Controls for floor heat

Ron Schroeder_3

Sorry Gentlemen, two strokes on the post key. My apologies.

Harvey_8

Just curious about how to control an infloor heat application with a Bosch Aquastar water heater. I am also trying to keep the costs low, it's for a family member. My original thought was to install a 120V thermostat to the pump, so when the pump runs, the water heater comes on. The only drawback is the water doesn't circulate unless there is a call for heat. Is it possible to install a 3 way valve to open with the stat, proving flow to the water heater so it fires? Thanks in advance for your input.

Joe Mattiello

Use Taco 570 series

Apparently, you need a positive shut off for the radiant heat zone while using a hot water heater as the heat source. If it’s a closed system you can use the 571-2 ¾” sweat connection designed for closed systems If you are heating with the water heater that also supplies domestic water, and it’s an open system, then a Taco, geothermal valve 556G ¾” sweat, designed for open systems, will work nicely. You will also need a power source for the valve, taco advocates a 40 va transformer. Follow the wiring diagram located on the instruction sheet for the valve.



Taco, Inc.
Joe Mattiello
Technical Service Technician
joemat@taco-hvac.com
401-942-8000 X 484
www.taco-hvac.com

Ron Schroeder_3

Tankless water heater

Hello. Please pardon what might seem to be a self serving response.

The Auquastar has been built to be a water heater. It is not a heating boiler that can produce domestic hot water. You are proposing to misapply a gas fire appliance.

Please consider using a heating boiler and proper system control strategy for your customer's as well as your well being. You do not do your family or yourself the disservice of installing a piece of equipment in an application that the designer did not intend. The controls necessary fo safety and comfort are just not there.

Harvey_8

Joe and Fred thanks for your input, the Taco 570 is what I had in mind. Fred I don't understand why you cannot use a hot water heater for infloor heat. I see it all the time, a water heater's job is to HEAT WATER regardless of the type of water. And no it is not the same heater that will be used for heating the domestic water. As far as safety's what do I need, it has a relief valve, and will not run without proven flow of water, and the chimney is a no brainer. Don't take this as war of words, you are entitled to your opinion, and I respect that. The water heater method for infloor heating is proven effective, at least in my state, to work well and save $$$ in installation, and operation costs.

hydronicsmike

Well, Harvey...

...if you are planning on using the water heater, which I assume to be an instantaneous type, you may also want to entertain the following thought:

Use a tekmar 704 (Literature attached) or a TACO RMB (Radiant Mixing Block??)(same device) with 2 built-in pumps. One is an injection pump that will vary the flow through your water heater to provide mixing for the radiant to a supply water temperature that is based on Outdoor Reset. The other pump is your system pump. All you would need then, is a standard thermostat to enable this Mixing Block with built-in reset control.

What you would gain, is outdoor reset which will result in lower stand-by and distribution losses since operating at lower temperatures. It will also provide more of a continuous circulation system while eliminating temperature swings in the space and possible expansion noises if this is a stable-up / low mass radiant system.

Would it over complicate things? Well, it is more complicated than what you had suggested by using a 120V thermostat that cycles the pump on and off. But it would minimize the amount of heat (energy) that is drawn out of the water heater, as it may only need a fraction of the flow through the water heater compared to what your system flow would be. The goal would be to have both pumps run at 100% to provide full system flow at the coldest day of the year, while when it is milder out, the pump responsible for the flow through the water heater would slow down and therefore use less heat from the heater when the supply water temperature is lowered to the radiant system.

Does this sound crazy??

I hope this makes sense. If not, please don’t hesitate to call me at 250-545-7749, Ext. 214.

Regards,

Mike

Harvey_8

Thanks Mike

This is the kind of info I was looking for, you can bet I will be contacting you. I don't suppose you have a price tag for any of the listed equiptment??? Do you sell direct?

Ron Schroeder_3

water heater instead of boiler

While water heaters may "work" as heat sources for radiant or any other heat delivery system, they are not necessarily approved for such an application. Check with your local authority.

Water heaters are not ordinarily designed for continuous operation, a condition that boilers were intended for.

Lisa at Bosch (www.controlledenergy.com
or call 1-800-503-5028). just informed me that the Aquastar is not intended or suited for space heating at this time. She confirmed that it is a point of use DHW heater only.

