Reply
 
Thread Tools Display Modes
 
Old 02-26-2015, 10:23 AM   #31
Bus Geek
 
Join Date: Aug 2011
Location: Stony Plain Alberta Canada
Posts: 2,939
Year: 1992
Coachwork: Bluebird
Chassis: TC2000 FE
Engine: 190hp 5.9 Cummins
Rated Cap: 72
A tankless water heater WILL NOT WORK. That is what prompted me to start this thread.

I have to run to work. I will tell you why tonight.

Nat
__________________
"Don't argue with stupid people. They will just drag you down to their level, and beat you up with experience."

Patently waiting for the apocalypses to level the playing field in this physiological game of life commonly known as Civilization
nat_ster is offline   Reply With Quote
Old 02-26-2015, 08:11 PM   #32
Mini-Skoolie
 
Join Date: Jan 2014
Posts: 27
Quote:
Originally Posted by nat_ster View Post
A tankless water heater WILL NOT WORK. That is what prompted me to start this thread.

I have to run to work. I will tell you why tonight.

Nat
Good thing I asked!

I appreciate all your help, I'll look forward to your reasoning!
That Guy in Maine is offline   Reply With Quote
Old 02-27-2015, 09:44 AM   #33
Bus Nut
 
Join Date: Feb 2015
Posts: 258
We're coming out of a home where I did a DIY hydronic wood boiler and DHW setup, with a custom Raspberry-Pi controller running the thing. That means I'm super comfortable with hydronic itself and the electrical and plumbing involved, so I plan to take advantage of that in our conversion.

After toying with the thought of a wood stove (no power required, romantic look and feel) we decided to go the boiler route too. In our case I was seriously looking at the diesel "coolant heater" options that Espar and Webasto make. These are pretty cheap on eBay, they're small enough to fit in the "basement" (big advantage IMO) and it makes a lot of sense to me to use a fuel that I already have a 100-gal tank for as part of the bus.

As for heat output, I'm not worried about this. We heat our very poorly insulated 2400 sq. ft. house in CT winters (it's 9F outside right now, and the wind is blowing) full time with an ancient 100kBTU Energy-Mate wood boiler. We have to run the thing flat out to do it, but in a well-insulated 300 sq. ft. space these coolant heaters may be a good option.

For the electric backup, one thing I am NOT is a good welder. I don't trust myself to make a pressure vessel out of stainless like nat_ster, so I'm going to keep the boiler itself pretty much as-is. What I'll do is install a 20- to 30-gal domestic hot water heater in a cabinet under the master bedroom closet. I'll configure the plumbing such that the diesel boiler can heat this tank, or the electric element can be activated instead. That storage tank is an important part of a hydronic system. Properly configured, a storage tank can greatly increase a hydronic system's efficiency and reduce the cycling on your boiler, especially in the "shoulder season".

With this setup, if I have "shore power" I can heat using that, and get both DHW and cabin heating the other times. You have to be careful to pick the right unit if you do this because a lot of these units expect a beefy 240V feed, but there are plenty of low-power 120V options available. They don't have enough "oomph" to heat a whole house, but they're fine for a camper with a low-flow shower head and no water-hungry appliances like dishwasher/washing machine.

I don't plan to install one right away, but I'll plumb to add solar hot water later. I'm a fan of both electric and hot water and will probably add both eventually, we're just on a budget getting started and I want to be realistic. Solar hot water is really efficient and very easy to do. In areas where it's hot out I expect to be able to supply most/all of our DHW needs just from this source. That'll let us do a lot more boondocking in the summer.

I don't plan to run glycol in any of these lines, which eliminates some components (and concerns). We're going to be full-time and I wouldn't let these pipes freeze any more than I'd let them freeze in my house. There's an additional advantage here - pure water has WAY more thermal capacity than glycol - it's always the best choice, when you HAVE a choice. If we add solar I'll have to make a decision about that. I may do a drain-back setup in that case, which also eliminates the risk of overheating in the solar panels themselves. These systems are so small that you don't need a big tank for that. A length of 2" pipe in a wall has enough volumetric capacity to be the "tank".

