Floor Heat Boiler Bypass?

[2Biz]

To start with, I’ve searched the forum and read every thread that contained “Boiler”, “Bypass”, and “Boiler Temperature”. So far I haven’t found direct answers to a few questions I have. Also there are a lot of owners who have posted similar questions as mine who have not received clear answers. So I’m hoping this helps them as well as me.

Last winter, after buying this wash in January, I was lucky to find the switch that turned the boiler and pump on, Let alone know how it all worked. And lucky for me it worked! Or so I thought. One thing I remember is the output temperature NEVER got over 70° and the boiler ran continuously until the outside thermostat turned it off or I switched it off. But at the 70° outlet temperature it did keep my bays clear of ice. (I have a 4 bay with one bay being an outside bay for trucks and semi’s, totally exposed).

What I have learned from almost every manual I’ve read online for floor heat boilers, is the input water temp to the boiler should never be below 125°. And most boiler high temp/output settings should be in the range of 160° to 200°. Again this is what I’m seeing in manuals and boiler forums, not here. What the manuals say is, if the water/coolant is pumped in the boiler at below 125°, condensation is formed in the flu and on the boiler coils which is very acidic and will destroy the coils eventually. Makes sense to me, maybe that’s what those greenish particles are at the base of my boiler? But it also makes me wonder if you can damage a slab at these temps?

Anyway observation number two…The type system we should have in a car wash, since our zones are open to outside air, is called a low temperature system. Our systems are supposed to have a “Bypass” at the boiler so heated water can be directed back into the boiler which allows us to control boiler inlet and outlet temps for optimum performance. A high temperature system is one that heats an inside floor and the return line temperature is usually warmer allowing for plumbing that does not require a bypass. Makes sense.

Continued to next post!

 

[2Biz]

So I guess my system was purchased incorrectly or set up as a high temperature system! All I have is a gate valve between the pump and boiler which was set to wide open, full water flow. No Bypass. With the valve wide open, the water in the boiler doesn’t have time to heat because it is flowing through the boiler too fast. Anyway here is my question and which will hopefully help others as well. I’ve enclosed pictures for reference. Since all I have are my zone valves and gate valve between the pump and inlet of the boiler, should I restrict water flow to my boiler to get the temperature up so the system is more efficient? The way my system currently runs is like a car without a thermostat in the winter, the water will never heat up. So I need to add a thermostat, in my case restrict water flow through the gate valve to raise the boiler temp. If so, what high and low temp should I try to get to? I don’t know with my current configuration (without a bypass) whether I’ll every get my inlet temp above 125° to keep from hurting the boiler, but I can bring up the outlet temp to be more efficient. But I don’t want to damage the slab either with too high of temps. Should I add the bypass? My boiler is old but it sure would be nice IF I made the CORRECT changes to where it might last a few more years till I can afford new.

As always anyone’s input on this will be most appreciated. And sorry for such a long post again, but there is a lot going on with floor heat that I didn’t ever dream existed. Same as other aspects of owning a CW.

Open pdf file to see a boiler with a bypass:

http://bcoweb.com/photos/boiler_with_bypass.pdf


This is a photo of my boiler, no bypass, only a gate valve between the pump and boiler inlet...

 

[Jeff_L]

I don't pretend to be a boiler expert, so take what I say with caution.

Personally, I wouldn't restrict the incoming water to your boiler, rather, I would regulate the output side instead. That way your boiler stays full and can heat the water to what you want before exiting. HOWEVER, for safety you should have a pressure relief valve on the output side of your boiler before the gate valve.

