Too much water?

EBEBRATT-Ed

Maybe constant circulation and insulation wil help. Do they get domestic hot water off this ?? Tankless heater??
I have seen jobs with a tankless and large water content constantly hitting low limit and shutting off circulators causing high fuel bills==just an idea.

Ed

Don \"Grumpy\" Walsh

Too much water

I was called in on a baseboard system that has very high fuel bills for the amount of conditioned space. The house is 25 years old, well insulated and with good windows. It has a SlantFin 95,000btuh boiler in good repair. The problem that I see is with the method it is piped. This boiler in in a garage mechanical room, it is an eight zone(valves) system and all the piping is homerun style from the boiler room to each zone. I think there is a lot of wasted heat being produced that never gets used in the intended zone. I have proposed a re-pipe down to 3 zones (1st, 2nd, and family room) and the installation of a new Munchkin centrally located in the basement area of the house. What are your thoughts? Is all this idle water being heated over and over causing high fuel consumption with little benefit to the heated space? My customer seems to feel the re-pipe is unnecessary. What do you think?

Brad White_11

How much

of the homerun piping is in the (presumed unheated) garage and how much of that is insulated to what degree, Grumpy? Basically if most of the piping goes into the heated house pretty quickly, it at least benefits the house as a whole, but perhaps not the zone that is calling.

I would have to assess what the measure of the worst case might be and see if that makes sense. Here is a quick take with assumptions noted:

Say the piping for any circuit is 3/4 inch, uninsulated and is in an ambient temperature of 40 degrees. 180 degree water, 2 gpm flow: Every ten feet of pipe will lose 700 BTU's per hour (and about 0.7 degrees over that length). The return circuit if at 160 degree water will lose about 580 BTUH for every 10 feet of pipe. 1280 BTUH loss per zone/circuit.

So if you have 20 feet exposed HWS &R for each of eight circuits (160 feet total!??) you would be losing about 10,200 BTUH to the atmosphere or at least not to the house nor respective zone.

If you insulated this pipe with one-inch fiberglass you would knock this down to about 1,900 BTUH. If you used 3/4" Armaflex you would knock this down to about 2,400 BTUH. If truly in a cold ambient I would not be shy about doubling the thicknesses or boxing them in. If they are not currently a concern about freezing, that is an indicator of the degree of loss.

Essentially, yes, it is a measurable amount of uneccesary heat loss but does not seem like a huge percentage of the total. (Not like 30% is being lost before it reaches the house).

As for using a condensing boiler is the radiation generously sized relative to heat loss to work better with lower water temperatures? Just another thought.

Don \"Grumpy\" Walsh

Virtually non of the piping is exposed to "cold" areas. It leaves the boiler room and then travels under the family room floor to the main part of the house. The family room is over an insulated crawl space, so no real heat loss there to be concerned with, but some of the runs are as long as 120' of uninsulated pipe in the basement of the house.

The baseboard is wall to wall element. The system has been running at 160 degree supply and the rooms do heat well. The problem is the delta t on the long runs will approach 40 degrees when the zone first calls for heat. That moderates to a 20 degree delta in about 3 minutes, but that is what causes me to think they are heating a heck of a lot of water that will lay idle once the zone is satisfied. Yes the residual heat is being used to heat the basement, but maybe it should just be piped on a zone by itself for efficiency. I also do not like the fact that the end switches on the zone valves are wired to fire the boiler on each call for heat. I am more inclined to find a method of repiping for constant circulation with outdoor reset. Either way, the pipes will all be insulated in the immediate future.

Tundra

It sounds as if you are already planning on insulating the pipes, good. What is the heat load of the home? If you can put in a smaller boiler that will save energy. The munchkin is a cold start boiler, good. I would change the tree and I prefer circulator zoning. If they turn down unused zones that will help, especially with so many areas to isolate. Have you considered potential problems with the envelope?

Brad White_11

Sounds like

it would not be worth re-piping to reduct the # of zones but should be worth it to make it constant circulation with OD reset. Insulating in my opinion is always a good call even indoors. Put heat only where you want it as much as you can.

The 3-minute warm-up to drop the delta-T from 40 to 20 sounds entirely normal. 120 feet of 3/4" pipe would hold about 2.75 gallons or about 23 lbs. of water (times degrees per hour equals BTU's) so there is a benchmark.

Constant flow with OD reset makes abundant sense if you protect the boiler with primary/secondary and boiler offset above the radiation loop temperature (any means or method). With this means, although the "losses" will be more constant, the insulation will help. And it stays in the house for the most part too.

Weezbo

Grumpy,

as there is alot of heat being released to the garage as it is now, i would wonder what type of heat the garage has at present. is it a small modine or beacon morris? the other question that comes to mind is the fill water piping and or water main ,water filter,softener or laundry sink.... perhaps it wouldnt be a good idea to lose the heat plant and the "periheral" heating benifits of the existing piping..if there were no potblae water supply lines or untreated water lines to an outside hose bib...then you would likely benifit 12000 to 20000 btu,s by relocation of the boiler and bagging off the associated piping. if there is a need for heat in the garage (no radiant slab,unit heater) then something would have to be done to replace that heat right.if you use the new modulating condesing boilers there isnt a lot of jacket losses as with older strong pieces of iron. so you might consider tweaking in some convectors to the space you have intended for its "home". location of the headers and the like are purely what Works for you and what would be considerate if you had to trouble shoot or service the boiler for the homeowner.

thats some of my pain in the perspective. you probably already thought all this stuff already so just look at it like a second to your thought.