Plumbing Radiators with PEX

Richard Winter

I have an 80 year old house that has a 2 pipe hot water radiator system with a fairly new Bryant(Dunkirk) gas boiler. I am rehabbing the old basement garage into living space and would like to install radiant floor heating in that area. I know that I have to install a mixing station for that and am trying find out what are the necessary components of a mixing station (ie mixing valve, pump, shut off valves, temperature gauge, bleed station, etc.). Does anyone make a premade mixing staion for a one zone system? Also, I read a post on this board about supplying cast iron radiators with pex tubing. I would love to gain some head room in my basement by replacing or moving my steel distribution and return systems. Can I replumb some of my radiators with pex tubing? Finally, I have a 20+ year old Spacepak system that supplies airconditioning. I am getting ready to replace the condensor (original GE) and was going to pelace the Spacepak unit with a newer one but have decided to keep it and make some slight modifications after talking to the Spacepak people. It is noisy and they recommend moving the unit and installing a longer air intake and installing a few more ducts which I can use anyway. My question is this. I am thinking of installing an electric resistance heater on the Spacepak to provide heat to the house on spring and fall days rather then firing up the boiler (I live in Missouri). Has anyone had experience with these units? Thanks for any help you could give me. Also, I am having difficulty finding someone that really knows boilers and how to retrofit them for radiant heat in my area (St. Louis). Any recommendations would be appreciated.

Ted_9

Look at the Buderus Quick mix station for your radiant.
www.buderus.net

Mike T., Swampeast MO

80 years old sounds like the system was installed before circulating pumps, e.g. gravity circulation.

If so, the pipes are BIG. Likely two pairs of BIG main pipes. In this case, DON'T start replacing branch lines to radiators with smaller PEX. (If you can do it in the same size, OK, but still try to be considerate when it comes time to drain/fill/air purge the system, e.g. STILL make it pitch back to the boiler.)

Don't even think of making the mains smaller unless you also reduce the size of ALL of the branches.

No experience with Spacepak, but electric resistance heat in the shoulder seasons will significantly reduce the cost of heating considering our low winter electric rate.

Richard Winter

Thanks for the advice. Yes I think you are right, the system was probably gravity fed when it was first installed, but now has a circulation pump. the supply and return pipes coming out of the boiler(five years old) are newer and are I think 1 1/2 inch.They transition at the ceiling to the original supply and return pipes which I think are 2 inch. These old mains are the ones I would like to change. Wouldn't it make sense that I could at least downsize them to the same size pipes coming out of the boiler? Could I swap these pipes for 1 1/2 iron or copper? Further more, if I home runned the radiators with 3/4 inch pex to a 1 1/2 inch or 2 inck supply/return header, would that work? As I said before, getting answers to these questions are hard when all I can find in my area is air guys. Thanks again for your response.

Richard Winter

Thanks for the information. I had found that valve on their wedsite before but thought it might be more then I need because I think (not sure)it also provides a high temperature loop that I don't think I need. I can tap off the high temperature circuit near the boiler and just need mixing valve, pump, and associated hardware to drop the temp for the radiant. Maybe I misread the web page, or don't understand it and the Buderus may be exactly what I need. Thanks again for the reply.

Boilerpro_3

Another thing to consider

> Thanks for the advice. Yes I think you are right,

> the system was probably gravity fed when it was

> first installed, but now has a circulation pump.

> the supply and return pipes coming out of the

> boiler(five years old) are newer and are I think

> 1 1/2 inch.They transition at the ceiling to the

> original supply and return pipes which I think

> are 2 inch. These old mains are the ones I would

> like to change. Wouldn't it make sense that I

> could at least downsize them to the same size

> pipes coming out of the boiler? Could I swap

> these pipes for 1 1/2 iron or copper? Further

> more, if I home runned the radiators with 3/4

> inch pex to a 1 1/2 inch or 2 inck supply/return

> header, would that work? As I said before,

> getting answers to these questions are hard when

> all I can find in my area is air guys. Thanks

> again for your response.

S Davis

Pex

Be careful using pex for high temp supply and return as it has a high expansion rate and can cause noise issues, you would be better off using a PAP piping which has a lower expansion rate.

S Davis


Apex Radiant Heating

Ted_8

Sizing is key

The best bet is to calculate the btu's needed at each radiator and then size your lines accordingly. Dan has a great book that will help with this, it's called EDR. Also, products like alumapex from W/M or multicore from Wirsbo are great for this as they do not expand and contract any more than copper.


Ted

leo g_13

yes

> Thanks for the advice. Yes I think you are right,

> the system was probably gravity fed when it was

> first installed, but now has a circulation pump.

> the supply and return pipes coming out of the

> boiler(five years old) are newer and are I think

> 1 1/2 inch.They transition at the ceiling to the

> original supply and return pipes which I think

> are 2 inch. These old mains are the ones I would

> like to change. Wouldn't it make sense that I

> could at least downsize them to the same size

> pipes coming out of the boiler? Could I swap

> these pipes for 1 1/2 iron or copper? Further

> more, if I home runned the radiators with 3/4

> inch pex to a 1 1/2 inch or 2 inck supply/return

> header, would that work? As I said before,

> getting answers to these questions are hard when

> all I can find in my area is air guys. Thanks

> again for your response.





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leo g_13

yes

homerun is a beautiful way to run rads, especially with a TRV on each rad. This is the way that we install all our new panel rad and if possible, we do it on retrofits. It helps to take the "size" out of oversized radiation. We also use pex for our runs, and get by the noise issue with a tekmar mixing control, usually the 361. Then we add a programmaable t-stat, so that we can incorporate night setback.

remember, to size your radiation, and you will probably find that you can run much cooler temps, thus again helping with the noise issue.

To me, this style system, mixed with a bit of infloor in the tile areas, is THE BEST system there is!

Hope it works out for you!

Leo G

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