Hot Water Options

RayH

I have a customer with a two family house. He has a hot water heater off the boiler that he uses in the winter. In the summer he has two separate electric hot water heaters. The house uses well water so there is really no cost like in city water. I see no reason for the separation. I plan to replace the old boiler in the near future and I'm looking for some options for this situation. Thanks, Ray

heatpro02920

oil or gas

Do the math for his heatloss and his DHW consumption and then I could give you some options...

RayH

Water Heaters

The water use for each unit is satisfied by two 40 gal electric hot water heaters during the summer months. One unit has a family with two kids and the other has three kids. I'd estimate average water consumption for both. As for the heat loss, there is less than 25ft of pipe for the hot water supply to each unit. 

heatpro02920

When I say heat loss

I mean for the space heating.



You want to come up with an accurate number for DHW and Heat..



So say each unit needs 5gpm at 70 degree rise and the entire building needs 60K BTUS of heat... I would look into a small natural gas boiler with a pair of natural gas water heaters {if there are 2 gas meters if there is one, go with a larger gas fired tank for both units...

kcopp

Who pays for....

the heat? Personally in rental property situations I have the tenant pay for the hot water. Electric water heaters make this easy to do. If the tenant is getting free hot water they will not conserve.

icesailor

Electric water heaters:

Most would be amazed at how much hot water a 40 gallon electric hot water can provide. In a Rental, people learn to adjust. They all use the same elements. The recovery is the same. Just how much is stored.

RayH

Oil heat

I so agree that gas would be the bettter way to go. But I am working with a 140,000 Btu existing oil burner with a 40 gal.Hot Water heater. The customer also has two 40 gal electric hot water heaters that he uses in the summer. I plan to install a new boiler and would like to improve the situation. Would eliminating the two electric water heaters and install a 60 gal one off the boiler be a good idea in your opinion?  The water comes from a well so there is no water bill. 

heatpro02920

What is the heatloss

Like I said a couple times, you need to do a proper heatloss calc and then take a walk around the apartments and see what their DHW load is {dish washers, washing machines, bath fixtures, ect}. That 140K is most likely way over sized..



Now as far as not running the boiler in the summer months, I like the idea, BUT not at the cost of having to maintain an additional pair of hot water tanks...



If the current 40 ga indirect is working in the winter I also don't see the point in going up to a 60...



If the 2 electrics are in good shape and working leave them alone, if they have no complaints about the 40 gallon indirect then either install another one or if that one is still in good shape leave that alone too... You would do your customer more good, just installing a proper sized boiler with their existing DHW system...



Now if they do actually have a 140k BTU heat load and you want to do something "fancy", you can install dual boilers, I have done this many times in larger homes



Last year I installed dual OWT3's {ci oil fired with tankless}, the buildings heat loss was rite under 150K, I set the burners up for the load then wired them so burner 1 would only fire until 2 was needed, I piped them so both boilers were hot all the time, primary secondary with the primary loop going in and out of both boilers. I only used 1 aquastat and it was placed in boiler 2's well so both boilers would stay to temp letting both tanklesses stay hot....



That gave them a lot of hot water and gave them the efficiency of running a single small boiler when thats all they needed and then in the colder months running them both to keep up with the load....



That house was very large and also 2 family {rented inlaw}, it had 7 zones and held a lot of water, I did the near boiler piping with 1 1/2" {could have done 1 1/4} and insulated it very well, I used an alpha delta P pump for the primary loop and 007s for each zone {piped in with closely spaced tees}...

I spoke to them about a month ago and they said their automatic delivery company told them they were down a good amount from the previous year per degree day... Granted they were firing a 20 year old 210K BTU burnham with an amtrol 60 both of which had seen better days, but a savings is a savings..



Another plus to this is when one burner goes down you still have heat, it takes a little thinking {I have the drawings and pics if you need them} and a little more work but the outcome will be better than a single big boiler and indirect... The cost in materials is not as different as you may think though, when comparing dual OWT3's to say a G215-4 and indirect it can come out to less money in materials, the 150K plus oil fired units have a good jump in price...



The owts also get 86-1/2% eff. This would allow you to get rid of the 40 gallon indirect, and stop the stagnant water issues they are most likely getting from having the tank not flow for the summer....





PS: I'm not sure I understand what the well water difference makes in costs? I would much rather pay for city water and not maintain a well and pay for the electricity it uses... And they are going to use the same amonut of water no matter which way you go with the dhw equipment, am I missing something?