in floor heat, temperature, freezing pipes

Mark Custis

Get us a make and model number for that electric boiler and we will tell you if it is staged. Running the wiring diagram through a scanner to PDF would work too.


Then post it as an attachment.

It is starting to sound like you tightening the house up will help reduce fuel costs.

Kara

in floor heat, pipes

I recently purchased a patio home with in floor heat. When the temperature hits 0, the in floor mini-boiler runs all day, nonstop. Is this normal considering the weather? I'm worried that the slab wasn't insulated.

Also, I've been wondering if I could ever drop the in floor heat and rely upon the backup forced air system to save heating expenses. However, my concern is that my hot & cold water piping would freeze because it is in the slab. Could I ever rely exclusively upon my forced air system despite the location of my water lines? If not, how low could I drop my in floor heat without harming my pipes?

Brad White_191

Depending on

what your real low design temperature is and if the house temperature keeps up, a boiler running straight out, 100% and non-stop is an ideal situation.

In other words, if your design temperature is in fact zero (F? C?), and the house is maintaining setpoint, you are OK. If your design outdoor temperature is -40 (C or F, same thing, for once), then maybe you have an issue...


Running at 100% on your coldest day means a very good thing, that your boiler is not over-sized. We have seen too many boilers operate 10 minutes on, ten minutes off, on days below a "design day". That says it is about double the capacity it needs to be and that means inefficiency every degree warmer the weather is.

To determine if the slab is insulated: Short of an Infrared scan, see how far away the snow-melt band is around the house. An uninsulated slab edge will have a band greater than three feet I have seen. If a foot or less there is at least some insulation. If snow gathers there as well as anyplace, I would assume very good insulation.

If the house is an original (and where would this be?), I doubt there was any insulation nor even a vapor barrier. Some perimeter insulation "might" have been added later, but I doubt that and doubt it would be that effective.

If your domestic piping is in the slab, I would not drop the radiant heat all the way, but rather keep it so that the floor is at least within ten degrees of room temperature. Relocating those lines is the best insurance in my opinion.

Kara

freezing pipes

My slab of my patio home (built in 2005) is surrounded by lots of snow here in in Minnesota. I have a 9KW mini-boiler in my 1200 sqft patio home. Overnight our temperature dropped from a balmy 14 F to -1 F. This morning while the boiler was still running, I watched the ambient indoor temperature drop 1 F. After having the curtains open for an hour/solar heat gain my boiler did go off. Also, minus a two small spots, the overall floor never has any distinguishable "cozy" warmth to it. Are all these things normal?

I'm both new to home ownership and in floor heating systems, so please excuse my naiveness. I've just been alarmed by the first heating bill and after noticing how quickly the forced air raises my ambient temperature I assumed something is wrong.

Mark Custis

I would have to look up Minnasota,

as I design for Cleveland, Ohio and I agree with Mr. White, (old guys stick together), that you are at about perfect design for your home. I do know that you will find it more comfortable with warm feet at say 68* than at 72* WITH COLD FEET. I would run the the floor flat out and let the forced air supliment the radiant. You can expect a 30% +/- savings on the floor heat no matter what the fuel. I assume you have tightened up the infiltration and it is not possible to add additional ceiling insulation.

Brad White_191

I agree except... \"old guys\"?

Kara, it sounds like your house has good edge insulation- you would know otherwise.

As Mark (that young upstart) said, the floor is your friend here. Any infiltration improvement is spot-on; that is such a variable but depletes heat faster than anything. (Air has no mass to speak of compared to your walls, roof and slab. Thus half an air change per hour is half your heated environment, gone every hour.

The floor itself may not ever feel "warm" because it well could be 80 degrees, your space at 68 and your feet at 84... no way 80 feels warm to an 84 degree foot.

If you place your feet squarely in the small of your husband's back, you will have the opposite effect. My wife knows this....

Plumdog_2

Kilowatts You Say?

I wouldn't be suprised if the electric boiler was designed to run constantly and stage the elements as needed to maintain a particular return temperature.

Mark Custis

Good thought

Mark Custis

Good thought

I know that is true for electric hot air.

We could send her to radioshack for a cheap ampmeter and help her sleep better.

Kara

in floor heat

Thanks guys. I'm feeling better about the in floor heat - how it operates as well as what is "normal." I've been plugging up some spots in the home where cold air has been seeping in and consequently think that might be where the heat loss was from.

Kara

in floor heat

It is EMB - 9.