Note: for you waste-oil (WMO/WVO) lovers, these coolant heaters won't work well with that fuel. They're blower-driven burners like a typical house boiler, not compression-fired diesels, so they're less tolerant of thicker fuels and I don't plan to modify mine just to support that. I figure if I'm going to mix fuels or use WMO/WVO, I'll do it with a separate tank and just for the bus engine itself. That's in the "we'll see" category in our plan.
taskswap is offline   Reply With Quote
Old 03-04-2015, 11:24 AM   #34
Bus Geek
 
Join Date: Aug 2011
Location: Stony Plain Alberta Canada
Posts: 2,939
Year: 1992
Coachwork: Bluebird
Chassis: TC2000 FE
Engine: 190hp 5.9 Cummins
Rated Cap: 72
Sorry for the delay, that was a good 4 days of work I just finished. Roofing with metal in the -20 C with blowing snow and 60 kmh winds is no fun.

My next project starting tomorrow is hanging drywall in a warehouse. Four more days of good $$.

Quote:
Originally Posted by That Guy in Maine View Post
Good thing I asked!

I appreciate all your help, I'll look forward to your reasoning!
Quote:
Originally Posted by taskswap View Post
Properly configured, a storage tank can greatly increase a hydronic system's efficiency and reduce the cycling on your boiler, especially in the "shoulder season".
Other reasons are:

High install Cost.

Hard to find model specific parts.

Not nearly efficient as claimed.

Low duty cycle. Unit will burn out under continues use.

Highly restrictive flow. Tankless units restrict the flow to insure the water is fully heated. This would cause you to need a massive high cost circulating pump.

And many many other reasons I can't think of right now.

In my opinion, a water heating system is no good without the heat storage reservoir. This is the single biggest mistake in most hot water heating systems.

Quote:
Originally Posted by taskswap View Post
With this setup, if I have "shore power" I can heat using that, and get both DHW and cabin heating the other times. You have to be careful to pick the right unit if you do this because a lot of these units expect a beefy 240V feed, but there are plenty of low-power 120V options available. They don't have enough "oomph" to heat a whole house, but they're fine for a camper with a low-flow shower head and no water-hungry appliances like dishwasher/washing machine.
I agree.

Many many sources of 15 amp 120 volt power. Even big road signs in parking lots have a 15 amp connection at the bottom for Christmas lights ect.

This is why I'm making that stainless steel tank with 6 one inch ports for heating elements.

I can have 2 running 240 volt. one at 5500 watts, and one at 3500 watts for versatility.

Two more running 120 volt. One at 750 watts and one at 1500 watts. This will give the ability to use half a 15 amp feed for heating, or use the full 15 amps.

And last the two low voltage heating elements for use of renewable electricity. Depending on my solar / wind generating system, the elements will be used as dump systems for when my storage battery's are full. This way my wind turbines will always have a restrictive load on them to prevent over speeding.

If I can build enough wind turbines and set up enough solar, I should be able to heat with only electricity in the spring / fall shoulder season.

Nat
__________________
"Don't argue with stupid people. They will just drag you down to their level, and beat you up with experience."

Patently waiting for the apocalypses to level the playing field in this physiological game of life commonly known as Civilization
nat_ster is offline   Reply With Quote
Old 03-04-2015, 11:39 PM   #35
Mini-Skoolie
 
Join Date: Jan 2014
Posts: 27
Nat,

I know you mentioned using the Polaris unit in your bus. I looked at that unit and while it's high priced it's worth it from what I conclude. My biggest worry is that it's specifically mentioned in the manual as being not fit for use in an RV.

As for a storage tank...do you mean plumbing your system something like this?



I might have made some mistakes here, but the basic idea is that the small black boxes are valves that would be controlled by DHW needs, a switch to pre-heat the engine, and the thermostats opening loops for different zones in the bus for heat.

