MANIFOLDS RADIANT HEAT

PORKCHOP

  WHAT ARE THE BEST THINGS TO LOOK FOR WHEN PURCHASING A RADIANT HEAT MANIFOLD.  I HAVE LOOKED AT THE INFLOOR AND EVERHOT MANIFOLDS BIG DIFFERENCE IN PRICE. 

  HAS ANYONE OUT THERE USED EITHER PRODUCT AND IF THERE IS WHAT HAS BEEN THE RESULTS?

  I AM LOOKING AT SETTING UP THE SYSTEM WITH SEVERAL CIRCULATORS THAT WILL SERVE VARIOUS MANIFOLDS.  THE MANIFOLDS WOULD HAVE ACUATORS,  FLOW METERS AND BALANCING VALVE THAT WOULD SERVE VARIOUS ZONES.

Brad White

I think that your last sentence

sums up my wish list.



Uponor, Caleffi, Heatway, Viega, all pretty decent. I prefer to specify the brass or stainless steel types and not the engineered thermo-plastic ones. Not for any reason of knowing something is wrong with them, just that metal is more permanent in the scheme of things and that is worth more than the cost difference to me.



Now, you did say that you were going to use a single circulator serving multiple manifolds, so that implies to me a wider distribution (versus a single large manifold and lots of long home-runs).



But I wanted to be sure that you grasp that these would all have the same temperature. Temperature is defined by a mixing valve and by default, a circulator to go with that.



So if all of your floors have the same flooring materials, spacing, depth, heat loss requirements, that is great.



But if you are serving different areas defined by carpet, wood, concrete, tile and different heat losses, you may need more than just manifolds, but manifolds, mixing valves and circulators for each type.



My rule of thumb is, if the requirements of each floor type need average water temperatures ten or more degrees apart, they would have their own mixing control. There are exceptions of course, but one needs to have a basis and point of departure.

PORKCHOP

radiant heat manifolds

we will be using primary secondary piping at the boiler, heat loss for the structure is 60 k btu, boiler will operate at 125 deg. ,  zones are designed with a 10 delta t,  boiler circuit is designed for 20 deltat t in the primary loop,  we will have three circulators,  the first will not require a mixing device supply water temps will be between 115 to 123 with 4 manifolds,  second will use a mixing device supply water temps between 73-89 with two manifolds,  third will use a mixing device supply water temps between 90-104 with 10 manifolds.  each manifold will be controlled with a zone control that will use an end switch to activate the circulator,  the manifolds that i had seen on line were by EVERHOT and REFIENG both were attractive in price and have the flow meter, manual adj. temp indicator,  drain valve,  air bleeder and ball valves with an optional acuator.  since we are new to the design and installation of radiant floor systems i was trying to avoid using a product that would not deliver satisfactory results.  with the amount of manifolds that we are using here the price diff. between the name brand products and products i listed above could be substantial difference. do you think it is necessary to have all of these extras on the manifold or just use a standard copper manifold with a zone valve, ball valves and air vent and boiler drain?

you seem to have a good grasp on the radiant floor systems. i would appreciate any advise you may have

Brad White

Sounds like

you thought it out pretty well already.



This is obviously no small job you have here!  Sixteen manifolds?? At 60 mbh the building does not sound all that big and might be over-controlled, just asking. If the house has a heat load of 25 BTUH per SF, that is one manifold for every 150 SF. Even the dog will have one and so will the cat. Or do you mean 16 circuits?



As for manifold brands, I am not familiar with the two names you mentioned. May be good, may not be, I just do not know. Never heard of them.



My concern with odd brands is getting replacement parts and the quality of the metallurgy. For example, some brass, notably from overseas, has been known to dezincify, leaving a crumbling mass of demi-copper. Basically it is a breakdown of the alloy due to stray currents and other oxidizing factors.  So stainless to me is "safer". Brand names too, where you can get new hardware, replacement meters, valves, etc. Short money in the long run and a minor part of the cost.



