cold showers with slantfin tankless boiler (oil)

dfehr401

I recently installed a slant fin tankless boiler I believe I have a TR30. My issue is that during the winter months especially when the supply is 30 degrees the shower will start off warm then cool off dramatically within a minute. My question is can I add something to my system so I can heat the shower water only so I we can take more than a 2 minute shower? Is and indirect water heater the way to go, or is there something else I should be looking for?

Thank you in advance,

Dustin

Kakashi

What are your limits set at?

dfehr401

the high is at 180 the low is at 79. I think that is pretty much the highest I can go.

Kakashi

79? Take a picture of your control with the cover off or open the door if you have a digital one.

dfehr401

Ok I will double check the low it may be 140.

dfehr401

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Ironman

You'd be much better served by an indirect than by a tankless coil. You would also see significant fuel savings since the boiler would not have to remain hot all the time to heat the tankless coil.

dfehr401

Is this an add on feature? This unit is only a year old and I'm not looking to replace it just make it more efficient. What size indirext do you recomment? I have 2 full bathrooms would a 40 gallon do the job?

Kakashi

A indirect tank is your best bet if you want nice even water temperature.
I would at least set the low to 140 and the high to 180 and maybe a little higher if you don't have any little kids.
You can also try to turn your mixing valve down.
You also may have a bad sensor for that control.
Could also be a bad control...that 7 looks like it's a 3 without the bottom or a 7 with something in the middle.

Turn off all of your zones and see if the coil can keep up while you're taking a shower.

icesailor

Whatever.

The control is set improperly. The high is OK set at 180 degrees or higher. The "LO" needs to be set a minimum of 20 degrees lower than the "HI". or 160 degrees.

That looks like a replacement boiler. There needs to be a flow control valve on the cold water inlet to the coil to match what it says in the I/O manual so that cold water isn't going through the coil faster than the boiler can heat it.

That digital control will replace a whole tribe of analog controls. Whoever installed the boiler, doesn't understand how to program it. They need to come back and finish the job. They are actually a PITA because they have to do a self check before they start the burner. Which causes a lag on boilers needing a quick recovery. Like oil boilers with a tankless.

If you are at all techno-savvy, they are easy to adjust. Just read the instructions.

SWEI

Does he really need an indirect with that tankless coil? Why not just add a buffer tank?

icesailor

@SWEI:

SWEI said:

Does he really need an indirect with that tankless coil? Why not just add a buffer tank?

I've used water heaters in the past as buffer tanks. They don't work well because they only get new hot water when you run a faucet. There is little to no recovery.

That's where and how I came up with my using electric water heaters (with the electric elements not used) and a circulator to transfer hot water out of the coil and into the tank.

The pump makes it a buffer tank.

The control is still set wrong.

dfehr401

Thanks for the help, I will check the manual and see if I can set the control correctly. the guy who installed it was a space shot that is why I started asking on here. Thanks again!

icesailor

Look for the individual packet for that control. If should be there somewhere. There's a procedure to do it.

If you can't find the instruction sheet, look on-line. It will be there. Its really easy. Just set the High and Low. The rest should be OK. I don't know how the boiler even makes hot water with the low set for 79 degrees. That makes it a cold start boiler and the only way to get heat is by turning up a thermostat and making the zone run.

dfehr401

Quick update: I set the control box to 200 H and 180 L (as it states in the manual) and so far showers are nice and toasty. I will keep my eye on consumption of fuel the H setting was at 170 and the L was 140.

Thank you for your help

STEVEusaPA

That's way too high. This will result in high fuel consumption. I would put it back to 140/170 and turn your mixing valve up. Like ice said, you have to restrict the flow. The cold water, that cold, plus high flow, runs thru the coil too fast.

icesailor

Did anyone read the I/O manual?

http://www.slantfin.com/images/stories/Technical-Literature/installmanual_intrepid_tr_40.pdf

Page #2. The Potable cold to the tankless needs a 3 GPM flow restrictor, depending on how high it is fired. That boiler can be fired at 4 different rates. If it is being fired at .85 GPH, go to 1.00 GPH or higher. You don't have enough NUTS to make hot water.

Page 9 says that they "Recommend" them.

You have to have the flow control valve, properly heat trapped to make the coil work. The LOW Must be set for a minimum of 160 degrees. Many of us set them to 170 degrees with the Hi limit at 190. You must keep a 20 degree differential. I see that already someone is grousing about the higher temperature will use more fuel. If I used that excuse on my wife, when she only had lukewarm water to get the soap out of her hair, she would be initiating a discussion on the division of the house. She's be getting the inside, and I'd be getting the outside. With the garden hose to wash my hair. And any other personal needs.

For all the "My heat loss is only 40,000 BTU's but they don't make one small enough" crowd, this is what happens when the rubber meets the road. No nuts. You need nuts to heat water. Whether its heating or potable water. Way more than you need to heat a house.