There are two heat exchanges, one for the engine loop and the other for DHW loop. Then there is another valve that would basically allow hot/warm water to bypass the heater and get pumped back into the storage tank and then if it's needed it would be pumped into the loops. If the storage tank gets below a certain temperature then the water heater would turn on and circulate water as needed to get the storage tank up to temp again.

Am I designing that right?
That Guy in Maine is offline   Reply With Quote
Old 03-05-2015, 07:54 AM   #36
Bus Crazy
 
somewhereinusa's Avatar
 
Join Date: Nov 2010
Location: Andrews,Indiana
Posts: 1,636
Year: 1991
Coachwork: Bluebird
Chassis: AARE
Engine: 3116 Cat 250hp
Rated Cap: Her, me and Molly
Quote:
My biggest worry is that it's specifically mentioned in the manual as being not fit for use in an RV.
It's probably a liability thing. This covers them if you do it and something goes wrong and you try to sue them. Also, might be hard to keep fire lit while moving, but I don't think you are going to try that anyway since you are tying into engine heat.

I've been told you need a pressure relief valve in the domestic hot water, since you are getting heat from the engine. Mine is built into the water heater. I also have what amounts to a pressure relief valve in the heating loop, I built it using an automotive radiator cap with a catch can.
somewhereinusa is offline   Reply With Quote
Old 03-05-2015, 09:49 AM   #37
Bus Nut
 
Join Date: Feb 2015
Posts: 258
Usually with a radiant system you do this with a mixing valve. It stops you from short-cycling your boiler, increasing its life (and lowering its overall duty cycle), increases the return water temperature to the boiler (which is important if your boiler isn't stainless), and greatly increases the temperature stability of the system. Here are two options - the 3-way is passive and the 4-way is motorized (takes power... but then so does the circulator, so...)





The reason for this, plus storage, has everything to do with the reason we use water in these systems in the first place. The literal definition of a BTU is the "heat" stored in a pound of water raised 1degF. If you have a hydronic system that is meant to heat well from 110F-130F, that's a 20 degree difference. Now, say you have 200' of 1/2" PEX. Per this chart here:

Radiant PEX Tubing. Radiant Heat Systems. PEX Pipe Tube Underfloor Heat

that gives you about .92 gallons, or 7.67lbs of water. (Water weighs 8.34 lbs/gal.)

Now stay with me. If you heat that water from 110F to 130F with your boiler, you have stored 153 BTU in it. That's some heat... but not a lot. A 34kBTU/hr (10kW Webasto) boiler is going to cycle on and off a lot doing that.

Now suppose you add a 20-gal domestic hot water heater, just an off-the-shelf unit from Home Depot. (And no, I don't buy that entry-temperature argument I've seen elsewhere - these things are designed to HOLD water up to 180F or higher - having water enter at some number lower than that be a damaging factor makes no sense.)

Now you have 21 gallons of water in your system - 20, plus the 1 gallon in the pipes. (Again, not counting whatever's in the boiler.) Again you heat it 20F, but now you have 175lbs of water, so you store 3500 BTU in it. That's going to last a lot longer!

Not done yet, tho. Now you add a mixing valve and you run that hot water heater up to 180F or whatever it's rated for (I live on the edge and do mine to 190F - gasp). Now you're looking at a 70F temperature rise on that same water, so you're storing 12,500 BTU in it!

Doing this increases the system's overall efficiency although there are negative impacts too because even the best insulation in the world is going to leak some heat from that tank - but what the heck, it's leaking into your living space. Usually with a system like this where you want some extra efficiency you add what's called an "outdoor reset", which is a temperature sensor added to your aquastat. When it's warm out and it knows you're only heating shower water, it lowers the temperature it runs the system at to like 130F or so.

