Include Indirect WH load in boiler sizing

Todd Schliphack_2

I wouldn't add extra BTU's for the indirect unless you have little patience and a high demand. If you want the best efficiency overall, I would go by the heat load and maybe oversize the tank (for additional dump load), or just run it at a higher temp and mix it down. I would bet that 95% of residential boilers are oversized "just to be safe".

[Deleted User]

hot water heater load used in boiler sizing?

We're replacing our oil boiler. Some contractors insist the indirect hot water heater load should be included in the boiler sizing. Others have said put a priority on the water heater. The few days you might need both isn't worth bumping up to a bigger boiler. A heat loss calc was completed at 70k btu/hr and we have a 40 gal superstor. Is there a right answer? thanks.

kevin coppinger_4

unless you have....

a huge hot water demand don't add the water heater to the the boiler size. the only exception I make is if the heat load is right on the cusp of being too small...the priority will work well. kpc

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Unknown

I'm with Todd

DON'T oversize the boiler, oversize the TANK.

Efficiency takes priority over speed, these days.

Noel

laurence salvatore_2

concur

I have never added for the indirect and have not had any callbacks while using a priority relay properly wired. My own home has 100k boiler with a 40 gal. superstore stainless less priority relay and we can stll get 3 baths or showers back to back and from what I can see 2 of my kids are unaware its cusomary to mix a little cold water with the hot. Be aware superstore makes 2 40 gal. indirects; a 3/4" coil and a 1" insist on the 1" coil and insist the coil is piped at with least 11/4" pipe.

[Deleted User]

great and thanks.

[Deleted User]

DO NOT ADD....

As part of my job, I do this many times a week for various cantractors. I have to say that often it is like beating my head against a wall.... which may explain my general appearance!

I almost never add for average residential DHW load, assuming the heat loss is accurate - which, believe it or not is another whole problem. Generally speaking, our heating systems are sized to handle the heating load on the coldest days of the year. At any time other than those coldest times - there are BTU's to spare. Very often there are lots of BTU's to spare.... that will almost always handle the DHW demand (assuming the tank is large enough to do it's job). If that notion scares you then put the DWH on priority ... or upsize the tank.

HTH

Mike