| Author | Message | ||
| Phil Smith (Phil_smith)
Registered Member Username: Phil_smith Post Number: 24 Registered: 3-2006 Posted From: 24.117.40.105 Rating: N/A |
This summer I installed a webasto in my bus. After making a few changes as I went along, I finally settled on the current layout and configuration. So now, the playing part.. I live in Prescott Az - alt - 5300 ft.- now it's getting cold enough to see how this thing performs. This morning I checked the inside temp of the bus and it was 33 deg. ( not living in the bus - it's in the backyard ).. anyway, here's what I'm doing.. I turn on the webasto to see how much it warms the interior in 30 min. - 45 min. - 1 hour. etc. I've done this a few mornings ago and did not write anything down, but it seems that after 45 mins. the temp got up to 56 degs from starting at 34 degs. Has anyone else done any testing like this? Or am I just weird and have to much ( morning time ) on my hands?. | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 22 Registered: 7-2006 Posted From: 4.240.144.184 Rating: N/A |
Interesting study, Phil...it seems to me that it would depend somewhat on how many heat exchangers you have running and whether or not it is a continuous run, or cycle as the Webasto does, and the thermostat settings. Also whether or not you are heating your engine, etc, etc. The longer the run, the more appliances it has to go thru will also make a big difference. My exchangers are not set by thermostat and are manually turned on at my discretion. I usually let the Webasto do it's thing till I know the fluid is hot, then turn on the exchangers fans. At the price of today's diesel fuel I usually do a run up prior to a trip to see that all is functioning as it should and let it go at that. FWIW  RCB | ||
| Phil Smith (Phil_smith)
Registered Member Username: Phil_smith Post Number: 25 Registered: 3-2006 Posted From: 24.117.40.105 Rating: N/A |
R.C. I totally agree. It completely depends on all those variables and I'd bet that every Webasto installation is different in many ways. I'm just trying things out to see if I can get more efficiency out of MY setup. It's not too late to make changes if I see it's weak in certain areas. Just having a little fun and getting to know it. My general setup is with Two fan-coil units feeding ductwork in two zones ( front and rear ). 3-speed fans and separate thermostats for each zone. Also with some ball valves in the engine area, I can pre-heat the engine only or include it with the house heat or house heat only.. just trying keep it fun.. and by the way, it's now been running for 1.5 hours and the interior is up to 58 degs. | ||
| Ross Carlisle (Rrc62)
Registered Member Username: Rrc62 Post Number: 154 Registered: 5-2005 Posted From: 67.142.130.16 Rating: N/A |
Something doesn't sound right. Sure you don't have a window open. I have a 40K Suburban propane furnace and it takes less than 15 minutes from below freezing to 70 degrees. I'm installing a 45K Proheat soon and I'm using radiant baseboards. You might be losing a lot in the ductwork. Those fan units are not really designed to feed long ductwork. Too much air resistance there. How may BTU are the fan units rated for? If each one can only shed 5000BTU then thats all you'll get for heat regardless of the size of the Webasto. Ross | ||
| Phil Smith (Phil_smith)
Registered Member Username: Phil_smith Post Number: 26 Registered: 3-2006 Posted From: 24.117.40.105 Rating: N/A |
Just a comment on what I observed... To you engineering types... Shouldn't the air-handlers be able to Shed the same or greater amount of heat than the webasto can create ( and transfer to the air-handlers ) ? Mine does not ! With all my fan-coils on High -- the burner will still get to ( 167 deg ) and then cycle off.. Phil (Message edited by Phil_Smith on October 28, 2006) | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 30 Registered: 8-2006 Posted From: 207.231.80.150 Rating: N/A |
