HWBB boiler choice?

Ross_7

What's wrong with the MCBA controller? Seems to work just with every application I've seen. Including my own TT.

Timco

Is a Munchkin or Triangle or even a Crown 94% unit the best choice for HWBB? It is the CI BB, not the fin type. Nat gas system. Will perform heatloss when I get the job, first need to write proposal. My guess is around 140K btuh...

Tim

Brad White

TT

would be my choice of the three but the real answer is, how much radiation do you have relative to heat loss and what is the maximum normal operating temperature that the boiler can develop?

The type of radiation does not matter as much as some people think so long as there is enough of it. That it is CIBB is all the better as it has a larger radiant component than convective fin-tube.

EVEN if you have the radiation sized dead-nuts to the heat loss, so long as your boiler can generate the temperature to which you sized the radiation, any boiler will work.

Key point is that you have to use outdoor reset and apply it correctly to create a proper curve. Even if it was sized for 180 F. HWS water, there are enough hours in temperate climates that allow operation of the boiler, on reset, to be in the condensing range.

Aidan (UK)

Prestige

Is a great product, 439 SS, vertical design, self cleaning heat exchanger, with I believe the highest water content all and lowest head loss of all the modcons. It uses the MCBA logic board - same as Weil McClain, Burnham, Dunkirk, & Utica. Extremely easy to access all internal parts, swing out control panel.

You can pump straight through if you want and not use a primary secondary system. Keep in mind, the efficiencies you will see are a function of the temperature and delta T you run the system at. The unit is very simple if you were to look under the hood.

We've been selling them for almost 3 years now. Had only a fan go bad. Highly recomend.

Floyd_44

WM Ultra....

Look for the series three, coming soon... and No More MCBA... but a much better control with way more possibilities....

Floyd

Timco

So is ODR a real must with the mod / cons? I have been really pricing the units to sell them, and it looks like I may have yet another shot at selling one, but have been installing 83% units as well as mini-therms. This would be the first mod/con unit. We have a few weeks a year with nothing over 30*, and design temp is 0*, 180* water. I am also learning that unless the flow rates of the system are diffeent than the boiler, direct return with no bypass is the piping method of choice?

Good to see you posting again, Brad! I did not see your name for a while there, but maybe I am not the most observent guy around...

Tim

Floyd_44

Sounds to me like your...

selling, or thinking like you need to sell on price, only...
May I suggest that you forget about competeing on price and sell the many benifits of modern hi-eff. mod. con. boilers....more money for you and happier customers...
Have sold only one boiler that wasn't a mod con in the last four or five years, and that was to a retired old Gent. that figgered he wasn't going to have to pay the gas bills for long anyway....

Floyd

Tom Hopkins

sell green

Your customers will have a greener solution and fork out the less of the green stuff for fuel if you sell them on both green aspects. It's the right thing to do, the technology is just too good to pass up for being only 83% when you could be conserving far more resources. BTW, the savings difference as a percentage is way more then the condensing boiler's efficiency - 83%. Few customers might understand that. Perhaps you pros here with clout could get a better rating system for combustion heating devices sold here in North America or eben simpler just adopt the same rating standards as Europe.

Brad White

Hey Tim

Sorry to be so sporadic but thanks for the sentiment. Back from a busy patch after vacation and it is still busy. Doing what I can do. I will also respond to your off-line e-mail soon. Thanks for that.

My ideal setup with any boiler is to use outdoor reset and with a ModCon there is no better way to promote more condensing in the shoulder-seasons. The Brookhaven National Lab study pretty well made that clear. I assume you are connecting to existing radiation, therefore the high design temperature is dictated for you? Do check it against the heat loss and maybe you will find a surplus allowing some lower design hot water temperatures.

For piping, only if you have a high internal pressure drop would I go Primary-Secondary. In fact, if you have but one heating zone and there is sufficient residual head from the primary circulator to take care of your radiation, I would hook it up directly.

If I just HAD to go P/S, I would set it up with a low-loss header such that the boiler flow is a bit less than the radiation flow. In this way the coldest water from the radiation goes back to the boiler.

If the reverse was true (more boiler flow than radiation), the boiler return would be warmed up by the excess boiler supply flow being passed to the return. Ideally, all hot water in any system should pass through a radiator/emitter before going back to the boiler. An exception would be return water protection in a cast iron boiler.

You can see the paradox of P/S flow here with the ModCons- on the radiation side you want a wider delta-T (to save pump Watts and to extract more heat) and this lower flow "fights" the desire to have lower boiler-side flow. This is why I like variable primary and variable secondary circulators....another topic.

Timco

Well, these two jobs that mod cons are possibilities on are both 4-zone jobs and one is a 4-plex where the owner wants a new boiler, but not the added $$ of the install price. Funny how income property owners get. I can see how a LLH would work well with multiple zones, and how direct ret would work with one zone. As I mentioned, this would be the first mod con and I have not seen the piping diagrams yet..

Thanks a million, Tim

Brendan_4

Brad If you hook it up directly which is best for condensing purposes to an 80K boiler you will have to provide pipeing large enough to carry 8gpm around the emitters. will this call for a larger pump or how does one assertain the headloss of their emitter circuit?

Thanks Brendan

Brad White

Brendan

That could be a long answer but I can offer this as a general guide:

If your original system you are connecting to was an older gravity HW system, chances are your system head loss will be negligible. You may have less than a foot of head and in fact, gravity flow itself may be stronger than the circulator has available to you. That is the ideal, very little head.

If your flow requirements are, say, 8 GPM, that might call for a 1" pipe size although I am conservative and would use 1.25" pipe size for that flow rate. Now, say you ran 6 GPM or your piping was restrictive that it balanced out at 6 GPM. No big deal, really!

Instead of running 8.0 GPM at a 20 degree drop (say 140 out and 120 return), you run 6.0 GPM at a 26.7 degree drop.

Your average water temperature (where it all happens), drops from 130 degrees to 126.65 degrees. Yawn.

You will still get practically 95 percent of your capacity. Cut your flow in half you will get 90% capacity from your radiators.

To figure piping only as a rule of thumb, take your total length or piping, round-trip, in feet. Multiply that by 1.5 (adds 50% for fittings). Multiply that by 0.04 (assumes 0.40 feet of head loss per 100 equivalent feet of pipe, doubtful but conservative).

Say you have 150 feet of pipe in your longest round-trip circuit. Not all your piping, mind you, just your longest run.

(150 x 1.5)= 225 equivalent linear feet.

225 x 0.04 = 9.0 feet of head.

Very conservative in that I usually size my piping for 2.4 feet per 100' friction loss. I would have maybe one pipe size larger and by this method my head loss would be 5.4 feet of head.