replacing my old black pipe with pex al pex and trying to determine correct size tubing to use

moebeeza

My 80 year old home has been getting upgraded one step at at time. my furnace is an efm pk450 and I have circulating hot water. When previous owner had this installed they ran copper up the old black pipe. It starts out at 2" and reduces down to 1" at most of the radiators. One room had 3/4" going to the radiator. The whole layout and floor plan was changed 13 years ago and a few radiators were eliminated. My current system is a supply and return, teed off creating 2 lines and surrounding the perimeter, and was most likely originally a gravity system, judging by the angle of the pipe. I want to Run a central line and branch. My feed and return runs will be approximately 30' feeding 5-6 radiators. The radiators furthest away from the furnace are the largest. living room rad is triple core,14 tube,36"w X 10"d X 20" h. master bedroom rad is triple core,10 tube,26"w X 10'd X 20"h. I did not include feet which raise the height to almost 22&1/2". the other 2 bedrooms are smaller ~120' sq. rads are triple core 9 tube, 23"w X 5"d X 18"h. The location of the radiators in those rooms is going to be changed to maximize efficiency and space. Instead of being under the window, they will be moved closer to the bedroom door, so that when the doors are open that heat will circulate into open area. The bathroom rad is triple core, 4 tube 10"w X 8"d X 36"h. If I feel the need I will also use one of the small bed room rads in dining area as the living room rad has a large space to heat, basically all the open space which is approx 450-500 'sq w/cathedral ceiling. I plan to use the old valves, and have my pex al pex connect into a 1" black elbows connected to black nipple to valve. I plan to put 360 loops in system for expansion and contraction. Should I use 3/4", 1", 1/2"??? Should I use a manifold and different size line depending on radiator size??? should I use pressure regulators??? Are there mechanical type tuneable regulators or do I also have to become an electrician lol??? By doing this I hope to greatly reduce the amount of water that I need to keep hot in the winter and utilize more of my garage which is below living space and pipes prevent utilizing the 10'+ ceiling because in some areas they are less than 8' from the floor.

hot_rod

Start with a room by room halted calc. Then determine if you have enough radiator surface to cover that load. lower water temperatures require more surface area, regardless of the heat emitter type.

Once you know the load, chose a supply temperature. then the pipe is sized to the known load and flow required. Generally 1/2, 5/8, or 3/4 will work in most residential jobs.

You could add a TRV thermostatic radiator valve to each radiator and have ultimate temperature control. A homerun system is another option.

start here, page 18-20 describes homer with TRVs
.
http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_5_0.pdf

Ironman

A couple of things to also consider:
1. The large pipes that you now have provide a buffer due to their mass. This prevents the boiler from short cycling which would result in decreased life expectancy and lowered efficiency. They also cause the system to have a sort of built "reset" which means the water temperature will naturally adjust to the load and produce greater comfort and economy. In other words, they are an asset to the operation of the system. I would not recommend removing them unless there's an issue necessitating it.
2. If you do choose to do so, be advised that you'll need to do the entire system, not just pieces. Water takes the path of least resistance and if ALL of your piping is not proportionately sized, you'll have insufficient flow in areas where you've installed smaller piping. A 1/2" to 3/4"" line is usually all that's needed for most rads, but not if others of the same capacity have 1" or 1.25" lines.

I totally agree with HR that a load calculation should be your first step. The Idronics article is loaded with great info.

moebeeza

Thanks for the feedback, I will be investigating very soon. Dropped rads off this week to get blasted and powdercoated. There is a necessity. It's efficiency of area, I am losing a lot of space in garage ceiling for these pipes. I dropped off 6 rads. When I bought this place there were 9 rads and all were hooked up, place was arm as hell and oil was $1.25/gallon. There was no insulation. I now have R-52 in roof system and R-22 in walls. I am working towards being passive solar, and tightening up all areas of draft for increased efficiency. I am running .65g/hr kero jet, and if it'll burn it goes in the tank lol. I use and have used recycled motor oil and tranny fluid for almost a decade. I mix whatever I have with the no.2/diesel, I change filters a lil more frequently but I don't have to run to recycler w/used oil anymore.

moebeeza

Thank you to Hot rod and Ironman, that was very interesting read and with the btu and necessities calculations, I was a lil amazed. most of my rooms have rads that are midway between min. and max. requirements. My bathroom rad could heat a much bigger room, lol and my living room/kitchen/dining/ cathedraled ceiling area is under serviced. I usually set my furnaces hi temp at 160 and lo temp 140 with 25 degree variable and have been quite comfortable for last 13-14 yrs. I also realize that my uninsulated black pipe also acts as a heat emitter
I think I am going to consider 3/4" line manifold system w/Trvs. I was hoping to go with a similar system as to what I have now which seems to be a branch system. But manifold with Trv may work best for now and make further upgrades like outdoor sensor and reset controller and pressure regulated circulator down the road. I noticed all these schematics have the pump on the feed line, mine is on the return line, and from what I've been reading there is great debate over where best to locate the pump; feed or return??? If I can use existing pump with this planned project, I wont change location. Where do you believe the pump works with greater ease and efficiency ??? What is the best kind pex al pex fitting for hydronic systems utlizing cast iron rads and steel furnace ????
Thank you for informing/educating an old woodchuck

hot_rod

You will be happy with TRVs on radiators like that, they are an amazing, accurate and simple control.

The pump can be on the return, but move the expansion connection to the suction side of the circulator. Some higher boilers actually prefer the pump on the return.

The air eliminator should be at the supply outlet of the boiler, the hottest point in the system.

I like the Viega fostaPex, but it does require some special tools to strip the outer layer and crimp the stainless collars.

A delta P circulator, and possible ODR added later would make this a top notch system.

Here is more reading on manifold distribution. It is a few years old, more delta P circulators have been added since this writing.


http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_4.pdf

moebeeza

I will see if I can get a good pic of current setup, because it sounds like it may not have some of those components, or they may be in different locations. My expansion tank is directly after feed valve, and my air eliminator is right above and before my pressure relief valve. I do believe my furnace produces more btu's than my house requires. I have Efm pk450, single zone and a buddy of mine whose house is almost 3 times the size of mine is running a pk400 w/ 2 zones

vaporvac

Just a note on radiator placement: they were put under windows for a reason. It greatly increases heat distribution. Somewhere on this site there's a group of pics showing how rad placement affects this. The colder air from the window sinks pushing the hot air well into the room and also helping to mix it with the cold. This is why rads work by convection as well as radiation. By changing this you'll get a hot spot near the rad, but colder elsewhere, NOT the better distribution you envision. I have one room in my house where they piped it this way originally and it does make a difference.
This is also the reason why ill-designed rad covers can DECREASE heat output by as much as 30%.

Whatever you do, put a reflective backing behind the rads.

Personally, I'd keep the larger distribution pipes for the above mentioned reasons especially in a garage!, but I can't comment on it at all. Sometimes a huge change like this can have very unexpected consequences.