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Need help designing controls for multi-zone hydronic system

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hydro heat hydronic air handler radiant hydronic in-floor pex heat
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Jbeard9

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Discussion starter · #1 ·
First off I do forced air systems and this is for my personal shop/office I wouldn’t venture into this for a customer.
So here is what I have:
-zone one-First floor in slab radiant heat (shop area) 4-300’ loops to manifold
-zone two- First floor in slab radiant heat (garage area) 3-300’ loops to manifold
-zone 3- Second floor forced air unit with hydronic
Coil.
I am using an air-to-water heat pump and want to use an electric hot water tank for storage/auxiliary heat.
Not sure if I should use one large pump and zone valves or if each zone should have it’s own pump?
I also didn’t know about some of the new hydronic pumps out there that are variable speed. I know what my head loss and gpm requirements are for each zone just now sure how to put it all together.

Thanks
 
#5 ·
You posted in a Controls forum but didn't give any specifics!? You didn't mention how you were thinking fo controlling it or your comfort level of programming. I've seen guys put a stat on the wall and cycle a pump. When you say 'each zone to have it's own pump' that kind of scares me. Some of the challenges are night setback, recovery time, temperature overshoot, hysteresis. I've also seen the pipe laid incorrectly a couple of times to where the flow starts at an inside wall and ends up by an outside wall. It should flow to the outside first and cool down on it's way back. If it is piped correctly then a mixing valve would probably be best. Cycling a pump is very difficult to maintain a good space temperature. If you do cycle pumps it has to be done on a pulse width program and not on/off. Your zone valves should be proportional and not two position also. Are you going to reset the slab from the space or try to control by space temp?
 
#7 ·
Your distributor should set you up. Your could look at the TEKMAR controllers for you education. I like zone valves in our commercial work, but this floor stuff really works better with pumps on each zone. Tricky part is the 2nd floor hydronic coil is likely going to need water at a hotter temperature than the Floor loops. So a mixing valve may be required to separate the 2 types of demands. With the proper temperature of water feeding the Floor loops the pump cycles should be PWM proportional from their controller with the minimum cycle time measured in Minutes. Something like a 10 to 30 min timebase.

So this is not a simple system, but it is nothing out of the ordinary for anyone doing this regularly.
 
#8 ·
He can just add a supplemental electric duct heater after the 2nd floor coil, and forego the mix valves and use smaller pumps. If you have the money then put in mixing valves for better zone control.
my 2cents,
cheers amigo
 
#9 ·
FYI

http://www.tekmarcontrols.com/images/_literature/a0002_m_07.pdf?lbisphpreq=1

http://www.tekmarcontrols.com/images/_literature/p9336_02.pdf?lbisphpreq=1

I have nothing to do with Tekmar, I just find it is easy to look up their equipment.
What I have used from Tekmar has worked well if you follow their applications to the letter. ( Don't try to go half way or add something from outside their application. Unexpected results may be achieved.

You do need to get someone to design this for you (Distributer?).
 
Discussion starter · #10 ·
My air-to-water heatpump will give me 110-120 degree water and my hydronic coil is rated at 32kbtu at 110 degrees @4gpm, my heating load is 25kbtu but I do have a 15kw electric heat element for aux heat.
 
Discussion starter · #12 ·
I checked with my Supplier and they are a Tekmar distributor so I’m going to check that route out for the controls as long as the pricing isn’t out of my budget.
FYI for anyone wanting to do this at their house it is definitely not cheap but after all the research it’s the next best thing to geothermal especially if you have no access to natural gas.
 
#13 ·
Ok, with the added info you should need something similar to the middle picture of the tekmar 2 page sheet. Just take out the boiler and add the electric for the tank. You and your supplier should be able to take it from here. Now can your duct guys run pipe?:whistle:
 
Discussion starter · #14 ·
I can run pipe lol, already have all appropriate piping ran to the utility room just have to put it all together. Definitely been a fun/challenging project.
 
#15 ·
using dedicated pumps per zone is typical in radiant. and even fan coils. In radiant you almost need to to get proper flow with the head loss in the piping.
With anything there is always multiple ways to control a system. I don't mind talking to jbeard about it.

Floors max temp varies depending on what the floor surface is. Concrete, warm board, plated under the sub floor,, then what on top, hard wood pergo rug tile etc.
Run the boiler at 125. and have separate mixing valves per loop so you can adjust as needed.

Do you want this on an automation system.. thats easy also. They do make zone panels as listed elsewhere in this post. I usually use the taco panel. Its just zone relays, nothing fancy.

What boiler are you using. cast iron, condensing or a storage tank?
 
Discussion starter · #16 ·
I am not using a boiler, I’m using an air-to-water heat pump with a buffer tank for storage and dhw. The heat pump produces water temps of 110-120 degrees depending on outside air temp. I have looked into the zone pump controls such as taco but was unsure if this was a better route than zone valves.
 
#17 ·
Jbeard9 said:
I am not using a boiler, I’m using an air-to-water heat pump with a buffer tank for storage and dhw. The heat pump produces water temps of 110-120 degrees depending on outside air temp. I have looked into the zone pump controls such as taco but was unsure if this was a better route than zone valves.
Click to expand...
separate pumps than zone valves. make sure you use check valves though

did i read right that the tank is also the dhw? if so you should put a low temp sensor on it controlling the pumps off if the tank temp is to low. DHW before space heating.
 
#18 ·
a lot of heatpumps claim the can do 120 deg water, but what they don't tell you that they have OAT cutoffs when it gets cold. So be sure you triple check that your equipment will run in your local oat conditions
good luck.
 
#19 ·
amigo said:
a lot of heatpumps claim the can do 120 deg water, but what they don't tell you that they have OAT cutoffs when it gets cold. So be sure you triple check that your equipment will run in your local oat conditions
good luck.
Click to expand...

good point to bring up. They also do 120 discharge. hey cant take 120 deg in. we did a geo water to water and I had that issue.
 
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