returning cold water to condensating boiler

the nose

I installed my first munchkin boiler almost 2 years back with primary secondary pumping with no problems in system performance. By the way it was a 140,000 btu modle and I used a 0010 taco pump on the primary loop.Now my problem is I attended the latest ISH convention and got over educated and I'm now trying to send low temp water back to the system for greater eff.My pending installation is a 140,000 btu munchkin with a 5 zone radiant slab system of about 2600 sq. ft. and a 45 gallon indirct water heater. My latest and greatest idea was to use a motorized three way mixing valve with outdoor reset on the 5 zone radiant panel and just use that pump for the radiant panal and pushing it through the boiler with a 3/4 presure differincial bypass valve to keep good flow through the boiler.I was going to take the water heater off the supply with its own priority pump and spring loaded check valve before the radiant panel mixing valve and pump and return it on the down stream side of the 3 way return and put a check in between even though the water heater would be running independently on priority. My main problem is the water heater ceating 2 tempreture system otherwise I could just turn the munchkin down to 130 degree and go or even modulate the boiler with the outdoor reset. I hear that munchkin is coming out with a new control that can differenciate between a call for heat or domestic water and adjust boioler temp accordingly but its not out yet. Allso the hot water demand will be very marginal as it is just an office building it has one shower but will probably only be used if one of the Architects owners gets lucky, in hind sight I probably should have gone with an electric water heater to keep it simple. My other question is on a modulating boiler how important is the flow since it fires down by sensing supply and return water.Any good ideas on a piping scm.or controls or how I could kick the boiler temp. up and down between heating and domestic water heating I could use the help I've over thought this one. Thanks For Any Tips Possibly I should take anouther trip to Central America the heating down there is beautifully simplistic. The Nose

heretic

New HTP controls

Just an FYI:
I was recently told by HTP that the nifty new "925" control board that would solve your 'mixed temp' dilemma right at the source has been delayed due to redesign work.
They were not willing to commit to a new date.

Larry Ticknor

I'm no expert

I don't know of an easy way to kick the Munchkin temp up and down. HTP told me a couple times it couldn't be done.

If you go off the wall to "books and more" and check out "bright ideas" number 97 asks the question how to control low temp radiant and domestic hot water with a condensing boiler. Check it out, it may help.

Larry

James_2

Munchkin

I have designed several jobs with Munchkins and used Tekmar boiler controls with good results. I like using 4-way valves and turn off the boiler protection feature. The boiler modulates which helps to match input to load based on inlet/outlet temperature as well as setpoint. Depending on DHW demand, boiler sizing, and radiant load the system will still be very efficient(min. 92%). The Tekmar will help even out boiler cycles and some setpoint setback is possible even if the boiler aquastat is set at 180. The 4-way valve will operate at maximum flow since boiler protection is not an issue you will get low temperature back to the boiler (maximizing efficiency) during high load demands. I like turning off the priority feature and allowing the lower temperature water returned from the DHW indirect to be used in the mix. Eventually the Super-Stor Vision system will make the highest efficiency easy to obtain. Run your Munchkin set point as low as possible to satisfy the system demand. Running at 180 is not always necessary. System sizing and system design is more important that boiler efficiency. Oversizing is still the biggest waste of energy. Modulation and load matching is still the best way to save $$$$

Bigheadtodd

Hey nose

could you clarify for me what you meant when you said " if one of the architects get lucky they will need a shower?".

BHT