Boiler Replacement Options - Win a $25 Restuarant Card!

[Ghetto Wash]

I've got nothing to add, so don't add me to the drawing.

I'd just like to say that I like your creative idea to get so many responses. When I logged in today, I saw this thread with so many responses and was sure that I must have missed it last time I was here as no thread gets this many responses in 24 hours. No, I didn't miss it. You got more responses in one day than I've seen in a long time!

 

[MEP001]

Would it not be as simple as replacing the existing boiler with a wall-mount heater and leaving the rest as it is?

 

[mjwalsh]

We just installed the Navien 240NPE. So far they are absolutely wonderful. Three units putting out 12gpm total and a 200gal storage tank and constant 120 degreee water with no temp drop on the busiest of days. On slower days only one or two fire as necessary.

MC

Mr. Clean,

Are these the ones with an already built in circulating pump so you don't have to worry about the minimum flow rate as much? We are leaning to getting one of the built in circulator types of whatever brand .... so our three stainless steel 40 gallon storage tanks keep up better.

mike

 

[6t7gto]

Of course you are in! Are you using a Lochinvar? Does it require a holding tank?

Not yet. My nephew sells and installs them.
I saw one at a nearby wash.
He is on this forum but I don't know his handle on here.
Maybe he will see this and respond.
David

 

[2Biz]

At true peak times I would need as much as 12 gallons per minute. But I would be okay with the temp dropping a bit during these times (obviously as long as the pumps are not starved for water).

How is your current boiler plumbed. Does it have a circulating pump between the boiler and holding tank? If so why couldn't you set up a wall mount heater and alter the current plumbing and pump you have? If you could get 8 gallons a minute of 120° water going back into the holding tank, an 80 gallon tank would last 20 minutes at 12gpm flow to the bays. But how often are all your bays running HP Rinse or Soap at the same time? A single wall unit putting out 8 gpm of 120° water will heat 3,840 gallons of water in 8 hrs. Do you have this kind of volumn? Something to consider when sizing your system.

You mentioned starving your pumps above, You don't don't have to worry about starving your pumps if your drawing water from the holding tank and your water supply is going directly to the holding tank and you're circulating water from the tank to your boiler. At the least, your water temp will drop slightly, but you shouldn't starve your pumps because your boiler isn't keeping up. But if your water supply goes through your boiler first, which it shouldn't, then you might have a problem. The new wall units "throttle" the water flow to get the exact output temperature you dial in based on incoming water temperature. Something else to consider when comparing demand heaters.

 

[2Biz]

Would having hot water get you more customers is an interesting question. I believe hot water will help your chemicals work better and help cars leave cleaner. Are there other washes nearby that potential customers use? If your customers leave with a good experience and a clean car, they will come back. That is probably even more important than attracting new customers. If every customers that comes is pleased, your business will grow.

I compete with two other washes in our town. BUT they are newer and both are for sale...When I bought our wash two years ago, it was in need of attention. Turning a wash around is a slow process. Although we are seeing a 30% increase over the same time last year...Even though our wash is older, customers tell us we have the best wash in town!

It would cost me about $3000 to put in a new boiler for hot water including plumbing and a holding tank like you have. BUT will it gain me anything over what I currently offer? I turn off my NG from April to about November. This saves me $110 a month in rider and service fee's they charge even if I don't use a single Cubic Foot of NG. So to recapture the cost, I would have to raise my price in order to pay for the install and the additional $200 a month it would take to run it. Would it be worth it?

 

[Turbo]

Consider an Eternal tankless. I removed my 600k btu (I think) 82% efficient ( when new) boil and tank with recirculating pump with an Eternal mounted up on the wall. Very efficient (95% i think) and no maintenance. It keeps up with my 3 self serv and 1 automatic (presoak only). I set at 110 degrees, if it cant make 110 it lets water through ( so no starving pumps). I think it was $3500 installed.

Turbo
Chicago

 

[RockyMountain]

I've got nothing to add, so don't add me to the drawing.

I'd just like to say that I like your creative idea to get so many responses. When I logged in today, I saw this thread with so many responses and was sure that I must have missed it last time I was here as no thread gets this many responses in 24 hours. No, I didn't miss it. You got more responses in one day than I've seen in a long time!

Too bad you don't want to be in the drawing, but the rules state that you must be included! Good luck!

 

[RockyMountain]

Would it not be as simple as replacing the existing boiler with a wall-mount heater and leaving the rest as it is?

That is exactly what I was hoping! And I don't know... Our current boiler has water running through it 24-7. I don't think that would be a good option for a tankless takagi/navian/rinnai. I assume I would need a way to measure the temperature of the water and then cycle it through the heater as needed...

 

[MEP001]

I assume I would need a way to measure the temperature of the water and then cycle it through the heater as needed...