If the manufacturer does not agree to this application of their product who am I as a heating professional to cousel my client tht it would in fact be alright after all.

Regardless of all the work arounds available, are you prepared to expose yourself to all of the liability associated with your editorial decision? Additionally, are you pleased to provide your client, your relative no less, anything other than what is in their long term best interest performance and comfort wise? I sure wouldn't be.

Any of the condensing boilers and a small indirect tank would serve them better than a water heater. Shucks, you could give them the parts at cost and throww in the labor as an early Christmas present if price were the only criterion.

Does this clear things up?

hydronicsmike

Will be glad to chat with you Harvey,

but we don't sell direct. Please contact your local wholesaler or distributor for pricing available on the parts mentioned.

If you have any other questions, please dont hesitate to contact me.

Regards,

Mike

hydronicsmike

Will be glad to chat with you Harvey,

but we don't sell direct. Please contact your local wholesaler or distributor for pricing available on the parts mentioned.

If you have any other questions, please dont hesitate to contact me.

Regards,

Mike

Harvey_8

Thank you Fred

Thanks for you input, I realize Bosch does not want their heaters used for space heating. I assume A.O. Smith, Rheem, or any other water heater manufacturer do not approve of this either. So why are professional contractors still doing it? And why are building/HVAC inspectors not putting their foot down to stop it? Simple, because they work just fine for the application. If a water heater cycles for 10 minutes to heat 30 gallons of domestic water, or cycles for 10 minutes to heat a zone in a floor, which is less than 20 gallons of water, what is the difference? The heater knows no difference. It's basicly a price savings of $500 to $700 dollars depending on which type of boiler I choose compared to a water heater. For this job, only 1200' of pex tubing in 4 zones @275' per loop, I think a boiler is overkill. Ultimately it is my decision on what to use, being in the trade for 15+ years, I trust my judgement. Thanks again for your concern in the matter. I value your input as a professional.

marc

water heater

Try using a water heater listed for doing both domestic and space heating, they are available, AO Smith, Bradford White both make them, (not combi core) marc

Unknown

Last I knew, using Aquastar units in a radiant heating application would void the warranty and send the unit to an early demise. "Last I knew" means a couple years ago in this case, as I haven't looked at Aquastar recently. has this changed?

Unknown

First, there is a big difference. The radiant loop's delta T is very small. This means less heat is needed, but it's losing heat constantly. The cycling requirements are very, very different. If you can get a good clean burn once in awhile then so be it.. but you need a buffer tank for that. You have four zones as well? The thing will be cycling like Lance Armstrong.

Use a regular tank water heater if you're trying to go for a cheap heat source here. Or perhaps something like a Takagi, or if electric is an option something like a Seisco. Aquastar in particular is a poor choice.

Ron Schroeder_3

everybody's doing it

No matter what "it" might happen to be, this is the classic defense for the indefensible. I hear it less regularly now that my youngest is recently graduated high school and incommunicado.

You give voice to an question that desperately needs an answer when you ask "I realize Bosch does not want their heaters used for space heating. I assume A.O. Smith, Rheem, or any other water heater manufacturer do not approve of this either. So why are professional contractors still doing it? And why are building/HVAC inspectors not putting their foot down to stop it? ". YOur simple answer that these things work just fine for the application, does not answer the question of why unapproved appliances still get misapplied.

The real answer is that these, unapproved for the application, appliances are simply cheaper to buy than an appliance that has had to pass muster as a space heating boiler and is priced accordingly.

The same unscrupulous installers are installing and the same ignorant (not stupid) inspectors are inspecting as were active during the Entran I and polyB heydays. Can you remember? Unsuspecting consumers are being sold these installations with the advice that they are as good as (fill in the blank) only cheaper. The contractors reincorporate and the inspectors retire and the end user has to live with Holohan's proverbial lobster traps.

In the end the industry, that is you and I, suffers along with the consumer.

It is the responsibility of any and all professionals to do the best they can. It is not our job to give the customer what he thinks he wants at any cost. WE already know the consequences of doing t cheaper. There are some instances when the best we can do for our prospective client is to say we canot in conscience do what they are asking us to.

Sometimes we have just to say NO.

For a far more articulate article on this topic read Lawrence Drake's excellent tome in the July 2005 Radiant Panel Report. He does a far better job than I have.