Marc&Kem
New Member
Posts:50
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| 18 Feb 2008 01:15 AM |
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Hi All,
The calcs on my future SIP Home is only 19,000 BTUS Loss. I am not familiar with boilers. Being the house radiant floor heat will only be used maybe 6 months out of the year (except for Hot Water - solar & HWHP used) is it worth it to have a boiler for back up? Will the boiler (propane) idle for an extended period of time and is this bad for it? Is a Demand system a better fit?
Oh boy, so many questions.......
Thanks,
Marc and Kemella Allyn |
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NRT.Rob
Veteran Member
Posts:1741
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| 18 Feb 2008 11:14 AM |
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where are you?
slab on grade home, or framed over a basement?
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| Rockport Mechanical<br>RockportMechanical.com |
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David hot
New Member
Posts:22
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| 18 Feb 2008 11:22 AM |
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WOW only 19,000 ? Why bother with anything other than a hot water tank ? Sounds like a great application for tankless? Most places won't let you heat with your drinking water but some units have a heat exchanger to avoid this.
The 19,000 BTU's / hr makes it sound like you are in a winter free zone? Don't beleive the numbers unless they take into account solar gain & window loss . Also wind exposure & window & door leakage can drive your heating needs up. New modulating boilers don't mind idling but again why bothr |
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Marc&Kem
New Member
Posts:50
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| 21 Feb 2008 03:13 AM |
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I'm building a floor over basement. After looking there were many things not included in the online calculator. fresh air ventilation and doors and the basement.
We are still working on the house design so I'll have a better calc then. |
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vhehn
New Member
Posts:91
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| 21 Feb 2008 02:24 PM |
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i put electric mats under the tile in my new home. i think its the only way to go. |
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Marc&Kem
New Member
Posts:50
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| 21 Feb 2008 06:01 PM |
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Sounds good. I considered that. How big is the area and what method did you use? What was the cost per square foot? |
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Dteltech
New Member
Posts:27
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| 28 Feb 2008 05:04 PM |
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You need to be sure to use a boiler/heater that is rated for space heating. UL 843 approval. |
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| Here comes the sun |
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Peter Kinsey
New Member
Posts:3
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| 29 Feb 2008 07:08 PM |
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With a heat loss of only 19,000 btu's, most on demand and wall hung boilers only modulate down that far! The trick would be to add some storage, so the heat source doesn't constantly short cycle. |
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NRT.Rob
Veteran Member
Posts:1741
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| 29 Feb 2008 09:53 PM |
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still wondering where you are? |
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| Rockport Mechanical<br>RockportMechanical.com |
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Marc&Kem
New Member
Posts:50
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| 01 Mar 2008 08:09 AM |
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So in the winter it would probably be alright with the radiant floor and Hot water demand. But in the summer there could be an issue with short cycling. Maybe a demand HW heater would be the waY to go?
I really think the load wold have to be higher. My pre-calcs would have to be off.
Thanks,
Marc |
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NRT.Rob
Veteran Member
Posts:1741
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| 01 Mar 2008 09:12 AM |
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Domestic is not a "short cycle" demand. a hot water tank is a buffer tank; or, if you have a boiler with an on demand instantaneous coil in it (not a constant-hot setup), even 1 GPM at a 50 degree rise is 50 x 8.4 x 60 = 25200 BTUs/hr.
generally I would use a tank water heater for a load that small, depending on where you are located. If you have a lot of degree days it may be worthwhile to upgrade. the water heater would require a heat exchanger to do radiant.
A demand heater is a poor choice. Generally, either a real modulating boiler, or a tank heater are better fits. |
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| Rockport Mechanical<br>RockportMechanical.com |
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Klorinth
New Member
Posts:33
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| 12 Sep 2008 06:24 AM |
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Sorry for bringing back an older thread...
Am I reading this all right? For a small space or small load requirement you can use a Hot Water Tank as a heat source? I have read multiple discussions on heat source selection and in almost every situation people seem to recommend not using a tank heater. Seems to me this is because of efficiency comparisions when taking into account large numbers of btu's. Am I wrong?
I am building a new home that has a btu requirment of about 33K. We are installing a Geothermal system for heating and cooling, with a desuper preheating our DHW. I have installed the radiant piping in the basement slab as a just incase thing for later. I had no plans of finishing the system right away, because it is not strictly needed due to the geo system. If I could hook it up to a small tank heater though, it might be worth doing sooner than later. i would only be running the radiant at a very low temp in order to assist the geo system if it was worth it.
I still plan to use the geo system for a year exclusively in order to assess its performance before I would run a radiant assist. But I would start looking for a good used tank.
Any thoughts would be very helpful. Thanks |
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dmaceld
Veteran Member
Posts:1465
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| 13 Sep 2008 10:56 PM |
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Posted By Klorinth on 09/12/2008 6:24 AM
I am building a new home that has a btu requirment of about 33K. We are installing a Geothermal system for heating and cooling, with a desuper preheating our DHW.
How far down the path are you with your geo system? Where are you located and what is the min temperature you're dealing with. The reason I ask is because the house I'm now building has a heat load reqm't of only about 33 to 36K Btus. This is in Idaho with a min design temp of 9F. I was planning on using a geosource heat pump with radiant heating and cooling but the cost was a concern. I then learned about the Daikin air to air heat pump. It will put out heat with a COP of 3 down to 10F, and colder. This contrasts with most heat pumps shutting down and switching to backup electric strips at about 25F. One local HVAC installer told me that of the half dozen or so Daikin systems they installed last year around the Boise area not a single one switched to backup heat this past winter. I'm installing a 3 ton Daikin outdoor unit, a 3 ton indoor unit in the house, and a 9000 Btu indoor unit in the garage. The Daikin is a multi split system. One outdoor unit will support up to eight indoor units. So with a heating/cooling load as low as you and I have, the Daikin system is a viable alternative to geosource, particularly if you're planning on a forced air system anyway. I am in no way knocking geosource. It is the most efficient way to heat and cool a house. It's just that the Daikin system is worth looking at for smaller requirements.
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| Even a retired engineer can build a house successfully w/ GBT help! |
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Klorinth
New Member
Posts:33
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| 13 Sep 2008 11:53 PM |
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dmaceld,
We should have the Geo system up and running in the next two weeks. Way past the point of no return... That being said... We are in Manitoba Canada. As you can guess our winter temps are well below what and Air to Air can handle. -30 F is very common, and a lot of winter winds. For our previous house we had looked at something similar for summer A/C though. Nice system.
Right now I am looking at the different ways to finish this new house, or fine tune my future plans for it. Hence the question of using a HWT for the radiant heat source. I'm only using it as an addition to the Geo system which is why I was thinking I might be able to get away with a small tank. I would only want the temp to minimal anyway. Our dogs sleep in the basement, so I don't want the floor to truely be warm, they can't handle that. They are cold climate hunting dogs that live outside during the days so don't need much heat.
Thank you for the thoughts. |
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