heating system simply wont keep up

S Ebels

Very doubtful..........make that a definite no.

Your problem is somewhere in the piping. The fact that you have very little temp drop tells me that something is amiss with the circulation or you insulated over top of your pex ;)

A concrete slab sitting at 65* should suck temperature out of the tube like a Hoover on steriods. Any possibility that there's a loop in your piping tha's allowing the water to bypass the floor? Can you post a picture(s) of the installation?

The water heater not shutting off and the small temperature difference supply/return don't add up to me. Something else is going on.

Jim Hall

electric water heater not keeping up

I have a 1200 sq ft slab 10' below grade stays at 58 degrees year round. I have 4 loops of 1/2" pex (250 foot loops)on one zone. I am trying to heat space with 80 gallon electric water heater running constantly but having trouble getting space to warm up to even 65 degrees. Water going into the loops is only about 98 degrees water returning from loops is 92-95. Any suggestions?
Also, One of four loops is cold at supply and at return from manifold. Thought maybe have air pocket or plugged fitting or plugged tubing. Any ideas?

Jeff Lawrence_25

Two questions to start.

First, what's the wattage of the elements in the WH?

Second, is the WH wired with 220 volts at the terminals and not 110 volts? (I've run into this before)

jp_2

2 more questions

Is the slab insulated?

are you sure you have flow? and not a lot of air as seems to be in one of your loops.

Chris_82

loops

I won't ask if the manufacturer or rep did a layout before whatever was poured or if there is insulation under the slab. Without a computer in front of me, it seems that those are long loops, for a 10 x 12 slab; did I get that part correct? And the cure might be to add insulation to the ceiling above, if at all possible or what is the floor covering? Is it a wall to wall rug? Otherwise you might consider raising the temperature. When you mention water heater, type, recovery, and how is the temp currently regulated? Flow rate as well, however some can make a good guess based on amount of tubing installed and return temp values. Others will need this information. As far as one loop cold, air bubbles, kinks, plugged fitting all possible, these a few possibilities but most likely depending on which manifold system in use the number of turns in all of the loops may need to be adjusted. As an example to get any flow in a longer than the rest of them loop, either the other three would need to be restricted, or the one opened if possible. Try shutting a few of the others down and see if the problem child heats up. Basically you can raise the temp, decrease heat loss, or increase flow, but more btus are being lost than being provided. Most reps will make a site visit, there are enough of them here, wait a moment and one will come along shortly. Chris

Jed_2

Chris

And HOW does 10x12= 1200 SqFT?

Jed

Ted_9

question

Is the circ even running? Can you verify this?

Massachusetts

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Guy_6

98 out and 95 back sounds like some sort of flow issue to me. I can't see how the slab won't heat , yet the delta is so low.

Jim Hall

water heater has 4500 watt elements and is correctly wired 240 volts. Slab was insulated with 2" thick blue rigid insulation then wire mat then tubing then 3 or 4 inches of concrete. Once again this slab is 10' below ground level all walls are insulated and ceiling is insulated. Temperatures outside here have been in low teens to near zero. Tubing was installed about 12" apart. Just doesn't seem like water heater is keeping up. I was looking at new 80 gallon electric water heaters and noticed some have 5500 watt elements. Don't know if extra 1000 watts would solve problem plus would like to think eventually the slab would warm up and heater would not have to run 24/7.

Jim Hall

System has 1 zone controlled by a grundfos 3 speed recirc pump controlled by a 120 volt stat which turns pump on and off. I dont have any pressure guages in system but room and floor are definately warm however not 70 degrees like I would like it to be. Laminate flooring over concretee slab. Also, If loop that is plugged isn't working now, then once it is working I will have less effectiveness which is not good. I would like to not have to get a boiler or gas water heater if possible.

jp_2

start up?

how did the system start up? supply & return temps.

whats the speed setting of the pump?

delta T of 3F doesn;t sound right in concrete, sounds like a flow problem still.

do you know the heatloss?

got any picture of the system?

Jed_2

Jim

You need a site visit by a Pro. 80 gal. Elec water heater should heat that basement fine, if set up properly. Doesn't sound like you are willing to bring a Pro.

Jed

kevin coppinger_4

was a heatloss..

done? 1- 4500 watt element will give you just over 15,000 btu...that does sound a bit on the small side. you could jack up the element but I would check w/ the manufactuer 1st....I would increase the water temp to 105-110F and see where that gets you...just remember that it will take 24 hours to notice a diff....kpc

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Chris_82

Jed

oops, . From the latter post, someone check my math thats 15,000 btus for this space, 30 x 40 space, what did the heat calc call for?

Timco

No gauges?? How did they fill / purge it?? You MUST have a 30# relief valve somewhere on the system, and here you MUST leave the original water heater T&P valve in place. ANY heating system using water NEEDS a gauge!! Do you have an expansion tank?

