Tankless boiler not providing enough hot water---help!!

I bought a house last year that has a Weil-McLain boiler/tankless heater. I believe it was installed in 1992. It looks pretty beat up---more rust and the like than I would expect on a boiler that's about 15 years old---but I'm told that the water around here is pretty hard and that it eats up boiler. (On the other hand, I have a water softener system, so what's that all about?)
Anyway, the boiler simply doesn't provide enough hot water. We can't fill up the bathtub, and showers get cool after a short period of time. Even when the boiler kicks back on, the water only becomes warm, not hot. I can deal with this in the shower, but I'm concerned about the washing machine and dishwasher.
The heater part of the boiler has three controls as far as I can tell. There are two thermostat controls that determine when the boiler fires on and off, and a valve that blends the hot water from the heater with cold water to deliver to hot water faucets.
If I want more hot water, how should I adjust these things to serve us better?
Also, I read on the Weil-McLain web site about an indirect-fired water heater. Is this something that adds onto a tankless system to provide extra hot water? (I have no idea if this could physically fit into our mechanicals closet, but it's somethng to look at if it would take care of the problem we are having.)
Any suggestions appreciated!
Thanks, -Ben
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I think I'd be looking at that mixing valve first, to make sure it's not adding too much cold water.
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Doug Miller (alphageek at milmac dot com)
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Find the operating manual (it should be kept near the appliance or download from Weil-McLain's website) and read the troubleshooting section. It's short and to the point. It looks and sounds to me like you need to call a pro to service the appliance.
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Ben,
First, Don't touch the setings for the hi and low limit. They are the dials on the primary controller. Typically it's a Honeywell. The settings(typically) should be around 180 for the hi and 160 for the low. Leave the other dial for the differential at 20. Lets start here!
Okay, now to fill a bath tube with water is going to use up a lot of hot water. The typical tankless is about five gallons. YOur boiler should be firing during this time. It may cycle a few times, but for the most part it should be firing. Anyways, since you mentioned hard water you may have two problems. The tankless coils could be caked with scale and or the mixing valve could be fried. Have you tried to incease the level of hot water? If the dial is maxed out then you may want to start with this. Do you have any plumbing skills? Start with the smaller and cheaper parts before doing anything to the boiler. I'd replace the mixing value first.
You mentioned indirect hot water. This is your next option. I say this because replcing the tankless is almost next to impossible. Most of the time the a stud or several tend to break cause more of a problem. If the tankless is not leaking I'd leave it be. You can add a booster/holding tank onto the tankless. Let the tankless heat the water and store it in a 40 or 50 gallon tnak. The indirect is tied into the boiler as another zone and will require additional electronics to turn on the circulator for heating the water.
Another good site to check is heatinghelp.com. Lots of resources there.
-paul
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On Wed, 20 Jun 2007 12:40:34 -0700, Paul Flansburg

I'd agree with the above except that a tankless coil CAN be replaced. Many boilers about the age of your Weil-McClain and newer have used stainless bolts to fasten the tankless coil. In any event, with some caution, time and penetrating oil, I've removed tankless coils. A replacement coil is only about $150 plus labor if you don't do it yourself.
The tankless coil is simply a copper coil submerged into the boiler water. Typical output flows from a tankless coil is about 2.5 to 5 Gallons Per Minute. That's up to 5 GPM of VERY hot water. Thus the mixing or tempering valve is often used to reduce the likelihood of scalding.
Another treatment for a "limed up" tankless coil is to flow hydrochloric acid through it. I've done it myself and fumed up the basement quite a bit so it has to be done with plenty of ventilation and extremem caution, with protective rubber gloves, etc. It was quite successful and restored the hot water output flowly to normal. Most of the younger techs in the HVAC world won't do the acid cleaning. Most old timers will.
An indirect water heater is an option. As the poster above states, it runs as a seperate "zone" off of the boiler. However, such an installation is fairly expensive and will consume a good amount of space in your utility room. An indirect water heater will take up nearly as much space as your boiler.
Doug
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Here's a picture from the inspectors report that shows the boiler. You can see that there's a lot of rust at the bolts that hold the coil in place. One of the oil company service people said that we could try to replace the coil, but the risk is that we'd have to end up replacing the whole boiler if things go bad...
http://tinyurl.com/2vwbl9
-Ben
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That rust is from water leakage. It looks like the tankless coil gasket might already be leaking. It should be fixed one way or another.
Obvously, I can't tell you what to do but I'd have a crack at replacing that coil while the weather is still warm. Try loosening a bolt or two. If bolts snap, they can then be drilled out, the holes can be retapped and things should go well. Auto mechanics drill and rethread cast iron for helicoils to repair stripped spark plug holes. This operation is no different. What's the worse case? Replacing the boiler? That will cost you about $2000 to $4000. Installing an indirect water heater will likely cost you a good $2000.
I find that HVAC pros won't do jobs like this because they don't want the risk and don't want to spend the time when easier dollars can be made elsewhere. The fact they don't want to do it doesn't mean that it can't be done. None of them will attempt acid cleaning of the coil?
Or leave it as is and install an electric water heater as another poster suggested. It will work fine but your electric bill will skyrocket. With the limited space that you have, your options are also limited.
Doug
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there are also oil fired hot water tanks, quick easy solution. entire boiler need not run to heat water
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If you didn't always have the water softener, deposits can be lining the inside of the domestic coil, insulating it from the hot water around it. As the others have said, do the simple things first, and if they don't solve the problem, definitely go with an indirect. It will need to be connected as a separate zone, with a relay if you have separate circulators, or by way of an additional zone valve, if that's how the system is set up, in any event you will have plenty of hot water

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Maybe not what you and the others want to hear, but years ago, when my kids were in their teens, it became impossible to meet all of the shower, bath, laundry demands. I simply installed an electric hot water heater in series with tankless coil output. The boiler then preheated the water and the HWH kept it hot. Thru a set of judiciously placed valves I can cut the HWH system out of the system (In hurricane aftermath, the generator will handle the boiler, but not the HWH) My Burnham is 40+ years old; no way would I ever attempt to replace that coil - nor would my HVAC guy. Works for me
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I have the same setup you have. Weil-McClain tankless oil boiler...their smallest one too. It was installed in 1999 and has had no issues since. I believe my hot water supply is endless. We have used to for filling large bathtubs, running dishwasher laundry often at the same time. Our issue has been a notice in pressure drop more than anything else. Our water though is always very very hot and we have never run out. Boiler is set at 180F high and 160F low. Our water is not hard at all, all have is a whole house filter. It's either you mixing valve or your coil...or the aquastadt. These units are generally very reliable.
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