If it was me, I'd be suggesting a El Cheapo 40 or 50 gallon electric water heater, connected to the potable water, and the coil connected to the water heater with a pump to turn it into an indirect. Because the coil is already in the boiler, (why have two) the pump wired through the bottom thermostat, and a cord whip into an extension cord. Until Sparky comes.

If you don't do that, install a 2.5 GPM flow control valve. It will make it work better than the 3.

Lance

It takes about 150,000 btuh input at 90% efficiency netting you 135,000 BTUH to maintain 3 GPM of constant hot water all day long. 1.0 GPH oil nozzle = 140,000 btuh at even 80% AFUE that leaves you with 112,000 BTU net to work with. Forget the house heat, if you have a priority zone setup. The best you can hope for is to limit cold inflow to 2.5GPM running into the coil, send the hot water out through a mixing valve set at 120F. give or take, higher if scalding protection is done at point of use. Set boiler water temp at minimum 150-160F and high limit at 190F- 200F. the next best thing is to insulate all hot water pipe to the shower.
Next best is to make sure your chimney can handle it and increase your boiler oil nozzle to maximum up to no more than 170,000 input, netting you about 136,000 btu.
You do have a barometric draft regulator and a proper combustion test adjustments? Without this all is lost up the flue.

Now with the higher temp coil water is mixed with cold you may get a net 3 GPM at 120F and with the higher boiler input you could go 3GPM all day. Just make sure you are not running 6GPM at the shower. Test it and see how long it takes to fill a 1 gallon bucket. Should take no more than 20 seconds.

For peak savings play with the high limit and set it as low as possible without sacrificing comfort or hot water. Once you find this you will know what your design heating water temp is to heat the house on the coldest day you choose.

icesailor

You need a flow control valve.

Donald Rumsfeld said that you go to war with the Army you have. Not the one that you wish you had.

The maximum that boiler can fire is 1.25 GPH and it would run more efficiently at a lower temperature. High stack temperatures don't mean higher efficiencies.

Page 2 of the posted I/O manual for that boiler says less than 3 GPM. 3.0 with a .85 nozzle. Its still a 5# bag. The more you try to put in it, the faster it fills up.

Watts advertises those mixing valves as "Hot Water Extenders. That's exactly how they work. They "extend" the hot water available by mixing a regulated amount of cold with the hot. The cooler the mix, the more you have. The hotter the mix, the less you have. The flow control is absolutely necessary. There isn't one. It takes NUTS to make hot water. That example suffers from premature castration. Add a hot water storage tank. Store the NUTS in there. And save money by running the LO at 140 as boiler protection, and the high at 160. To heat the building. If it gets down to zero, and the building won't heat up, raise the HI to 180 until it warms up.

Another third world solution from the world of cheap and efficient.

icesailor

You don't know what your talking about.

If a coil is rated at 3 GPM, and you try to run 6 GPM through it, you run out of hot water. Or actually, it cools to a rate that the coil and the source can transfer energy. The coil makes 3 GPM of how ever much hot water it will make at whatever the temperature comes out of the coil. If the hot water comes out of the coil at 150 degrees, at whatever pressure, and you mix it down at a shower valve, and the temperature is 105 degrees, you add lot of cold water to the 150 degree hot before it comes out of the shower head. What do you think they make pressure balance valves for. To balance the pressure between the hot and cold.

The reason you put the hot water in a storage tank is to eliminate the need for flow control/restriction valves. They are used all the time. Like NASCAR restrictor plate racing.

If you have a deep potable well that is 400' deep, and the casing is 4" with the water at 200', but the well only flows at 6 GPM and you have a 8 GPM pump because you need the pressure to get the water pressure up, how do you do it? You put a restrictor on the water line from the well. You take the volume of the 4" casing (200' +/-) and how many GPH the well can deliver (6 GPM) and you have a heck of a lot more water available.

Don't try to school me on my acquired skill of finding gremlins in potable hot water systems.

http://www.eddington-ind.com/gallery4.htm

A 1/2" valve is good up to 6 GPM. The flow is automatically adjusted by the design of the valve.

Weezbo

A buffer tank and mixer circulator back thru the coil is almost as much work and effort as an indirect with domestic priority overide. You can always run more hotwater out of taps if you have either the buffer or indirect vs. a coil. because the reservoir of heated water is allowing you to get something that is stored . that simple. Tankless coils are also being replaced by on demand gas or propane fired water heaters . Take a look on line for Rennai or Toyotomi oil fired water heaters. completely different world from a domestic coil.

icesailor

A house with a well pump in a cellar with a 40/20 pressure switch will have inadequate pressure in a second floor bathroom. The most popular shallow well pump is a 2/1 HP single stage pump. They all come with 40/20# pressure switches.