Good evening, Phil, Will you settle for an air conditioning contractor type that does a whole lot of hydronic heating? I design a house heating system with air handlers large enough to heat the house in cold weather, then buy a water heater large enough to supply hot water to the air handlers. There will always be one limiting factor in a hydronic transfer forced air heating system, (the fancy name for hot water heat) that will be either the air handlers, or the water heater. Without knowing what size of Webasto you have, or what size air handlers, or if your bus is insulated, or the plumbing layout and pump size, it SOUNDS like the air handler portion of your system is under sized... Since the Webasto cycles on high limit, you can increase output by adding air handlers. IF the Webasto never shut off, then you would need a larger one, which would be expensive! I hope your air handlers are plumbed in parallel? HTH | ||
| Phil Smith (Phil_smith)
Registered Member Username: Phil_smith Post Number: 27 Registered: 3-2006 Posted From: 24.117.40.105 Rating: N/A |
Good morning George, Here's the short version of what I've got. Webasto 45Kbtu- (2)- 28kbtu air handlers w/3sp fans with short <8Ft ducts/ea. and in parallel. Lots of good air-flo.. I think my tubing dia in my entire loop is too small - I'm using 3/4 PEX - inside dia is 5/8" at best and I think it's too small and restricting the whole system. I'm going to change the size to 1" PEX ( id - 13/16") and change any of the fittings that would be restrictive for the new size. What do you think? Here's more: bus insulated, pump is 15-20 gpm, parallel loop, using engine coolant ( not Heat Ex )but isolated from wasting heat in the engine with ball valves ( various added plumbing in engine comp to choose - house heat only - engine pre-heat only or house and engine together ). At least I used the larger fittings and valves in the engine area so the change to 1" PEX for the loop won't be as traumatic ! Phil | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 31 Registered: 8-2006 Posted From: 207.231.80.150 Rating: N/A |
Good morning Phil, I think you may have the diagnosis! A couple of other thoughts are, maybe water flow backwards through the air handlers? The hot water MUST go in the OUTLET-DOWNSTREAM (air) side of the air handler. This way the hottest water is exposed to the warmest air. If the water flow is the other way, the hot water is exposed to the coldest air first, and loses a lot of heat. In the next coil row, the water is cooler, the air warmer, and not much heat transfer takes place, and so on. Can you take temperature readings of the air temperature in and out of the air handlers? 160+ water temp. is real exciting to a hydronic heating person, and should produce a delta t (another fancy term for temperature rise) of about 50 degrees with proper water flow. Your pump size is fine, and a thought would be to enlarge the pipe to the tee between the two air handlers, if that's the way the system is built. FWIW, residential air handlers for four tons of cooling with a four row heating coil are rated 68,000BTU net output @140 degree entering water, and 70 degree entering air, with a 3/4" copper pipe. As the entering air temperature DECREASES, and/or the entering water temp. INCREASES, the output increases. So, at 33 entering air, and 167 entering water, your net output SHOULD be about 40,000 each, and the Webasto should never stop. Also, the combustion efficiency of Webastos, and most other types of RV heaters is only about 80%. This means that the Webasto's net output is 36,000. So, if it cycles, you're not getting 36,000 out into your bus. As you have told us "good air flow," I feel you don't have 'good water flow'! Note Ross's post above, 32,000 net+-, and what it does. We do need to consider heat loss, however. A 40 X 102 is going to need a whole lot more heat than a 35 X 96, before we count windows!!! Further questions by e are welcome! George toddelec@psyber.com | ||
| Phil Smith (Phil_smith)
Registered Member Username: Phil_smith Post Number: 28 Registered: 3-2006 Posted From: 24.117.40.105 Rating: N/A |
George, I did a quickee test to see if I was close... I started the webasto and turned off the fans to let the water heat up in the loop ( house heat only ) to what I thought was max. temp.. 5 minutes or so.. then I turned on the fans to HIGH and felt the air temp output.. I observed that, at first, the temp was very hot and seemed adequate... then the air temp started dropping very noticebly to warm... I concluded that the air-handlers were capable, but there was inadequate hot water going thru them.. kinda of a backyard mechanic way to do things, but I don't have one of those IR temp guns ( might get one soon.).. Anyway, that's what I thought might be happening considering what I know about physics(little) and what I've read here and there. | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 32 Registered: 8-2006 Posted From: 207.231.80.150 Rating: N/A |
