No hot water for several minutes

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Dannyboy

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A few times in the last week or so I am getting almost no hot water it is luke warm. If I run the water for several minutes the boiler will fire up and within a few more minutes I will get ample hot water. Any idea why the water isn't staying heated? It is the same at all sources such as shower heads faucets etc. Looking for ideas at cost for having problem repaired
 

Theodore

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I defer to the other very capable and experienced folks on this forum to help diagnose, but I recommend you may wish to provide more details on your setup. For example, do you have:
1. a boiler with an indirect water heater (if so, rough size, or # of gallons of indirect water heater tank) ?
2. a boiler with internal hot water coil (no separate water heater)?
3. a stand-alone water heater, separate from boiler?
4. the manufacturer of the boiler (and/or water heater, if applicable)?
5. last time boiler was serviced?
If you don't know the answer to these, then maybe some photos.
 

Dannyboy

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It is a Burnham v 8 series with internal coil no water heater. I bought the house in April but the previous how had boiler serviced annually. I will have it serviced professionally but am looking to figure out problem ahead of time so I have an idea on cost
 

Dana

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If this is a recent symptom it's probably an aquastat that's gone off calibration or the sensor for the aquastat needs some heat conductive goop to get better contact. If it's been like that since the end of the heating season it may be a matter of tweaking up the idling standby lo-limit temp on the boiler.

Embedded coils are a PITA- they lime up, develop pinhole leaks between the heating system water & potable water, and deliver mediocre hot water capacity (on a maximum gallons per minute basis), at atrocious fuel-use efficiency. If you're planning to live there for several years using an oil boiler for both heat & hot water it will pay to install an indirect fired hot water heater operating as the "priority" zone. That way the boiler can idle at a lower, less-lossy temperature during the summers (or even cold-start, which may be an option with the V8- I'd have to look that up.) That's not a cheap solution, but it'll pay off in lower oil use (and better hot water delivery), usually within 5 years at recent-years' oil pricing, well under 10 years even at this year's pricing. In most cases an indirect installation would run $1200-1500, but could be as high as $2K in high-priced neighborhoods during periods when the contractors aren't that hungry. (In some places there are rebate subsidies for installing indirect hot water heaters.)

You may even be better off with an electric hot water heater, turning the beast off for the summer, depending on just how much hot water you use.
 

Dana

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If you are idling the boiler at 190F you are paying HUGE standby losses, and probably paying to remove that excess heat in summer via air conditioning. That's more than a 100F difference in temperature between the boiler room air and the water temp, and this boiler isn't exactly super-insulated! Most boilers with embedded coils can be idled at 150F in summer, 160F in winter and still deliver sorta-reasonable hot water performance, as long as the coil wasn't completely limed up. At 150F the standby losses will be reduced by more than 25% from a boiler standing by at 190F.

If the gauge was indicating 120F or something the water would be pretty tepid, but should be fine with a 190F boiler.

It's remotely conceivable that it's not the boiler at all, and that the tempering valve at the output of the coil is sticking. The tempering valve mixes cold water with the coil output to reduce the water going into the hot water distribution plumbing to safe levels. If it is malfunctioning and feeding more cold water than it should the output would be tepid no matter what the boiler temp was, until the vibration from flow gets it past it's sticky point.

Have a competent tech come debug the system, but have them quote installing an indirect HW heater, and have them include a heat-purging economizer control (eg. Intellicon 3250 ) as part of the package. With an indirect and an economizer control the standby temp can safely be reduced to ~140F without negatively impacting hot water performance, and at typical 3x over sizing would reduce wintertime oil use by 10-15%, and cutting summertime oil use by 25-30%. You need enough space for the indirect tank (it doesn't need to be right next to the boiler, if somehow it doesn't fit):

V83%20and%20SL%20indirect.jpg


The smarter controls would probably add something like another $300 to the quote if quoted as a package, $500-600 if done after the fact, though as a DIY for those with electrician skills it can cost ~$200, sometimes less.

With typically oversized oil boilers smarter controls pay for themselves in less than one heating season at the recent 5 year average price of heating oil, and still less than 2 heating seasons at this past winter's lower oil pricing.
 
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