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Joined on January 19, 2012

Last Post on July 30, 2014

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@ August 15, 2012 12:53 AM in Carwash glycol floor and hot water system

Are you thinking about going with a direct water heater in order to save some costs?
This makes sense only if you are planning to sell the business soon. You will install 2 of the systems you are describing or 1 "real boiler" in the same time period. Think long term if you plan to own long term.
Just a thought,


@ August 15, 2012 12:46 AM in Carwash glycol floor and hot water system

I have yet to find a condensing water heater design that I am comfortable with especially in a commercial application.
That being said, the easiest way to size you exchanger is to cheat. Once you know your designed gpm and delta t for both sides as well as your glycol percentage, just have the manufacture do the math.
Someone on here probably has a quick formula for this.You are basically trying to figure out how much surface area you need.

There are advantages

@ August 14, 2012 1:00 AM in Carwash glycol floor and hot water system

The advantage to not running the city water through the boiler is longevity. The smart does a nice job of shedding the calcium and other deposits that you don't want in your boiler. You don't lose the glycol deration btu's the fluid simply cannot carry as many btu's as water. With a good sized tank you will get nice long boiler cycles as opposed to the the constant start stop of the instantaneous. The boiler will heat the domestic water at high temp during you domestic water priority then turn down to the ultra efficient low temp for slab heating.


@ August 13, 2012 11:41 PM in Carwash glycol floor and hot water system

The hot water load looks like 9gpm x 500 x 60 delta T = 270,000 BTUhr. You will also have to derate for glycol and altitude if needed.
I would consider a Triangle Tube 399 with 330,000 output. I would use a smart 120 heat exchanger. The low head boiler design will allow the glycol to be piped directly without a heat exchanger.Pipe it primary secondary just like the manual says
For controls I think you need a slab sensor with a setpoint controller. You could use the boilers outdoor reset so that you are only heating the slab as much as you need.


@ August 13, 2012 1:41 AM in Mod Con Boiler sizing

How in the world do you type that little "delta" symbol?
I have to know!

I'm with Robert

@ August 13, 2012 1:39 AM in Mod Con Boiler sizing

On the Domestic, say you have some load "spikes" of 6gpm but generally you average 2gpm. You could use a boiler capable of 2 gpm or less then use a larger and/or hotter DHW tank to take care of the spikes.

Condensing boilers are most efficient when modulated the fire all the way down with the lowest possible return water temp. The limit to this is a boiler that is "short cycling". I think it is important to look at the boiler and system water volume as well as the modulation rate when looking at boilers. I have heard but not confirmed that some of the manufactures claiming ultra low turndown ratios are suffering efficiency at low fire.


What are your loads?

@ August 13, 2012 1:20 AM in Carwash glycol floor and hot water system

First the hot water. How much hot water do you need in the summer? How much in the winter. What temp does it start at and what do you heat it to? If you are reclaiming some of the water, this may be tricky to figure out and you may need to check with the manufacture.If you are just heating water and putting it down the drain you could just observe the water meter during peak times and see how many gallons per hour you are using. It's all getting heated right? Get that info and we can size the water load.

What do you do with the snow melt? The car wash is covered right? It sounds like you have a bunch of covered self service bays. Are you just trying to keep the slab warm enough to prevent icing or are you melting snow? Is the system on all winter with no controls? Do you know if the slab has insulation under it? What part of the country?

It sounds like a condensing boiler with an indirect hot water heater would save you tons of money. You need to spend some time figuring the loads and some money on the right equipment and controls.Take a long look at the upfront costs and the savings down the road.

Keep in mind you don't need to add the 2 loads together. How often do people wash cars when it is 20 degrees out?


6 per hour

@ August 9, 2012 9:03 AM in Oil Hot Water Boiler Cycling

The number that is thrown around for short cycling is more than 6  per hour. You seem to be right about there. What is the differential between the boiler on vs boiler off? Stretching this number may be the easiest way to optimize you cycles. You want to be sure not to go so low that you impact performance or cause boiler condensing.It may be possible to combine this with Robert's suggestion of ODR.
On a warm day you could run 150-170 and on cold day 170-190.
Doubling your on off delta t will double your run time (almost).


@ August 9, 2012 8:45 AM in trying to trim circulators

I wasn't suggesting a total redesign. The original design looks like it works fine. The expansion tank location could use some improvement.

There is potential for the circulators to "compete" with each other. As the mixing valves turn the forces and flows change making for a potential for some undesirable results.

In my mind, a better overall design would have a big loop with the boiler, storage tank, and a heat mixing pump tied into it using closely spaced tee's. The boiler return temp would be protected via controls on the storage tank and mixing injection pump.I also prefer Chevy Trucks.

I think the other comments regarding your modification are valid. I am thinking you may be better off leaving well enough alone. You system works albeit a bit clumsy.

Pumping Away

@ August 8, 2012 9:39 AM in trying to trim circulators

You should be pumping away from the expansion tank.
You must control and this in manner that will prevent low return temps as Clammy pointed out. The gravity dump is also essential,in the event of a power outage.
I  prefer a design that has more "hydrolic separation" and uses injection mixing with outdoor rest on the radiant side and something a little less clumsy for the storage tank. I am having trouble getting my head around the "2 way traffic" on the storage tank. Just my opinion.This design must work fairly well or they would change it.
You could consolidate the 3 zone pumps to one and use zone valves.

