Munchkin Help!!!

Dave_13

I can't believe the Munchkin Man or any other HTP haven't piped up here.... It seems like they are always responding to Munchkin questions. What gives??????

Dave_13

Munchkin!!!

Went to look at my friends 2yr. old Munchkin yesterday. He was having a problem with the air proving switch. When I was there I noticed this thing was short cycling like mad. It has 3 zone valves off 1 Taco 007 (F5) pump, (6 runs total off the 3 zones). It also has a Tekmar 260 with outdoor reset. Only 1 zone was calling for heat and I believe that the flow through the Munchkin was so slow that even on low fire the boiler would overheat and shutdown. The water was getting up over 180 before it would shutdown. So it was on for about 30 sec. off 30 sec. If it is flow, is there a way to fix it without ripping it out and going prim/sec.???? Thanks a bunch.

Bryan_16

nope

only way to get proper flow is p/s. Good luck.

Troy_3

Pres. bypass valve

Install a pres. bypass valve. When only one zone is running some of the water will bypass back to the return. Might be a little tricky to find the right setting if the system is small.

Dave_13

This seems like it would be the easiest solution to implement. I guess I would have to look into these valves to see if it would work. I wouldn't want it to open and "rob" all the flow from the zones. Who would make these, so I could get some information?????

mac

Pressure bypass

Oventhrop makes these along with thermostatic radiator valves (TRV's). My understanding is to set these up, you close all zones except shortest loop, with shorterst loop calling, adjust valve till you get the proper delta T or temperature drop across the loop (ex: 20*F). Once you get that you all done.

Good Luck

Dave_13

Valves....

Thank you very much- I will take a look. Any other ideas on possible ways to fix, or are these about my only options????

Dave_13

Also....

Does anyone know if we can change the length of time that the munchkin takes during it's modulation steps???? I think this is a pre-925 control. Error codes are blinking LED type. Thanks.

Bryan_16

maintence

IMHO by-pass valves are guaranteed trouble. Bellows, pressure settings, seats, anything that can happen will. You are going to have to re-pipe some of it to get the valve in anyway. Go p/s, piping and pump will be cheaper than piping and valve.

Jim Eastman

I believe that the Munchkin requires a Taco 0010 to achieve the proper flow. Could it be that the 007 isn't providing enough flow? A pressure by-pass valve (I use the Oventrop) would help, too. Primary/secondary piping: I have one Munchkin installed that has a Taco 007 on the primary (or boiler) loop with no problems, even though the 140M requires a 0010. Hope this helps.

Jim Eastman
Precision Plumbing
Boulder, CO

Dave_13

Yes

I believe that is exactly what going on. when all zones are open, your head pressure is lower and the pump moves on the curve(more flow). When only 1 zone is on, there is more head pressure and the pump again moves on the curve (less flow). But how to fix?????? Maybe a bigger pump.... I guess i need more info from him. He has 1/2 PEX...

Mark Eatherton1

Can not change step stages...

they're fixed at one minute intervals. If you have Vision 1 capability, on a call fo DHW it goes immediately to high fire, and modulates as it approaces a preset temperature.

ME

GMC

you need a primary loop

It seems to be that the the way you have your pipe c0nfigure to the boiler is not enough flow going thru the boiler. your going to need a pump just to recirculate the water thru the boiler like primary loop them, get the other zones out of the primary loop this way you would always have a good flow of water going thru the boiler. sorry to say i don't see another you can fix this problem. i had a similar problem with one that I installed. same problem as yours. and this seems to work. good lcuk

