Cast iron radiator piping issues

jublack2000

Hi there,



We are renovating a 7-unit apartment building with old cast rads (hot water).



The 1st two units have been piped with pex "heat link"... They've been separately zoned, each apartment having a wall thermostat that controls all rads in the apartment.



With the first two complete, I have some concerns that I wanted to get some input on here before we pipe the others:



1. is reverse return overkill for small 600 - 800 sq ft apartments with 4 - 6 rads per apartment? The 1st two were direct return.



2. The heat link pex does make quite bait of noise expanding and contracting. I'm scared to do all 7 units wih this product. The tenants may think the building is haunted! I read some posts about using PAP... Is that what should have been used?



3. I read some posts about cast iron and copper being incompatible. The plumber used some copper fittings (in the actual pipe holes in the rads) to connect some rads to the pex... Will this cause the rad to rust? Also there is a lot of copper in the basement for the manifold setup... This won't pose a problem will it?



4. The connections to the rads above the floor look awful! It really cheapens the look of the old rads... Any suggestions on how to tackle this? Is it possible to connect pex to a metal piping material? I would like it to look like it was always there.



5. Last but not least... The water in the pex line looks a bit brown. Is that normal? Is it just the pex making it look that way?



Thanks,



Juliana

nicholas bonham-carter

Haunted system

I don't see why you could not use iron pipe to connect the radiator inlet, and return to the pex below the floor. Usually, the connection from copper fittings to iron is with a brass transition. Dialectic unions are not recommended, as they will leak.

Usually, any pipe should be properly supported to a framing member to prevent strange noises, and more importantly abrasion.

The color of the water is not important, as long as the Ph is correct.

Was this system always hot water?

It may have been better to use thermostatic radiator valves rather than thermostats for each apartment.--nbc

bob eck

piping issues

take a look at using Viega Fostapex pipe. It is pex pipe with a aluminum barrier. the aluminum works as the oxygen barrier and this pipe does not expand (grow) like regular radiant pex does. if you can run lower water temps that also helps with expansion. you can get fostapex in 1/2" x 150' rolls Viega FostaPEXback

Fosta stands for Form-Stable PEX, so the piping will keep its shape after it is bent. A distinctively versatile product, FostaPEX balances stability with flexibility to create a unique tubing system that not only bends with ease but also holds its shape. Outer layers of aluminum and PE make this feature possible, while simultaneously extending UV protection. FostaPEX is a lead-free oxygen barrier pipe, which makes it compatible not only with potable water systems but also in hydronic applications. FostaPEX also has a low coefficient of expansion compared to standard PEX products and, since one fitting system connects to all types of ViegaPEX tubing including FostaPEX, distributors need only one inventory and contractors need only one tool set.



Viega began production of FostaPEX in November 2009 at the Viega Manufacturing and Distribution Facility in McPherson, KS. Viega’s FostaPEX production line in McPherson is currently the only multilayer production line in North America that produces pipe for both plumbing and heating applications. Viega FostaPEX is the only product on the market with a fully dimensional PEX tubing wall, allowing it to be used with the standard Viega PEX Press fitting system. Other PEX-AL-PEX tubing products require special fittings

icesailor

Pex Issues:

Responses:

#1: Reverse return is always a better choice than a direct return. In MY opinion. Water will always take the path of least resistance.

#2: Plastic of any type will always have a larger expansion coefficient that copper and copper is greater than steel. I use expansion clips and sleeves. I never let pipe touch the woof. Anyone who doesn't do this is guilty of bad piping practices.

#3: Copper is connected to steel and cast iron regularly. Since before WW II. I see PEX connected to Cast Iron Boilers regularly and the PEX is all black inside. The longer it is in place, the worse it gets.

#4: Sure, leave the through the floor connections in place and connect it below the floor. Connecting it with PEX above the floor looks like the rodent with the rounded ears connected it was at work.

$5: Nice plug for FostaPEX.

jublack2000

Why thermostatic valves better?

Thanks for your input... Why do you think Trv's would have been bett than a wall thermostat?



I'm not sure if the system was always water or was converted from steam at some point. The building was built in 1880 so maybe.

jublack2000

Thanks

I'll ask our heating contractor about this product. I'm not sure if it is a special order item or not. Does it cost a lot more than PAP products? So you wouldn't recommend pap products because of the special fittings needed?

CMadatMe

Wrong Approach

Should have used a radiant manifold, feed each rad 1/2" and maybe even 3/8" pex, trv's and a Alpha or Taco VDT pump. Noise issue gone, rooms nice and comfortable. Could even have gone to the point of installing a Taco I-Valve providing ODR.



No different then Page 19 here....



http://www.caleffi.us/en_US/caleffi/Details/Magazines/pdf/idronics_5_us.pdf

jublack2000

too technical

Unfortunately I don't really understand your suggestions. I know a bit from doing my own research on websites like this, and I'm trying my best to make sure that the correct methods are being used in this installation.



The diagram in the link you sent doesn't look like it would be possible. Running a separate supply/return line to each rad would cost me a fortune I don't have... if i understand you correctly.



Also, they are currently using 3/4" pipe, and there will be a circulating pump on every loop. Not sure if that info is relevant.



Thanks again...

CMadatMe

Pex

You said they ran pex to all the rads, whats the difference? I would only have to use 1/2" maybe even 3/8" and no fittings. Less money and a whole heck of alot easier to pull, ie labor to run it. Manifold would go in each apartment so your only bringing a supply and return from the boiler room.



I dont necessarily need a pump on every loop. Could zone with a zone valve and have a smart pump do all the water moving. Sorry about the tech stuff but what I gave you anwsers any question you may have about zoning a hydronic heating system. Next step would be balancing the system so you get no noise. The Pex isn't the cause the installation is.

jublack2000

Thanks Chris,

For clarifying... It is making more sense. That is interesting about putting each manifold in each apartment... All have been installed in the basement already unfortunately.



You also mentioned trv's. Why do ythink that's better than a wall thermostat on each loop? Is it more about comfort?



And finally why is the smaller 1/2" line better than 3/4"? Is it that it is all that's necessary?



Thanks again for taking the time...



Juliana

CMadatMe

TRV's

Will allow you to tune in each radiator to each room. If no heat loss and rad capable output was done how do you know if the radiators are sized correctly? Say they heatloss in the bedroom was 2,500 btu's and the rad is putting out 4,000 I can easily turn the radiator down without effecting the entire system. You still keep the main thermostat to have the zone come on or off. I only need the smaller pex because I can deliver the btu's with it to each rad. Again, if no heat loss and capable btu output of emmitters done no way to give you a anwser that exactly pertains to your application.

jublack2000

I had a heat calc done by room...

we also calculated the max output of each rad. It makes sense though to still be able to control the rads individually... i would assume we can add that later if we want. will leave it out for now to save on cost... or maybe you would just add one to the bedroom rads.



thanks for your help.



Juliana