radiant floor with no manifold

Snowmelt

Not trying to be cheap just trying to be economical , If i have 2 zones, one loop each. would anything scientific speaking going to happen if I don't use a manifold? I will have 2 pumps and 2 mixing valves. just don't want extra material in boiler room. would it just heat up a little quicker because the water won't be throttled down.

Gordy

They are separately controlled in flow. Shouldn’t be a problem.

Question, why two pumps, and two mixing valves? Different temperature requirements?

psb75

submit a drawing of your proposed plans and you will get a better response.

hot_rod

Unless the temperature requirements of the two zones are 15 degrees of more apart, really no need for multiple mixing stations?
Or run the heat source at the high temperature requirement and mix down the other.

If you have ODR or other temperature modulation on the heat source you can use a "dumb" 3 way mix valve, a manually adjusted one. It will track along with the boiler temperature modulation, no need for a thermostatic valve.

Single loop circuits probably only need a small DHW recirc type circulator.

Gordy

I don't think people give enough credit to the "dumb" mixing valves. As you say they track boiler temperature output. The colder it is outside the longer the call the warmer the supply temp gets. Mimics indoor feed back.

Served systems well for a few decades

EBEBRATT-Ed

Depends on the length of the loop. Two much pex and you won't get flow if the loop is too long. A manifold splits the flow between loops if you need to

Snowmelt

The reason for two pumps and two mixing is because one is bathroom and one is the kitchen. Also the house has an addded back two rooms that I want to put on its own zone. So for the whole job I want to add two radiant floor. ( small zone ) bathroom 25 square , kitchen100 square one loop each one is below with plates other is climate boards since the floor is going to be picked up & new tiles. And split the rest of home in two zones. I offered a new boiler for job but the customer said they need 2 more years to save the money for the job. So second question is how do I protect the boiler from condensing.

roysmith

nice thread

Ironman

"Condensing"?

How about the short cycling from micro zones that would cause condensing? Sounds like you're gonna need some buffer. Or mixing valve at the boiler.

Snowmelt

iron man i was thinking same thing , and advised homowner of this, but will change out the boiler in a few years. they know its a big expense but one thing at a time

HomerJSmith

I assume you are using PEX.

What kind of mixing valves do you have in mind? Do you control the temperature in each circuit independently with separate thermostats? How are you going to control flow thru each circuit since they are of different lengths?

I think, if I were to save money, I would use a cheap Chinese manifold like Rifeng which would control the flow and add actuators which would control room temperature and a single Alpha 1 ECM pump to run it all. You can of course choose the cheapest ECM pump that can handle the flow, most can.

https://www.pexuniverse.com/ssm102-steel-radiant-heat-manifold

https://www.pexuniverse.com/grundfos-alpha1-15-55-f-lc-circulator-pump-99285998

If you control temperature with actuators, you will need a transformer and thermostats--
https://www.pexuniverse.com/ssm101-24v-manifold-actuator

If you are going to upgrade to two more pex zones later than buy a manifold with the required ports and block the unneeded ones off.

Gordy

The original question was if he needed a manifold for two loops. Each loop being independently controlled by flow, and temperature via a pump on each loop, and mixing valve on each loop being that the two zones require different temps. I say no as the question was initially stated, however question the reasoning of the tactic, which is now developing into more than the initial question.

The reasoning to not use a manifold was to save space in the boiler room.

Use a taco I series 3 way with ODR also for boiler protection. since I assume a CI boiler is in place, and you asked about protecting the boiler.

HomerJSmith

One must use a mixing valve if the boiler supply temp is higher than the circuit temps (probably). If the temp requirements of both circuits are the same or closely matched, you could use one Taco mixing valve, one Alpha 1 pump, two Taco Accu-flo or Caleffi balancing valves, two Honeywell or Caleffi zone valves if separate room temperature control is needed with two thermostats, and a transformer.

If both rooms operate at the same temperature at the same time with one thermostat (highly improbable for a lot of reasons). You need one Taco I-series mixing valve, one Alpha pump, one zone valve, two circuit balancing valves, one thermostat and one transformer.

As originally stated, "If i have 2 zones, one loop each. would anything scientific speaking going to happen if I don't use a manifold? I will have 2 pumps and 2 mixing valves."

Snowmelt, you didn't express all your needs or your present boiler system. Scientifically speaking, it will all end up in a 'Black Hole' of unregulation. You have to regulate water temperature, room temperature and flow to achieve the desired results. Yes, the world isn't going to end if you use 2 pumps and 2 mixing valves, scientifically speaking. To make it work, you need 2 Alpha 1 pumps, 2 Taco I-series mixing valves, two circuit balancing valves for flow control, two zone valves and thermostats for room temperature control and a 24V transformer.

Add up all the cost of each method + your time and go with the cheapest way because, like me, you are an economically thinking person, then choose a manifold.

Snowmelt

I’m not totally convinced on flow control, these would be two different rooms. I would have the loops even. I would just throw on a simple honey well mixing valve - or taco and a delta tee pump. Then just let the thermostat decide to turn on and off. I want to keep it simple. With boiler protection like goody said.

HomerJSmith

O.K., I'm getting the picture.

I guess it is a CI boiler with a fixed operating limit and you want to run the water temp from the boiler at a higher temp than the required temp of the pex tubing, which is about 90 to 120 degs. The return water to the boiler must be above 130 deg. If the return water is less than 130 deg, you need to funnel some of the supply water back into the return on the boiler. You'll need a bypass from the outlet to the inlet of the boiler. I use a Taco I series setpoint two port mixing valve with a sensor on the return set at 135 deg. This works for cold startups.

You can also set the boiler up as a primary/ secondary system and run it so the return water is always above 135 deg and do away with the Taco I series mixing valve. You can connect the pex circuits thru closely spaced tees with a ECM pump, a thermostatic proportional mixing valve like the Honeywell AM100R-USTG-1 with a set temperature, a zone valve, thermostats and a transformer. Notice that there is no flow control. You can run both zones with one pump, but you will need a balancing valve if you have different sized circuits of more than 10% or most of your flow will go thru the shorter circuit.

That is about as cheap as you can get. Also, you would have a fixed water temperature regardless of outdoor temps.

HomerJSmith

You say you are going to keep the two circuits the same length. How are you going to do that? One room is 25 sq ft and one is 100 sq ft. You are going to over heat the one and under heat the other. But, if you use two mixing valve you could set the smaller room at a much lower temperature than the kitchen and the BTU output would more closely match. You would also have to expand the distance between the pex in the kitchen and cramp the pex in the bathroom. It's better to figure out how many BTU's you are going to need for each room and plan the pex layout and water temp to achieve those results and use two balancing valves.

You never said whether you wanted one thermostat to control both room or you wanted each room controlled separately.

Snowmelt

2 thermostats- I think it may be more beneficial to the customer to just throw a 30 gallon water heater into play and forgot about mixing valve and just add two zone valves to it there's space close to the chimney, the gas is right there. just put the temp on 125 and put a smart pump on it. that way we don't have to worry about short cycling or condensation in the boiler. does that make since again there are 2 small room. 9,000 BTU total. After they get a high eff. boiler ( that maybe next year it may be never) then worry about tying in the 2 zones with the boiler. would that make sense.....