Yet another hydronic heat question?

PE

pepepito

Senior Member
Joined
Dec 16, 2015
Posts
152
Hi.

I have been reading and studying many threads about the subjet and I have few questions, the threads that I read are :

Big thread lots of info
Somewhereinusa design
Alde systems

So Basically I have my bus ready to do the subfloor and I decided to go with hydronic heat so I was about to buy the materials and decide to stop and ask to people with experience before I regret it.

The system I want to build is basically like somewhereintheusa but just one zone and no additional heaters , just the floor.

The questions :

1.- I was going to build a frame, put foam insulation and then plywood = should I do 1 inch pink foam, then aluminium reflective pex plates and then more foam and then plywood on top or can I just get thicker pink foam and use a router to make a channel to route the pex through ? what will be the best way to do it ? is it better to have a reflective surface ?

2.- My bus is 22 ft long , what diameter pex should I use if I use a system with and espar diesel coolant heater , how do I calculate that ? ( since the system is just one zone I didn't know if I need 1 inch pex or less).

3.- is it recommended to use a storage tank with an element inside ?

4.- If I want to heat the engine can I just use a 3 way valve and route hot coolant/glycol to the engine or is it a different liquid used in for the hydronic heating ? ( instead of using a heat exchanger ?)

5.- is there any rules on how apart the pex has to be when routing each row ?

6.- If I use an espar coolant heater do I still need to a recirculating pump for short bus?

7.- in the case of using a heat exchanger for coolant heating do you install it inside or outside of the bus ?

8.- What is a recommended heat exchanger that is safe to use to heat potable water ?

I think this is for now, sorry for the many questions.

Thanks.
 
The questions :

1.- I was going to build a frame, put foam insulation and then plywood = should I do 1 inch pink foam, then aluminium reflective pex plates and then more foam and then plywood on top or can I just get thicker pink foam and use a router to make a channel to route the pex through ? what will be the best way to do it ? is it better to have a reflective surface ?

You don't want any insulation between your pex/aluminum plates and the bottom surface of your flooring, that would defeat the purpose. The idea is to heat the floor. I originally wasn't going to use the aluminum plates and was advised that it wouldn't work right without them. In the few places that don't have the plates the floor isn't really all that warm, it just isn't cold. In the pictures of my build you can see the aluminum "H" channel that I put between my floor sheets. Since they get direct transfer of heat they get hot enough that you don't want to stand on them in bare feet.


2.- My bus is 22 ft long , what diameter pex should I use if I use a system with and espar diesel coolant heater , how do I calculate that ? ( since the system is just one zone I didn't know if I need 1 inch pex or less).

All of the installations, even in large houses, I have seen use 1/2" pex. You would never be able to bend any of the larger sizes sharp enough.

3.- is it recommended to use a storage tank with an element inside ?

I don't have one, I don't really see the need. I'm not sure about other units, the Espar unit, when operating, stays lit and cycles between a high and low. Even in below zero temps it doesn't run on high all that much.

4.- If I want to heat the engine can I just use a 3 way valve and route hot coolant/glycol to the engine or is it a different liquid used in for the hydronic heating ? ( instead of using a heat exchanger ?)

While it is possible you want to be very careful. If, as you indicate in a later question you want to heat domestic hot water you need to seperate the toxic antifreeze from your potable water. Also be aware that engine water temp is at or above the temperature limit for pex.My system has basically three separate kinds of water. The engine cooling system uses standard automotive antifreeze, poison. Separated from the the heating system by a heat exchanger and uses hydronic heat antifreeze, not poison. Separated from the domestic hot water by the heat exchanger in the water heater. There is no danger of the poison antifreeze getting into the domestic water.
5.- is there any rules on how apart the pex has to be when routing each row ?

There is a minimum bend radius for pex. If I remember right it is 4" for 1/2". I fudged just a bit and used about 3 1/4". The pex expands quite a bit lengthwise so you need to allow for that.

6.- If I use an espar coolant heater do I still need to a recirculating pump for short bus?

The Espar keeps the water temp at a certain temp as determined by it's controller, I don't think that is changable. The internal waterpump is on whenever the unit is running. It wouldn't do well to turn the whole unit off and on to control room temp. I think that the best bet would be to have the main loop with a "heat" loop drawing and returning to the main loop with an extra pump controlled by a thermostat.Using a heat exchanger from the engine gives the advantage of using your hydronic heat for the bus when driving, to do that you need to tie into the Espar main pump so that you can turn it on when the unit is not running.

