I had a 30 gallon indirect hot water heater ("HWH" installed in November 2013 by my oil company. I also just replaced my PRV because it was giving me approximately 100 lbs of pressure. The oil company replaced the expansion tank with a larger one (smaller only had 35 lbs) since I was experiencing noise at all hours of the night. That fixed the problem. I have noticed since the HWH was installed, I sometimes run out of hot water. The oil company now wants to put a water mixing valve and increase the temp of the HWH. Is this going to solve the problem and/or damage the HWH?

Thanks.

it will help a little but the proper solution is a larger tank.
you should have discussed your hot water needs BEFORE sizing the tank.

Thanks Packy for your response. There are only two of us and I ran out of hot water after I cleaned the shower (10/15 mins) and during my shower. No other showers were taken before or laundry done.

these suggestions may not mean much to you as they are technical in nature.

what is the high limit temperature set on the boiler?

does the boiler maintain temperature?

is the water heater relay set for priority?

is the feed and return to the water heater coil run full size 1 inch pipe?

did they use a high speed circulator? if not, a grundfos 3 speed set on HI will help.

you have to realize that you will get about 70-75% of the total capacity of your water heater and then the water will start to run cool. so 75% of 30 gallons will only give you about 22 gallons of hot water. now this water is mixed with cold so you will have to run(maybe) 35-40 gallons of warm water to use uo the 22 gallons of straight hot.
so, it is a complicated matter to give a customer sufficient hot water without giving them a giant tank that is grossly oversized.personally the smallest size indirect tank i use is 45 gallons. if i feel there is a large demand i use a 60 and if the people have a shower that will fit a volkswagen and resembles a car wash, i give them a 120 indirect.
good luck..

What Packy said. A 30 gallon tank is only going to deliver about 21 gallons of hot water on a fast draw bfore you start to notice it going cold. A flow restrictor in the shower head or switching to a lower flow head may help too. Setting the temperture up higher adn installing a mixing valve will help but my not solve the problem entirely.

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