Yes, you would put a thermostat in the tank to control the pump, which would circulate water through the heater, which will activate it. It's how most boilers with an insulated tank work already, and if yours is not set up like that it's already way more wasteful than it needs to be.

 

[mjwalsh]

That is exactly what I was hoping! And I don't know... Our current boiler has water running through it 24-7. I don't think that would be a good option for a tankless takagi/navian/rinnai. I assume I would need a way to measure the temperature of the water and then cycle it through the heater as needed...

Rocky,

I am thinking that the aquastat within the tankless would be an adequate control for maintaining the temperature. Since you said you are 24/7 ... the needed circulating pump would run constantly. Typically those kinds of small pumps are made to run continuously at almost no cost if they use the kind that I am used to. Like a small Grundfos. If there is no built in pump inside the tankless ... a small stainless steel Grundfos could be put in line ... round trip between a beginning tee just before your 2 storage tanks, the tankless, then the outlet of the tankless could go into the storage tanks themselves. In our situation, we are closed for about 10 hours at nighttime so I am thinking in our case it might be worth it to have the pump & the tankless on a time clock. I would say rely just on the pressurized water but it seems like that would not do the recirculation that you need to maintain the useful storage hot water reserve.

Whatever you do ... make sure the pump is stainless steel. We had the bad experience of a contractor once putting in a pump for the domestic not stainless & within 2 years we had to replace the pump.

Best thing is to make sure you have a sketch of your visualization before you actually start the soldering (sweat) process. I am a bit pushed for time ... otherwise ... I could possibly come up with a simulation animation of the process via a flash file or whatever. In the meantime, hopefully some other forum member will volunteer that because it could be useful.

mike

 

[MEP001]

I am thinking that the aquastat within the tankless would be an adequate control for maintaining the temperature.

That's not how tankless heaters are intended to operate, plus when you circulate water through a heat exchanger it acts like a radiator and heat is lost through the vent for no good reason. Using a tank-mounted aquastat to switch the pump on to trigger the heater would be more efficient and follow the design of the unit.

Since you said you are 24/7 ... the needed circulating pump would run constantly.

There would be no need for a pump to run 24/7 with a tankless heater circulating from an insulated, pressurized storage tank.

I would say rely just on the pressurized water but it seems like that would not do the recirculation that you need to maintain the useful storage hot water reserve.

It should maintain it unless the heater is severely undersized. 80 gallons of storage, remember?

Whatever you do ... make sure the pump is stainless steel. We had the bad experience of a contractor once putting in a pump for the domestic not stainless & within 2 years we had to replace the pump.

Using a domestic pump in a commercial application was your problem, not using a pump that wasn't stainless. I've seen boilers with 30 year old bronze pumps that had been running 24/7. Recommending a stainless pump based on your anecdotal data of a misapplied item is nonsensical.

 

[2Biz]

I am thinking that the aquastat within the tankless would be an adequate control for maintaining the temperature. Since you said you are 24/7 ... the needed circulating pump would run constantly. Typically those kinds of small pumps are made to run continuously at almost no cost if they use the kind that I am used to.

Mike,

I think the demand heater you refer to with the circulating pump built in is for a different application than ours. It is designed to circulate water in a "Looped" household system where the hot water is always circulated (at very low volumn) to keep hot water at the fixtures at all times. I don't think this would give the volumn needed for a car wash application.

I would think there should be a circulation pump between the storage tank and boiler. What would keep the storage tank hot on less busy or rainy days? If the storage tank was supplied from the boiler alone, the water in the tank will have a chance to cool off on less busy or rainy days. Then you would have 80 gallons of cold water for the first few cars when the rain stops...

 

[mjwalsh]

Mike,

I think the demand heater you refer to with the circulating pump built in is for a different application than ours. It is designed to circulate water in a "Looped" household system where the hot water is always circulated (at very low volumn) to keep hot water at the fixtures at all times. I don't think this would give the volume needed for a car wash application.
QUOTE]

2Biz,

Hmmm ... so those built in pumps are just to facilitate the triggering of the tankless on or off. I wonder if some tankless are not just on or off but modulate the level of btu usage based on flow?

I agree if the internal Tankless pump does not have enough GPM to keep Rocky's (now) gravity outlet tanks filled adequately .... the externally mounted & properly sized pump with the proper water lift - GPM range would be necessary. With my specific project ... but possibly not Rocky's & for sure not your floor heating hydronic application ... my description should work because I am planning to just supplement my existing capacity to heat the domestic water.

Using a domestic pump in a commercial application was your problem, not using a pump that wasn't stainless. I've seen boilers with 30 year old bronze pumps that had been running 24/7. Recommending a stainless pump based on your anecdotal data of a misapplied item is nonsensical.

