Installer wants to increase size of boiler

dkr

I have a family of five. 2 teenagers my wife and I shower in the morning pretty much back to back. I live in a 3 bedroom ranch about 1600 square feet with a finished basement that rarely needs heat. My installer originally recommended a Burnham MPO-IQ115 and 80 gallon Amtrol Champion water tank. He spoke to someone about the tank and the temperature can be set at 130 degrees and not 140(not sure what that means). So his new proposal is to bump me up to a Burnham MPO-IQ1147 and a SSU 80 stainless steel indirect fired water tank. He says we could get four 15 minute showers with no problem in the morning.

My question is: Is it a waste to get that much bigger of a boiler to take four showers in the morning? Does having a bigger boiler waste energy or efficiency? Again I am a  complete donkey when he starts to explain the technical side of everything, does it make sense? 

Zman

Questions

What part of the country are you in?

This sounds like a replacement boiler, What was there originally.

What age is the house?

Carl

kcopp

We need more....

information.  Lets go back to the begining.... Was a heatloss done? How many baths.? Did you look at reducing the shower flow rate? Not sure a bigger boiler will help you much. The SSU will have a bit faster recovery rate... What is your water like? Well, City? Harder Water? What do you have Now for water heater and boiler?

Generally speaking unless you have crazy hot water demand...like a "car wash" shower you size the boiler for the heat demand and dont add more BTU to the boiler for the hot water heater.

In my home I have had 5-6 peolpe living here for close to 10 years.. I have a Buderus 115-21 oil boiler and a 60 gal SSU w/ a mixing valve. A Tekmar 260 prioritizes the indirect. Even w/ company here I have never run out of hot water.

dkr

North of Boston

North of Boston. House was built in '57 and is wel insulated. Arcoleader from 1967.

dkr

Is it wasteful having a bgger boiler

Dont think heat loss was done. We have 2 showers but usually only one being used at a time. We have a 1967 Arcoleader with a tankless coil so we always have hot water just not efficent I guess. We have city water not sure about hardness. So do you think our hot water will be as good as yors with a Burnham MPO.

Does having a bigger MPO waste efficency or it does it not matter?

Zman

Yes

Yes,

Going with a single stage boiler that is significantly oversized for your heating load will short cycle and reduce efficiency.

I would steer away from the Amtrol tank. It has limited capacity to exchange heat and has coil design which has a tendency to foul.

The MPO 115 will produce about 2.8 gpm of hot water, forever. That should be enough for 1 or 2 showers continuously. The tank will give you a buffer for times when you need more.

I agree with Kcopp. A MPO 115 and ss60 would ideal for hot water.

Carl

CMadatMe

The 115

Is even to large of a boiler. If someone actually does their job correctly and does a heat loss the MPO84IQ is going to be the boiler of choice..

Zman

Good point

Chris,

I should have looked at the original post. A 115 single stage is a bad idea for a 1600 ft house. Your installer should do a heat loss calc.  The 84k model will give you 2 gpm of hot water. An 80 gallon tank would be a good call if you feel like you need more storage.

Carl

hot_rod

the larger load

in many new homes is the DHW. Really you need to define how much DHW you desire, how fast, and how much time between the peak loads.



It sound like you have a large dump load similar to hotels where everyone wants a shower back to back over a 1 hour period of time. For that type of load, a large storage is one solution, or a heater that could generate the required GPM on a continous basis, tankless style water heaters are good for that if properly sized, installed and maintained.



Or look for ways to reduce the consumption, lower flow shower heads. Coin meters on the shower



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