Afternoon Phil, Once again, I think you have it! An easy way to confirm is to fire up the Webasto and bring the water temp up. Then turn on the fans, and when things start to cool off, CAREFULLY feel a metal part of an inlet water line to an air handler. It should be REAL hot. Then feel an outlet connection. If the water flow is low, the outlet will be cool. If Webasto output is low, or the air handlers are out-running the Web, the inlet won't be real hot. If it is a low air flow issue, inlet line will be real hot, outlet line will be fairly hot. Your system, operating normally, should have a fairly hot inlet line, a cool at first, then 'warm' outlet line, and the Web should run all the time both air handlers are on, and cycle with one a/h on. Another thought is antifreeze percentage. Antifreeze doesn't absorb or dissipate heat as well as water does. If you're protected to minus 20 or something, 60% glycol?, that MAY be some of the problem. Consider adding water to plus 5 or 10? Don't apologize for "backyard" either, I have an IR gun, but I would put my hands on pipes first, the gun is last resort, but very necessary for refrigeration! | ||
| Phil Smith (Phil_smith)
Registered Member Username: Phil_smith Post Number: 29 Registered: 3-2006 Posted From: 24.117.40.105 Rating: N/A |
George good afternoon, Well just got back from Lowe's with the 1" PEX and fittings. Next week after Halloween and the grandkids, I'll take a day and get the loop changed up to the air handler T's with the 1". In the meantime, I'll try those suggested tests and see what I find.. Seems to me, my antifreeze is at 40%, I'll check into that as well. I really appreciate your input and expertise on this.. Very helpful. Thanks, Phil | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 24 Registered: 7-2006 Posted From: 4.240.144.76 Rating: N/A |
Very interesting and helpful discussion between you two...wish there was more of this kind of thing on this board. George, the Webasto, as you may already know, is designed to cycle off when the fluid temp going thru the boiler reaches a certain level. (forgotten what that is, but I was thinking lower than 167) so it is normal that once the level is met at that point, it would cycle off; conversely when the temp drops below that level, it cycles on. Mine operates pretty much within that framework. I think you have, however hit a couple of big key factors. The amount of glycol in the lines makes a big difference. Also as you pointed out, the amount of glass, which allows much much quicker cooling in the length of the bus. Mine has not only large front and a large rear window, but several original sliders of full length...69 inches, as I recall, plus others that are not quite as large. This , of course makes a huge difference in the way the coach cools as well as heats. I have often wondered if the very small heat exchangers proposed by Webasto might be a consideration (as opposed to longer types) thereby condensing to more, perhaps smaller areas, each controlled by a thermostat. Our coash has one inch lines throughout and it doesn't take long for each exchanger to begin to provide good amounts of heat. Another thought, Phil...I had an air bleed situation this past spring when I relocated the Webasto. It about drove me nuts...not at the Webasto, but in consistent heating at the various exchangers. I now run engine at 1500rpm, turn all bleeds when I check fluid level a couple of times a year. Drain into containers until a stream is flowing, not just bubbling). My guess is It required up to 4 gallons of antifreeze running thru the bleeds to get it resolved. Poured it all back in, of course, plus a bit to make up for the air. My system runs thru the engine and I usually do not exclude it when checking the system. That way all the things that can go wrong are included in the "check". FWIW... Thanx for the thread.! RCB '64 Crown Supercoach (HWC) | ||
| George M. Todd (George_mc6)
Registered Member Username: George_mc6 Post Number: 33 Registered: 8-2006 Posted From: 207.231.80.150 Rating: N/A |