 

[CCAR]

My boiler is different brand but the same concept. I also did not have a bypass line in mine. It seems as though at one time this was an acceptable way to do it, probably when gas was cheap. I installed a bypass my self. You want to run about 1/4 to 1/3 of your volume back into the boiler. After doing this I could get the proper heat settings from my boiler. Saved a bunch on natural gas. This idea came from some Raypak people, they told me that this is the current way of doing the plumbing. I also did not have a return line thermostat which I also installed at the same time. About 64 to 66 degrees seems to keep my bays from icing up

 

[2Biz]

There is a pressure relief valve right at the outlet on the boiler. You can't see it in the pic. The gate valve is is on the inlet plumbing, not the outlet. Its actually plumbed different than what I expected. Cold in to the boiler is on top, hot out is below then expansion tank then to bays...Cold in from bays then goes to pump, then to top connection on boiler. This is a prebuilt system just like KR sells only without the bypass plumbing:

http://www.kleen-ritecorp.com/p-23904-floor-heat-system-350000-btu.aspx

 

[2Biz]

You want to run about 1/4 to 1/3 of your volume back into the boiler.

About 64 to 66 degrees seems to keep my bays from icing up

If you can get 64°/66° return temps back to your boiler, what temp do you have your boiler set at?

Thanks for the feedback! I was thinking I need to add the bypass, but don't really know how long this old boiler is going to last, even with running it correctly. Unfortunately, most of us new owners run things like they've always been ran because we don't know any different...Some of the old timers didn't have the internet to bounce idea's off of to learn or come up with anything new. We are lucky!

 

[CCAR]

If you can get 64°/66° return temps back to your boiler, what temp do you have your boiler set at?

Thanks for the feedback! I was thinking I need to add the bypass, but don't really know how long this old boiler is going to last, even with running it correctly. Unfortunately, most of us new owners run things like they've always been ran because we don't know any different...Some of the old timers didn't have the internet to bounce idea's off of to learn or come up with anything new. We are lucky!

I have the boiler temperature at 115 degrees. Mine is a raypak with a modulating valve. I can adjust the temperature up or down if I need to.

 

[Earl Weiss]

I am not an expert but heere are my thoughts.
1. I think most manulas for this type of equipment are not intended for car wash floor heat. In a house you need to get the temp to 70 degrees or so. Aslo, the incoming temp of system water would be around room temp. The slab needs to be 40 degrees or so at the coils to do it's job and return fluid (An anti freeze mix, not just water) would be low as well. In order to exhaust the cooler post combustion air, and avoid condensation, my systems all have an exhaust fan in the flue that kicks on the the burner. Check to you see if you haveone, or get one istalled. I see no reason to worry about higher temp incoming liquid, and higher temp to the slab may cause addittional expansion issues. (Know one huy whose employee thought he was helping by raisingf it to 120 degrees and needed lots of repairs.

 

[cantbreak80]

Also...systems of that vintage frequently were installed with poly pipe (black irrigation pipe) which should never see temperatures above 80-85 degrees.

 

[2Biz]

I don't have an exhaust fan in my flu pipe. I do have a "hood" that mixes ER air with the flu gasses. I was more concerned about the condensation and the fact that my outgoing temps never get above 70°. Incoming is very cold...I need to check it with an infrared thermometer the next time I turn it on. Just haven't had to run it other than testing so far this winter.

Thats good information to know about the tubing. Mine is black, but it is very stiff and not like the flexible clear poly stuff I use for my mix tanks. I would think it would withstand temps higher than 80°-85°....But then again, if higher temps cause slab issues, then its a mute point. Maybe I do need to install the bypass to control temps to both boiler and output to bays. Sounds like the only solution to make it work more efficiently. Right now my boiler never turns off unless I turn it off or if the outside air temp goes above 30°. The lowest temp setting on the thermostat controlling the output from the boiler is 100°. Minimum temp setting on the input is 70°. I don't get close to either setting with the gate valve wide open... So it will run constant once the outside temps are below 30° if I have the breaker on. I've read that others are having the same issue...Some are putting the boilers on timers: On a certain length of time, off a certain length of time. I'm not the only one seeing this issue...

 

[dogwasher]

On a "house" boiler your boiler should run between 140-180 degrees any lower and it could condense and ruin the heat exchanger. The return water should be mixed into the supply water so no more than 120 degree water enters the cement slab.
I don't know much about these PVC piped boilers? Most of the time the cold concrete on outside systems never gets to the 140-160 temp anyway since the heat gets convected to the cold concrete so fast the boiler never gets up to temp(on very cold days) Sorry I cant help much here.