Boiler Reset Controller

[nate379]

I was watching "Ask This Old House" the other day and they were installing a boiler reset control at a guy's place.

His normal water temp of the boiler was 180* year round and this controller would take the outside temp, do some calcs and adjust the boiler temp to reflect that.

For example, when it's 50* out, the boiler water might only be 130* and when it's -10* out it'd be at 200*
Richard said it's good for roughly a 10% savings. It was something the guy that did my energy audit recommended as well.

Something like this: http://www.pexuniverse.com/store/pro...-reset-control

Instructions: https://www.pexuniverse.com/docs/pdf...102-097).pdf

I'm wondering, is this worth it? I talked to a couple HVAC folks locally and they had no knowledge of this. It makes me almost think it's some "gadget" that isn't really worth it.

I have radiant floor heat. My boiler is a Burham SVG unit and I have an "indirect fired" water heating tied into the system as well.

 

[72Tunaboat]

A lot of the new condensing boilers have this feature built into them. Since your boiler is a standard type atmospheric vented cast iron unit, you can NOT vary the temperature on the actual boiler, but you can run a outdoor reset on a mixing valve or injection pump.

I have a similar boiler to yours(Buderus G124X) and radiant floor heat also. I installed a Tekmar 360 control with a 4-way mixing valve. It controls the mixing valve according to what the outside temp is.

I can't say if it has saved me any money, but I do know the floors are warmer on the cold days than they are on warm days. That alone is good enough for me. I've been running this system for a few years, and it has'nt let me down yet.

I installed it myself so the the labor was free. The control and the mixing valve motor were not cheap, even getting them at wholesale(well over $400 about 7 years ago). To have a licensed contractor install and set it up will not be cheap. For me, it was worth it just for the comfort factor. I can imagine over a bunch of years it might pay itself off.

 

[nate379]

Why can't the water temp vary?

If no thermostat is calling for heat, the boiler doesn't fire. (Cold Start Boiler)

 

[walrus]

I was watching "Ask This Old House" the other day and they were installing a boiler reset control at a guy's place.

His normal water temp of the boiler was 180* year round and this controller would take the outside temp, do some calcs and adjust the boiler temp to reflect that.

For example, when it's 50* out, the boiler water might only be 130* and when it's -10* out it'd be at 200*
Richard said it's good for roughly a 10% savings. It was something the guy that did my energy audit recommended as well.

Something like this: http://www.pexuniverse.com/store/pro...-reset-control

Instructions: https://www.pexuniverse.com/docs/pdf...102-097).pdf

I'm wondering, is this worth it? I talked to a couple HVAC folks locally and they had no knowledge of this. It makes me almost think it's some "gadget" that isn't really worth it.

I have radiant floor heat. My boiler is a Burham SVG unit and I have an "indirect fired" water heating tied into the system as well.

Outdoor resets are very common in Maine, especially with radiant. I don't have one so I don't know about savings but it makes sense?

 

[72Tunaboat]

Why can't the water temp vary?

If no thermostat is calling for heat, the boiler doesn't fire. (Cold Start Boiler)

The following are quotes from the documents provided by TACO:

Most boilers require a minimum supply water temperature in order to
prevent corrosion from flue gas condensation. The control should
therefore only modulate the boiler supply water temperature down to
the boiler manufacturer’s minimum recommended operating temperature.
Some boilers are designed to condense and should be operated
at low water temperatures as much as possible for maximum efficiency

Boiler Minimum Supply Temperature (BOIL MIN)

Most boilers require a minimum operating temperature to prevent corrosion from flue gas condensation. The minimum boiler setting
should be programmed to the lowest supply water temperature at which the boiler can operate without causing the boiler flue gases
to condense. Consult the boiler manufacturer for recommended minimum boiler supply temperatures. Some typical settings are as
follows:
Steel fire tube boiler ….......... 140 to 160°F (60 to 71°C)
Condensing boiler ................. Off
Cast iron boiler ….................. 135 to 160°F (57 to 71°C)
Electric boiler ........................ Off
Copper tube boiler …............. 125 to 150°F (52 to 66°C)

 

[72Tunaboat]

Will you post a photo of you boiler piping? I would like to see what you are currently using to mix the water down for your floor heat.

Thanks

Roger

 

[nate379]

I don't have any pics on this computer, but if you search in the thread dealing with pics of radiant heat, I have a couple in there.



As far as min temp, that is correct.

Right now the min temp while a T Stat is calling for heat is 160* and the max is 180* When it's not calling for heat the boiler will go down to whatever. I have seen it as low as 55-60* (air temp in the garage)

If I can run it down to around 140* the water could be 20-40* cooler. Also if I need 200* water when it's -30* outside, well it would kick the boiler up a bit.