I've continued to use in floor system rather than use the forced air. However, now I've got another question. (Sorry, I'm feeling so naive - the in floor is so new to me.) Anyway, I noticed that when the boiler is running and flushing newly heated water into the slab, the small triangle of the city water gauge moves ever so slightly. Is this indicative of a small leak or is a small use of water normal? Also, I've noticed that when the boiler starts up after being off for some time the water running through it is quite noisy, almost like it has air in it. It makes a spitting/hissing sound.

Thanks so much for your help! I am truly grateful!

Kara

In floor heat

I left out that it is an Electro Mini Boiler.

Mark Custis

Here you go

Kara:

I am not sure this link will work. http://www.electromn.com/pdf/manuals/BI301D.pdf

If it does not try a copy/paste.

There are two elements in this boiler and they can be staged for more efficiant opperation.

hot_rod

that boiler has OD reset

as I recall. So it may be modulating based on outdoor temperature. It's a very nice electric boiler.

hr

neilc

meter spin

Kara,
Hi,
you've got some good guys here, trust them on the boiler.

Did you say water meter spinning slightly ?

They may have missed your last note about the water meter spinning slightly during heating.
This might be a problem.

You must be absolutely sure no other domestic water flow occurs, such as a leaking toilet, dripping sink,,,during the heat call.

If that meter stays still without a heat call,
and spins slightly on a call for heat,
you may have a leak in the heating system, in the slab,
and the noisey air sound when pumping may support this.

You could confirm this next time pumping, and spinning the meter,
try closing the heating sytem makeup water supply,
if that meter stops, bingo.
Don't leave it shut too long ( confirm meter spin and turn it back on) or you'll be buying a new boiler also.

And this leak would cause increased utilities as that is cold water you'll be heating while heated water leaks away.
If it's leaking and making up you'll also be adding oxygen in the makeup water and that is no good for the boiler either.

It may be time to call in a pro.

Mark Eatherton

Find the leak....

If it is in the closed loop portion of the heating system, it IS trouble.

Even if it is not in the heating system, you need to find it and fix it.

To eliminate the heating system, while the heating system is running, TEMPORARILY shut off the make up water, and see if the leak indicator (moving triangle) stops. If it does, you need to find and fix the leak. Check the relief waste pipes coming from the boiler pressure relief valve. If it is submerged into the floor drain piping, it could be hiding a problem. Cut it off within 6" of the floor, and you will then be able to see when you've got an issue.

If you do have a leak (anywhere) in the heating system, your electric elements will eventually scale up and cost you not only for energy cost, but also maintenance (element replacement, possibly boiler vessel failure) costs.

Find it and fix it.

Don't forget to turn the make up back on until you can get a means of low water cut off protection.

ME

Kara

leak

Thanks for your help. I found the leak.

Mark Custis

All is well that

ends well. Did the leak get fixed?

Kara

leak

After spending more time investigating it I found out that the leak is not part of the in floor system, rather it is a hot water plumbing leak in the slab. The city confirmed that whatever leak it was it was pretty small.

Kara

staging / in floor heat

When you spoke of my Electro 9KW Mini Boiler having two elements that can be staged for more efficient operation what did you mean? Are the two elements in regards to having two thermostats/zones in the home or did you mean something different?

Also, how can I tell if the system is modulating based off of outdoor temperature?

Thanks for your help. I am starting to get a better understanding of the in floor system.

Jean-David Beyer

On my system, there is a little plastic box on the outside of the "north" side of my house wired to the electronics of the boiler. The little plastic box is an electronic thermometer (Negative Temperature Coefficient resistor to those in the electronics business) that tells the boiler electronics what the outside temperature is. The electronics has the boiler produce less and less heat as the outside temperature goes up.

KevinCorr

I never heard of slab radiant pipe that could take all the heat from a boiler and keep it running. Slab heat is not domestic hot water going down a drain which can keep a boiler on constantly. Radiant pipe in a slab just isn't that fast. I would say the boiler is undersized.

You should have glycol in the heating water especially in a slab. If that zone fails and the water sits for a time before you realize it, it is ruined.

Also I always put a pressure gage on the pipe to the slab so I can shut off the fill or make up water to the system and see if the floor holds pressure.

Also purge valves on the supply and return from the floor so you can push water through the floor in and out of a bucket to see that it runs clear and purge the air out. If it is air locked

Unknown

Kevin, to say that, you would need to know about the boiler being used.

A modulating boiler of any kind most certainly could run continuously. heat is being pulled out of the slab at X BTUs/hr. if you only replace it at that rate, you have a continuous heat demand.

Undersized heat sources are as rare as hen's teeth. Oversizing is a much, much more common problem.

KevinCorr

NRT.Rob- Thanks for that. I see what you mean. I am thinking of a different system for floor heat. I have been doing it another way for many years (back to the 80s and am now learning new methods.