7.- in the case of using a heat exchanger for coolant heating do you install it inside or outside of the bus ?

I put mine in the engine compartment. They get pretty hot when the engine is running, you don't want that inside the bus in the summertime.

8.- What is a recommended heat exchanger that is safe to use to heat potable water ?

There are marine water heaters that have built in heat exchangers made for that purpose.
[/QUOTE]
 
somewhereinusa said:
The questions :

1.- I was going to build a frame, put foam insulation and then plywood = should I do 1 inch pink foam, then aluminium reflective pex plates and then more foam and then plywood on top or can I just get thicker pink foam and use a router to make a channel to route the pex through ? what will be the best way to do it ? is it better to have a reflective surface ?

You don't want any insulation between your pex/aluminum plates and the bottom surface of your flooring, that would defeat the purpose. The idea is to heat the floor. I originally wasn't going to use the aluminum plates and was advised that it wouldn't work right without them. In the few places that don't have the plates the floor isn't really all that warm, it just isn't cold. In the pictures of my build you can see the aluminum "H" channel that I put between my floor sheets. Since they get direct transfer of heat they get hot enough that you don't want to stand on them in bare feet.
Click to expand...

Understood then it is pex+aluminium plates then pink foam and then plywood

2.- My bus is 22 ft long , what diameter pex should I use if I use a system with and espar diesel coolant heater , how do I calculate that ? ( since the system is just one zone I didn't know if I need 1 inch pex or less).

All of the installations, even in large houses, I have seen use 1/2" pex. You would never be able to bend any of the larger sizes sharp enough.
Click to expand...

Half it is then.

3.- is it recommended to use a storage tank with an element inside ?

I don't have one, I don't really see the need. I'm not sure about other units, the Espar unit, when operating, stays lit and cycles between a high and low. Even in below zero temps it doesn't run on high all that much.
Click to expand...

Easier if I don't need to use the tank :)

4.- If I want to heat the engine can I just use a 3 way valve and route hot coolant/glycol to the engine or is it a different liquid used in for the hydronic heating ? ( instead of using a heat exchanger ?)

While it is possible you want to be very careful. If, as you indicate in a later question you want to heat domestic hot water you need to seperate the toxic antifreeze from your potable water. Also be aware that engine water temp is at or above the temperature limit for pex.My system has basically three separate kinds of water. The engine cooling system uses standard automotive antifreeze, poison. Separated from the the heating system by a heat exchanger and uses hydronic heat antifreeze, not poison. Separated from the domestic hot water by the heat exchanger in the water heater. There is no danger of the poison antifreeze getting into the domestic water.
Click to expand...

Ok that sounds much safer, I will do that.

6.- If I use an espar coolant heater do I still need to a recirculating pump for short bus?

The Espar keeps the water temp at a certain temp as determined by it's controller, I don't think that is changable. The internal waterpump is on whenever the unit is running. It wouldn't do well to turn the whole unit off and on to control room temp. I think that the best bet would be to have the main loop with a "heat" loop drawing and returning to the main loop with an extra pump controlled by a thermostat.Using a heat exchanger from the engine gives the advantage of using your hydronic heat for the bus when driving, to do that you need to tie into the Espar main pump so that you can turn it on when the unit is not running.
Click to expand...

I see, I will get a pump then, any out there that is powerfull enough and runs in 12v , or is better to go with 120v ?

If I use a 3way/4way electrical valve could I just bypass the Eapar pump and run it with the circulation pump while running heat from the engine?(while driving)

How do you decided the model of Espar heater , base on BTU, Flow , available parts ? ( I waswondering if I could go with one a bit smaller and cheaper)

Thanks.
 
I see, I will get a pump then, any out there that is powerfull enough and runs in 12v , or is better to go with 120v ?

Many buses have a circulation pump for the rear heaters, perhaps someone here might have one, I might have one if I can find it. If you go 120V you will need an inverter to run it while driving.
If I use a 3way/4way electrical valve could I just bypass the Eapar pump and run it with the circulation pump while running heat from the engine?(while driving)

Probably but, it would be less complicated and cheaper to use the pump already in the unit. Also without some way to run the Espar pump on it's own I found it difficult to impossible to bleed the air out of the system.
How do you decided the model of Espar heater , base on BTU, Flow , available parts ? ( I waswondering if I could go with one a bit smaller and cheaper)

As with many things I do, I went with what I got a good deal on. I don't know much about them but, I think one of the heaters made to preheat a bus would be large enough. You might find a used one. I'm not sure if Espar makes one. I know Webasto does.
 
somewhereinusa said:
I see, I will get a pump then, any out there that is powerfull enough and runs in 12v , or is better to go with 120v ?

