3/4 with 1 inch pipe - same boiler, new zone - Problems?

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Old 08-15-12, 09:42 AM
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Question 3/4 with 1 inch pipe - same boiler, new zone - Problems?

Hot water baseboard heat with a ridiculously large boiler. I have 3 existing zones run on 3/4" copper; I intend to add a 4th zone and would like to use the 1" copper I have harvested from a passive solar heating system that was originally used in the house 40 years ago. Any concerns combining the existing 3 zones on 3/4" with a new zone on 1" (feeds only, the fins themselves will sit on 3/4", I will adapt at each fin run).

Thoughts?
 
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Old 08-15-12, 10:18 AM
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Welcome to the forum.
Although not an expert, I've picked up a lot of info in a short time with my hot water system.

A couple questions for you about your system....
Are your rads setup in series or Parrallel to a feed loop (don't remember the correct term here)?
I am thinking they are in series as 3/4" loop with 3/4" tees going to and from each rad might not work too well.
Is the new zone a new addition to the living space?

How big is the place you are heating with (soon to be) 4 zones?

How did you confirm your boiler is too big?
It probably is too big as most tend to be oversized initially, then added insulation, etc.
Have you done a heat loss calc yet?

If you have a circulation pump on each zone, it could work. 3/4" existing sounds pretty small though. I'm running 1 1/2" pipe for my main loops (2 zones) with 3/4" feed and return to each rad.
 
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Old 08-15-12, 11:04 AM
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Four zones

Water always takes the easy route, if it was not zoned and controlled by motorized valve, then probably most would head for the much larger pipe.
Your proposal will work just fine. Keep in mind that you can never tell what the future weather may be, taking the continental European route and having a larger boiler and larger radiators may make the difference between keeping pleasantly warm and being cold and miserable some time in the future.
 
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Old 08-15-12, 11:47 AM
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Perry525,

The problem with oversizing a boiler is it cycles too often (on/off), burning more fuel and really impacting the equipment.
Check this stickied thread; http://www.doityourself.com/forum/bo...nt-boiler.html
 
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Old 08-15-12, 12:23 PM
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No expert on piping and there are some factors or additional info you would need to give.

IMO you may want to split the loop to utilize some of the 1" you have. 3/4 feed split in two directions and a 1" common return. I believe your flow rate will stay the same. I dont know of any other way to keep your flow rates the same.

Something like this. ( pros will be on to answer more)




heatinghelp.com


What is the total amount of baseboard fin footage only for the new zone?
How about your other zones? Possibly you can modify all the zones to make them longer/ more btu per zone? Possibly make 2 or 3 zones instead of 4.

But again it depends on what you have.

Whats the make and model of the boiler? Circulatrr?
 
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Old 08-15-12, 09:55 PM
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The house has an existing 3 zones, covering 3700 sq ft. The 4th zone to be will cover an additional 1200 sq ft.

The existing three zones are all maxed at around 67 ft (one is 71, another is 62, etc.).

It's a Burnham (nat gas) with a single pump, which is appropriately sized for the capacity of the boiler (the boiler is around 350-).

The zones leave the boiler in a single run, 3/4" copper and return. It's a closed system with an automatic airvent after the valves, on the return, just ahead of the boiler. The total amount of water the system holds in the current 3 zones is about 13 gallons. From our point of view, it's efficient; we'd spend about twice as much a month heating if the house were forced air.

- An interesting idea to split out and join for the return, but the layout of the rooms/space won't easily allow for this. Further, there is no regulatory system in place to route properly. We expect to include approximately 60 linear feet of heat fin for this zone, with two of the baseboard units carrying two rows of fins, stacked.

My biggest concern is whether the system, with it's auto air/bleed closed attribute, will compensate for the two sizes of pipe on the 4th zone (which is not independent of the other three zones, as far as return to the boiler, which could increase air accumulation or allow the water to return too cooled, resulting in internal condensation and loads of issues in the future).
 
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Old 08-16-12, 02:19 AM
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Zones?

When you write about "Zones"?
It is normally accepted that each zone is controlled by its own room thermostat and motorized valve with a direct lead to the pump and boiler.
You need this type of setup to obtain maximum saving of fuel.
If you only have one thermostat on the boiler and another in your living room....then the other rooms will either be too cold or too hot.

With a zoned system, as each zone will run separately, with only one zone on at a time (usually) and the possibility of all being on sometimes, it is impossible to have the perfectly sized boiler.

I find that having one zone on the sunny side of a home, another on the north side, with another in the bathrooms and toilets, and the hot water in its own zone, leads to a comfortable home.

Another way (probably the best) is to have the living rooms as one zone, the bedrooms, the bathrooms and toilets, and the kitchen as separate zones as each are used at different times. If the kitchen is not controlled by itself it can get very hot when cooking.
 
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Old 08-16-12, 04:44 AM
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Perry525 brings up a good question with the term zones.

In my house, I have 2 zones (4020sqft living space if you include the basement). I have a circulation pump per zone controled by a 7 day programmable t-stat in each zone.
Because my home is fairly square, zone 1 covers the basement and main floor and zone 2 covers the second and third floor.

To the OP;
Are your rads connected to a supply loop or does one rad feed into the next rad (series)?
your 3/4" piping leads me to believe your rads are connected in series, which probably means you've noticed the first room in the loop is a lot warmer then the last rad in the loop.

I really would like to suggest upgrading your piping to 1" or 1 1/2" PEX piping for a supply loop with a t-stat and circulation pump per zone.
You'll loss less heat on your supply pipes and will hope the heat better with more water.

The sketch below (right or wrong) is basically the system I have (with a few extra gauges added). It works really well and allows me to turn down the heat in areas of the house we don't always use. I'm actually thinking of maybe splitting it into 3 zones as there are parts of the house we rarely use, and would not need to be kept at the same temp as the other parts.
Pardon the symbology. I tossed this together over a lunch break and was too lazy to get the proper symbols.
Name:  NewboilerSetup.jpg
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Old 08-16-12, 04:01 PM
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If your zones are separately controlled using zone valves and a thermostat for each one, the using 1" pipe will be fine for your new zone.

You boiler is WAY over sized. Your boiler is 350,000 BTU? With a 3/4" pipe leaving your boiler, you can only supply 39,000 BTU to your house. I see no reason in upgrading the size of your piping as Northern Mike suggests.
 
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