Floor Heat Tankless Water Heater Question

[cdreed06]

I know this has probably been discussed on here numerous times but I can't find the info I need. Our truck bay was added on to our wash after it was built. It has a separate stand alone Paloma PH12 tankless water heater and a Grundfos pump. I have fought this thing all year so far. First the pilot wouldn't light and I had to replace the thermocouple which has to be a Polama part, a universal won't work, then replaced the pilot tube and burner. Then it would fire and run but not long. So I noticed the clear tubes going out into the bay had big air pockets. So I hooked up a swimming pool pump in a bucket and filled it with antifreeze, connected it to the system and put my drain hose from the system into the bucket and got all the air out. So then it still wouldn't fire. So I jumped the safety switches on the gas valve and still nothing. Paloma's website has a troubleshooting part that says I need to rebuild the water valve. Rebuild kit is $65. Long story short I am sick of the Paloma and can get a cheap tankless water heater on ebay for less than $300. Is this a smart thing to do? Will it do what it needs? What do I need to look for as far as specs? It will only be heating the truck bay floor. Thanks in advance.

 

[Eric H]

I am sick of the Paloma and can get a cheap tankless water heater on ebay for less than $300. Is this a smart thing to do? Will it do what it needs? What do I need to look for as far as specs? It will only be heating the truck bay floor. Thanks in advance.

What are the specs on the $300 ebay tankless unit? How many sq ft is the slab you are trying to heat?

 

[JGinther]

I feel your paloma pain, as I dealt with the same thing a year and a half ago. Chances are, you could take the valve out and clean the pilot rod that moves with the diaphragm. The diaphragm probably isn't actually bad, just needs to move free to push the gas valve pilot. I thought the same thing was needed on one, so I cleaned and lubed it just to try to get by til parts came in. Well, its still working now.
By the way, not sure if your area requires it or not, but most boiler inpectors are up on the ASME requirement for hydronic heating. Hydronic heat requires the blessing of the ASME stamp, and I have seen operators have to rip out and install new heaters for this reason. (The inspector also has to be a jerk). Other than that, pretty much any commercial tankless heater of similar btu which is set up for recirculation will work just fine, but your venting may have to be changed due to condensation with higher efficiency or blower motor units.

 

[cdreed06]

Eric: not sure on the specs just was browsing. I'll check them out further. The bay is about 20'x32' I think
JGinther: I will definitely check the rod on that. Knock on wood we haven't had any inspectors here yet. Thank you both for answering.

 

[trentu]

I just put in a Navien house unit for 2 bays and only problem I see with it is that lowest value I can set it to is 90 degrees, would really like to be able to heat to only around 60 but it is doing the job just fine.

 

[cdreed06]

Trentu, what is the specs on that? I found one that has 4.23 gpm and 109,000 btu/ hour. Less than $300. What do you all think?

 

[Keith Baker]

Trentu, what is the specs on that? I found one that has 4.23 gpm and 109,000 btu/ hour. Less than $300. What do you all think?

I was told by a boiler salesman sometime ago to plan on 100 BTU per square foot for a typical self serve floor heat in my area (Omaha). Your 109000 BTU at 80% efficiency would take care of 872 square feet of floor space if this is right.

I use a 179000 BTU Takagi for my 6 bay, with a Paloma that I can run in parallel when the temperature stays below +10 for any length of time. As I write this is is 5 below and the wind is blowing about 25 MPH. I have 3 bays roped off and the other 3 bay floors salted down liberally in case someone is stupid enough to want to wash.

Hopefully it will warm up some by next weekend, this is getting expensive.

Keith

 

[cdreed06]

Thank you very much!

 

[trentu]

I used a 199k btu and for 2 bays 18x30 it seems to do the job. I didn't scientifically size it but I like Keith's numbers approach. I am in a bit more of a temperate climate.

 

[2Biz]

I think for our area, Southern Ohio, the charts recommended 125BTU per sq ft...I used those figures when calculating for my 4 bay. I bought the Takagi 199K BTU model and Its more than enough. So that figure seems a little high. 100 btu sounds like a better number. Mine keeps the floors ice free with it set @ 105° output at about 6.8 gpm primary and 16gpm secondary out to the bays. I get 90-95° glycol going out to the bays and 60-70° coming back. The boiler kicks off @ 72° and kicks back on @ 60° return temps...The bays stay between 35° and 40° surface temps even down to 0°. Its getting down to -10°, so I'll see how it looks when I get home from work!