Could you use copper manifolds and valves? Sure of course. Your tube layout wants each circuit to be within 10 percent of each other and I would also pipe them reverse-return (supply manifold fed from the left, return fed from the right, for example), to even out imbalance potential. The flow meters are nice when you want to fine-tune imbalanced circuits but also when you commission the entire system. If accurate, the sum of flow rates speaks to pump output. But a purchased manifold, with purge valves, isolation, temperature gauges, master isolation and drain valves, to me saves time and time is money. Even copper manifolds will have you making up an assembly.



You mentioned end switches to activate circulators. I do not know the type of flooring you have, the mass of the building and the overall control strategy, but radiant floors, even the lower mass ones, are much slower to respond than a baseboard or air system. Even low mass floors from a cold start might take half an hour to come to temperature. High mass floors could take a day or more. I can only suggest you re-think that, go with slab sensors and room sensors, constant flow and vary the temperature based on a departure from setpoint. More money on controls but the comfort is superior and constant without a wait. Circulator control puts an on-off mode in what is otherwise a modulating mode. Spikes over gentle waves. You want gentle waves.

meplumber

Just my $.02 worth.

We had a contractor in this area using the thermoplastic manifolds a few years back.  He was beating the pants off all of us on price.  The flip side is that the manifolds developed stress cracks after periods of cylcing from hot to cold.  Huge liability issue for water damage. One of maybe a dozen reasons that he is no longer in business.



As Brad stated, you want to ensure that the zones are modulated and sized to take advantage of the flywheel effect.



We do a lot of radiant.  Concrete imbed, underfloor and above subfloor and I will not use thermoplastic.  Good price or not.  I personally prefer the Caleffi manifolds, but that is my preference.  Uponor, Watts, Viega all make great manifolds that I have used to meet spec's with no problems yet.  The balancing feature as opposed to a copper manifold is worth its weight in gold.  If you have designed your system correctly, you can dial the flows in tight and the system will increase the customer comfort.



Stick with one of the major brands, they will be there if a problem arises.  Also, if you contact their reps, they will usually assist with the design and first install.



Good Luck.

PORKCHOP

radiant heat control strategy

the job is a 1-1/2" lightweight overpour to the subfloor, we have a mix of hardwood and ceramic tile,  we attached the tubing to the subfloor and buried the tails through the subfloor to the crawl below,  we were careful to keep circuits lengths within in the 10% rule and most of them are within 2-3%,  the house is approx. 4000 sq. feet,  the btu's per sq ft. avg. about 15,  you are right the system is probably over controled,  i will probably reconsider the control strategy to reduce the manifolds and t'stats needed,  i have planned on using the tekmar 508 with slab sensor for limiting floor temp as well as dual temp sensing, 

what are your thoughts on the 10 deg. delta tee,  from most of the info i have read i have designed at a 20 deg. delta,  should i be designing at a 10 degree for all radiant floor heat,  i have seen this 10 deg. figure on a couple of posts from this sight but no where else.  i do understand that my gpm will increase as well as my pump size.  if i do use the 10 degree for my floor loops, would i keep my primary loop at the 20 delta t?

i went to the web site for caleffi manifolds and seems to be a stought product,  probably will go this way.

one more question,  the boiler is setting up in a mechanical room off of the garage,  all of our manifolds are in the crawl area,  what are your thoughts on using pex pipe to come off of our primary loop to our system pump then to the crawl with pex pipe to be piped in a reverse return arrangement that will connect to our manifolds in the crawl?  should i be using copper for the system piping and then pex from the maifold to the floor circuits?

PORKCHOP

MANIFOLDS RADIANT HEAT

got it,  i looked at the caleffi manifolds online and seem to be a sound choice,  these other ones i mentioned were a stainless steel product but,  after reading what you and brad said about the the reliability and availabilty of replacement parts i am considering the name brand products,  since we will be the responsible party for servicing this system in years to come, 

  we have been servicing and replacing hydronic and steam systems for years but these systems are the ones that were installed during the 30's thru the 60's,  air to air systems have taken over for the past 45 years,  very little hydronic work in this area,  however we are seeing an intrest in radiant floor heat so now we are involved in the design and installation of these systems,  thats why i may seem a little out of touch with the various ways for the radiant floor systems.  we have been reading studying alot just to get up to speed. 

if you have any good recommendations that i may be able to use in introducing this product to our customer let me know.  we are in the central va. area

really appreciate the input from all of you guys. 

Gordy

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