the H valve, and bypass the heater when running on the generator. When we (now just the wife and I) wanted a shower, we lit off the boiler, waited half an hour, took our showers, and turned the boiler back off. That worked great for us also.
 
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Old 02-09-10, 07:21 AM
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I will repeat, It is not a good energy decision to heat the water in the coil and dump it into the electric water heater or any other type of self fired water heater.
Do ether an IWH and cold start the boiler or go to a stand alone water heater of some type.
I personally feel any boiler that maintains temperature today should be converted or replaced. Making hot water with a domestic hot water coil in a boiler is the most expensive way to make hot water.
 
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Old 02-16-10, 08:28 AM
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Same issue as bigchiefoldguy

Hi rbeck,

I'm basically in the same boat as bigchiefoldguy. Our tankless coil doesn't deliver consistent hot water. We are looking to install a tank and I have heard from many guys that electric is not a good way to go.
Can you tell me why electric isn't way to go ? I know that oil seem to be more economical, but isn't boiler still have to work even with indirect ? And how efficient is that that the whole boiler has to heat up in order to heat water in indirect tank ?
Just asking all this question because indirect seems to be very costly to install, so same as bigchiefoldguy, I'm looking into electric heaters. Any thoughts ?
 
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Old 02-16-10, 09:16 AM
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I agree with rbeck, either convert your your boiler to a cold start and get a stand alone water heater (not electric, unless you get your electricity for free). Or use an indirect hot water setup.
 
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Old 02-16-10, 09:37 AM
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esalman, thank you for your responce!
Can you tell me what is cold start boiler ? Isn't that a setup in which boiler will only start when call comes from a thermostat ? If so, what happens in the summer ? Boiler never starts ? Isn't that bad for the boiler ?
 
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Old 02-16-10, 10:13 AM
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Originally Posted by AndrewB11 View Post
Isn't that a setup in which boiler will only start when call comes from a thermostat ? the boiler ?
Correct this exactly what cold start mean.

Originally Posted by AndrewB11 View Post
If so, what happens in the summer ? Boiler never starts ? Isn't that bad for the boiler
If you get the boiler cleaned and coated with oil after shutting down for the season the boiler is going to be ok.
 
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Old 02-16-10, 04:16 PM
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The key to keeping hot water efficient is to utilize an IWH properly piped. The boiler will operate over the summer but only on demand. The input of the boiler should re-heat the tank within 8 - 12 minutes. The tanks today have very high R-value insulation with stand-by losses of about 1/3 - 1f per hour providing you trap the domestic hot.
The provide as much hot water as you want at a minimal operating cost.
With that said and most here know how much I hate domestic hot water coils in the boiler as they are one of the most expensive way to make hot water, but they should not run out of hot water as long as they are not over drawn.
Do you have a mixing valve? A mixing valve will assist in suppling enough hot water. Get a 5 gallon bucket and take it to the bathtub. Adjust the hot water as you would for a bath or shower. Turn off the cold and run the water into a bucket for one minute. How much water is in the bucket? How does it compare to the coil rating? If you are over drawing the coil add a flow restrictor and a mixing valve and you will have endless hot water. The mixing valve will keep the volume up as the hot water through the coil is reduced. Keep the aquastat low setting 15 - 20 degrees above the mixing valve setting and at least a 20f differential setting.
 
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Old 02-16-10, 05:09 PM
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rbeck, thanks a lot for the explanations ! I already asked you in another thread - what is "properly piped" IWH ? Also, I know that tank has very little heat loss, but isn't boiler will first need to heat itself up in order to heat water in the tank ? Is that efficient enough ? Why everybody is so afraid of electric ?


On the subject of thankless coil - we had three different oil companies who told us that our coil is very old and inefficient and need to be replaced. Yes, we do have mixing valve but it is in most "hot" position and we get just a few seconds of hot water in the shower (only one shower at a time, nothing else in the house using hot water), after that water is less than even warm. We are not looking to fix the coil because kids are teenagers now and we want to be able to run two showers at the same time.
 
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Old 02-16-10, 08:28 PM
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Is the water cooling down coming out of the coil to the mixing valve or only after the mixing valve?
The IWH is again the most efficient way to make hot water as the boiler flow rate through the coil is sized to transfer much heat. The boiler heats very rapidly with such a small volume of water going through it with many tanks.
Many people want to shy away from the electric water heater as it is one of the most expensive ways to heat water but the recovery is very slow. I doubt you would be able to run two showers at the same time. The only chance you may have would be with an 80 gal electric tank.
Look at brochures on both and compare the hot water available if the electric units even list it.
 
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Old 02-17-10, 06:26 PM
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Why do you think two showers are not possible out of 50 gallons electric tank ? Maximum allowed flow for shower head is 2.5 gal/min. Assuming that shower takes 10 minutes, one will use 25 gallons of hot water. Two showers at the same time = 50 gallons.

Also the water in the tank is 120 degree and I think a typical human shower is 104 degree, which means some cold water is being mixed in. The First Hour Rate on the electric tank that I'm looking at is 63 gallons. Looks like more than enough for two showers.

Am I missing something and fooling myself thinking its enough ?
 
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