Good evening RC, Thanks for the thanks! When we put our heads together, we can make things work! Everybody on this thread has said the same thing in different ways.... Phil posted in the middle that his Web cycled, which can only mean that it can't get rid of all the heat it generates. Now we have to figure out why. Phil has also said "good air flow," so we rule that out. I think all that is left is low water flow, as his last post says 40% glycol, which shouldn't cause this problem? (I'm spoiled, I work with potable water.) I'm also having a problem with 3/4 pex being the problem, as one brand of air handler I use has 1/2 copper connections up to almost 60,000BTU. Granted, we use 3/4 copper or pex beyond it, so there's only about 3 feet of 1/2 in the unit, but. So do we tell Phil to hurry and not burn his fingers because we want to find out what the problem was? Aerated glycol is a DEFINITE possibility!!! Anyhow, thanks again, I appreciate the warm fuzzy, George. | ||
| Phil Smith (Phil_smith)
Registered Member Username: Phil_smith Post Number: 30 Registered: 3-2006 Posted From: 24.117.40.105 Rating: N/A |
George & RC, This morning, while it was still 40's inside the bus, I used a basic thermometer( I'm going to get a good one today )and measured the output air from the air handlers. I tried various combinations of fan speed ( bath on High while Liv Rm on Low for example - both on High - both Low -etc.) and found that the output air temp was between 50 and 60 deg C. The input air was lower than the thermometer could measure accurately ( scale problem ). I did notice that the air was about 9 deg C Higher when the Fan was on Low speed. Also noticed that the highest air temp on any setting was 60 deg C for both A/H's. I'm wondering if a lower fan speed is better to heat the bus from Cold - than High speed is?... I should mention that once the bus is up to 70 deg F -comfort zone for me, the system works fine and maintains this without issue all night ( I got up in the middle of night to check it out once ! )..outside temp was 30's.. I might be nitpickin this thing, but this is a hobby and I enjoy squeezing the best out of it. I want the webasto system to work the best it can.. so bare with me.. AND I haven't opened the 1" PEX or the fittings yet and will return them if not needed.. further testing coming soon. Phil | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1725 Registered: 1-2001 Posted From: 75.108.82.163 Rating: N/A |
I think the main point now is if the Webasto is cycling off and back on before the vehicle gets up to temperature. If this is happening, then you are not getting out all the heat the Webasto is capable of producing and you need to increase water flow to do this. Or increase the number of radiators, or both. Richard | ||
| Tom Hamrick (Tomhamrick)
Registered Member Username: Tomhamrick Post Number: 69 Registered: 12-2000 Posted From: 167.83.101.23 Rating: N/A |
When I first installed my Webasto, it was as if the boiler could not keep the water hot enough for the heaters. I could not get the bus warm at all. What I did was to install a 12 gallon electric water heater from Lowes that has 4 connections on it. I plumbed the output from the Webasto to one of the top connections of the Lowes heater and the return to the Webasto to the bottom connection of the Lowes heater. I then connected the input of the loop to my heat exchanger to the other bottom connection on the Lowes heater with the return from this loop connected to the remaining top connector. Having this 12 gallon resevoir of hot water makes a huge difference. If I have not explained this well what I have is two loops into the 12 gallon Lowes heater, one from the Webasto that keeps the water hot and the second loop feeding my heat exchanger to warm the bus. We used our Eagle last February in 19 degree weather and were nice and toasty. Tom Hamrick 1984 Eagle 10S | ||
| Richard Bowyer (Drivingmisslazy)
Registered Member Username: Drivingmisslazy Post Number: 1728 Registered: 1-2001 Posted From: 75.108.82.163 Rating: N/A |
WOW. I can not imagine a 40,000 Webasto not providing enough heat to keep a bus warm. I know that mine had no trouble at all keeping me toasty even below 20 degree nights. And it cycled on and off, even at that temperature. I would strongly suspect a problem of some kind with the heater. Richard | ||
