boiler protection:which valves on bypass loop?

Joe_30

Despite the claims of the German boiler manufacturer, that its boiler is protected by stopping the system circulator if the "boiler temperature drops below a selected point [ as low a 104 degrees, they say}, I am buying into John Siegenthaler's statements that there should be a sensor at the return water, and a valve on the bypass loop which receives the signal and allows hot supply water to join the cool return water, for protection of the iron boiler.

Who makes a good reliable device for this.?? We have a single pump 5 zone system.

John also says there should be a differential pressure bypass valve on [ in effect, a second parellel bypass], to take the unneeded pressure of the pump which results after a number of the zones have closed. This loop would also route water back to the return side. So, who makes a good one of those pressure sensitive devices?

Is there one device which combines the functions? Or should I just make a little pressure relief bypass around the boiler protection valve on the boiler bypass piping?? Seems simple enough. Thanks for your ideas. Joe

Terry

boiler bypass

I prefer the Braukmann D146M Series Pressure Differential Valves (avail in 3/4 or 1-1/4). But you may want to analyze press min/max/diff on your 5 zone system. If the primary pump is large (too large to efficiently pump on a 1 zone call) then the above valve would work. I find that press diff valves are not required until you get into large systems that require a large pump & many zones. (Large enough that 1 zone calls will create "cavitation' of the pump. (Perhaps - a small 1/2 or 3/8 bypass, valved, slightly opened would suffice?)

For Return Boiler Protection, I like the Tekmar #150 Setpoint control. with this control you can open/close a zone valve on the bypass or run a small "shunt" pump to ensure that min boiler temps are maintained. It has both N.Open & N.Closed contacts allowing a wide range of strategies. An Aquastat could also be used similarily

Hope this is helpful !

kf_2

If the

Boiler control is stopping return water flow through the boiler why the need for added controls or valves for protection.

kf

Bill Clinton

bypass

When installing radiant floor heating I have slowly become convinced a bypass is necessary to maintain boiler temperature. On residential size jobs, I do this by installing a full-size bypass and equipping it with a thermostatic valve that has a remote bulb and capillary tube. The bulb goes in a well on the return pipe, right at the boiler. When cold-starting, most of the flow goes through the bypass. As the system warms up, the thermostatic valve starts closing and will modulate to the return temperature you set. Needs only one pump. Failure mode will be valve open, so boiler is always protected.

In residential radiant systems, I don't usually see a need for a pressure bypass, unless to maintain minimum flow through boiler in a multiple zone system.

Bill

Mark J Strawcutter

Danfoss ESBE TV

might be what you're looking for.

hr

The more I look at return protection

when connecting non condensing equipment to low temperature radiant, the more I like the injection mixing. For the cost of the additional pump and tekmar, Grundfos, pick your favorite control brand, you get absolute protection via a return sensor, very accurate temperature supply, the ability to use outdoor reset, dhw priority, etc, in a fairly simple to pipe package.

On a recent snowmelt with a low mass copper boiler I just didn't feel comfortable with the ability of a 3 way thermostatic to provide adequate flow through the hx across the entire range of the 3 way.

Heck for the price of the V/S injection pumps with the tekmar brain built in it's a simple plug, pipe, and play install.

Just another option.

hot rod

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Boilerpro

One problem I've found with using only one pump with Esbe

When the valee is bypassing only a little flow goes to the system, so heat balance can be effected. When installing a boiler with an Esbe on the return I always pipe it P/S, so the system pump can provide full flow to the system no matter what the return temps are.

Boilerpro

Mark J Strawcutter

boiler vs system bypass

if system flow is of concern, pipe it as a boiler bypass instead of system bypass.

don't know if ESBE makes a TV valve you can use for boiler bypass - the ones I've seen are designed for system bypass.

with boiler bypass you have a similar problem, but with boiler flow.

There's only so much water so any bypass has to come from somewhere :-) I agree that P/S is probably the best solution.