Many buses have a circulation pump for the rear heaters, perhaps someone here might have one, I might have one if I can find it. If you go 120V you will need an inverter to run it while driving.
Click to expand...


I do have an inverter and I was thinking to get a smaller one for the pump.
If I use a 3way/4way electrical valve could I just bypass the Eapar pump and run it with the circulation pump while running heat from the engine?(while driving)

Probably but, it would be less complicated and cheaper to use the pump already in the unit. Also without some way to run the Espar pump on it's own I found it difficult to impossible to bleed the air out of the system.
Click to expand...

Good point.
How do you decided the model of Espar heater , base on BTU, Flow , available parts ? ( I waswondering if I could go with one a bit smaller and cheaper)

As with many things I do, I went with what I got a good deal on. I don't know much about them but, I think one of the heaters made to preheat a bus would be large enough. You might find a used one. I'm not sure if Espar makes one. I know Webasto does.
Click to expand...

ok I will look around to see if I can find a good used one, I can't really spend 2k on it.
 
Hydronic heat is awesome...in a house. My ex-in-laws place in NC stayed temp stable year round thanks to a deep well system.

But I am having trouble getting my head around mobile systems. All that Pex inside inaccessible wooden floors with permanent furniture on top of it in a rattling, flexing bus chassis all just seems like a disaster waiting to happen. I'm sure you folks must have thought it through and probably have a great plan...it's probably just me, but I find it all a bit scary.
 
Tango said:
All that Pex inside inaccessible wooden floors with permanent furniture on top of it in a rattling, flexing bus chassis all just seems like a disaster waiting to happen. I'm sure you folks must have thought it through and probably have a great plan...it's probably just me, but I find it all a bit scary.
Click to expand...

Well, pretty much everything I ever do is experimental. The way my floor is installed it is "kinda" removable. The pex is very flexible. Your bus rattles? Mine doesn't. :whistling:.

Haven't you learned by now that life is either scary or it isn't. I don't sweat the small stuff. If I was a worrier I wouldn't have driven a truck all those years and just slept where ever I could find a place to park.:hide:
 
Just bid on the Webasto, nice find and thanks for the link. It's only a couple hrs away from me... $75 bucks seems reasonable to me...
 
Last edited:
All this talk of heating got me thinking... You could put all that under the floor, and I like the idea of doing so, but I'm too tall for my bus already plus it could be hard to service. I do want to find a way to use my tankless WH to heat the back of the bus near the bed. I took out the original rear heater. I'm thinking I could re-plumb it so the hot water recirculator uses the "rad" and fans from the original heater. I could probably even use the original cockpit controls for it too.

Maybe this would be a more simple way of using hot fresh water to heat the bus, just be sure to super clean or replace the heat exchanger (radiator part) so there are no chemicals in it of course.... But you guys get the idea right?
 
somewhereinusa said:
I see, I will get a pump then, any out there that is powerfull enough and runs in 12v , or is better to go with 120v ?

Many buses have a circulation pump for the rear heaters, perhaps someone here might have one, I might have one if I can find it. If you go 120V you will need an inverter to run it while driving.
Click to expand...

If you find one or point me to a link of the one you are refering too, I will appreciatte.
 
Ebay doesn't show much, maybe are called something else.

I guess I could use an electric water pump, or it has to be for coolant ?

Any heat rating I should be worried ?
 
How about one of these off a school bus, circulates water for the heaters. Look up places that sell school bus parts
17-09530-2.jpg
 
You must log in or register to reply here.

Similar threads

Bjorkinman
What about PEX for hydronic heater
somewhereinusa
somewhereinusa
Crlefley
Another Hydronic Thread?
2
somewhereinusa
somewhereinusa
JF
40 degree temp difference between floor and cieling
jfmusic@me.com
JF
BR
1997 DT466 coolant service
Bjorkinman
Bjorkinman

New posts

Featured Campgrounds

Reviews provided by

Try RV LIFE Pro Free for 7 Days

  • New Ad-Free experience on this RV LIFE Community.
  • Plan the best RV Safe travel with RV LIFE Trip Wizard.
  • Navigate with our RV Safe GPS mobile app.
  • and much more...
Try RV LIFE Pro Today
Back
Top