hot water heat with tankless water heater

charlie holmes

Andrew, I have decided to go with an indirect water heater with the oil fired boiler. Do you have any experience with Tekmar 260 with outdoor reset? Will this save fuel? Also, the contractor I am working with has suggested as an alternative to use a Buderus oil fired boiler & indirect and one of their controls (quite pricey)which they say will save up to 30% in fuel costs. What do you think?

charlie holmes

I am replacing a 50 year old boiler that has a tankless water heater. When sizing the boiler how do I factor the domestic water requirements into the sizing? Also, because of the price of heating oil I am considering adding an electric water heater in some of the vast space made available when the "giant" old boiler is replaced and turning off the boiler during the non heating months. What is the best way to pipe the electric water heater into the system. For example, should I run water from the tankless water heater through the water heater, the water heater acting as a storage tank during the heating months? Or pipe the water heater as a stand alone with valves allowing me to switch between the two sytems depending on the season?

Andrew Hagen_2

Hot Water

If you have a hot water heating system, a condensing boiler with an indirect water heater is the most efficient option. A solar domestic hot water pre-heat system would be an excellent addition to minimize the run-time of the boiler for domestic hot water production.

charlie holmes

Thanks, Andrew. I have considered the indirect water heater and condensing boiler but I have a limited amount of funds available. What are your thoughts on best way to proceed with options as I described them?

ALH_4

Options

What is your heat loss? If it is under 50,000 btu/h, you might consider a combination water heater like the Bradford White Combi2 that has a coil inside the tank for space heating. Looked at as a water heater, it seems expensive, but when you consider it takes care of both space heating and domestic hot water with a minimum of installation labor, the price is very good.

I'm not sure hot limited of a budget you are talking, but have you looked at the Triangle Tube Prestige Excellence? it has a built-in 14gal water heater that essentially makes instantaneous hot water, but unlike an instantaneous water heater, it has water volume to avoid slugs of cold water with intermittent loads. The pricing is very reasonable for what you get.

I hate to recommend installing a direct fired water heater with a boiler sitting next to it because the cost savings over an indirect are not huge and the performance and efficiency of the indirect are better.

charlie holmes

My heat loss is somewhere around 90,000BTU. My first thoughts were to replace the oil-fired boiler with another oil-fired and put an indirect water heater like a Superstore next to it. I can probably afford to do this but with heating oil having tripled in the last couple of years with no end in sight I started considering the electric water heater for non-heating months and shutting the boiler off. I don't know but it seems to me that using the boiler to heat domestic water during the non-heating months, whether it be by tankless water heater or indirect water heater, can't be the most economical way to do it. If you feel that using the boiler to provide domestic hot water is cost effective, the tankless is the cheapest way to go in so far as installation cost is concerned. What are your thoughts on tankless water heaters vs indirect water heaters?

ALH_4

Oil

Somehow I missed that you were oil. Reading too quickly I guess.

Fuel cost-wise, you're very likely better off with the indirect. You're probably spending a couple hundred bucks a year on wasted heat with an indirect, but electricity is generally much more expensive than fuel oil. The tankless is a little different situation because the boiler has to fire every time you turn on a faucet. You will save money by installing an indirect. If it was me, I would ditch the tankless and go with an indirect.

charlie holmes

Isn't a tankless water heater essentially a domestic coil immersed in the 180deg heating hot water and consequently the boiler fires when the water in the boiler drops to whatever you have it set on for low temperature? What our your thoughts on indirects as far as manufacturer? I am somewhat familiar with Superstore but know there are many out there.

ALH_4

Indirects

You are correct about the operation of the tankless. it's a pretty inefficient way to produce domestic hot water, but the initial investment is low.

Most of the water heaters on the market are on a fairly level playing field as far as performance and quality. Superstor water heaters are very good. Triangle Tube's Phase 3 tanks are a unique tank-in-tank design that also works well. Crown's Megastor water heaters are all stainless steel and also work quite well. The only manufacturer I would stay away from is Amtrol.

ALH_4

Tekmar

The 260 would be a great choice for a situation like yours with a high temperature system and an indirect water heater. I have installed many. They are very reliable, and relatively economical compared to most other controls.

I am not sure what oil boiler is the alternative to the Buderus, but as long as they have similar efficiency ratings, the Tekmar 260 will give you every advantage the Buderus controls would. It's tough to beat Tekmar.

charlie holmes

The other boiler they are proposing is a Lennox. They are suggesting I add a timer (032) to the 260 to equal the Boderus control. It adds approx $250.00 to the cost . Do you think it is necessary?

ALH_4

Stats

I would install programmable thermostats and call it good. The nice thing about programmable stats is that you can set back each zone independently. With your setup there really is very little efficiency to be gained by setting back the reset curve.

Buderus is an excellent high-quality product, but the efficiency of the Lennox with the Tekmar and indirect will be very close.

charlie holmes

The indirect they are proposing is a Triangle Phase III Smart 30. Any feedback on those?

ALH_4

Smart 30

Excellent tank. 30 gallons is on the smaller side, but if you don't use a lot of hot water, you should be fine.

charlie holmes

We have a full house at holidays (4 Kids & significant others). Just my wife & I other times, Would the Smart 40 be better?

ALH_4

Tank Size

There are a few variables, like your shower head flow rate and the incoming cold temperature, but assuming you have a showerhead that flows 3gpm or less, you will probably have nearly endless hot water with the Smart 40. I would set it at 140°F and use a tempering valve to reduce it. That way you kill any bacteria that might be in the water and you have that extra capacity when needed. Plus you have the safety of a tempering valve to reduce the possibility of scalding. Actually, the ideal situation is to have individual tempering valves at each bathroom so you can completely prevent the possibility of scalding.