Not Enough Hot Water From 520

If we were talking about a 10-unit building I don't think there would be any discussion. With a 4-unit building, if the OP were to receive a bill for a 119 gallon indirect or storage tank, plus installation, I'm guessing his first question would be whether everything reasonable had been done to get the most out of the existing system. The answer to that, so far, is "no". No doubt the 520 would have to be pushed hard to have a shot, but I sure don't want anyone to be telling me to spend serious $ on the basis of the unsatisfactory performance of a machine at idle. Crank it up to the settings that correspond to the boiler water intake settings and flow rates assumed in the indirect specs (like maybe 180 deg. and 7 teeth?) and then tell me it doesn't provide reasonable performance.

Mike

Larry, IIRC the post of yours I was referring to involved some kind of test of boiler output that was measured by the temp increase and flow rate of water through the DHW coil holding the boiler temp constant. Unless I'm hallucinating, it demonstrated the effectiveness of coils at extracting BTU's from boiler water.

Sorry if I missed it, but has it been established that this problem existed during the winter?

Mike

Jeff1491 wrote:The boiler is only about 7 years old and it is well maintained. Im not sure if thats enough time to build up deposits on the coil.
I noticed that the line coming off the coil is only 1/2''. Is that normal ? Id rather not put a bigger load on the boiler since im using 12-18 tons per year already. The tenants never complain about heat in the winter so thats not a problem for the boiler at the settings I have it on now. Just the hot water. Im thinking about removing 1 unit from the system altogether and putting electric baseboard heaters in there plus the hot water heater to reduce the load. Id have wait till the tenant moved out though, but for now I will raise the settings and hope that is good enough.

You can render a tankless coil useless in 1 year if the water is hard.

Do the tenants complain about lack of hot water in the winter? If not, then your problem is not lack of boiler capacity.

What is the goal here anyway? To try and make the existing equipment work or to engineer something different?

Fair enough.....but the REAL World test still won't work. Anything to provide additional tankage will help...or a used 80 gallon (or 2 or 3 40's) electric water heat tank.....water to water to water heat exchanger...

I am purposely not mentioning water quality, because hard water is a killer to coils...quick, quiet deaths. Up in the Newport, Derby, Derby Line area of VT, if you didn't see it happen, you would not believe it. TOUGH on piping, coils, PRV's, some zone valves, and especially water tempering valves. Clean them every 4 months, or you will lose them to scaling.

My point is that tenants will find a new place to reside quickly if you get too cheap with the shower heads, etc. You, Mike, have lots of experience with large systems, and lots of kids, who use a lot of water...and create lots of laundry, so I am listening, but still skeptical!! lol

Thanks Hophead...perhaps I need to get you on the 'all alone island', too!) I KNOW you have been there, done that....also.

Tell ya what. You have him set it up any way you think it'll work. Them give him YOUR phone number to handle the no hot water calls for a year. Think about this too. Doing it right will take about 2 months rental income.

WN, thanks for your patience with me. I tend to be ...uhh...frugal, but I do want stuff to work acceptably well.

Hophead, what's the problem with checking whether there are settings that work acceptably well? They'll still sell indirects next week, if one is really needed.

Mike

hophead wrote:Tell ya what. You have him set it up any way you think it'll work. Them give him YOUR phone number to handle the no hot water calls for a year. Think about this too. Doing it right will take about 2 months rental income.

You don't have to lecture me about it, I already have the right setup in my own home...an 80 gallon indirect that would be perfect for this situation. I was simply trying to point out some easy things to check that might relieve the problem.

Good point about the return on investment, it is certainly not worth losing tenants over.

Water to water plate exchangers do the DHW for our 2 houses,no lack of hot water,simple,low cost setup,works in warm weather & cold weather,at 3 teeth setting to 7 tooth setting. Keep It Sensibly Simple & enjoy life.

WH, I agree with KISS, and to me a coil in a boiler is about as simple as it gets, as long as it works.

Mike

Pacowy,I agree on the coil being simple,but the plate exchanger is a simpler & cheaper setup then many alternatives suggested . I also strongly agree with the suggestion of making the boiler water HOT instead of tepid. The OP stated he is burning 12-13 tons of coal /yr & doesn't want to increase that amount ? A few more tons per yr would be easier & cheaper than many of the suggestions.Turn up the settings (feed/air) so the beast can work as it is designed,turn up the water temp to maximize available BTU usage,clean the coil to maximize BTU transfer. Has this problem only now come up after 7 yrs of success ?

Jeff1491 wrote:Thanks, I will look into cleaning the coil then. The house is about 1 hour drive from me and I willnt be able to look at it for a week or 2.

You may want to make the trip sooner, rather than later. Tenants have a lot of rights and you, as a landlord, have a lot of obligations to said tenants.

Best of luck.

IMHO try setting it at 180 and 200 and let it cook. Sure you will burn a little more coal but your phone might stop ringing. You will also keep that two months rent from each tenant you might have to invest to buy an indirect. I have used plate type heat exchangers and storage tanks which were nothing more than two 40 gallon electric water heaters being used for storage. One tank is the out and one is the in. Put a small circ pump to recirculate the tank water constantly through heat exchanger.

It might be a bit cheaper than 2K for an indirect and storage on top of that.

What's so much better about an indirect as compared to just using a second hand electric hot water tank for storage? And why couldn't he set it up to naturally convect instead of using a circulator? And why the extra heat exchangers, isn't the coil in the boiler enough if there is 100 gallons of hot water storage in place? Wouldn't the solution be to spread out the heat demand on the coil in the boiler? And a water storage unit would do that, no? Seems like a coupla Franklin's would be plenty..

I am no scientific mathamagition ,but IF the coil is clean & only capable of 5 gal/min ,more hot water BTU's will be available IF the boiler water temp is 180* rather then 150*. Either temp is tempered by the mixing valve. Hotter boiler water temp = more BTU storage !!!! There is extra BTU storage just waiting to be utilized , crank up the temp & the feed & air. FEED THE BEAST !! There is a side benefit to this option ~~~~~~~~~~~~~~~~ no $$$$$$$$$$$ out !!!!!!!!!!!! Another side benefit is that this option costs nothing to try,no wasted $$ if it fails,very little time spent to test this option. EASY,easy,easy..................

Seems like the best solution for more hot water would be a storage tank but If I can get away with adjusting the the limits and possibly feed and air settings that would be better. Recently, there has been more complaints about the hot water, some with no hot water at all, so im thinking it could be a clogged coil. Is this an easy job ? Just shut down boiler and pump the cleaning liquid through the coil ? Also there in no mixing valve, guess this could cause problems also. Other that scalding the tenants