This kind of system takes a little extra work to set up but has some other benefits that make it worth it IMO. The solar is the big plus - it's super easy to add to this kind of system and "store" heat in that hot water tank. Solar is kind of useless without some form of storage, IMO, and this kills two birds with one stone. And with an electric element (or whatever nat_ster is doing - six or something???? <grin>) you can get your hot water that way when electricity can be had. Three heat sources (diesel, electric, solar), one storage tank, a mixing valve, and your radiant, and you're done!
taskswap is offline   Reply With Quote
Old 03-05-2015, 10:22 AM   #38
Bus Geek
 
Join Date: Aug 2011
Location: Stony Plain Alberta Canada
Posts: 2,939
Year: 1992
Coachwork: Bluebird
Chassis: TC2000 FE
Engine: 190hp 5.9 Cummins
Rated Cap: 72
Quote:
Originally Posted by That Guy in Maine View Post
Nat,

Am I designing that right?
That's close to what I have in mind. If possible, combine the heating tank with the storage tank. My heating tank will be my storage tank.

I don't use or like zone valves. I feel it is too hard to balance a system that way.

Try to use as few zones and as few circulating pumps as you can.
Pumps are expensive, and use electricity.
A bus is small so only a few zones are really needed.

Mine will be 1 zone for the entire floor.
Then a zone for keeping the tanks in the basement of the bus from freezing.
One more zone will be wrapped around the bathtub so I can sit in the tub for hours without it cooling off.
Last zone will be a future connection for heating the stacker trailer I will pull with my bus.

Quote:
Originally Posted by somewhereinusa View Post
It's probably a liability thing. This covers them if you do it and something goes wrong and you try to sue them. Also, might be hard to keep fire lit while moving, but I don't think you are going to try that anyway since you are tying into engine heat.

I've been told you need a pressure relief valve in the domestic hot water, since you are getting heat from the engine. Mine is built into the water heater. I also have what amounts to a pressure relief valve in the heating loop, I built it using an automotive radiator cap with a catch can.
I would agree. They also may fear what the vibration will do to the unit.
__________________
"Don't argue with stupid people. They will just drag you down to their level, and beat you up with experience."

Patently waiting for the apocalypses to level the playing field in this physiological game of life commonly known as Civilization
nat_ster is offline   Reply With Quote
Old 03-05-2015, 11:07 AM   #39
Bus Crazy
 
opus's Avatar
 
Join Date: May 2010
Location: Montana
Posts: 1,615
Year: 1995
Coachwork: Blue Bird
Chassis: All-American R/E
Engine: 8.3 Cummins
Rated Cap: 72
I've not read this whole post but why dont you skip to the chase and use a Webasto dbw2010?
opus is offline   Reply With Quote
Old 03-05-2015, 12:59 PM   #40
Bus Geek
 
Join Date: Aug 2011
Location: Stony Plain Alberta Canada
Posts: 2,939
Year: 1992
Coachwork: Bluebird
Chassis: TC2000 FE
Engine: 190hp 5.9 Cummins
Rated Cap: 72
Tankswap

Heating the heat storage water to hot can have disadvantages depending on what system is used for heating.

In a closed loop electric heated system, you can heat the water to just under the boiling point with no loss in efficiency.

With a $400 propane hot water tank, you want to heat the water to the lowest heat that can still effectively heat the space. The hotter you have it set, the lower the efficiency.

I don't use mixing valves because I don't heat the tanks that hot.

Quote:
Originally Posted by opus View Post
I've not read this whole post but why dont you skip to the chase and use a Webasto dbw2010?
I will have one for back up and versatility. However many of us need more than it offers at a much lower operating cost than it has to offer.

Nat
__________________
"Don't argue with stupid people. They will just drag you down to their level, and beat you up with experience."

Patently waiting for the apocalypses to level the playing field in this physiological game of life commonly known as Civilization
nat_ster is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Radiant Floor Heating......feedback requested Shawn C Heating, Cooling and Appliances 14 12-30-2012 11:18 AM
Propane Heating - Radiant vs Blue Flame Stuff Heating, Cooling and Appliances 12 11-08-2012 05:19 PM
Radiant Floor Heating Reference zim Heating, Cooling and Appliances 16 01-08-2011 02:41 PM
Radiant Floor Heating oldog12 Conversion General Discussions 8 08-24-2006 02:05 PM
Modify stock heating system or seak alt heating? phillbus914 Conversion General Discussions 4 09-14-2005 06:14 PM

» Virginia Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 12:17 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.