Eye opening

@ August 8, 2012 9:26 AM in Polybutylene

This thread has been an eye opener for me. I really expected with 210 views I would here a few stories of failed poly in low temp closed loop heating. I think I should ask the inspector and consultant to provide some cases to back up their opinions.
I suspected that this was the buyer's "out" earlier. I just wish they had picked a different one.
Thank you all,

Uphill Battle

@ August 7, 2012 10:01 PM in Polybutylene

Looks like this may be a deal killer. The Buyer has found a "consultant" who has painted a dim view of PB.He claims failure is certain and that the home may be uninsurable.
Does anyone know of resource that has "case studies" or other research on the longevity of PB in this application.

Thank You

@ August 3, 2012 2:12 PM in Polybutylene

With all the information (and misinformation) out there, it is always good to get a reality check.


@ August 3, 2012 2:09 PM in DHW Tank Temp

I set mine just over 140 off and about 125 on. I use a thermostatic mixing valve at the heater to prevent scalding. Many of the newer exchangers are designed to reduce mineral build up. I have good lick with Triangle Tube Smart and Heat-Flo.


@ August 3, 2012 11:24 AM in Polybutylene

I am working with a client who is trying to sell his home.
The heating system consists of polybutylene tubing. It is grey vanguard circa 1993. 3/4" mains feed 3/8" tubing embedded in gypcrete. The manifolds are also PB (infloor brand block style). The boiler is the second for the house and is a teledyne endurance (formerly heatmaker). The boiler show signs of corrosion and the water is rusty. The system has outdoor reset mixing and runs at a max temp of 130.The tubing shows no sign of discoloration and is pliable.

The buyer had an inspection performed in which the inspector noted the corrosion on the boiler. He also noted the polybutylene tubing and made reference to the class action lawsuits of the 90's.

The buyer is very concerned about the tubing.

I have tried to educate the buyer that the lawsuits were more about the fittings and that his larger problem is the lack of oxygen barrier,poor quality manifolds and failing boiler.

I have recommended the following:
The system should be cleaned
The manifolds should be replaced
The boiler, DHW exchanger and circulators exp tank ect.should be replaced with stainless.
I would probably use TT prestige solo with a heat-flo exchanger.

My question is,
Does anyone have reservations about the polybutylene's longevity in this application?
Has anyone seen failure of polybutylene in this type of system (low temp heating).
Any thoughts on a better solution?
Thank you in advance,

Non issue

@ August 2, 2012 10:05 PM in Baseboard Heating and Electrical Outlet

Hot water baseboards do not run anywhere near as hot as there electric counterparts.The water inside will never exceed 200 degrees and generally is under 180. They do not present  fire hazard and I am unaware of any code issues.

You could...

@ August 1, 2012 9:19 PM in Mod-Con Boiler Pump Speeds

You could add up the pipe sizes and fittings on the secondary then draw out the system curve for the loop. You would then calculate the heat emitted by the radiators on this loop being sure to derate each for the loss in temperature from the previous. This will give you your target GPM. You would then compare this info to the pump curve at the various settings.
My head hurts just thinking about it!
I would use a gauge


@ August 1, 2012 9:02 PM in Indirect HW design question

The only issue I see with your drawing is that you are not "pumping away" I also think it will be difficult to get an accurate temp to the radiators (especially with outdoor reset)
I agree with the firetube hx comments. Personally I would pipe It as shown in the triangle tube manual posted above. I would run the boiler on outdoor reset and domestic priority. The smart 100 basically has no head loss. It is just a big vat of water. The smart has so much surface area that at a slow circ speed you will likely condense the boiler through much of the DHW cycle

How old is it?

@ August 1, 2012 11:51 AM in What are my options?

How much mileage did you get out of this one?
I would suggest a mod/con combi unit. Triangle tube challenger comes to mind. What are you domestic water needs? What part of the country are you in?
Is it possible to replace the vent? ABS may be an issue.

Take some time

@ August 1, 2012 11:44 AM in Mod-Con Boiler Pump Speeds

I would suggest taking some time to get your head around the "hydronic formula".
Check out this gauge .
With the clamps you can quickly see how circulator speeds are effecting your system performance.
It looks like Medium is a decent starting point for the primary (I did not see a minimum flow in the manual).
If you get the secondary speeds to low you may get poor performance on the return side radiators.
I would start with a 20 degree delta t on the heat and see how it goes.

Pump Curves

@ August 1, 2012 12:37 AM in Mod-Con Boiler Pump Speeds

I think you may be misunderstanding the speeds on the circulators. I am assuming you have grundfos 15-58s? The gpm produced by the circulators is determined by the point at which the pump curve intersects the system curve (page 27 of the manual) The 15-58 on the boiler set on high will produce about 5.5 gpm (assuming the near boiler piping is short). To figure out the system curve and gpm for the rest of the circulators you would need the pipe lengths and resistance of those components. It would be easier to measure the delta t (supply temp-return temp) of the pipes and adjust the circulators accordingly.
The only way to increase boiler efficiency is to reduce the return water temp. Slowing the boiler circ. will do this (at some point performance will suffer). Slowing the secondary circs may not have an effect on the boiler return temps. Doubling the secondary delta t will have no effect on the primary return temp if you cut the flow rate in half to do it.
Get a gauge and check it out,

Thanks for the follow up

@ July 31, 2012 11:51 PM in Hot Water Heater Problem

I absolutely think the issue is with the end switch on the DHW zone valve. You can slide the lever on those valves and tell if the valve is open. An open valve will slide with no resistance. If you valve is open and the boiler is not firing it is an end switch problem. I agree that the wiring is a bit on the ugly side. You may have a loose end switch wire. Next time it fails, try wiggling the groups of red wires. I am 99% sure a new zone valve will solve this. Be sure the contractor has one on his truck. 
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