Siesco boiler vs. hot water heater for radiant floor

Ok, I've gone through every single post on this site about heating a radiant floor in my search for the best setup.

It seems most are saying to avoid a domestic hot water heater and use something like the Siesco tankless boiler. Note, I'm only talking electric here.

Someone I know is trying to tell me that the hot water heater is the way to go and not the Siesco. He said a tankless unit will run constantly and burn up as in "short life."

Not being very knowledgable on this subject, I could only argue with him using information from this site about it. Basically, both would do the same thing and run for the same amount of time. It didn't work, I can't get through to him on this.

How about a list of pros/cons on hot water heater vs. the Siesco SH series boilers. I can think of a few already:


Hot water heater: (cons)
Is not designed for heating a radiant floor.
Heating elements would have to be wired together
No idea of BTU's
Takes up alot of room

Hot water heater: (pros)
A lower purchase price.

Siesco: (cons)
A higher purchase price.

Siesco: (pros)
It is designed for heating a radiant floor.
I believe these are modulating? If so, only one element would run when demand is low making them more economical. (correct?)
Known BTU output.
Does not take up much space.


Well, that's just a few I tossed out there. Anyone care to add more or to help explain the benefits of the Siesco over a typical water heater? I'd really appreciate it. I'm still searching for the best way.


Bob

BTW, since building my garage, the heating system decision is at the top of the list in aggravation! Argh!!!

bobs409 said:

Someone I know is trying to tell me that the hot water heater is the way to go and not the Siesco. He said a tankless unit will run constantly and burn up as in "short life."

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Uh?? The tankless is designed to run constantly, as in taking in 55* or less ground temperature water and outputting 120* domestic hot water. CONTINUOUSLY, by design.

On the other hand, a tank type water heater is designed for intermittent use.
Takes in 55* water and outputs 120* water INTERMITTENTLY, for a short time. Immediately after the water starts flowing the water in the tank starts mixing with cold incoming water, the temperature starts dropping.
A 40 gallon heater will get less than 1/2 of it's total capacity of full temperature water before it starts losing ground. Recovery time is very long simply because you only have 4500W of heating capacity. Even if the elements are wired together, which is a BAD idea IMO, you still only get 9000W of heating power.


OK, personal experience.
I have a 16x30 shop heated with a 40 gallon electric water heater.
Works fine if you start it before the floor drops below the temp needed to maintain the t-stat setting, which means you start it early in the fall.
Once up to temp it maintains the temp fine since the pump only has to run a few minutes each time in order to satisfy the t-stat. It will raise the temp 2-3 degrees if needed. Trying to raise temp any amount that requires the pump to run more than about 20 minutes results in losing ground, the heating element will not keep up with the demand. Eventually the tank temp equalizes with the floor temp and you run into a stagnant situation, the pump continues to run, the water heater continues to heat, but you go nowhere.

Rewiring the heater so that both elements run would help slightly, however you still only get 9000W output, about the minimum you get get in a tankless system. Doing this rewire is dangerous IMO and requires that the entire heater be rewired to handle the extra element load, plus you should replace the controller to handle the extra current.

Go with the tankless, which is the direction I will be going once I get the rest of my building finished out.

I take it gas is not an option for you in this install? Because if it is you would be much happier with it than electric.

A friend of mine has a 60x80 Morton shed that has in floor radiant heating and he runs a 40 gallon high efficiency natural gas water heater. Even if he starts it up stone cold in the middle of winter, that water heater brings it up to temp in less than 40 minutes.

I helped him install that water heater, and when we first filled it up and turned on the gas, it only took 20-25 minutes to fully heat up the tank from ice cold. Talk about efficient!

A cold 60 x 80 heating up in less then 40 min with a radiant floor


I did not think radiant could warm a building that fast. When I worked in a shop using a gas boiler made for the purpose. It took awhile for the building to come up to temp when first turned on.

I have been looking into the Seisco units myself and been talking to seisco about options and operational costs. They have alot of information on their web site including some studies vs a 40 gallon electric hot water unit .

A seisco SH is fully modulating so it will only heat what you need to keep your desired temperature provided your unit is sized correctly. When the water cycles around the Seisco only needs to warm it back up to say 120 again and depending on the load of your slab that may be alot or not very much.