Mep,

Guulleee .... I would hate to think that from this day forward ... the other members of our dear forum would start defining "domestic water" as non-commercial. BTW in my humble opinion ... unless you're designing a swimming pool I personally would be leaning towards a properly sized stainless Grundfos or stainless Taco pump considering the price difference.

mike

 

[MEP001]

Guulleee .... I would hate to think that from this day forward ... the other members of our dear forum would start defining "domestic water" as non-commercial. BTW in my humble opinion ... unless you're designing a swimming pool I personally would be leaning towards a properly sized stainless Grundfos or stainless Taco pump considering the price difference.

http://dictionary.reference.com/browse/domestic

do·mes·tic [duh-mes-tik]
adjective
1. of or pertaining to the home, the household, household affairs, or the family

So you can see why I gleaned when you posted in a thread about a commercial application that your domestic-use pump failed that there might be a misunderstanding.

 

[2Biz]

If you research circulating pumps like a Grundfos or Taco, I think you'll find you use a castiron pump housing when using it in a closed loop system where there is no oxygen present in the water/glycol. Oxygen in the water is what causes corrosion and rust. In a system like what is being used in this thread, there is oxygen in the water which requires a pump housing that will not rust or corrode. I think in this case, either a bronze or more expensive Stainless housing is the way to go.

 

[2Biz]

2Biz,

Hmmm ... so those built in pumps are just to facilitate the triggering of the tankless on or off. I wonder if some tankless are not just on or off but modulate the level of btu usage based on flow?

mike

From what I've read, those little pumps are programmed to turn on and off at preset intervals to maintain temperature in the loop. If the temp is low, the boiler kicks on at a low modulated temp to reheat the loop. But if full flow is needed, then the boiler senses this and heats the water based on incoming temp and flow. I don't know how the small circulating pump could be used in our configuration. A larger pump will be needed with enough capacity and pressure to supply enough water to the boilers rated output. Every boiler documentation will have a graph that shows how many gallons a minute throughput the boiler has at a specific incoming water temerature. It will also list head pressure through the boiler at different GPM's. You have to size your pump accordingly. Pumps have the same graph. You use both graphs to make sure you size both boiler and pump correctly.

 

[MEP001]

I wonder if some tankless are not just on or off but modulate the level of btu usage based on flow?

It wouldn't matter - if one was used that's set to maintain a constant temperature water output, it can just circulate water in the pressurized, insulated tank until the water temp reaches the level set on the thermostat. To maximize yield on the tankless heater, one would just use a pump big enough to ensure the peak flow of the heater is met.

I agree if the internal Tankless pump does not have enough GPM to keep Rocky's (now) gravity outlet tanks filled adequately .... the externally mounted & properly sized pump with the proper water lift - GPM range would be necessary.

In a recirculating system like he already has with the boiler and insulated, pressurized tank, the heater has no bearing whatsoever on keeping the gravity tanks full. Removing the boiler and replacing it with an on-demand heater controlled by a pump would not change that. Worse-case scenario, it won't maintain the temperature at the desired level, but I doubt that would ever be an issue with a 3-bay wash and 80 gallons of hot water reserve.

 

[RockyMountain]

Great posts- thanks! Replacing the boiler with a pump and tankless heater and keeping the current tank sure seems like a good option.

So is there a resource anyone knows of that can provide a diagram that includes the location of the pump/ pressure relief valves/ gages/ and heater for my situation, as well as recommendations on pump sizing based on the heater chosen? Do individual water heater companies provide this?

I've got a couple local companies that are going to provide a bid, but as I mentioned I'm not sure they understand our needs.

 

[2Biz]

I think you'll find you won't get much help from a supplier/manufacturer. I listened to a Takagi Rep, and he told me a Taco 009 would be enough to supply water to my Takagi T-H3-DV ....The best it would do is 2-3 gpm and its rated at 10gpm...But the 10gpm rating is at zero head pressure! In order to get 8gpm through my Takagi, it needs 50 feet of head pressure....So, as mentioned earlier, I had to put (2) Taco 013's in series to get 8gpm at 50 ft of head pressure.

I've been researching this more lately and Taco offers a higher end circulating pump, the 2400's series. The 2400-50s ("S" for stainless steel) will supply about 10 gpm @ 48ft of head or 21 psi. Maybe a better route to go since the output of the 2400-50 is almost equal to (2) Taco 013's in series. When you settle on a heater, you need to compare the head pressure of the boiler with the pump you select to make sure the pump supplies enough GPM and head pressure needed for the boiler to achieve maximum output.. Keep in mind ALL demand heaters are designed to run off city pressure. Most of these heaters need 50 feet of head pressure to achieve max flow. Another factor, comparing temperature rise and through-put! Another piece of the puzzel.

Go to Pexsupply.com and look at the different pumps and compare the head pressure graphs with the boiler specification graphs....It will take some studying, but if you want to do it right, you need to do a little homework to make sure you size everything correctly...