Tim

Jim Hall

set system up with help of local plumber who seemed somewhat knowlegable. pump is set on medium speed. The 3 loops that are functioning are all reading 98 degrees on supply and about 93 on return. It is a pretty simple set up. System does have micro bubbler and expansion tank and backflow preventer in system even though it is a closed system. If I shut off pump for about an hour then water heater will recover and start out deliveing 140 degree water to the supply side but will fall to 98 degrees withing about an hour. The water heater is piped with return pipe coming into top cold of water heate and supply coming out of hot side top of water heater. Don't know if it would have made any difference to come into bottom drain of wate heate for cold return. Also the water heater is ordinary off shelf residential grade wirlpool 80 gallon tank.

Tombig_5

Jim

Are you reading tose temps in and out of the slab or in and out of the heater? Is there a bypass pipe between supply an return at the water heater with a balancing valve?

You are not giving up enough Btu's to the slab if those temps are accurate. Slow that pump to low speed, let the HW catch up temp-wise and give up some heat to the slab. The non=flow loop might be an adjustment at the manifold.

jp_2

one point

I would turn the tank down to the lowest setting, do not leave it at 140F.

Jim Hall

system is filled with shut off valve from house water supply. It has a backflow preventer. We poured about 10 gallons of food grade antifreeze in system. Filled system with house water. Factory Pressure relief valve is in place. No pressure relief valve was installed.

Timco

I make the WH drain into my return & drain, and the cold port into the fill port...and remove the long tube. Do you have a 30# relief? With no gauge, you really need to know what pressure you are at and be safe. A bypass would help get the water temp up. You might try the lowest setting on the circ and let the hot water radiate...after a good sucessful purge. The larger element would also help make water hot quicker.

Tim

Tombig_5

Dip Tube?

Jim, The return from the system should be piped to the bottom of the water heater at the drain valve. Your pump is short circuiting around the top of the tank (dip tube or not). Return to the bottom of the tank where you can get some serious temperature stratification inside the tank and your problem will probably go away.

Chris_82

What did the heat calc show?

Jim Hall

what heat calc?

S Ebels

Hmmmm

4,500 Watts = 15,354 btu's giving you a capacity of 12.2 btu's per sq ft of heated floor. Not a lot of power but for a WELL INSULATED basement slab you should be OK. So I'd say your problem is circulation. Air, kinked off pex, not enough circ power for the loop lengths or a combination of those are probably the cause of the problem. Set up correctly a radiant floor should see about a 10* drop. Set your water heater thermostat to no more than 100* and correct your circulation problem. IF you slab is insulated correctly the HWH should do it.

S Ebels

Jim

You need to install a 30PSI relief valve because you are now maintaining safe conditions in a heating system not a water heater. Your heating system includes components which are NOT rated for the 150PSI that the T&P valve relieves itself at.

Tombig_5

Good Point, Guys

Anyone who decides to use a domestic water for a closed heating system DON"T FORGET TO INSTALL A 30psi RELIEF VALVE!!!! Your family will thank you.

Jim Hall

would changing elements to 5500 watts help and is there a circ. pump sizing chart to determing size of pump i need for 1000' of 1/2" pex tubing(4 250' loops)

S Ebels

Duplicate

S Ebels

5500 watts

> would changing elements to 5500 watts help and is

> there a circ. pump sizing chart to determing size

> of pump i need for 1000' of 1/2" pex tubing(4

> 250' loops)

jp_2

how long?

how long has the system been running?

if 4500w output, would take about 16 hrs to raise 1200sq ft of concrete from 58F to 78F. this is the concrete itself, walls will slow down this process and the ground under neath too. they steal heat from the slab.

S Ebels

That would be

The heat loss calc that should have been done before the project was started. It would have told you how much heat was needed, what size tube to use, along with the correct spacing and from that you derive the proper circulator and so on and so forth. It ALL starts with the heat loss calc.

Jim Hall

system has been running for about 9 days constant slab is once again 10' below grade well insulated and tubing is on top of insulation then concrete questioning grundfos pump install however floor is warm

John V

purge valves

Does each loop have it's own isolation valve on the supply and return along with a purge valve on the loop side of the return valve ?

jp_2

walls

how are the walls insulated? did the basement pour go right up against the wall? no insulating break?

i wonder if both elements are working?

S Ebels

Both elements

A standard residential water heater never runs both elements at the same time, you'd need #6 copper and a 50 amp breaker to hold that kind of juice. The top element kicks on first and when that thermostat is satified, it switches to the bottom element until until cycling off.

S Ebels

Jim

Tube on bottom was just a Friday night funny.

Do you have any way to accurately measure the temp across the floor? If the floor is not even temp wise, it would indicate that one or more loops are not circulating. That would give you high GPM flow in the remianing loop(s) which would result in the low delta T you are seeing.

jp_2

but steve....

i agree, but if you had low delta T, or low loss to the floor then the tank would reach a higher temp? thats the puzzling part? thats why I suggested bad heating element, not real familar with ele hot water heaters.

Jim Hall

no isolation valves and no individual purge valves. Micro bubler on supply side.

Jeff Lawrence_25

how are the loops set up?

is there any kind of a manifold? One zone could be getting all the flow.

Jim Hall

1 zone 1 pump 1 manifold for 4 loops supply and 1 manifold for 4 loops return.

Jeff Lawrence_25

Again

Can you post a picture?

(This request was from other people)