I'm going to look into the Taco 700 reset since I think it will be pretty much plug and play with my Taco controller and valves.

 

[chevelle67]

Tekmar makes the 700 for Taco. You sound plenty capable of installing your own control. The same control from Tekmar is a 256 which is also about $120 cheaper. They are incredibly easy to install. Then you would just have to figure out what tools to buy with the left $120

 

[tacoon]

Your link is broken and I find working links
Taco PC700-2 Boiler Reset Control

Instruction Sheet for Taco PC700-2 Boiler Reset Control (pdf)

 

[GaryRoushkolb]

Glad I read this post. My flue pipe is showing rust streaks from where the water vapors are condensing and the top had a large chunk of ice on the outside earlier this winter. The water temp of my boiler is around 80 to 100 degrees in my floor heat and seem to be working fine. Should I mess around with the water temp or just replace the flue pipe with stainless. I really like the way everything works now but for the rusted pipe.

 

[nate379]

That is really cold for a cast iron boiler based on the info I have read.

My system is setup where I have a "double loop" where the boiler has a loop and the floor heat is on an another. There is a mixing valve between. The idea is the boiler water stays warmer than the floor water. I'm sure an HVAC pro can chime in on here how to set that up, I'm not really sure myself.

 

[nate379]

I have been getting mixed stories on what to do and it's becoming a head ache. Some guys are saying an outdoor reset is a waste, air sensors (what I have) aren't the way to run slab heat, etc.

What I wanted to do was run a Tekmar 421 controller which is an outdoor reset as well as a mixing valve controller. It would control a 3 way valve, which would replace my fixed temp mixing valve.

That would keep the boiler at the 150* min temp and the pex at 120* or so. I have read that the pex is ok to 180* so when it's really cold out I could set it up for the outdoor reset would bump up the supply temp for a bit faster recovery time.

This is all how I understand it to work.

The 421 outdoor reset, valve and valve motor is $960 though.

Other option is to just do a Tekmar 420 outdoor reset, $345 OR

Update my current Taco zone controller to one that accepts a TACO outdoor reset, cost would be $515. That would be more or less plug and play.

10% savings, if that is really correct, would amount to about $200 a year, so the payback isn't too bad.

 

[danski0224]

Glad I read this post. My flue pipe is showing rust streaks from where the water vapors are condensing and the top had a large chunk of ice on the outside earlier this winter. The water temp of my boiler is around 80 to 100 degrees in my floor heat and seem to be working fine. Should I mess around with the water temp or just replace the flue pipe with stainless. I really like the way everything works now but for the rusted pipe.

If your boiler is cast iron, copper, or has cast iron parts you will destroy it from the flue gas condensation.

The problem needs to be fixed.

 

[72Tunaboat]

If you want to save some money and still utilize the outdoor reset feature, look into the Taco I series mixing valve. it is pretty much self contained(mixing valve, motor, controls) all in one piece. You just have to mount the outdoor sensor outside.

I have installed a few of these, and have had no problems with them.

Click on the link below for more info.

Taco I- Series Mixing Valve

 

[nate379]

Will have to look into those. I need 1.25" valves and the only thing they have is a 4 way in that size (need a 3 way).

 

[nate379]

I picked up the Tekmar 421 for now. The mixing valve and motor for it would have been about $600, but I can add that later on if I decide to.

I hope it will help a bit with the overheating going on lately. Will be 40* in the AM and warms to 60* in afternoon... well house is getting around 73-74* because of that and I have to open windows cause I'm sweating my nads off!

 

[StumpFJ40]

If you set an outdoor reset to control a mixing valve, you are defeating the purpose of the outdoor reset: to lower the heating demand on the boiler during warmer days when you don't need 180 degree water to warm the house 5-10 from outside temp (short cycling). Otherwise, you are likely to cause the boiler to run longer as you are cooling the water it just heated to 180 degrees. As long as the outdoor reset is programmed to run a minimum temperature (140 or so) to prevent condensation in the exhaust the outdoor reset will reduce the heating demand and fuel usage of your boiler during those warmer days when you don't need 180 degree water to warm the the house.
Disclaimer: Not a heating professional or expert just a guy with oil heat who is very interested in reducing his fuel costs (simple insulation, programmable setback thermostat, air intrusion elimination and new, quality, storm windows reduced my heating expenses 40% over last year in my 265 year old farmhouse). I expect to get another 10% better with an outdoor reset next year.

Please let me know if I have this wrong, as I said, I am not an expert.

 

[nate379]

The mixing valve would be to replace the manual primary/secondary loop mixer.