Indirect waterheaters opperating costs

Andrew Hagen_2

Could it be possible that more hot water is used now that more hot water is available than before? I'm assuming you have a gas fired atmospheric boiler and you replaced a direct fired gas water heater.

I doubt the problem is the indirect tank. Even at 116MBH, it would only take 11 minutes to raise the tank temperature 50°F once the boiler was hot.

The mass of the boiler is hurting you more than it would if you had a smaller cast iron boiler. I do not think this would accound for 8X more fuel use for DHW.

Have your utility rates increased significantly? There may be a combination of factors.

Jim Wy.

Indirect waterheaters operating costs

I have a home with a 180 MBH output c.i. boiler & a 50 gal. Crown Maxi-Therm indirect,the cost to heat domestic hot water is 8 times higher than it used to be during warm months. The water heaters perfomance is awesome and during cold monthes everythinng seems reasonable.I think the problem is heating up all of that c.i. & boiler water for no other reason. The boiler is a 2004 82% atmospheric unit & the domestic system does not have a recirc. line. Any ideas to help lower summer energy consumption? Thankyou so much.

tim smith

Re: indirect & cast iron

I would say it is not the most efficient method due to having to heat up the content of boiler and the cast. With that said, the cost to upgrade the hot water side of things probably would not be worth while. It may be a good time to consider upgrading the boiler to condensing boiler technology as they are an efficient heat method for both heating and DHW supply. Again hard to always justify the expense. my .02 worth. Tim

Andrew Hagen_2

System

You have a good setup for excellent hot water production. The Maxi Therms work great. However, as Tim said, the boiler has to heat up each time the indirect calls. You have a relatively large boiler for domestic hot water production during the summer. Verify that the water heater is controlled and piped properly. The indirect should have its own circulator, not a zone valve. I also recommend installing a Tekmar 260 outdoor reset/water heater control.(assuming you have hot water baseboard or radiators). A modulating condensing boiler would be ideal, particularly for your hig heat loss, but if your boiler is 4 years old it would be difficult to justify the cost.

8 times seems like a big difference. Is there a chance that the boiler is sitting there hot all the time? It is not unheard of that systems will have the wires that call the boiler simply twisted together rather than wired properly.

A solar domestic hot water system would prevent the boiler from firing nearly as often in the summer as it does now. The best way to save fuel is not to fire the boiler at all.

Jim Wy.

All zones are controled w/ pumps & check valves. D.H.W. zone is on priority. It may be a little late for solar. I may be able to squeze a regular waterheater in the mech. room. Sence the mech. room is located in the middle of the finished basement in a large home my options seem limited. I e-mailed Crown asking how many btu's the waterheater can absorb but have not heard back yet. The min. suggested boiler output is 116MBH.

bob eck

Like Andrew said you could go solar befor going into the indirect or go tankless. But how much will you save and how long will it be for the pay back period?

Jim Wy.

I'm going by decatherms used not the $ spent. I think I've probably misused a good indirect waterheater by installing it w/ a 180MBH output c.i. boiler.Any cost effective ideas as to how I could rectify this mistake?

Rod Kotiga

Tankless all the way. But I guess that leaves you with tank that will just sit around your shop forever huh ?

Rod

hot_rod

get a water meter

and stick it on the cold supply to that tank. I suspect a lot more water is being heated than they claim. Without stable data it's just guessing.

Check the delta t across the HX. If the coil is limed up the performance drops considerably and boiler run time extends. Very in-efficient heat exchange could be driving consumption.

I doubt a tank type heater would be more economical with stack and standby loss and in-efficient heat exchanger.

The set up you have should be fast and cost effective, if installed, controlled, and serviced properly.

hot rod