Running a gas furnace and tankless water heater = PROBLEM!
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fyi. have your hvac guy take his manometer and take a working pressure at the water heater when furnace is on also.that will tell a lot. what pressure is your gas main? what pressure is your service? what size gas service piping,what size house piping ,how far from gas meter to water heater in gas piping, all of this plays into a good working water heater and furnace . and what size gas meter,they come in btu s , most house s have a 250 btu meter,most houses have a 150 btu furnace and a 40btu waterheater and a 40btu gas range add that up =230 btu,now put in your new waterheater that will use about 240 btu by itself............240+ 150+40+40=470 btu ,= new meter. as an old gasman I have upsize lots of meters because of the new tankless waterheaters. call your dang gas man.
similar to what earlier poster said... we are converting to gas now and having line run to house.
what I was told is.. that for almost all residentials in my area the gas line is the same diameter but for whatever reason they use different sized meters depending on gas flow needs (I mean... not really sure why they wouldn't just go larger for everyone... but I guess the larger meters are too expensive to just give to all)
anyway.. our new heater is 80k btu... and the tankless water heater requires 190k!!
2 1/2 times the btu of heater!
So in the simple questionnaire the gas rep reviewed with me, it added up to "yes we the gas company will give you the larger meter".
All that being said.. call the gas company and have them check you meter size, or just the have them check out your problem in general
Was this an existing setup in a house you just bought? Unless something has gone wrong since then, whoever did the install fell down on the job pretty seriously. Given pipe size and given pressure means only so much gas can flow. They should have accounted for that. Again, assuming the gas company hasn't changed their supply or your meter or regulator did not go bad. You will need a higher pressure meter or a higher pressure regulator or both. Definitely call the gas company.
fyi; remember that 1950 house you own,the one with oil heat and just a gas stove in 1950 with 1950 gaspiping,well its now 2014.......gas heat,dryer ,water heater,stove,pool heater,gas light..........all on 1950 gas piping see what I mean.back then most gaspiping was 3/4 or 1 inch today if you put in a poolheater or gas gen, you may need 2inch piping,the more btu you use the bigger the gas pipe and regulator and gas meter you need. and I would say 80% of all tankless water heaters need a bigger gas meter........just an old gasman
Sounds like your supply lines are too small. We had the same exact issue. We got a tankless and professional stove installed and no sales men even mentioned are as pipes might need to be upgraded. While that probably wouldn't have made us not purchase those items, we could have been a little more prepared.
This is the first time I have ever had a gas furnace and a gas tankless water heater. I like the water heater BUT if my heater is on then I can't get hot water. The display pad of the water heater says it is not getting enough gas (roughly). The water heater is for a small house and I have no idea about the furnace. What could be causing this problem? None of the guys I have out to look at it have any idea. They have never heard of the brand of water heater (Paloma) and they say the pipes are large enough.
Does the amount of gas flow get reduced as things use it? Could it be that the gas runs to the heater first then it runs out of enough for the water heater? The only thing I can relate it to is cable the is being split with splicers if anyone remembers those.
I have not heard anything bad about the brand of water heater but they keep recommending a locally known brand.
Other replies pretty much have nailed it; your natural gas supply is too small to serve both heating and hot water at same time.
Gas fired instant water heaters require more "juice" than a standard tank type. If a tank unit was swapped out for tank-less but no one ran the numbers to see if current gas main could handle, you have problems.
Sadly HAVC contractors can sometimes be a bit of hit or miss. You can have one, two or more *professionals* look at a system and all either say different things and or agree with each other, but nothing solves your problem. Most likely it will be suggested you need a "new" this or that installed...
Try to find out who did the original installation of the tank-less hot water system. Also seek out a highly recommended guy who is known for getting to the bottom of things without pushing an agenda.
IIRC Paloma tank-less water heaters are a Rheem product. So maybe try contacting that company or searching for solutions using the latter corporate name.
This is the first time I have ever had a gas furnace and a gas tankless water heater. I like the water heater BUT if my heater is on then I can't get hot water. The display pad of the water heater says it is not getting enough gas (roughly).
Are you hooked up to a natural gas main, or are you on propane?
If the latter, the pipes could all be the right size, but with a small tank the tank may just not be able to supply sufficient gas pressure, especially when it is very cold outside.
Sounds like your supply lines are too small. We had the same exact issue. We got a tankless and professional stove installed and no sales men even mentioned are as pipes might need to be upgraded. While that probably wouldn't have made us not purchase those items, we could have been a little more prepared.
A "load" test "should have" been done by the company installing the Tankless Water Heater. Wanted a quick sale not doing his job.
I would like to go Tankless but we do not have the usage to justify the expense.
I would like to go Tankless but we do not have the usage to justify the expense.
I actually switched to tankless because I use very little hot water each month, but sometimes need 100 gallons at a time (to fill a large tub).
I calculated fully half my water heating costs were going towards "standby losses", keeping the water in the storage tank hot. Then the old tank failed and the state offered several hundred bucks in rebates for switching to tankless.
Because I am on propane, when I had them put the tanks in the installation was planned from the beginning to be able to handle the expected volume needed, both in terms of regulator/piping and also tank size -- with larger demands, propane setup needs a larger tank to ensure a sufficient volume of gas.
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Propane gas or natural gas?