Shower heads sold today are coming with less than 2 GPM flow restrictors so shower heads will work with undersized Mod-Con beer cooler water heaters. It has been fond that it isn't the size of the flow restrictor that causes the low flow, its the design of the shower head and the spray. I had a $300 Grohe satin pewter adjustable shower head with the rubber restrictor removed, I recently bought a Kohler polished chrome 8" wide head that had a non removable 1.75 GPM restrictor in it for less than $100. It has a better spray than the old $300.00 one.

I don't need Eddington to tell me what my customers would have liked.

Two showers in a row and running the dishwasher or washing machine on a 38 gallon electric water heater with 3300 watt elements. Anything you buy today is heavily flow restricted. To save people money.

bmwpowere36m3

We had a Burnham with domestic coil... when it was put 15 yrs ago it was connected to a storage tank.

Recently we put in a 50 gal. indirect tank. Its connected as a zone on the main header and wired as a priority. Plenty of hot water.

SWEI

icesailor said:

I had a $300 Grohe satin pewter adjustable shower head with the rubber restrictor removed, I recently bought a Kohler polished chrome 8" wide head that had a non removable 1.75 GPM restrictor in it for less than $100. It has a better spray than the old $300.00 one.

I don't need Eddington to tell me what my customers would have liked.

If it's got the same internals as the ~6" diameter 1.75 PM models we've been using, they really are impressive. I hear Kohler spent some serious time and money on the design and tooling for it. There are very carefully designed internal passages that keep the water for each hole just where it's supposed to be so they all come out at the same pressure and flow. And they don't (so far) clog up with calmag. Just wipe the front every so often and (at least here, with ~12 gpg) they stay clear.

icesailor

bmwpowere36m3 said:

We had a Burnham with domestic coil... when it was put 15 yrs ago it was connected to a storage tank.



Recently we put in a 50 gal. indirect tank. Its connected as a zone on the main header and wired as a priority. Plenty of hot water.

Bet you had plenty of hot water with the tankless/storage tank for 15 years. Just like today with the indirect.

Both use the same principal. Store it when there isn't a load so when you have a load, you have plenty. If you add the DHW load to a heating load at the same time, you never have enough.

icesailor

SWEI said:

icesailor said:

I had a $300 Grohe satin pewter adjustable shower head with the rubber restrictor removed, I recently bought a Kohler polished chrome 8" wide head that had a non removable 1.75 GPM restrictor in it for less than $100. It has a better spray than the old $300.00 one.

I don't need Eddington to tell me what my customers would have liked.

If it's got the same internals as the ~6" diameter 1.75 PM models we've been using, they really are impressive. I hear Kohler spent some serious time and money on the design and tooling for it. There are very carefully designed internal passages that keep the water for each hole just where it's supposed to be so they all come out at the same pressure and flow. And they don't (so far) clog up with calmag. Just wipe the front every so often and (at least here, with ~12 gpg) they stay clear.

I put in a lot of Speakman fancy/expensive shower heads, and some ugly expensive "Sign of the Crab" ones from all the Gucci Bath faucet outlets bought buy others.

I have never seen a better shower head that the Kohler. If someone is looking for a reasonably priced low flow shower head, that's the one.

No calcium build up from the Florida water. The Asians will have a knock off soon for $25.00.

SWEI

icesailor said:

I have never seen a better shower head that the Kohler. If someone is looking for a reasonably priced low flow shower head, that's the one.

We tested about ten different options before choosing them on a hotel project a few years back. When you have 78 showers, a more efficient option has a huge impact on the sizing of the heating plant. These things really work. Nobody thinks they are using a low flow head. The front desk agents tell me they actually get compliments from guests on how nice the showers are there. I bought one for the house.

icesailor

Hatterasguy said:

icesailor said:

I put in a lot of Speakman fancy/expensive shower heads,

How does Speakman stay in business?

Every single one of their showerheads works like crap and they charge a fortune for them.

Vulture capitalists bought the brand, everything is made in Asia, cheap, and no one noticed the Made In Asia on the box. Or the parts are made in Asia, by American Private Equity Firms, who have the parts assembled in the USA so they can put "Made In USA on the box. Or maybe they just live off past good will and public perception. Why do architects specify American Standard? They were bought out by the Private Equity folks years ago and most professionals consider it the bottom of the line. At one time, they were the major boiler manufacturer in the USA. Then, someone made a command decision to get out of the cast iron foundry business rather than meet environmental pollution standards. They sold their boiler business to Burnham, and Kohler is the only US manufacturer of cast iron plumbing fixtures, American Standard got out of the Fiberglass Tub business. Any "Standard" part you get for an American Standard fixture will be "Standard" for only them.

SWEI

Don't know much about their bath faucets. The showerheads we used were model# K-10240-CP.

icesailor

I think that this is the one. I threw away the box.

http://www.us.kohler.com/us/Devonshire-2.0-gpm-single-function-showerhead-with-Katalyst-air-induction-spray/productDetail/Shower-Faucets/429038.htm?brandId=1000227&categoryId=999508