| Robert Fischer (Rbt137)
Registered Member Username: Rbt137 Post Number: 3 Registered: 7-2006 Posted From: 71.111.85.88 Rating: N/A |
I have the 2010 (I think) webasto rated at approximately 40K btu. I have two 30k btu heater cores, located at each end of the coach. I am regularly in the mountains during the winters. I am of the opinion that 45 minutes to warm up from a cold start is not unreasonable. depending upon fan speed, the webasto may or may not cycle off during that warmup period. The heater cores are coupled to 53 volt, 415 CFM blowers (obtained from surpluscenter.com). Depending upon the amount of noise I'm willing to tolerate, I can really push air through those cores. With the exception of the windshield, all windows are dual pane. Of course, depending upon the weather, ontime for the webasto (maintaining a heated condition) is eight minutes with a 20 minute off for each heating request. | ||
| Robert Fischer (Rbt137)
Registered Member Username: Rbt137 Post Number: 4 Registered: 7-2006 Posted From: 71.111.85.88 Rating: N/A |
One other thing. I regularly move from sea level to 5000 ft of elevation. In consultation with the OEM, when at elevation, due to excess soot in the exhaust, I change the air setting for the webasto. When using an IR temperature gizmo, I regularly see exhaust tube temperatures of 250 some degrees. I am currently plumbing in a pyrometer and an oxygen sensor into the exhaust tube to monitor this stuff. FWIW | ||
| Phil Smith (Phil_smith)
Registered Member Username: Phil_smith Post Number: 31 Registered: 3-2006 Posted From: 24.117.40.105 Rating: N/A |
Robert, That's very interesting. I'm thinking my air-adj. is fine because I see no smoke in the exhaust at this alt- 5300 ft. Maybe if I went skiing or up to a higher alt., it may smoke some. Just a guess though. I do remember a post quite awhile back (yrs or?) that a fellow with an Eagle went on a ski trip and dumped a bunch of soot on the ground when at a high alt... I don't remember the remedy or cause.. Phil | ||
| Jack Gregg (Jackinkc)
Registered Member Username: Jackinkc Post Number: 90 Registered: 8-2003 Posted From: 72.129.232.62 Rating: N/A |
I am replacing my 20-year-old Webasto with an aqua-hot. The heat in the aqua-hot comes from a Webasto. The aqua-hot installation instructions say to use only wide sweeping curves in the hot water run. I am sure sharp curves and Ts could be overcome by a more powerful pump but water constrictions are a consideration. The old system had several baseboard passive radiators. Basically these radiators are straight sections ¾ copper pipe with fins mechanically attached to the outside. I plan to route the water through these radiators on the way to the fan-driven air boxes. In the future, I will put in one of the rich-folks towel heaters too. FWIW Jack (Message edited by JackInKC on November 01, 2006) | ||
| Tim Strommen (Tim_strommen)
Registered Member Username: Tim_strommen Post Number: 244 Registered: 11-2004 Posted From: 64.186.173.26 Rating: N/A |
A while ago I created an MS Excel spreadsheet for heat loss (or negative loss) for 'yall. A fellow BusNut Jim Behr was nice enough to host the zip file on his webpage. Looks like the link to file is still okay: HeatCalc V2 I tuned it for busses but it could be used for other structures. It accounts for inter-"zone" temperatures and internal occupacy and power consumption.  It's really eye opening how quickly a large single pane window will dump heat outside your rig . Cheers! -Tim | ||
| Robert Fischer (Rbt137)
Registered Member Username: Rbt137 Post Number: 5 Registered: 7-2006 Posted From: 71.111.85.88 Rating: N/A |
One other additional comment: currently I have a single March magnetic coupled pump in the heating curcuit. Occassionally (something less than 5% of the time) the March pump will stall. Under such circumstances, the Webasto will heat up to temperature and shutoff. The pump remains in the stall condition because it sees a continous request for heat. Recycling the heater system is all that is required but you have to be there to do that. These circumstances suggest that the 50' loop is a bit much for a single pump. I am currently building a 6' heat exchanger which will provide additional exposure of coolant and hot water to exhaust gases of the webasto and the generator. When the "proof of concept" is tested next year, the 2nd March pump used for the "stand alone" test for the 6' heat exchanger will then be installed in the return line and should over come the minor stall problem. | ||