Fester Bestertester

Munchkin Help

You didn't mention whether the Munchkin was an 80M, 140M,or 199M. I'm assuming an 80M since you only have a 007 circulator on it.I also will assume that your heat emmitters are high temp baseboard since you have set the output temp of the boiler to 180*F. The use of a pressure bypass on a one circ system with an extremely low mass boiler such as the Munchkin is mandatory. But that's just one of the problems with this system. You have employed the use of a Tekmar 260 to control the boiler based on an outdoor reset curve. The 260 will ramp the supply temp up or down based on the temperature outside. However, you've fixed the output of the Munchkin at 180*F. If for example you have a warmer heating day and only one or two zones are calling for heat, the 260 may call for heat, but only need to see 160*F at the supply sensor. If the 260 wants to see a 20*F Delta-T, then it will fire the boiler at 140*F. The boiler is still trying to get to 180*F so it will most likely be running flat out. The low flow situation caused by the lack of a pressure bypass in the system, in conjunction with the burner running flat out means you've essentially got (about)73,600 BTU/HR heating a teacup full of water. The temperature of the water in the boiler will rise at an extremely fast rate. When the 260 senses that the supply temp has reached the 160*F (in this hypothetical case) that it wants to see, it shuts the boiler off. The pump should still running since there is still one or two zones calling for heat. Because the heat emitters in this case are also low mass, they tend to drop heat quickly. If these zones are at any distance from the boiler, the 260 may shut the Munchkin down before the heated water can reach the baseboards. Shortly after the control shuts the boiler down, the 260's supply sensor sees the 20*F drop and fires the boiler again. This will cause a situation where the boiler cycles excessively and sends out pulses of heated water. You will more than likely need to replace the air pressure switch in short order when this starts happening.
What I would do in this situation: Well for one I sure wouldn't use a condensing boiler on a high temp system. I bet it's only running marginally better than 85% efficient at 180*F if that. Great idea, wrong application. I'd go cast iron.
Anyway, add the differential pressure bypass to the system for sure and turf the 260. It's a wonderful control, but not for this application. Add an indirect water heater to the system to get some efficiency back. if there already is one on the system, run it off an aquastat, not the 260. Check to make sure that the condensate line isn't leaking (you put the boiler on a stand, right?)and make sure that there is water in the trap. Running the boiler at high temp may require you to keep an eye on the condensate line to make sure it does not melt at the connection.
If there is enough baseboard in the zones you may be able to drop the supply temp and get some additional eficiency points back. I'd do a room by room heatloss then count the lineal feet of baseboard (average 580btu/ft @180*F)and see if there is more than required to heat the room. If so, use manufacturer's info to plot a graph showing supply temp Vs output. Compare that to the lineal footage of baseboard in each room to come up with a common supply temperature which will adequately heat all zones. You may be able to get the boiler into a temperature range that facilitates condensation. Remember the 3 to 1 golden rule of hydronics: for every 3*F that you are able to drop the supply temperature, you get back 1%in efficiency.
Hope this helps.

Dave_13

Thanks

Yes- I probably did leave some info out. It is an 80M and all radiant- in slab and under flooring with plates. I haven't got into the 260 yet, but a quick look and it looked like the target was 130. I think the boiler shuts off first on the Munchkin high temp. switch. The 260 is still showing the call for the boiler to run and it's temp probe is a little slow to react. The boiler shuts down and when the 260's temp reading reaches 150- it turns off its boiler call. As soon as the temp. gets back to 90- it calls for the boiler again. I downloaded a Munchkin manual with sample pipng and they show a bypass valve between the supply and return. It also tells to set it to make sure that there is 3 GPM through it under worse conditions. ie- 1 zone calling for heat. Couldn't i just use a ball valve and tweek it in until i got the right flow????

Mark Eatherton1

I spect...

they're swamped and haven't got time to hang at the Wall...

Between the new T series and their new 399, they're working day and night just trying to catch up.

ME

Fester Bestertester

Munckin Bypass

Using a a ball valve for a bypass is like trying to do needlepoint with a baseball bat. Spend a few more dollars and get the job done right. If you use a ball valve in place of a pressure bypass, you may get proper flow through the boiler when most of the zones are shut down, but will you have proper flow throughout the zones when they all open up? Maybe but I doubt it. A proper differential pressure bypass valve will open and close proportional to the pressure difference accross the inlet and outlet ports. Simplified, as the zones close, the bypass valve will open, and conversely, as the zones open, the bypass valve will close. This will keep both the boiler and the zones happy. Set the valve up so that when the zone valves are all open, you get a very small amount of water bypassing the system through it, and that's it. A 3/4 honewell D146M should work fine. Also, make sure your circulator can handle the pressure drop of the boiler and the system added together. If not better go to a 008F Taco. I'd still turf the 260, you can use it someplace else. If your customer has the cake, get him the 925 control and retrofit the boiler. Good luck.

Dave_13

So....

Do these valves modulate??? Will they let only a small amount of water through once they get over there setting- and more the higher the differential pressure??? I would think they would have to or they could continually open and close.... Any help?????

Mike T., Swampeast MO

Yes, they vary the amount of water flowing through the bypass.

If the differential pressure setting 3psi for instance whatever amount of water is required to MAINTAIN that differential of 3psi will flow through the bypass.