Once your slab is up to temperature it does not require much to keep it warm. They recommended a small SH-11 for my well insulated 42 x 32 shop. I would probably install a SH-14 or so just for some head room as we get really cold in the winter.

Polaris water heaters were recommended to me as the best option for space heating with a water heater however they are gas fired.

mmg440 said:

A cold 60 x 80 heating up in less then 40 min with a radiant floor


I did not think radiant could warm a building that fast. When I worked in a shop using a gas boiler made for the purpose. It took awhile for the building to come up to temp when first turned on.

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There is NO way a radiant system will heat a building fast. Radiant is not fast. Once it gets warm it is efficient, but to warm it occasionally, no way. It would take hours if not days to accomplish that in a building that size.

Tim

GSSFC said:

There is NO way a radiant system will heat a building fast. Radiant is not fast. Once it gets warm it is efficient, but to warm it occasionally, no way. It would take hours if not days to accomplish that in a building that size.

Tim

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Sorry, I didn't mean the temperature in the building, I meant the floor itself. He's got temperature gauges on each side of the floor loop and it usually takes anywhere between 30-60 minutes to stabilize depending on how cold it is. The 17 year old water heater that was in there before used to take a couple hours for the same result.

He normally leaves it on all the time, but there have been a few times (including when we had to replace the water heater) that it was fired up stone cold.

It takes about a day to bring the building temp up to 60-65 degrees, which is what he usually keeps it set at.

I have PERSONALLY installed over 10 radiant floor heating systems using SEISCO "Boilers".

They are the ONLY way I would go. They are Small, Efficient and VERY reliable.

The oldest system I have was installed in 1999. STILL running on the SAME elements, Board and Pump.

A few Pointers though. SPEND a extra few bucks and purchase a 'pump relay' it is simply a relay that you hook up to a t-stat to turn your pump on and off.

The beauty of a Seisco boiler is that it SELF REGULATES. It regulates the elements based on the temperature difference between the output and the input sensors. If the set point temp is 100 deg. and water coming in is 65 degrees it will probably run at 100% the output temp will not be 100 deg, maybe only 80. As the unit runs for a while it will gradually increase both the input and output temps.

GENERALLY they will only add 15-20 degrees. THIS IS OK. Lower than 10 degrees you have TOO high volume a pump, higher than 20, you may have a restriction slowing your flow. BOTH are not FATAL flaws. But will cause issues. Worst being restricted flow, this can be by loops being over 300 ft (for 1/2" pipe MAX, 250' recommended) This will cause 'cold spots'. If one loop has a much higher restriction than the others you will end up with little to no flow in that loop. To fix this you need to add needle valves to the other loops to increase the pressure in those to even out the flow.

A quick way to determine this is to using a temp gun or by hand determine which loops are the hottest. apply slightly more pressure, let unit run at least 15 mins, recheck.

WOW, I got way off. But you can use the seisco and run it continuously. The boiler will ONLY turn on when it detects a drop in temp. You will wear out pumps quickly though.

The systems I have installed use MOSTLY RA-14's I do have ONE RA-28.

** MONEY SAVING TIP. If you are not going to have to have this unit inspected, the ONLY difference between RA-14 and SH-14 is a HIGH TEMP overlimit switch in the first chamber. This is a lower limit for domestic hot water. They will never see 90 degree water at the input. The SH units have a 120 deg limit switch in stead of 90 degree I think. What happens is when the pump shuts off it takes less than 2-3 seconds for the unit to react.

sometimes the water stops DEAD the element is still firing at full blast and instantly heats up that pint of water in the chamber to above that limit switch. That's it. So swaping this out will save you upgrading. IF you are going to have to have your installation "inspected" the RA-14 is not "Rated" for space heating applications. The additional cost is to cover the 'testing and rating' process that Seisco had to go through to get the units rated for space heating. SO Pay the $7-10 for the HIGH LIMIT limit switch swap it out with the first limit switch in the unit and you have the SAME THING.

IN SUMMARY Seisco ALL THE WAY!

Wow that is great info.

Im going to send you a PM