| joe padberg (Joemc7ab)
Registered Member Username: Joemc7ab Post Number: 41 Registered: 6-2004 Posted From: 66.38.159.33 Rating: N/A |
Robert Is your 50 ft heating loop using 3/4 inch piping and sharp corners and Ts ? Would like to know the details, as restriction to flow might be the cause of your pump stalling. Which # March pump are using? Acquired about 120 ft of 1 1/4 inch heatfin tubing recently. Joe. | ||
| Robert Fischer (Rbt137)
Registered Member Username: Rbt137 Post Number: 6 Registered: 7-2006 Posted From: 71.111.85.88 Rating: N/A |
Joe, the March pump is "809brhs" which is a 24V motor attached to a bronze housing which houses the magnetic impeller. Coolant circulates through 3/4 inch heater hose. While there are some 90 degree turns, it is something I'll have to live with for the short term. At the present time, the house heating circuit has its own loop seperate from the OEM (GM) coolant scheme. Currently, the building and testing of the heat exchanger, if successful, time permitting, will be plumbed into the existing loop with a seperate pump. Much of this setup will be changed next year. All of these house heating components (including the heat exchanger) will be migrated onto the OEM heating circuit. Currently, in a cold start situation (<30 degrees) I have to sink two to three hours of heat (electrical) into the 8V92. When the Webasto & the gen set are moved to the OEM coolant circuit, excess heat (or any heat at all) can then be dumped into the 8V92 eliminating that two to three hour electrical heating event. Keep in mind that adding a "three pass" (read many right angles) six foot heat exchanger will greatly increase the available heat to circulate, the theory being to reduce fuel consumption with a higher over all efficency rate. As this system currently sits, it does very well. The occasional (oops; dictionary under many books) stall is a very minor problem. The bigger problem is how complicated this system is to operate. There is much to be said for the KISS system and there is nothing KISS about this. Keep in mind, there is nothing simple about subsisting in the snow zone either. Know what your doing or it can get pretty cold pretty fast. Oh, one other thing about this heat exchanger. It has two basic modes of operation. In the house mode, it continues to heat coolant and hot water. In the transit mode, it will use hot coolant from the 8V92 to heat hot water. Again, this is complicated and the first thing to be sacrificed is "KISS". | ||
| joe padberg (Joemc7ab)
Registered Member Username: Joemc7ab Post Number: 42 Registered: 6-2004 Posted From: 66.38.159.33 Rating: N/A |
Robert Had hydronic heat on the brain when I woke up this morning. So I double checked some Bell&Gossett literature in my binder and in their baseboard rules of thumb for a 40000 btu heat load, using 3/4 inch piping they recommend a flow rate of 4 gallons per min. Could it be, that your pump you have been using 7.5 GPM is too large in your particular installation ? And that its little brother might be more suitable? And also your plan of a second pump installed during your revision might not be necessary? Hope I am giving you some food for thought. Joe. | ||
| Robert Fischer (Rbt137)
Registered Member Username: Rbt137 Post Number: 7 Registered: 7-2006 Posted From: 71.111.85.88 Rating: N/A |
Well, I wouldn't argue. In fact, before I plumb in the heat exchanger, I'll install the second pump. If your suggestion holds water, the stalls should substantially increase. In thinking about this, It seems to me that the instantaneous application of 24 volts and the rapid spin up of the motor working against the inertial resistance of the coolant is probably the better area to examine. If the coolant provides enough resistance, and the motor spins up fast enough, the magnetic lines of force decouple from the rotor and thus the stall. I could probably build a device that would ramp up the voltage over five or ten seconds which would then allow the coolant to catch up with the power/voltage curve. NAAAAAAA. too easy to reset the system. |